Atomic layer deposition (ALD) is a very surface-sensitive deposition technique. That sensitivity drives high quality film growth and also drives selective area deposition (SAD). SAD occurs when the precursors for the deposition are prevented from reacting with some areas of the substrate surface. Many groups have explored methods for selectively inhibiting the growth of ALD.[1] We have previously shown that selective inhibition of thin-film metal oxides can be accomplished using simple water soluble polymers that are readily patterned using inkjet printing, enabling fabrication of thin-film devices using strictly additive spatial ALD[2]. We have explored the SAD temperature and exposure-time process space for our most common precursors, and demonstrated that high-throughput spatial ALD is particularly well suited to this patterning process[3].
In this talk we describe improvements in both performance and yield for electronic devices fabricated by spatial ALD using SAD as the patterning method. Controlling individual layer quality and the interfaces between layers is essential for obtaining good quality thin-film transistors and capacitors. The improvements were obtained using a systematic approach which, perhaps unsurprisingly, highlights that the surface sensitivity that enables SAD can also present problems due to the influence of unintentional surface contaminants. The integrity of the gate insulator layer is particularly critical, and we will describe a multilayer dielectric which improves cross-over yield. We will also describe a method to achieve optimal mobility at the important interface between the semiconductor and the gate insulator. With transistors showing mobility in the range of 15 cm²/Vs, the integration of the best designs resulted in good yield of circuits, along with design flexibility. As the field of printed electronics matures, approaches such as these will help move towards practical high-performance devices.
1. See, for example: Rong Chen, Stacey F. Bent. Adv. Mater. 2006, 18, p.1086-1090; A. Sinha, D. W. Hess and C. L. Henderson, J. Electrochem Soc, 153, G465, (2006)
2. D. H. Levy, C. R.Ellinger, and S. F. Nelson, Appl. Phys. Lett. 103, 043505 (2013)
3. Carolyn R. Ellinger and Shelby F. Nelson, Chem. Mater., 2014, 26 (4), pp 1514-1522

Roll-to-Roll (R2R) production for Display applications (active matrix TFT backplanes, OLED frontplanes & touch screens) combine the advantages of the use of inexpensive, lightweight & flexible substrates with high throughput production to enable new form factor products with exceptional robustness and mechanical stability. Significant cost reduction opportunities can also be found in terms of processing tool capital cost, utilized substrate area and process gas flow when compared with batch processing systems. Nevertheless, material handling, device patterning and yield issues have limited widespread utilization of R2R manufacturing within the electronics industry. Recently, significant advances have been made in device patterning enabling the mass production of a variety of flexible electronic devices. These techniques are now so advanced that feature sizes of less than 40 nm can be produced on thin film layer stacks deposited on 50 µm thick polymeric substrates and features down to less than 20 µm on thick film processed screen printed metal layers for narrow bezel applications. Significant challenges also exist in terms of the layer deposition technologies used in R2R manufacture of these devices. Unlike traditional semiconductor or display based cluster tool platforms, R2R systems require to process substrates in a continuous fashion with rolls up to several kilometers in length. Depending upon the process itself, this imposes a limitation in terms of the mean time before cleaning (MTBC) and in some cases the particle management strategy.
Applied Materials has developed a variety of different web handling & coating technologies/platforms to enable high volume R2R manufacture of both active and passive components utilized in Display. The work presented in this paper therefore describes the principal challenges inherent in moving from lab/pilot scale manufacturing to high volume manufacturing. Results will be presented for both amorphous silicon and IGZO TFT backplanes, ITO based touch panel devices in addition to high barrier performance layers and stacks for both substrate encapsulation and barrier film for final device encapsulation. The paper also addresses areas where both thick and thin film processing technologies can be combined.

Macroelectronics is a field or research to extend the application range of electronic and optoelectronics devices. In macroelectronics “larger” is considered better which is in stark contrast to the conventional field of microelectronics where “smaller” and a high function density was the most important driver. In view of the recent trend towards large area integration traditional methods of robotic pick and place are challenged to integrate functional devices over large areas in an economical fashion. Directed/engineered self-assembly is uniquely suited as a mechanism to solve this challenge. This methodology allows for the redistribution of components over large areas and the ordering of unorganized parts in a massively parallel fashion. For example, a binned container full of semiconductor dies/chiplets of a certain type and quality can be redistributed and assembled at precise locations on a substrate at any desired pitch or required functional density using methods of directed self-assembly.
We report the implementation of an automated reel-to-reel fluidic self-assembly system based on surface tension driven self-assembly for macroelectronics application. The reported system incorporates precisely controlled and automated agitation, web moving and component recycling and dispensing system and enables continuous parallel assembly of semiconductor chips at a high rate (15k chips per hour using 2.5 cm wide web) and assembly yield (>99%) under optimal condition. In principle, scaling to any throughput should be possible considering the parallel nature of self-assembly. The system was carefully optimized to accomplish defect free assembly with computations and comparisons of the relevant forces under various operation conditions. The process overcomes the limitations on area and throughput of prior methods. It provides a new platform for macroelectronics to enable the integration of microscopic high performance inorganic semiconductors on flexible or stretchable substrates with any desired location, pitch, and integration density. As an example we demonstrate the fabrication of a solid state area lighting panel.
Keywords: reel-to-reel process, fluidic self-assembly, flexible electronics, solid state lighting.
Reference: Park, S.-C., Fang, J., Biswas, S., Mozafari, M., Stauden, T., Prof. Jacobs, H. O., "A First Implementation of an Automated Reel-to-Reel Fluidic Self-Assembly Machine," Advanced Materials (in press)

For many energy and electronic applications, single-crystal-like materials offer the best
performance. However in almost all cases, the single crystal form of the relevant
material is too expensive. In addition, for many applications, very long or wide materials
are required, a regime not accessible by conventional single crystal growth. This
necessitates the use of flexible, large-area, long-length, single-crystal-like substrates for
epitaxial growth of the relevant device layer for the electronic or energy application in
question. Details of substrate fabrication, the texture quality of the substrates, the nature
of grain boundaries, and the range of materials that can be epitaxially grown on such
substrates will be discussed. The substrate technology employs simple and industrially
scalable thermomechanical processing routes to obtain long lengths of near singlecrystal-
like substrates. Epitaxial buffer layers of various buffer layers (of rock salt,
flourite, perovskite and pyrochlore crystal structures) are then deposited in a roll-to-roll
configuration using web-coating employing electron-beam evaporation, sputtering,
MOCVD and/or chemical solution deposition. Addressing tension and web-handling
issues particularly for deposition at high temperatures (600-800°C) as well as entering
and existing vacuum deposition systems in series has been key to the success of the
technology. Results will be presented for growth of superconductors and
semiconductors (Si, GaAs, etc.) on such substrates. Kilometer long, single-crystal-like
high-temperature superconducting wires are now routinely fabricated using these
substrate technologies. Roll-to-roll depositions have also been used to create selfassembled
nanostructures in long-lengths. This technology is presently also being used
for low-cost, high-performance semiconductor devices such as photovoltaics (Si-based,
GaAs-based), ferroelectrics, multiferroics, and ultra-high density storage. This
technology could be combined with standard high-speed, roll-to-roll technologies such
as etching, etc. developed in the standard flexible electronics industry to enable lowcost,
high-performance devices.

Synthesized Ag nanowires (Ag NWs) are one of the most promising candidates as an alternative transparent electrode for conventional indium-tin-oxide (ITO) electrode based on excellent electrical resistance and high transmittance in large-area. Using Ag NWs as a transparent electrode, various applications have been realized such as light emitting diodes (LEDs), organic light emitting diodes (OLEDs), organic photovoltaics (OPVs), touch screen panels (TSPs), transparent heaters and so on. However, Ag NWs have some limitations of high cost, complex fabrication process and uncontrollability of its individual position and orientation. Instead of synthesized Ag NWs, here, we fabricated designable Ag nanofibers (Ag NFs) through simple, extremely fast and low-cost printing process called electrohydrodynamic nanowire printing. Ag NFs had a comparable resistivity of 5.13 µOmega;middot;cm with bulk Ag (Resistivity of bulk Ag = 1.59 µOmega;middot;cm) and an average diameter of 320 nm which is the smallest dimension among the directly-printed electrode ever reported. Highly-aligned Ag NF arrays with constant line spacing of 100 µm had very high transmittance over 98 % which is fully-transparent with naked eye. Based on unique properties of Ag NFs, we also successfully demonstrated diverse device applications with Ag NF electrodes such as field-effect transistors, transparent heaters, OLEDs, OPVs. Our approach will be a promising strategy in the field of next generation electronics.

As displays and electronics evolve to become lighter, thinner, and more flexible, the substrate choice continues to be critical to their overall optimization. The substrate directly affects improvements in the designs, materials, fabrication processes, and performance of advanced electronics. With their inherent benefits such as surface quality, optical transmission, hermeticity, and thermal and dimensional stability, glass substrates enable high-quality and long-life devices. As substrate thicknesses are reduced below 200um, ultra-slim flexible glass continues to provide these inherent benefits to high-performance flexible electronics. In addition, the reduction in glass thickness also allows for new device designs and high-throughput, continuous manufacturing enabled by roll-to-roll processes.
This invited paper provides an overview of Corning^® Willow^® Glass and how it enables flexible electronic device design and fabrication optimization. Demonstrations of roll-to-roll flexible glass processes such as conveyance, vacuum deposition, slot die coating, photolithography, laser patterning, screen printing, and lamination will be described. These basic capabilities enable continuous manufacturing methods for high-quality devices on flexible glass substrates.

The large volume production of plastic electronic devices by roll-to-roll (R2R) manufacturing technologies is a crucial step towards the commercial success of the organic electronics industry. Deposition of all functional structures from solution is a particularly interesting approach, since it removes the need for expensive vacuum processing methods. Devices such as organic light emitting diodes (OLEDs) and organic photovoltaic (OPV) cells consist of a stack of several functional layers, some of which need to be patterned with high resolution, whereas others are homogeneous coatings requiring precise thickness control.
In this contribution, approaches are presented for the R2R production of both patterned and homogenous layers of functional materials for flexible OLED panels on plastic foils. For ITO-free transparent electrodes, a combination of metallic shunting grids and a conductive polymer coating is used. The grid structures are produced by R2R inkjet or rotary screen printing of silver based conductive inks and pastes. In order to achieve high processing speeds, the traditional post-deposition treatment of thermal sintering was replaced by NIR drying and photonic flash sintering. At current state, functional structures with high specific conductivities (up to 20 % of the bulk Ag value) can be prepared at 10 m/min. Homogenous layers, such as PEDOT:PSS or the light emitting polymer, are prepared by R2R slot die coating followed by impingement drying (hot air or nitrogen). Coating process speeds above 100 m/min are not exceptional in the industry. On lab scale, 10 m/min was achieved, resulting in highly regular thin functional films with thickness variations below 2%. Currently, work is being carried out to connect and synchronise all necessary processing steps in order to enable the full solution manufacturing of OLED panels by R2R techniques.

One of the important current research issues in organic light-emitting diode (OLED) technology is the precise and low-cost pixel patterning which contributes to the fabrication of high-resoultion large-area flexible displays. In passive matrix OLEDs, the pixels are defined by forming matrix patterns of anode and cathode. In many cases, the patterning of anode, typically indium tin oxide (ITO), is conducted by conventional photolithography. However, the choice of patterning process for organic layers and cathode is limited because the patterning process should not damage the organic layers underneath. One typical method is the use of cathode separators which are formed on a pre-patterned ITO substrate by photolithography. However, photolithography has difficulty in applying fabrication of large-area flexible displays because of its disadvantages such as time-consuming complex process, high-cost processing, low throughput and possible damage to ITO. Furthermore, forming a precise pattern on a non-planar substrate by photolithography has been a major challenge because of diffraction of light and the limitation in depth of field. Here, we report a simple and rapid large-area pixel patterning method without damage to organic layers using highly-aligned organic fiber arrays fabricated by electro-hydrodynamic organic nanowire printing (ONP). ONP provides a straightforward and inexpensive way for fabricating cathode separators because it does not require any complex template-assisted procedure and expensive equipment. Also, this process allows a very high fiber printing speed and the accurate control of inter-fiber separation, which makes it suitable for large-area OLED sub-pixel fabrication. Furthermore, ONP can be applied to pixel patterning in flexible OLEDs due to the flexibility of organic fibers. The organic fibers with an average diameter of ~1.11 mu;m worked well as cathode separators, which was clearly demonstrated by scanning electron micrographs. The patterned OLEDs showed comparable current and luminous efficiencies compared to a reference device. Finally, we demonstrated the potential of this technique for flexible large-area OLED manufacturing by fabricating 3 cm x 3 cm large-area OLEDs with 25 pixels separated by organic fiber cathode separator arrays.

Roll-to-roll UV nanoimprint lithography (R2R-UV-NIL) gains increasing industrial interest because it combines nanometer-resolution with square meter per minute productivity.
In this study we report the set-up of a custom-made R2R-UV-NIL pilot machine which is able to process 10 inch wide polymer web with velocities up to 30 m/min based on in-house developed UV-curable resins for imprint material.
The UV-resins - based on urethane acrylates and thiol-ene chemistry - were designed to fulfill the requirements of R2R-UV-NIL applications being good adhesion to polymer substrates - e.g. PET, high curing speed, low shrinkage and clean demolding from nickel imprint shims.
The Young&’s modulus and surface energy of the cured resins both can be tuned independently over a wide range by the cross-linking density and surface active dopants. We have achieved Young&’s moduli between 5 MPa and 5 GPa and surface energies between 12 mN/m and 60 mN/m.
Furthermore, the highly cross-linked and low surface energy UV-resins show excellent capability for auto-replication and thus can be used for the manufacturing of polymeric working shims. The latter have the potential to replace the expensive and delicate nickel-shims in many R2R-NIL-processes.
A process for fast replicating large scale Ni-shims into polymer working shims on the R2R-machine has been developed as well as a - yet manual - step-&-repeat process for multiplexing small masters made of e.g. silicon or quartz onto large R2R polymer shims.
Thereby, line-space features - for e.g. microelectronic or optical applications - with critical dimensions down to 200 nm and nearly rectangular profiles have been successfully transferred from small Si masters onto polymer-shims and then R2R-imprinted onto large area polymer web.
First high throughput applications of the R2R-NIL-pilot machine and UV-resins targeted the wettability of surfaces. Control over the wettability of solid surfaces through surface chemistry and microscopic structure is key to a wide range of technological applications from dirt repellent and self-cleaning surface coatings to microfluidic lab-on-a-chip devices.
We have developed large area manufacturing processes for superhydrophobic surfaces with a water contact angles asymp; 170° and critical water roll-off angles < 3% as well as microfluidic devices with spontaneous capillary-driven water flow in open micro channels on flexible polymer substrates.
Furthermore, it was found that a precise control over the resist wetting in the NIL-stack substrate/resist/stamp enables residual layer free R2R-UV-NIL processes. Using a water-soluble UV-resist a process chain of µm-resolution R2R-UV-NIL structuring followed directly by an aqueous metal lift-off without the need for a residual layer removal etch was demonstrated.

Screen printing of metal based pastes is a mature and well-established technology for the deposition of fine conductive structures on an industrial scale. Current collecting grids consisting of highly conductive printed metallic lines are a viable replacement for Indium Tin Oxide (ITO) as transparent electrodes for large area plastic organic photovoltaic (OPV) cells. The OPV device architecture consists of several nm-thick functional layers which are very prone to pinholes resulting in electric short circuits. Therefore it is essential to achieve smooth interfaces, but typically the topology of screen printed metal structures comprises high spikes (in the order of a few microns) which prohibit their use in OPV devices.
In this contribution, we present a roll-to-roll approach in which screen printed silver grids are embedded into plastic substrates resulting in functional foils with low surface roughness. Topologies of above 5 microns are thereby reduced to less than 200 nanometres, without sacrificing the low sheet resistivity. The low roughness and absence of spikes allow for integration into OPV cells. The first step of the process is to screen print a silver structure on a donor substrate. This donor substrate is then laminated via a roll-to-roll process on an acceptor substrate coated with a UV curable resist. Subsequently, the resist is cured by UV light. Finally, the donor substrate is delaminated, leaving the silver embedded in the cured resist. To allow for complete transfer of the silver structures, silver paste and resist are selected such that the adhesion of both the silver and the resist to the donor substrate is lower than the adhesion of the silver to the resist and the resist to the acceptor substrate. In this way, ITO-free OPV cells have been prepared which have a significantly higher efficiency than otherwise identical flexible devices with ITO. The more general applicability of this approach to the printed electronics industry has been demonstrated by using the same technology also for successfully producing functional organic light emitting diodes.

Patterning photoresist on arbitrarily shaped surfaces is an enabling technology for developing highly integrated electronics in biomedical applications, such as external devices (body armor, helmets) and implants (eye, heart, and bone implants). However, few studies report methods to pattern curved and complex surfaces. A notable exception is John Roger&’s group, which has presented flexible electronics as a solution for conformal brain implants and a glove-like pericardium. To extend beyond this capability and into the realm of directly patterning objects, we present an algorithm and method for patterning of both stiff and soft arbitrarily curved surfaces (sphere and bone) by use of micro maskless lithography directed by a seven axis motion system.
The system we designed is comprised of a 6-axis robot and a rotary stage. The part to be patterned is mounted on a kinematic mount attached to the rotary stage. The maskless lithography system is mounted to the robot end effector and can be positioned anywhere within a 20x20x20 cm work envelope to manipulate the projection relative to the part. Using this system the process for depositing material onto the surface involves deposition of photoresist (405nm), mounting, 3D scanning, and then exposing sequentially over the entire part.
Design of a multi-axis micro lithography system is subject to mechanical error so we discuss the role of error build up in the system components. The measured repeatability and accuracy of the motion system and thus the projection is 20 microns and 30 microns, respectively. We also detail the design of a sub-10-micron resolution optics package with coaxial camera for imaging and focal adjustment. The dynamic mask is implemented using a Texas Instruments LightCrafter 4500 digital micromirror device mounted in a custom housing combined with a Mitutoyo 5X objective. We characterize the resolution and aberration performance of the system both optically and lithographically.
We present an algorithm for conformal patterning of arbitrary three dimensional objects implemented in C++. Three dimensional coverage is achieved by triangulating the surface of a digitally scanned object and associating the location of each triangle in the digital-space with that in the real space. Each triangle is then associated with the texture contained within its borders and stored in computer memory for later projection. The relationships between substrate curvature, triangle size, and distortion are discussed.
Using this framework, we finally demonstrate the patterning of traces onto a spherical ball and small bone. We highlight the ability to deposit metals onto the curved surfaces representative of circuitry emblazoned on potential implants. The ability to rapidly create custom two-dimensional patterns on three-dimensional substrates as demonstrated is expected to unlock new functionality in fields including, but not limited to, experimental semiconductors, personalized medical devices, and optics.

Roll-to-roll scale-up of contact lithography (microcontact printing, nanoimprint lithography, microflexography) will enable continuous, large-area, high-throughput lithographic surface patterning for flexible electronics and engineered meta-surfaces. Efforts to implement these hybrid processes have been limited by the lack of a continuous large-area tool and by the inability to monitor and control the lithographic process.
In this paper a new technique is presented to fabricate seamless tools using maskless lithography on a layered cylindrical substrate. This method produces cylindrical, large-area, high-resolution master patterns. Cylindrical PDMS stamps are then centrifugally cast on this pattern, producing seamless tools with very uniform thickness. These tools can then be used directly in a continuous roll-to-roll process.
In this work the patterning process is modeled for several resist and light dose combinations, and empirically verified on cylindrical patterning system. The process parameter space is identified, and one significant finding is that not just feature width, but the cross sectional shape can be varied with some independence. The resulting trapezoidal shape for the feature leads to a structure with improved mechanical stability.
In addition, the centrifugal casting technique allows for functionalized layers in the stamp. One example is presented whereby a fluorescent layer is cast behind the patterned layer. This layer is then used to enable in-situ visualization of the roll-to-roll printing process at both the individual feature and overall contact region level.

Successful implementation of a high-speed roll-to-roll nanoimprinting technique for continuous manufacturing of electronic devices has been hindered due to lack of simple substrate preparation steps, as well as lack of durable and long lasting molds that can faithfully replicate nanofeatures with high fidelity over hundreds or thousands of imprinting cycles. In this work, we demonstrate large-area high-speed continuous roll-to-roll nanoimprinting of 1D and 2D micron to sub-100 nm features on flexible substrate using perfluoropolyether (PFPE) hybrid molds on a custom designed roll-to-roll nanoimprinter. The efficiency and reliability of the PFPE based mold for the dynamic roll-to-roll patterning process was investigated. The PFPE hybrid mold replicated nanofeatures with high-fidelity and maintained superb mold performance in terms of dimensional integrity of the nanofeatures, nearly defect free pattern transfer and exceptional mold recovering capability throughout hundreds of imprinting cycles. The roll-to-roll nanoimprinted substrate was used to suspend multiwall carbon nanotubes applied via a simple roll-to-roll nanocoating process for the fabrication of highly sensitive infrared (IR) and terahertz (THz) sensors. The successful roll-to-roll sensor fabrication process developed in the present work has opened up a new low cost, high volume manufacturing technique for the production of sensors based on 1D nanomaterials.

Many plants and insects possess multi-functional surfaces covered by hierarchical structures. The fabrication of such nano- and microstructures is of high interest for various biomimetic applications ranging from self-cleaning to drag-reduction and oil-water separation. We developed hot embossing and hot pulling processes for the replication of multilevel hierarchical nano- and micro-structures [1,2]. A fully automated electromechanical sensor principle allows for the precise fabrication of hierarchies. With a hot pulling process, demolding forces are utilized to elongate the polymer structures. In this way, an aspect ratio of up to 10 can be achieved for nanopillars which are 140 nm in diameter. Combining classical hot embossing, hierarchical hot embossing, and hot pulling we fabricated several types of bio-inspired hierarchical nano- and microstructures. The enormous variety of applicable materials, the low inner stresses of the molded parts and the short cycle time make these processes economically interesting. Scaling-up of the processes to roll-to-roll machines open the path to the mass production of hierarchical micro- and nanostructures with high aspect ratios.
[1] M. Röhrig, M. Schneider, G. Etienne, F. Oulhadj, F. Pfannes, A. Kolew, M. Worgull, H. Hölscher, J. Micromech. Microeng. 23, 105014 (2013)
[2] M. Röhrig, M. Mail, M. Schneider, H. Louvin, A. Hopf, Th. Schimmel, M. Worgull, H. Hölscher, Adv. Mater. Interfaces (2014)

We report the development of an automated instrument for the rapid, roll-to-roll mass production of micro- and nanowires based upon Electroplate-and-Lift (E&L) lithography¹. E&L is a fast, simple, scalable technique which has been used for the controlled, solution-based, electrochemical synthesis of patterned wires composed of over 30 elemental metals, alloys, semiconductors, and conductive polymers. Unlike all other methods of producing patterning nanowires, E&L lithography employs a non-sacrificial template, which may be reused over 1000 times without any additional vacuum or clean room processing after the initial fabrication. Thus, E&L has the potential to scale the capacity of templated nanowire electroplating much as nanoimprint lithography (NIL) scaled the capabilities of electron beam lithography.
The E&L electrode is a multi-layered, lithographically patterned ultrananocrystalline diamond (UNCD)^TM template. The template is made from alternating thin layers of intrinsic UNCD, which is insulating, and nitrogen-incorporated UNCD (N-UNCD), which has semi-metallic conductivity. Intrinsic UNCD layers are used to isolate the top and bottom surfaces of the N-UNCD layer from the electrochemical bath. The diamond layers are lithographically patterned and reactive ion etched through the stack to expose only edges of the N-UNCD layer. The initial nucleation of the nanowire is thus confined to the exposed patterned edges of the 80 nm thick N-UNCD layer. The thickness of the N-UNCD layer thus establishes the minimum achievable diameter of the electrodeposited nanowire. The maximum wire diameter can be controlled by increasing the deposition time². In alloy systems, the composition of the deposited wires can be controlled by varying either voltage or solution composition. Following electrodeposition, the nanowires may be removed mechanically from the template, regenerating the template surface for subsequent depositions. Wires of the same or a different diameter, composed of any desired electrochemically depositable material, may subsequently be plated. In preliminary experiments, the liftoff was performed either manually using scotch tape or other polymers, or by ultrasonication.
In automated E&L, the template is attached to a wheel, and slowly rotated through an electrochemical plating bath to deposit the wires. Another wheel coated with an adhesive polymer removes and collects the wires, re-exposing the edges of the NUNCD for reuse. This process is calculated to be capable of producing either patterned wires with 100 nm < diameter < 10 mu;m at a rate of ~ 8 grams/day, or a single continuous wire <1 mu;m in diameter at a rate of >1 km/day.
References
(1) Seley, D.B. et. al., ACS Appl. Mater. Interfaces, 2011, 3 (4), pp 925-930 (cover story)
(2) Jones, D. et. al. Proc. Mater. Res. Soc. 2011, doi: 10.1557/opl.2012.664, 30 March 2012

Contact optical lithography&’s resolution is restricted by the wavelength of the illumination source and the diffraction limit of light. Furthermore, optical lithography is traditionally carried out on rigid substrates. We present a methodology, “Elastomer Assisted Manufacturing” (EAM), that leverages the unique elastic properties of stretchable substrates and well-established micron-scale contact optical lithography to overcome resolution limits while achieving fabrication of submicron-scale features. Micron-scale features are created using contact optical lithography with a photoresist layer that has been spin coated onto a stretched elastomeric substrate. After developing the photoresist, the release of the applied stress on the elastomer results in a size reduction of the photoresist features to the submicron regime. Employing EAM, we were able to achieve a size reduction factor of over 10. We uniaxially stretched the elastomer to obtain asymmetric features from symmetric designs and biaxially and radially stretched the elastomer to achieve isotropic feature reduction. We studied the effects of coupling of the applied tensile stress, substrate softening, photoresist and substrate buckling, photoresist thickness, uneven surface morphology, photoresist-substrate grain boundary, and interfacial interaction to achieve highly repeatable and consistent feature reduction. When a uniaxial stress was applied, the elastomeric substrate compressed in the planes perpendicular to the direction of the applied stress due to a coupled Poisson&’s ratio tensor. In addition, substrate softening occurred during cyclic applications of stress as predicted by the Mullen&’s effect. Optically written features ruptured due to buckling in the photoresist/substrate when there was a non-uniform application/release of stress and when there was a rapid application/release of stress. To overcome these undesirable effects, we spin coated an adhesion promoting layer between the photoresist and the substrate. Applying the adhesion promoter decreased slipping at the interface, resulting in a damping effect upon release of tensile stress. The adhesion promoter protected the optically written features, prevented photoresist delamination, and allowed photoresists to maintain adhesion to the substrate at higher strains. Feature size reduction demonstrated a nonlinear response to stretching that varied as a function of both photoresist thickness and feature critical dimension. Resulting from the elastomer&’s inherent advantages of extreme stretching limits, flexibility, low weight, low cost, and high-K dielectric, electronic devices on rubber elastomers have the capability to offer enhanced functionality at lower prices than silicon-based counterparts, enabling fabrication of stretchable circuits, sensors, transistors, and ultimately entirely new devices for the biomedical and wearable electronics.

A simple but highly efficient method, called Spin-on NanoPrinting (SNAP), was developed by our group to produce polymer nanopillar array which can stand on any substrates and be easily to scale up for a large printing area. This method allows us to simply and readily print a 1 cm × 1cm footprint with nanostructures within 3 minutes without using any expensive equipment. A large-area nanostructure could be easily obtained by stitching each printed nanostructure together. Moreover, different materials could be printed using SNAP. We have successfully printed nanostructure with polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polydimethylsiloxane (PDMS), and even conductive polymer like poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). These polymer nanopillar arrays can either serve as template for depositing active materials or use as active materials themselves for energy storage devices. Electrodes fabricated based on the printed nanostructure show remarkable charge/discharge ability, high power and energy densities, and good cycle stability. The simplicity of the nanoarchitectured electrodes and their phenomenal performances has shown promising features for future energy storage systems.

Light-emitting electrochemical cells (LECs) comprise a blend of an emissive conjugated compound and mobile ions (a dissolved salt) as the active material (AM) positioned between two-charge injecting electrodes. During operation the mobile ions redistribute, so that a light-emitting p-n junction doping structure can form in-situ. This unique operational mode allows for the utilization of thick and uneven AMs and air-stabile electrodes, which in turn paves the way for an attractive fault-tolerant and scalable fabrication in the ambient [1].
Here, we report a new easily adoptable and scalable fabrication technique, which effectively resolves problems with non-homogenous light-emission from large-area devices [2]. The merit of the technique is demonstrated in the form of homogenous light emission from large-area (>100 cm²) devices and via the realization of light-emission from highly complex-shaped objects. We further report that it is possible to attain high-quality white emission from single-emitter LECs [3], and that non-ionic small-molecule compounds can function as the electro-active and emissive compound in LECs [4].
A straightforward analysis reveals that the LEC performance is currently far from optimized, and that it is critically important to better control the in-situ doping process. We demonstrate that a “too-high” doping level and a non-optimum AM thickness are common LEC features, which are concomitant with significant exciton quenching and doping-induced self-absorption [5]. We further show that these setbacks can be effectively mitigated via a rational selection of salt concentration and AM thickness [5]. By following such well-motivated guidelines, we are today able to deliver LECs with an ambient operational lifetime (at a luminance >100 cd/m²) of > 6 months [6] and a power conversion efficacy of 16 lm/W [7].
[1] Sandström, A., et al., Nature Communications, 2012, 3, 1002.
[2] Sandström, A., et al., Adv. Mater. 2014, DOI: 10.1002/adma.201401286.
[3] Tang, S., et al., Journal of the American Chemical Society, 2013, 135, 3647.
[4] Tang, S., et al., Chemical Communications, 2013, 49, 4926.
[5] Fang, J., et al., Advanced Functional Materials, 2009, 19, 2671.
[6] Asadpoordarvish, et al. Applied Physics Letters, 2012, 100, 193508.
[7] Kaihovirta, N., et al., ACS Appl. Mater. Interfaces, 2014, 6, 2940.

Thin-film transistors with organic and oxide semiconductors fabricated on plastic substrates are primarily developed for backplanes of active-matrix flexible displays. We will discuss the use of thin-film circuits on plastic film for RF tags and integration with thin-film sensors.
By nature of the technology, thin-film ICs need mass markets to reach economy of scale. Electronic tags represent such market. Passive HF thin-film tags with increasing functionality have been shown in the last years, and NFC compatible tags are a nearby target. Their unique flexibility and thin-ness allow unobtrusive integration in products as security paper. Meanwhile, the appearance of the first thin-film UHF energy harvesters allow to envisage UHF tags in the near future. We will discuss the requirements to transistor performance and device types needed for these applications.
Next, we consider the requirements to realize integration of thin-film sensors with thin-film transistors. A first example are thin-film organic photodetectors integrated on thin-film transistor backplanes, resulting in large-area and flexible active-matrix imagers, applicable e.g. to X-ray imagers. More complex read-out TFT circuits, discussed in the presentation, will in the future enable applications such as thin-film (disposable) sensor patches.

Hierarchically porous materials with structural features spanning multiple length scales have potential applications in many areas such as energy conversion and storage, catalysis and membrane engineering. Here we describe the formation of hierarchical nanostructured materials directly from block copolymer structure formation. In a first example, we combine macroscopic spinodal decomposition and nanoscale block copolymer self-assembly concepts to synthesize bimodal structured polymeric scaffolds with porosity formation via solvent rinsing. In the second part, hierarchical porous structures are generated by coupling block copolymer self-assembly with laser annealing.

The integration of nanoscale materials into microelectronic devices is challenging and requires revisited and advanced approaches in the respective wafer manufacturing lines. We present a bottom-up approach for the functionalization of single-walled carbon nanotubes (SWCNTs) with metal nanoparticles at the wafer level. The process is directly applied on silicon wafers (diameter 150 mm) with arrays of SWCNT field-effect transistors (CNT-FETs) fabricated in a combined top-down/bottom-up strategy using standard lithography, metallization and SWCNT integration via dielectrophoresis [1]. Based on a chemical protocol for the functionalization of SWCNTs with (R-)oxocarbonylnitrene according to Hirsch and co-workers [2], we synthesized linkers consisting of comparatively long ethylene glycol chains. The motivation for that was to allow an effective coordination of metal nanoparticles (diameter 5-8 nm) to the SWCNT sidewalls. Gold nanoparticles of this size range offer narrow-band plasmon resonances around 505 nm, beneficial for optoelectronic devices and sensor operating in the visible range. For the functionalization of the CNT-FET arrays, a microfluidic channel system was designed and applied directly on a silicon wafer placed on a temperature-controlled heating stage. Using a stop-and-go flow profile and a direct suspension of the gold nanoparticles in triethyleneglycol diemethylether, a reliable decoration of the integrated SWCNTs with preformed gold nanoparticles could be obtained. The morphology and chemical composition of the deposited, functionalized CNTs in the FETs structures were investigated by AFM, SEM, Raman spectroscopy, and EDX. The electrical characterization proved that the transistor properties are preserved after the functionalization process. Spatially-resolved Raman microscopy revealed that the decoration with metal nanoparticles does not induce any significant increase in the defect concentration in the SWCNT sidewalls. Experiments with light illumination showed that a modulation of the source-drain current during irradiation at 488 nm is possible. These results mark a milestone in the hybrid integration of nanoscopic building blocks and wafer-level fabrication.
[1] S. Hermann et al. IEEE Proc. Systems, Signals, Devices (SSD), article ID 6198090 (2012).
[2] M. Holzinger et al., J. Am. Chem. Soc. 125, 8566-8580 (2003).

Organic field effect transistors (OFETs) offer a number of potential advantages for large area, low thermal budget, and flexible electronic systems. As the channel transconductance and current density in OFETs has improved over the past decade, thanks to the development of advanced semiconductor materials and improvements in processing, the performance of transistor contacts has become a primary concern. Good contact performance has primarily been achieved through the use of either thiol treated or pristine gold contacts. Surface treatments have been shown to improve contact performance both by decreasing the energy barrier to charge injection into organic semiconductors and by providing a surface on which semiconductors crystallize more readily, leading to improved performance.
As groups look towards the commercialization of OFETs, there is an increasing interest in the use of alternative metals to gold for transistor contacts. It is possible to engineer surface treatments for silver and copper electrodes that develop the same net effects as those developed on gold systems. In this presentation we will review how the understanding of surface treatments has evolved over the past decade, and in particular, discuss the use of both structural and energy resolved X-ray techniques to understand surface treatment performance on device behavior. We will also discuss recent demonstrations of many of the same surface treatment strategies on silver and copper electrodes using printed and lithographic approaches, opening the door to potentially lower cost, higher throughput fabrication of OFETs with improved contact performance.

Directed assembly of nanoelements has been used to fabricate devices for diverse applications. The challenge in using such techniques consists of developing high scalable, high-rate assembly techniques for placing nanoelements precisely on various surfaces. Several efforts have focused on developing approaches to integrate nanoelements directly on the insulating substrates. Template directed fluidic assembly, which employs interfacial capillary force, is an example of this approach. Withdrawing the substrate from nanoelement solution creates a capillary force at the air-liquid interface and this force guides nanoelements into desired structures. However, the withdrawal speed has to be slow such that the necessary nanoparticle concentration near template is replenished due to diffusion. Hence it requires hours to assemble small areas. On the other hand, electric field induced assembly techniques are very fast and robust. However, in these techniques assembly results on a conducting surfaces and in order to place them on insulating surfaces other fabrication processes have to be employed such as transfer, which makes the fabrication process complex and lowers the yield and reproducibility of the device.
Here, we introduce a new, high-rate electro-fluidic assembly technique that enables directed assembly of nanoelements on various types of insulating surfaces. No functionalization or any other chemical modification is needed on the surface. In the electro-fluidic assembly process, a conductive film is used beneath the insulating substrate and field is applied through that conducting layer. Under the influence of the applied field, nanoelements move towards the template, achieving the necessary nanoelement concentration near the patterned surface in a short time and by withdrawing the substrate from the solution nanoelements are directed into specifically patterned structures. The significance of this technique is that the assembly process is 100 times faster than fluidic assembly. For example, fluidic assembly on a 3-inch wafer takes 25 hours; however, the presented method takes only 15 minutes to obtain fully assembled structures. Governing parameters and process kinetics that influences the assembly is studied to establish a repeatable and robust assembly technique. We have showed the optimal assembly regime for different assembly conditions. We experimentally investigated the assembly of various nanoelements on different surfaces including flexible substrates such as polyimide, PEN, etc. We were able to show assembly of nanoparticles and nanotubes in monolayer or multilayer assemblies into different geometries down to the 100 nm scale. Assembly of polystyrene latex (PSL), silver, gold and copper nanoparticles, quantum dots and single walled carbon nanotubes (CNT) were demonstrated. Finally, we showed the use of the assembly technique to fabricate single wall carbon nanotube based NO₂ gas sensor.

A scalable solution for wafer-level integration of individual single-wall carbon nanotubes (SWCNTs) is the electrokinetic deposition from aqueous dispersions [1]. Due to high Van-der-Waals interaction between the single CNTs in a solid material, the first step of the dispersion preparation is to unbundle them effectively with the aim to get a homogeneous dispersion. For this task, a sequential workflow of homogenization, ultrasonication, and centrifugation was proposed [2]. Here we report on our recent results of using a systematic spectroscopic monitoring for the preparation of SWCNT dispersions which is able to estimate the dispersion quality during the preparation process. The set-up uses a flow cell and a microfluidic system enabling in-situ monitoring. It turns out that the degree of individualization of the SWCNTs is a function of both the absolute concentration of the SWCNTs and the relative concentration between the SWCNTs and the dispersion agents (sodium lauryl sulfate, sodium deoxycholate, etc.) With an in-situ monitoring of the optical absorption, a detailed analysis of the dispersion process for different surfactants, concentrations and preperation conditions is possible. The usage of an integrating sphere allows the determination of scattering related to aggregate formation that can be treated in the framework of the Mie theory.
[1] S. Hermann et al., IEEE Proceedings Systems, Signals, and Devices (SSD), article ID 6198090 (2012).
[2] H. B. Yu et al., Chemical Physics 408, 11-16 (2012).

Organic optoelectronic devices require the implementation of two electrodes enclosing a stack of photoactive and transport layers. At least one of these electrodes must be semitransparent, while the other may be transparent, reflective, or non-reflective. Most often, an evaporated and reflective metal such as Ag is used. Evaporation has a limited rate of deposition, hampering technological uptake for roll-to-roll production, while Ag is scarce and has an associated mounting cost. Solution processing affords an increased deposition rate over evaporation, and the exclusion of vacuum requirements. Carbon nanotubes (CNTs), offering an inexpensive and abundant alternative to Ag, have been used previously for the semitransparent contact for organic photovoltaics. However, by their nature, the absorption spectrum of CNT layers overlap that of the photoactive layer (PAL), limiting their figure of merit as transparent electrodes, and commonly require post-deposition treatments to attain high conductivities.
Here, CNT electrodes were ultrasonically spray coated as highly conductive, solution processed, and opaque top electrodes. Two types CNT inks were employed; single walled CNTs in an aqueous suspension, and a dissolution of multi-walled carbon nanotubes using a copolymer surfactant. Both inks were demonstrated to attain electrodes with sheet resistance down to 1 Omega;#9633;^-1, comparable to both evaporated Ag and sintered spray coated silver nanoparticle contacts. Both inks achieved a low sheet resistance while being free of post-deposition treatments, but MWCNT required a 10 times thickness increase. Spray coating allows for the accumulation of CNTs to thicknesses of approximately 3 mu;m, achieving sheet resistances comparable to metal electrodes. Kelvin probe measurements of both CNT electrodes show similar work functions of -5.3 eV.
Lacking the optical reflection of a metal electrode, the photocurrent generation relies on a single transit of the photoactive layer, requiring high absorption and/or thickness. Full organic photovoltaic devices utilizing either Ag or CNT electrodes were optically simulated, showing little difference in current density for P3HT:PCBM PAL thickness greater than 300 nm. At thicknesses above 600 nm, currents and fill factors decrease due to insufficient collection of photogenerated charge carriers. While spray coating offers limited interaction between the underlying layer and fast drying micron scale droplets, the use here of both aqueous and non-aqueous CNT solutions relaxes device structure constraints, permitting the CNT electrode deposition on a variety of transport layers and architectures. Fabricated inverted (top opaque anode) devices with thick photoactive layers and non-reflective CNT electrodes displayed comparable performance to solution processed and spray coated Ag nanoparticle devices; power conversion efficiencies and active layer thicknesses of 2.6% for 500 nm and 2.5% for 220 nm thick layers, respectively.

Transparent and conducting oxide (TCO) materials gain widespread use in most technological applications in recent years. They are used in optoelectronic applications like lasers, LEDs, solar cells, energy saving windows and touch panel displays. Fluorine doped tin dioxide (FTO) and indium-tin-oxide (ITO) are the most common TCO materials for thin film and dye sensitized solar cells. Production methods of these oxides include mostly vacuum based techniques like PVD or CVD methods. Spray deposition is a versatile and low cost technique for deposition of oxide materials which does not require costly vacuum systems or sophisticated production equipments. Ultrasonic spraying has been gaining popularity against conventional spraying which reduces chemical consumption and provides ability of precise control of spraying pattern over large area substrates. FTO and ITO thin films were grown by ultrasonic spraying technique using 1.7 MHz ultrasonic nebulizer equipped with an x-y scanner stepper motor. Deposition conditions, precursor and chemical recipe of the coating solutions (F/Sn or In/Sn ratios) were optimized for high performance FTO and ITO thin film TCOs. Industrial sized FTO films of 10x10 cm showed sheet resistance values down to 4 ohm/sq at a thickness of 800 nm and visible light transmission of 70% at 550 nm. Films are found to be homogeneous and continuous over 10x10 glass substrates without cracks or peeling off confirmed by AFM and profilometry studies. It was found that precursor concentration, scanning speed, carrier gas flow rate, nebulization volume are the critical parameters for deposition of high quality films. Thickness of the films and parameters like sheet resistance and visible light transmission can easily be controlled using this technique. After optimization of the chemistry and deposition conditions, 10x10 cm sized glass substrates could be produced for large area photovoltaic modules. Produced FTO films were used to construct dye sensitized solar cells and modules in comparison with commercial coatings. Efficiency value of 3% could be achieved which is slightly higher than commercial substrate proving the electronic conductivity and efficiency of electron collection power in addition to high visible light transmission of USP deposited films. We proved in this work that USP method can be an efficient and low cost alternative to common CVD and PVD techniques by means of deposition of high performance oxide layers employed in mass production of dye sensitized solar cells and thin film technologies.

Transparent conductors are generally used in organic electronic devices such as organic photovoltaics and organic light emitting diodes. The most widely used and commecially available transparent conductor is indium tin oxide (ITO). Recently, thin ITO films has been started to be used as transparent heaters in different applications, such as outdoor panel displays, avionic displays, liquid-crystal display (LCD) panels for use in harsh environments, periscopes, and vehicle window defrosters. However, ITO based film heaters have some limitations, such as slow thermal response and complex fabrication processes. Moreover, ever increasing indium prices, limited mechanical flexibility and low chemical stability remains as other problems to be solved. Hence, investigation of an alternative transparent conducting materials is essential. Among offered alternatives, silver (Ag) nanowire networks seem to be one of the most promising candidates. Figure of merit transparency and sheet resistance values of Ag nanowire networks are very close to that of ITO&’s [1]. Silver nanowires were synthesized through simple polyol process [2] and networks were deposited onto glass and polyethylene terephthalate (PET) substrates through spray coating. A thermal camera was used for mapping the temperature distribution of the fabricated heaters. The effect of nanowire density on the optoelectronic properties of the networks in conjunction with the temperature profile, applied voltage values as well as on turn on/off characteristics were investigated. The results presented herein demonstrates transparent heaters that can be fabricated over large areas through simple means.
[1] S. Coskun et al. Nanotechnology 24 (2013) 125202.
[2] S. Coskun et al. Cryst. Growth Des. 11 (2011) 4963.

We report recent progress of ultraflexible, largre-area, sensors with organic thin-film devices as one of the possible applications for flexible electronics. Organic devices, such as organic thin film transistors (OTFTs), organic photovoltaic cells (OPVs), and organic light-emitting diodes (OLEDs), are manufactured on ultrathin plastic film with the thickness of 1 mu;m. Ultraflexible organic devices exhibit extraordinary robustness in spite of being superthin. The electrical properties and mechanical performance of the transistor integrated circuits were practically unchanged even when squeezed to abending radius of 5 mu;m. Then, these organic transistor ICs have been utilized to develop various kinds of flexible sensor systems such as touch sensors, temperature sensors, and pressure sensors. Emerging applications will be presented from the context of wearable imperceptible electronics. Furthermore, the long-term stability and reliability issues will be addressed with latest experimental results of ultrathin encapsulations.

We present a complete wafer-level nanomanufacturing process chain for nanoscopic sensor devices based on individualized single-walled carbon nanotubes (SWCNTs). Our modular approach applies to wafers up to 150 mm in diameter and is based on an aligned planar integration of the SWCNTs from aqueous dispersions using microfluidic dielectrophoresis [1]. The process chain is monitored by in situ techniques such as UV-Vis-NIR and Raman spectroscopy. Field-effect transistors based on SWCNTs (CNT-FETs) are very promising electromechanical transducers for force sensing applications since the SWCNTs representing the transistor channel exhibit a particular intrinsic piezoresistivity. This property is directly exploitable in the ultra-sensitive detection of displacements (nm) and forces (nN). Envisaged applications comprise force sensing and condition monitoring. However, it is required that the SWCNTs are addressed individually and not as CNT networks or films. Even though the integration of the SWCNTs by formation of carbon-metal contacts remains a severe challenge, the fabrication of suspended arrays of SWCNTs in microelectromechanical systems (MEMS) was an important milestone of our integration approach. We discuss extended electrical and structural characterization of suspended SWCNTs under strain [2], introducing a MEMS test stage that will allow mechanical reliability tests on the CNT-metal contact to be performed. Recent results on the chiral distributions of the SWCNTs and the role of defect densities and impurities on the MEMS performance are highlighted as well. Furthermore, the CNT-FETs can be designed as optical or biochemical sensor elements after a decoration of the CNT sidewalls with metal nanoparticles. For this aim, we shortly discuss the modular implementation of appropriate tools for sidewall functionalization of the integrated SWCNTs at the wafer level as a key issue for manufacturing.
[1] S. Hermann et al.; IEEE Proc. Systems, Signals, Devices (SSD), article ID 6198090 (2012).
[2] S. Hartmann et al.; J. Appl. Phys. 115, 144301 (2014).

Blade coating and slot die coating are alternative thin film deposition methods to inkjet printing that enable higher throughputs at the expense of inherently being a one-dimensional coating method. We have developed printing methods and optimized material formulations for the fabrication of fully printed and flexible organic thin film transistors (OTFTs) and photodiodes. In our work, all layers are processed from solution and deposited and patterned by printing. These printed devices exhibit high reliability, low variability, ideal electrical behaviour and good mechanical properties. Blade coating on surface energy patterned (SEP) plastic substrates combines the scalable properties of a roll-to-roll compatible printing technique used to fabricate high quality homogeneous thin films with the practicality of generating two-dimensional patterns. Using this technique, scalable self-aligned blade-coated source and drain (SD) electrodes with minimal variability can be very reliably printed. Furthermore, blending polymers with high performance small molecules enables more reliable printing with higher boiling point solvents, improved device performance and yields. Finally, surface tension is utilized to print the gate electrodes. Fully-printed devices on plastic demonstrate a high yield of 96% with good carrier mobility (average 0.31 cm²/Vs), subthreshold swing (average 1.17 V/dec), high on-off ratio (average 2.2×10⁵), zero threshold voltage, very low variability in all aspects of device performance and good mechanical robustness. The high reliability and good performance of these arrays was achieved by characterizing the reliability and yield of each layer on the OTFT stack. The high yields combined with high device performance indicate that SEP blade coating is a scalable and robust technique which can be used to design electronic circuits where device reliability is required and could lead to all-printed systems on plastic.

Inorganic semiconducting nanowires make excellent building blocks for the next generation of printed electronic applications such as flexible circuits and field-effect transistors (FETs), chemical and biosensors, nano- light emitters and energy harvesting and storage systems. Solution processing of nanowires formulated into functional inks allows room temperature, large area deposition compatible with various flexible substrates including plastics. One of the main challenges in large area nanowire device fabrication is the ability to orient and deposit nanowires in pre-defined electrode positions in one processing step compatible with high-rate device fabrication technologies.
In this work we investigate self-alignment of semiconducting nanowires (NWs) in active channels in printable NW-FET, targeting reconfigurable RF antenna applications, where each transistor operates as a switch to turn on and off various parts of the antenna structures to change its frequency, radiation pattern or polarisation. To manipulate silicon and GaN nanowire deposition from solutions, dielectrophoresis technique (DEP) is applied to select, orient and position nanowires between source-drain transistor electrodes.
The quality of semiconducting nanowires, density of packing, precision of alignment, and the ability to form a semiconducting ‘monolayer&’ are vital for the efficient FET device operation.
Silicon nanowires, used in this work, demonstrate a distribution of lengths, diameters and conductivities, as well as presence of impurities, and require a purification step before device fabrication.
Dielectrophoresis and impedance spectroscopy were combined for the separation of silicon nanowires according to their length and electrical properties. FETs were fabricated with Si NWs collected at a wide range of DEP frequencies. The electrical properties of nanowires were analysed through FET I-V characteristics, and a relation was established between FET behaviour, the Clausius-Mossotti factor, and the Time Constant plot extracted from the impedance analysis corresponding to different collection frequencies. The best defect-free nanowires were collected at an optimal DEP AC frequency range of 460KHz - 1MHz. Corresponding bottom-gate field-effect transistors demonstrated very good performance with high on/off ratios of ~10⁷ and subthreshold swing of ~1V/decade.
In summary, we analyse FET devices performance produced with one-step DEP self-alignment and selection technique, evaluate the required deposition time scales, and provide outlook for DEP nanowire device assembly in relation to roll-to-roll and sheet-based fabrication.

New trends and digitalization of society are chancing the world. According to big visions like Internet-of-Things objects around us will have their own digital identity and have also connectivity to internet and other services. Needs for sensing and sensors are increasing dramatically as more and more objects have the connectivity. This massive growth set demands for current electronics production. New ways to pack electronics are needed to embed this intelligence into different objects.
Printed electronics and other large-area roll-roll -compatible processes are opening up the new opportunity for cost-efficient mass manufacturing of electronics among other functionalities, on large-area and flexible substrates such as plastic, paper, metal foils, glass and fabrics. Data processing power and other functionalities still require high performance microelectronics and therefore, also traditional electronic/semiconductor technology are also partly needed. These needs lead to technical manufacturing requirements that can be fulfilled best with concept of utilization combination of printed electronics and hybrid integration of silicon electronics to flexible printed platforms. Extending the continuous roll-to-roll manufacturing approach as far as possible (in air or/and in vacuum) in the manufacturing process to assembly and bonding, the manual assembly and handling phases can be almost fully eliminated. In this paper recent development to manufacture freeform, flexible and 3D electronics components and systems using hybrid integration to combine printing and chip/component assembly processes are discussed. Production examples of hybrid integration will be presented 1) flexible NFC-LED label, 2) flexible large area LED luminaire, 3) smart poster and 4) electronics voting card. In addition future visions and opportunities of embedded smart objects and gadget free society are discussed.

The rapid development of flexible printed electronics has involved development of components with various functions. However, to meet the requirements of the market and end users, solutions for complete autonomous smart labels are needed. Seamless and compatible ways to integrate components with different functions are of high importance. Example of components include, printed organic thin film transistors printed electrochromic displays printed batteries, printed diodes, printed antennas but also bare Si chips
In this work, we present different approaches for system integration. These ranges from monolithic intergration of components on one single flexible substrate to prefabrication of different printed components as well as Si chips and roll to roll assembly on one flexible substrate with printed interconnect patterns. The latter process is more flexible and allow for more complex system to be built, and by choosing different assembly methods and process parameters, the component integrity and functionality is best preserved. A novel integration method called “sticker-label” approach, wherein components and systems can be made by cutting and laminating thin membranes together is also presented. This method allows for even greater flexibility and is a new direction in the system integration. Examples of different integrated systems will be presented.

As the field of printed electronics matures the demand for scalable, high throughput printing methods grows. Spray deposition, or spray coating, has been used for decades in graphic arts and industrial painting, and shows significant promise as an alternate method for continuous, roll-to-roll fabrication of wide-area electronic devices due to its ability to quickly and evenly coat wide areas in a scalable manner.
Multilayer ceramic capacitors (MLCCs), in addition to being ubiquitous in the electronics industry, are useful to display the repeatability and quality of wide-area thin-film deposition techniques due to their reliance on consistent defect- and pinhole-free films. In this study, we demonstrate the fabrication of thin film MLCCs with composite dielectric materials fabricated by spray deposition at low temperature. Devices demonstrated include examples with single-layer pinhole-free dielectrics 8 square cm in area, and 6-layer structures with capacitance densities in excess of 0.75 nF per square mm while maintaining a dissipation factor below 0.1 at 1 MHz.

The majority of lab-scale organic and polymer solar cells (OPV) are very small with <<0.5 cm² using ITO glass, spin coating, evaporation, inert atmosphere, and optimum conditions. Obviously, the cells can lead to record efficiencies - but they are far beyond real world applications due to miniscule power output. Transfer to large-scale devices with an appropriate power output is hardly possible.
Here, we present the route from roll and roll-to-roll processed test devices to multi square meter large polymer solar cell modules with hundreds of Watts output - fully roll-to-roll (R2R) produced under vacuum-free and ambient conditions without using indium tin oxide (ITO) as transparent conductive electrode. ITO has the highest impact on the embodied energy in OPV devices and is replaced by an all additive printed and coated electrode based on flexo printed silver grid, rotary screen printed PEDOT:PSS, and slot-die coated zinc oxide (Flextrode). The production speed for each layer is beyond 10 m/min independently of the individual layout for different devices.
Model cells with at least 1 cm² are fabricated on a rollcoater, which allows easy transfer to the R2R line for larger test modules with e.g. 8 serially connected cells and the size of a postcard (freeOPV, active area >50 cm²). Both routes allow the testing of new polymers, functional inks, and device structures such as tandem stacks with minimum amount of material input but large number of devices for statistical analyses.
Finally, OPV modules with high power output for real-world applications and grid-connection can be easily produced based on the Infinity concept developed in our group. Virtually infinite large solar cell modules are based on thousands of serially connected cells entirely fabricated using very fast R2R printing and coating processes. No manual labour or proprietary processes are required for bussing and interconnection of submodules. The serial connection is completed throughout the print run due to an optimized pattern layout. The advantage of the Infinity concept is the fabrication of high-voltage OPV modules with active areas beyond several square meters (21000 cells = 14.7 m², 100 m long) and stabilized power outputs of >220 W using the standard active layer material P3HT:PCBM. The module has only two terminal connectors for minimized wiring during the setup of module arrays. The installation of a 100 m long module takes less than one minute. A parallel-connected array with outputs >1.3 kW and rather low efficient material (<2%) was built. An entire solarpark based on such OPV modules has a low energy payback time of just 0.5 years.

In this presentation we will describe the design rationale, synthesis, characterization, of several organic semiconducting polymers for printed thin-film transistors (TFTs) and photovoltaic cells (OPVs) and understand their charge-transport characteristics as a function of the device architecture and interface modifications. Particularly we will report the realization of printed organic TFTs with high charge carrier mobilities. Furthermore, we report our recent findings demonstrating OPV cell with high fill factors (~ 80%) and efficiencies >10% as well as all-polymer cells with efficiencies approaching 7%.

The use of chlorinated organic solvents is a significant drawback to the commercialization potential of polymer electronics. In this work, an alternative preparation of aqueous poly(3-hexylthiophene) (P3HT) colloids is described and P3HT field effect transistors (FETs) are fabricated by the doctor blade coating technique. These techniques target elimination of hazardous solvents associated with solution processing as well as establish large-area and continuous manufacture.
The morphology of both colloids and thin films coated from colloids were characterized using SEM and AFM. The crystallinity, optical properties of thin films and electrical performance of FETs were investigated and compared with specimens coated from organic solutions. We show that both size and crystallinity of these colloids and their films can be tuned by controlling the initial solution concentration, type of solvents and surfactants as well as manufacturing parameters. The presence of surfactant affects the crystal structure and optical properties of P3HT colloids, which influences the electronic transport properties of the thin films. The good performance of FETs produced by these colloids reveals their promising applications as alternative materials to eliminate the hazardous waste associated with the manufacture of organic electrical devices.

Significant efficiency increases are being made for bulk heterojunction organic photovoltaic prototype devices with world records at 11%. However the chlorinated solvents most frequently used in prototype manufacture would cause local health and safety concerns or large scale environmental pollution upon expansion of these techniques for commercialization. Moreover, research to bridge prototype and large-scale production of these solar cells is still in its infancy. Most prototype devices are made in inert glove box environments using spin-coating. There is a need to develop a non-toxic ink and incorporate it into a material deposition system that can be used in mass production.
We present research describing the development of nanoparticulate donor-acceptor complexes compatible for water based ink vehicles enabling ink-jet printing, spray coating or aerosol jet printing technologies compatible with large scale manufacture.
We will show characterizations of composite particle suspensions using both polymers (P3HT) and small molecules (Squaraines) along with fullerenes, demonstrating control over particle size and increased shelf lives necessary for ink-jet deposition. We will show data demonstrating the optimal blending of acceptor molecules in the nanoparticles that will be transferred to the active layer of the device. We will show modification of the substrate surface so as to enable reproducible coverage for a water-based ink vehicle and we will report printed photovoltaic devices that provide a significant bridge between prototype and future large scale manufacture.

The electron transport in conjugated polymers is hindered by a universal electron trap with a concentration of typically in the 10¹⁷-10¹⁸ cm^-3 range. Remarkably, the exciton diffusion length in a range of conjugated polymers amounts to about 5-7 nm. For polymers with less energetic disorder the resulting increase of the diffusion coefficient is compensated by a decrease of the PL decay time. A possible explanation for a disorder independent diffusion length could be that the PL decay time in pristine polymer films is determined not by the intrinsic exciton lifetime, but by the diffusion-limited exciton quenching at non-radiative recombination centers in the polymers. In that case the PL decay time reflects the time that excitons need to diffuse to these recombination centers. This will lead to shorter PL decay times in materials with faster diffusion and consequently to a constant exciton diffusion length if the different polymers would have an equal amount of non-radiative recombination centers. From time-resolved luminescence measurements, using randomly distributed fullerene quenchers, we demonstrate that the background concentration of exciton quenching defects in a range of conjugated polymers is nearly the same as the electron trap concentration. This observation strongly suggests that the exciton quenching defects and the electron traps share the same origin. Since the electron traps are universal this also explains why a similar exciton diffusion length of 5-8 nm is observed for a whole range of conjugated polymers.

Graphene is expected to play a significant role in future technologies that span a range from consumer electronics, to devices for the conversion and storage of energy, to conformable biomedical devices for healthcare. To realize these applications, however, a low-cost method of synthesizing large areas of high-quality graphene is required. Currently, the only method to generate large-area single-layer graphene that is compatible with roll-to-roll manufacturing destroys approximately 300 kg of copper foil (thickness = 25 µm) for every 1 g of graphene produced. This work describes a new environmentally benign and scalable process of transferring graphene to flexible substrates. The process is based on the preferential adhesion of certain thin metallic films to graphene; separation of the graphene from the catalytic copper foil is followed by lamination to a flexible target substrate in a process that is compatible with roll-to-roll manufacturing. The copper substrate is indefinitely reusable and the method is substantially greener than the current process that uses corrosive iron(III) chloride to etch the copper. The quality of the graphene produced by this new process is similar to that produced by the standard method, given the defects observable by Raman spectroscopy. Green, inexpensive syntheses of high-quality single-layer graphene will enable applications in flexible, stretchable, and disposable electronics, low-profile and lightweight barrier materials, and in large-area displays and photovoltaic modules that are inaccessible to expensive and environmentally deleterious methods for generating this versatile material.

High throughput and continuous deposition process of graphene is one of the most important technologies for graphene electronic and opto-electronic applications, such as conductive electrode, electronics and opto-electronic devices. Therefore, roll-to-roll processes based on plasma and thermal CVD have been proposed [1, 2]. However, the obtained graphene films deposited on Cu foils have wrinkles which degrade both electrical and optical properties in transferred graphene films. In order to reduce wrinkles in CVD graphene films, it is necessary to reduce and/or control tension during roll-to-roll process. Use of metals having low thermal expansion coefficient or those having elasticity would be expected to prevent the wrinkles from roll-to-roll process. We select two kinds of webs for roll-to-roll microwave plasma CVD. One is Ni foil, which was the low thermal coefficient metals, and the other was Cu/polyimide (Cu/PI), which is elasticity material.
Graphene films were deposited on Ni or Cu/PI by roll-to-roll microwave plasma CVD [1]. Our plasma system has four slot antennas to obtain plasma area of 600x600mm², and roll-to-roll system inside the CVD chamber has winder with motor to dominate web flow speed and un-winder with break to keep appropriate tension. CH₄, He and Ar were used as process gases to deposit graphene, total pressure was 5Pa and total microwave power was 18kW. Web flow speed was 1cm/min. The wrinkles in graphene films were decreased by using Ni and Cu/PI compared to use of Cu foil. Reduction of tensile stress inside the obtained graphene on Cu/PI was also confirmed in Raman spectra.
This work was partially supported by “Basic research and development of high-quality graphene” funded by the New Energy and Industrial Technology Development Organization (NEDO).
[1] T. Yamada et al., Carbon 50 (2012) 2615-2619.
[2] T. Kobayashi et al, Appl. Phys. Lett. 102 (2013) 023112.

Silver nanowires (Ag NWs) are one of the materials used in place of indium tin oxide (ITO) for transparent electrodes because they have remarkable electrical, optical, and mechanical performance following thermal annealing or welding using a laser or conductive polymer. However, these post-processes cannot be applied to continuous fabrication methods such as the roll-to-roll (R2R) process. A group has reported the effect of rolling on the electrical performance of Ag NW electrodes, and they suggested that the R2R process could be applied to the fabrication of Ag NW electrodes. In R2R systems, a pressing force is coupled with the tension of the substrate, which governs registration and web handling. In this study, R2R hot-press process parameters were studied for the fabrication of Ag NWs synthesized using polyol methods. Ag NW transparent electrodes were fabricated on 100 mu;m polyethylene terephthalate (PET) films by the Mayer rod-coating method. Isopropyl alcohol (IPA) with 0.3 wt% Ag NWs was used to fabricate the transparent electrodes. For the hot-press process, the Ag NW-coated PET films were laminated with 100 mu;m PET or 50 mu;m or 100 mu;m polytetrafluoroethylene (PTFE). The hot-press process was carried out using laminated substrates, varying parameters such as temperature, press force, and speed. The average length and diameter of the synthesized Ag NWs were 18 mu;m and 110 nm, respectively. The sheet resistance and transmittance at 550 nm of the pristine transparent electrodes were over 40 MOmega;/#8414; and 91.8%, respectively. After hot pressing, the performance of the transparent electrodes improved owing to connecting with NWs induced press force. However, too high a temperature and pressure caused transfer of the Ag NWs to the laminated film. These results indicate that optimization of the parameters is needed in order to fabricate high-quality transparent electrodes. We therefore fabricated transparent electrodes with a sheet resistance 0.2 Omega;/#8414; and a transmittance of 89.5% at 550 nm. This result indicates that transparent electrodes can be fabricated by a continuous process such as R2R using a coating module, such as slot-die or Mayer rod coating, and a pressing/heating module. Furthermore, the R2R process could be expanded to fabrication systems that can fabricate electric devices such as organic photovoltaic (OPV) devices.

Nanoimprint lithography (NIL) is a high-throughput nanofabrication technique that is capable of fabricating large-area nanoscale structures with great precision and low cost. In this project, NIL was employed to fabricate one-dimensional (1-D) and two-dimensional (2-D) metallic grating electrodes, for integration with organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs) in order to tune the optical response of the metallic electrodes.
To fabricate 1-D and 2-D silver grating electrodes using NIL, polydimethylsiloxane (PDMS) replicas of polycarbonate gratings from blank CD and DVD optical storage disks were used as the molds in this project. Optical storage disks were chosen to provide the master patterns for the PDMS NIL molds because: 1) they are inexpensive and 2) the grating pitch can be changed based on whether a CD, DVD, Blu-ray, or HD-DVD is employed. The patterned PDMS molds were then applied to ~350-nm-thick resist films of poly(methyl methacrylate) (PMMA). Upon heating above the melting temperature of PMMA (165 °C) while applying pressure (<100 psi) to the PDMS molds, the patterns of CD or DVD diffraction gratings were transferred into the PMMA films. 1-D metallic grating electrodes were fabricated by thermally evaporating silver onto the PMMA films after they were imprinted with the grating structures.
2-D PMMA gratings were fabricated by two-step nanoimprint lithography, in which both imprint steps were carried out at a temperature above the melting temperature of PMMA and the PDMS replica of the grating structure in the second nanoimprint step was rotated by 90 degrees from that of the first imprint. 2-D metallic grating electrodes were produced by thermally evaporating silver onto the 2-D PMMA films.
The optical response and surface morphology of the 1-D and 2-D metallic grating electrodes were characterized by optical microscopy, bright-field (BF) and dark-field (DF) imaging spectroscopy, and scanning electron microscopy (SEM). Future work includes preparing a library of metallic grating electrodes additionally consisting of 1D Blu-ray and HD-DVD metal electrode patterns; 2D grating electrodes made by combining each of the 4 types of optical disks (e.g., CD-CD, CD-DVD, CD-Blu-ray, etc.); and 2D grating electrodes replicated from optical storage disks with direct-write patterns burned onto them to create more complex patterned electrodes. The optical responses of these patterns will be characterized using BF and DF spectroscopy, and OPV and OLED devices will be fabricated employing these grating electrodes to assess their light management capabilities.

Hierarchical materials have the potential to be transformational for a variety of applications, providing components which simultaneously offer the best performance attributes of ceramics, metals, and plastics. Hierarchical materials are materials which concurrently realize functional features on multiple length scales (sub-micron up to a millimeter level). This allows large void space in a material structure to be filled with load bearing members, adding compliance to the material without significantly increasing the density. Researchers have pursued hierarchical material structures for almost 20 years, leveraging inspiration from both nature and architecture, but few have shown success in synthetically re-creating these structures at multiple length scales. Prior attempts to experimentally fabricate hierarchical structures using 3D printing have only produced structures at large (mm) scales while micro-fabrication techniques using expensive custom equipment to produce sub-micron structures do not translate well to high-volume, low-cost production. PARC has developed a novel approach for manufacturing large area hierarchical materials based on electrohydrodynamic film patterning (EHD-FP) that mitigates both of the aforementioned shortcomings. EHD-FP enables the rapid fabrication of hierarchical materials with features at multiple length scales while creating a process which scales to fabricate large-area patterned films at low cost. We present our mechanical testing data for two-dimensional (2D) hierarchical kagome and triangular truss structures made with EHD-FP and ultraviolet (UV) curable polymers. Using the EHD-FP process, hierarchical films are easily and rapidly created with low viscosity UV cross-linked polymers. PARC&’s batch EHD-FP process and conceptualization for a large-area roll-to-roll system for EHD-FP are also presented. Our results provide confirmation of some of the underlying mechanics for hierarchical materials, allowing for a path towards transformative, large-area hierarchical materials with superior functionality over bulk constituents.

High-resolution pattern printing techniques have been increasingly used as a means of fabricating organic photovoltaics and fast integrated circuits. The reduction in the grid electrodes could increase their transparency and decrease their resistance loss, thereby increasing the conversion efficiency of solar cells. For higher-performance thin-film transistors, it is necessary to scale the channel length below 10 mu;m to achieve superior transition frequency. Among various printing techniques, roll-to-roll (R2R) gravure printing has been researched for use in printed electronics owing to its advantages of mass production and low cost. Many computational and empirical studies have addressed ink transfer, scaling, and optimization in gravure printing. However, the guidelines and logic for gaining control over the ink transfer issue and for achieving high-resolution printed patterns are not yet defined, particularly for industrial-scale R2R gravure printing. The lack of an analytical method and systematic logic hinders the wide commercialization of the gravure printing technique.
In this study, the concept of four phases in the mechanism of the gravure printing process with corresponding ratios (inking, doctoring, printing, and setting ratios) was introduced based on a literature review in order to facilitate matching analysis the modeling of ink transfer. Furthermore, models were proposed for adhesion-based ink transfer and thermodynamics-based ink setting. Accordingly, the ink transfer mechanism was decomposed into intrinsic conditions, including cell geometry, cell surface energy, substrate surface energy, ink viscosity, and ink surface tension, and extrinsic conditions, including nip pressure and printing speed. The experimental data were found to agree well with the mathematical models. As a result, the matching conditions for ink transfer and ink setting were established based on nondimensionalized adhesion force difference and spreading coefficient. Finally, a matching window and logic were suggested to determine the intrinsic conditions for high-resolution gravure printing. The application of matching logic to achieve an average line width of 15.32 µm with a standard deviation of 0.89 µm and thickness of 220 nm confirmed its feasibility. The findings of this study could provide the initiative for developing matching conditions to establish guidelines for improving and applying R2R gravure printing to industrial-scale printed electronics.

Micro contact printing (mu;CP) is a simple, versatile method for preparations of micro- and nanostructured surfaces. In the last decade, a wide range of materials (e.g., self-assembled monolayers, nanotubes and graphene, functional polymers, DNA, photoresists, metals, and quantum dots) have been successfully transfer-printed using polydimethylsiloxane (PDMS) stamps. PDMS is widely used due to its low elastic modulus (~ 1.5 MPa), which allows a conformal contact even with rough surfaces, and low surface energy (~ 22 mJ/m²), which enables facile material transfer. In order for far-ranging applications and high-throughput production, however, further mechanical and/or chemical modifications of PDMS stamps are necessary. Recently different materials, such as hydrogel or poly(ether imide)/poly(vinyl pyrollidone) PEI/PVP, were suggested to satisfy the specific demands.
We introduce, for the first time, polymer-coated carbon nanotube (CNT) forests as an alternative stamp for mu;CP. Vertically aligned CNT arrays grown from thin-film catalysts on a substrate have many unique advantages, such as large porosity, high conductivity and high thermal strength. Moreover, the mechanical behavior of CNT microarrays is similar to that of open-cell foams when compressed, and thereby having comparable compliance to elastomers. However, randomly clustered surface layers of as-grown CNT arrays are relatively rough (R_a ~ 150 nm) and stiff (E_r ~ 200 MPa) to be in conformal contact with target substrates. It is shown that removing the clustered layer of CNT arrays allows the surface to be more compliant (E_r ~ 30 MPa) due to bending behaviors of individual CNTs. Analytical models are developed to understand the surface mechanics of CNT arrays in contact with rough surfaces. Capillary forming is another main drawback which obstructs the CNT forests to be “inked” by aqueous solutions. We show that conformal coating of poly-perfluorodecylacrylate, p(PFDA), by initiated Chemical Vapor Deposition (iCVD) provides the necessary mechanical strength against capillary forming while maintaining the surface compliance (E_r ~ 38 MPa) and having low surface energy (~ 10 mJ/m²). Compression tests are performed on pPFDA-CNT composite micro-structures to investigate the mechanical stability under repetitive contact. Finally, printing experiments are conducted to demonstrate the mu;CP process using the new polymer-CNT stamps.

Bulk heterojunction (BHJ) architectures are highly desirable for photovoltaic applications, with ideal ordered BHJ sample geometries consisting of domain sizes for the donor and acceptor commensurate to the exciton diffusion length (about 20 nm) and thicknesses on the order of hundreds of nm. Many demonstrations of ordered BHJs rely on expensive top-down approaches for generation of the nanostructure. Bulk metallic glasses (BMGs) enable affordable replication of expensive hard masks at feature sizes and aspect ratios unachievable by other template materials and can be reused multiple times to achieve sub-100 nm imprint. We demonstrate the optimization and application of amorphous aluminum oxide-templated BMG nanoimprint to enable two sorts of photovoltaic geometry: (1) a nanostructured BMG electrode imprinted directly into phase separated, nanoconfined BHJ of poly(3 hexylthiophene-2,5-diyl) (P3HT) and Phenyl-C61-butyric acid methyl ester (PCBM) and (2) an ordered BHJ of P3HT and PCBM with conventional electrode formed by imprint into P3HT, removal of the template, and subsequent orthogonal cospinning of PCBM into the template. Through BMG imprint, we demonstrate repeated generation of sub-100 nm feature size patterns with aspect ratios exceeding 3.

Ferroic oxides, i.e., having both of ferromagnetic and ferroelectric characters, have been attracted attention from a viewpoint of nonvolatile memory, sensor applications and so on, using their multi-functionalities. In particular, their nano-structures are expected to high density memories. Self-assembly synthesis has recently highlighted to fabricate ultra-small 3D nano-hetero-structure such as nano-dot and nano-pillar arrays embedded in a matrix in functional oxide materials by using pulsed laser deposition technique with single composite target [1]. However, in this synthesis, precise control of spatial positioning, structural shapes and sizes of the nanostructures are quite difficult. We report a well-advantageous technique of nanoimprint (NIL) based directed oxide self-assembly which is nano template-assisted position selective self-assemble oxide growth and have a fully potential to artificially realize well-positioning of nano-heterostructures, namely core-shell nano-heterostructure arrays consisting of ferromagnetic (Fe,Zn)₃O4 (FZO) and ferroelectric BiFeO₃ (BFO). To prepare initial nanotemplate, Molybdenum lifted off- NIL was used, which is a novel low cost nano-manufacturing method and can be applied down to several10-nm regions over large areas, in functional oxide materials [2]. By adapting epitaxial spinel FZO nano seed arrays on a perovskite SrTiO₃ substrate to templates for the self-assembled nano composite formation, well alighted FZO nano-dot surrounded by BFO shell layer was constructed whereas randomly distributed BFO nano-dot was embedded in FZO matrix without nano-template. Namely, artificial inversion on FZO matrix and BFO pillar was realized under the position control of their epitaxial growth [3] . The template with proper FZO dot size below 500 nm on a side encourages spontaneously well-position selective epitaxial growth of FZO cores and BFO shells, based on the standard diffusion model. This technique allows us to construct highly ordered and integrated functional oxide nanostructures, including ferroelectric/ferromagnetic/ semiconductive materials over the large area.
Reference
[1] H. Zheng et al, Science 303 (2004)661
[2] N.-G Cha, H. Tanaka et al, Nanotechnology 22 (2011)185306
[3] T. Sakamoto, H. Tanaka et al, J. Appl. Phys. 113 (2013) 104302

The DLC (diamond like carbon) coating technique is widely used in order to enhance the mechanical properties of components like increasing the hardness or lowering the frictional coefficient. However, the throughput of conventional CVD processes is not high. The authors have been developing a high-throughput CVD technique under open-air conditions. The open-air process also offers the advantage that a pin-point process becomes possible. In this study, a coaxial structure torch driven by microwave power initiated a small plasma (~Oslash;2 mm) on its tip. The process gases were supplied there through the torch under open-air conditions. In order to eliminate air mixing, a shielding gas was flowed outside the torch. In this configuration, a DLC film with hardness of 20 GPa was prepared with more than 10 mu;m/h throughput.

Flexible Electronic device is the key requisite in ubiquitous era owing to its thin, light-weight, foldable and non-breaking properties and broad researches focused on the device are being conducted. To make the flexible device in practical use, it is imperative to develop a packaging method which is compatible with bending conditions for signal and power distribution, heat dissipation, and protection. Despite the importance of packaging, however, packaging for flexible device has to be investigated further.
In this study, we present a simple but effective approach, using flip-chip bonding technology with anisotropic conductive film (ACF), for interconnecting very thin Si-based LSI (Large Scale Integration) to the flexible circuit board directly. By ‘thinning down the device to 1um after bonding&’ or ‘bonding the already thinned 1um device&’, we demonstrated that ACF bonding could be readily used for flexible device packaging. Mechanical stability and electrical interconnection reliability were demonstrated by bending tests and 4-point probe test.
By this methods, we demonstrated Si-based flexible NAND-type flash memory array with packaging-completed. The device is mechanically stable in bending condition and shows program/erase operation as in the rigid device. Furthermore, we are also investigating the roll-to-roll packaging process for continuous mass production.

Surface modification by polymers has become a very common approach to tune surface properties for meeting specific requirements such as conformal coverage over nonplanar substrates, patterning with nanometer-scale resolution, or responsiveness to the environment.
Many techniques are available in literature to obtain polymeric thin-films on a variety of substrates such as wet chemical methods and chemical vapor deposition (CVD). Initiated chemical vapor deposition (iCVD) represents a relatively new concept for producing coatings and enables the fabrication of chemically well-defined polymeric films with micro- and nano- scale features. In iCVD process, polymeric thin-films are fabricated by decomposing a free radical initiator in the gas phase and generating primary radicals, which when adsorbed together with monomer onto a cooled surface, set off a free radical polymerization reaction, yielding a polymer coating. The uniqueness of iCVD technology is that it requires low energy input at low surface temperatures, and allows close control of film thickness and also enables conformal coating on a variety of substrates without solvent usage and with the ability to protect chemical functionality. Therefore, iCVD technology has a wide range of potential applications in biotechnology, biosensing, microfluidics, electronics, photonics, photovoltaics and energy storage. In addition, high-rate roll-to-roll fabrication schemes can easily be incorporated into iCVD process enabling high-throughput fabrication.
Due to complex nature of iCVD processes there are many parameters that need to be dealt with related to gas-phase and surface reactions. A mathematical model of CVD system is created using COMSOL Inc. Multiphysics (MP) software and is extended to include iCVD process parameters for a homologous series of alkyl acrylates polymerization. This model serves as a pilot case for building up more complex chemistry and physics into a virtual reactor and provide predictive work to be validated by experiments. In this regard, this work aims to develop a computational model for large-scale iCVD process capable to describe and obtain with reasonable accuracy all relevant phenomena occuring in the reactor chamber, eventually leading up to incorporation of roll-to-roll fabrication.

Tungsten oxide (WO₃) is commonly utilized in electrochromic, photocatalytic and photovoltaic devices; however, its demonstration in supercapacitors is very limited. Conducting polymer polyaniline (PANI), on the other hand, is emerged as a promising active material for electrochromic and pseudocapacitive devices. In this work, we report on the fabrication and characterization of supercapacitors with ternary nanocomposite WO₃, PANI and single walled carbon nanotube (SWNT) network electrodes to investigate the synergistic effect of the ternary composite on capacitive properties. WO₃ and its nanocomposite with PANI were deposited onto SWNT thin film by electrodeposition method. Vacuum filtered SWNT thin films in this work provided high surface area, high conductivity and a template for the attachment of both WO₃ and PANI. Electrochemical properties such as specific capacity and cycling ability of solid-state supercapacitors with ternary composite electrodes were then investigated through cyclic voltammetry, chronopotentiometry, electrochemical impedance spectroscopy. Specific capacitance of ternary nanocomposite electrodes was obtained to be 242 F/g, which was higher than that of bare SWNTs and binary composite electrodes. We will present a detailed analysis of electrochemical properties of the fabricated supercapacitors to underline their capacitive behavior. Our results reveal the potential of the use of ternary nanocomposite WO₃-PANI- SWNT in supercapacitor electrodes that can be fabricated through simple solution based methods and the method investigated herein can be simply adapted to industrial scale fabrication.

One-dimension nanostructures ZnO in the forms of nanorods and nanowires have evolved into one of the most important materials for nanotechnology in the decade ^[1]. They have been demonstrated with versatile and promising applications such as nanogenerators ^[2], gas sensors ^[3], and UV lasers ^[4]. Recently, by using low temperature solution based method, monolithic integration of nanowires onto commercial cordierite honeycombs has been achieved in our laboratory, giving rise to a new type of structured catalysts with ultra-efficient materials utilization, excellent robustness, tunable and good catalytic performance.^[5][6] Uniform ZnO nanorod arrays have been successfully integrated upon commercial monolithic substrate with 3D multi-channel structure by using a mechanical agitation assisted hydrothermal batch processing ^[7]. However, from the perspective of industrial scale-up, this method has critical disadvantages such as time and labor waste, inefficient precursor utilization and high output undesired precipitates. Herein, we report a continuous flow synthesis (CFS) method with an enhanced growth efficiency and precursor utilization to generate large scale ZnO nanorods arrays inside large honeycomb channeled substrates, which poses a new way to further enhance the catalysts&’ performance towards automotive emission control. Using the CFS method, within 10 hours, up to 15 mm long and 100 nm thick nanorod arrays can be successfully fabricated onto 1 mm x 1mm square channels in the 4cm x 4cm x 4cm sized honeycomb substrate.
The ZnO nanoarrays achieved from CFS possesses longer length and greater density than that from batch. Furthermore, the interference of precipitates that generated in the growth solution was significantly suppressed as a result of being filtered during the waste solution recycle. In addition, by extending growth time, ZnO nanorods arrays with length up to 15 mm were successfully achieved in the honeycomb channeled substrate. In a word, the overall precursor utilization and growth efficiency of ZnO nanorods are greatly enhanced.
[1] Sheng Xu, Z. L. Wang. Nano Res. 2011, 4(11): 1013-1098.
[2] Z. L. Wang, R. Yang et al. Material Science and Engineering R, vol. 70, no. 3-6, pp. 320-329, 2010
[3] J. Xu, J. Han, Y. Zhang et al. Sensors and Actuators, B, vol. 132, no. 1, pp. 334-339, 2008
[4] S. Chu, G. Wang, W. Zhou et al. Nature Nanotechnology, vol.6, no.8, pp. 506-510, 2011
[5] Guo and Ren et. al, Nano Energy, 2013,2, 873-881
[6] Ren et.al, J. Mater. Chem. A , 2013, 1, 9897-9906.
[7] X. Wen, Guo. et al. Grystal Growth & Design 2013, 00672

In this communication we report about gas phase self-assembled nanostructured thin film synthesis obtained coupling PECVD technique and nanoparticles inseminated sonic jet technique in a single reactor design for one-step, high yield deposition (100 nm sec^-1) of nanostructured thin films with controlled porosity on large areas (100 cm²). ^[1] This novel process is based on the segmentation of the gas phase material synthesis in two separate steps: (i) metal-organic precursor dissociation chemistry control in a reactive plasma environment; (ii) nanoparticles nucleation and aggregation control by means of a sonic jet. The morphological properties of synthetized films range from aerogels through ordered dendritic nanostructures to compact films by controlling plasma process parameters and aerosol gas dynamic of the sonic jet flow field. A high degree of control can be achieved in order to tailor the optoelectrical and structural properties of synthesised material. With our technique, a variety of materials can be obtained, given the existence of a suitable gas-phase precursor. Functional test results of two materials of high technological interest will be presented, namely mesoporous titanium oxide and direct deposition of nano-crystalline silicon. The former is an important component for dye sensitized solar cell PV technology. TiO₂ photoanodes consisting of anatase single crystals assembled in quasi 1-D arrays of high aspect ratio hierarchical mesostructures are fabricated onto the F-doped SnO covered glass surfaces by self-assembly from the gas phase. Structural and morphological characteristics of TiO₂ nanostructured photoanodes can be optimized to achieve simultaneously high specific surface area for optimal dye uptake and broadband light scattering. As for the latter, size-tuneable optical, mechanical and thermal properties exhibited by nano-scale crystalline silicon, represent a promising choice for a wide variety of applications ranging from solar energy conversion to light-emitting devices and batteries. Films porosity, crystalline fraction and particle size can be controlled by tuning process parameters. Nano-crystals direct deposition via non-thermal plasma methods has recently attracted a great deal of interest given the simultaneous advantages of low temperature and narrow size distribution synthesis, not feasible with established chemical methods.
[1] Trifiletti V. et al. Dye-sensitized solar cells containing plasma jet deposited hierarchically nanostructured TiO2 thin photoanodes, J. Mater. Chem. A, 2013,1, 11665-11673.

Barium titanate (BTO) has been widely used for multilayer ceramic capacitor design as it has a low cost, and high dielectric constant and polarization values. However, its low breakdown field (~100 kV/cm) is preventing its use in energy storage applications. This low value for breakdown field is due to the high porosity and large pore sizes characteristic to ceramic material systems. By compositing with UV curing polymer, these detrimental attributes can be minimized so as to increase the total energy storage capability. The UV cure polymer reacts with a high-energy, high power xenon flash lamp that forms fully cured material in several milliseconds forming a hermetic seal around the BTO nanoparticles. As the main reason behind low breakdown fields for sintered ceramics are high-energy grain boundaries, sealing the nanoparticles in polymer increases the breakdown field by eliminating these charge concentration centers. Other methods have been used to reduce the porosity of ceramics, however they are energy and time intensive, which drives up the cost per energy stored. By using a high breakdown polymer that directly bonds to the nanoparticles, breakdown fields beyond 100% dense BTO can be obtained without the need for cost inefficient processing techniques. By using high throughput printing and curing techniques, multilayer devices can be rapidly built which helps drive down another important device property, the cost per kWh/kg to fractions of cents. Pentaerythritol tetrakis(3-mercaptopropionate) (PEMP), 1,7 Octadiene (OctD), and 1,3-Diisopropylbenzene (DPB) were mixed in order to match the stoichiometry between thiol and alkene functional groups, enabling for high degrees of cross-linking between the ceramic and polymer matrix. Films were printed using a Fujifilm Dimatrix 2300 inkjet printer. Flash curing employed a Pulseforge 1300 system from Novacentrix. The intensity and fluence of the flash lamp were varied to determine the optimal cure parameters. For inline testing, acetone wipe tests and connectivity tests via multimeter were used to test for chemical and mechanical stability. The degree of cross-linking was determined through comparative FTIR studies. Dielectric constant was measured using an Agilent 4294a impedance analyzer from 100 Hz-10 MHz with a two terminal set up. Weibull Analysis of the breakdown strength was taken using Radiant Technology's Precision Ferroelectric tester with a 10 kV source. The printed thick films averaged 2 microns thick as observed by an SEM cross-section. Energy densities were calculated from the linear dielectric capacitor equation. Energy densities of 25 J/cm³ were achieved for the characteristic breakdown strength of the printed films.

The development of solution-phase strategies for purifying, functionalizing, and assembling nanomaterials into functional arrays has created new opportunities for roll-to-roll manufacturing of flexible electronic devices and systems. Of particular interest are highly monodisperse nanomaterial inks prepared using density gradient ultracentrifugation (DGU), which is a post-synthetic technique for sorting nanomaterials by their physical and electronic structure. In particular, DGU enables the scalable production of high purity semiconducting carbon nanotube, metallic carbon nanotube, graphene, metal nanoparticle, and two-dimensional transition metal dichalcogenide based inks. The resulting monodisperse inks are compatible with a variety of roll-to-roll manufacturing methods including inkjet printing, aerosol jet printing, and gravure printing. In addition to demonstrating improvements in electronic device performance as function of nanomaterial purity, this talk will also explore the integration of disparate nanomaterials into heterostructures with well-defined interfaces. Specifically, by concurently combining the attributes of multiple nanomaterials, these heterostructure devices enable further enhancements in performance and the possibility of additional functionality. For example, the traditional trade-off between on/off ratio and mobility in semiconducting carbon nanotube (CNT) thin-film transistors (TFTs) is overcome by integrating semiconducting CNTs with solution-processed hybrid organic-inorganic self-assembled nanodielectrics, yielding on/off ratios approaching 10⁶ and mobilities of ~150 cm²/V-s. Similarly, by utilizing solution-processable benzyl viologen, the doping type and level in CNT TFTs can be tailored, which allows the realization of CNT CMOS logic gates with sub-nanowatt static power dissipation and full rail-to-rail voltage swing. Finally, p-type semiconducting CNT thin films are integrated with n-type single-layer MoS₂ to form p-n heterojunction diodes. The atomically thin nature of single-layer MoS₂ implies that an applied gate bias can electrostatically modulate both sides of the p-n heterojunction concurrently, thereby providing 5 orders of magnitude gate-tunability over the diode rectification ratio in addition to unprecedented anti-ambipolar behavior when operated as a three-terminal device. Overall, this work establishes monodisperse nanomaterial inks and their integration into heterostructure devices as foundational elements of next generation flexible electronics.

To make printed electronics a reality, it is necessary to deliver high resolution, good reproducibility, excellent pattern fidelity, high process throughput, and compatibility with the requisite semiconductor, dielectric, and conductors inks. Over the past decade, we have been developing detailed understanding of the technological and scientific underpinnings of printing, and have been applying this knowledge to push the limits of printing to realize high resolution, high performance printed transistors.
In this talk, I will discuss the physical underpinnings of gravure printing, and will show how gravure printing can be scaled to produce high-fidelity highly scaled patterns, including sub-2 micron features at printing speeds of ~1m/s. I will additionally review the physics of pattern formation from pixelated primitives, such as exist during gravure printing, and will show how control of drop merging and drying can be used to produce high-fidelity shapes, including lines, squares, and intersections. Finally, in conjunction with high-performance materials, I will describe our realization of high-performance fully-printed transistors on plastic, offering high-switching speed, excellent process throughput, and good fidelity over large areas.

Additive manufacturing techniques are now more affordable than ever but remain confined to custom and low volume production. The big opportunity lies in the ability to produce inexpensive functional devices in a continuous roll-to-roll format. To this end, new tools are designed to enhance processing capabilities and promote efficiency. High-powered flash lamps to rapidly heat printed metallic inks is now used for a range of new materials¹ and processing steps.^2-3 This process is commonly known as photonic curing. Photonic curing is inherently tailored towards large area processing and provides power densities similar to excimer lasers.
Roll-to-roll processing requires flexible substrates with low thermal thresholds - presenting a significant challenge for conventional oven processing. Materials properties restrictions, however, are circumvented with photonic curing. In this work, PET is heated to ten times the glass transition temperature and several times the decomposition temperature without physical damage. A computer model is designed to estimate the temperature gradient in the device stack and the resulting model is directly correlated to experimental results. This understanding is expanded to multilayered structures with complex responses to the photonic curing process. The findings of this research are integrated into roll-to-roll additive RFID antenna production.⁴ Photonic curing is currently investigated for processing of displays, photovoltaics, sensors, flexible batteries and others high volume products.
1. T. Araki, et. al., “Cu Salt Ink Formulation for Printed Electronics using Photonic Sintering” Langmuir2013, 29, 11192-11197.
2. C.J. Stolle, et. al., “Multiexciton Solar Cells of CuInSe₂ Nanocrystals” J. Phys. Chem. Lett.2014, 5, 304-309.
3. H. Kang, et. al., “Direct Intense Pulsed Light Sintering of Inkjet-Printed Copper Oxide Layers within Six Milliseconds” ACS Appl. Mater. Interfaces2014, 6, 1682-1687.
4. http://www.muhlbauer.com/39703/Solutions-Products/Products-Systems/RFID-Smart-Label/Antenna-Production/index.aspx

Inkjet printing of various nanoparticle inks, made from silver or copper nanoparticles, and its transformation into solid functional patterns is of high interest in the field of printed electronics. Liquid materials can be deposited as defined patterns in selected areas with micrometer precision. To convert these printed liquid films, consisting of solvents, additives and nanoparticles, into solid functional patterns a post-treatment is required. To this date, many investigations report on various sintering techniques to achieve e.g. high conductivity from the printed conductive materials.
Direct thermal sintering (via furnace or hotplate) requires high temperatures, which makes it not suitable for sensitive polymeric substrates. The novel method of intense pulsed light [IPL] sintering opens the window of opportunity to convert liquid or dried metal layers into solid functional layers within milliseconds without damaging the thermally fragile polymeric substrate.
In this work we present and analyze the application of the IPL sintering on inkjet printed silver patterns on various flexible substrates, like Poly(ethylene naphthalate) [PEN], Poly(ethylene terephthalate) [PET], Polyimide [PI] foils and paper.
A high dependency of the electrical and structural performance of the printed silver layers on the base substrate was observed when flashing with the IPL technique. Flashing parameters were varied and the resulting sheet resistance is presented.
With the analytical comparison of optical and electrical results, the flashing settings could be adapted to achieve highly conductive inkjet printed silver patterns on flexible substrates, when compared to other thermal sintering techniques. Furthermore the first integration of this post treatment methodology into semi-industrial roll-2-roll processing was successfully performed and will be demonstrated.

Printing technologies are highly sophisticated technologies for patterned material deposition. Due to different workflow demands a variety of technologies have been developed like inkjet, gravure, or screen printing technology. The initial intention was a well defined deposition of color ink dots to raise visual attraction or usability. The approach to use printing technologies for functional material deposition instead of color ink utilizes precise mass production technology in new application fields. Depending on the material an appropriate printing technology has to be chosen that matches material consistency and e.g. the viscosity range of the used printing technology.
In our contribution, we report of different activities in the field of printed and large area electronics. Printed power is one factor to drive applications like greeting cards or even medical measurement devices. Also the manufacturing procedures for electronic devices like transistors, diodes, resistors and capacitors are under investigation. Conductive structures consistent of silver or copper material can be used as conductive paths within a circuitry or as an antenna system. Several applications are presented.
For this research not only several machines based on inkjet printing technology are used, but also such based on screen and gravure printing. Both, flatbed and Roll-to-Roll machineries are employed to get the results. Therefore, machinery setups and concepts are also discussed. Also high speed Roll-to-Roll manufacturing technology based on photonic sintering is employed to produce highly conductive copper structures.

Digitally printed organic photodiodes have large potential for application in many fields, such as imaging, particle detection, or biomedical sensing. Digital contact-free aerosol jet printing enables novel possibilities in device fabrication as well as in device design, such as customer specific photodiode arrays. In this work we demonstrate efficient aerosol printed photodiodes based on the polymer:fullerene blend PTB7:PC₇₀BM on flexible PET substrates. This work comprises a detailed device characterization including a comprehensive electrical and optical characterization, as well as surface topography measurements as a function of processing parameters such as aerosol temperature and layer thickness. Additionally, infrared spectroscopy has been conducted to investigate the influence of ultra-sonic aerosol generation on molecular degradation. Devices with generic bulk-heterojunction as well as segregated deposited polymer and fullerene materials with partial intermixing have been investigated. Also, fully digitally designed flexible photo detector arrays with aerosol printed active material and conductive PEDOT:PSS as top anode on ZnO covered digitally structured ITO/PET substrates were fabricated. The devices show detectivities of 10¹³ Jones at -0.15 V, when illuminated with white light.

For the realization of flexible electronics, structuring of metal electrodes such as wavy, arc-shape or horse-shoe type patterns, has been reported to enhance the stretchability and stability. Our previous study showed that a specific nanohole structure of a metal electrode can improve its stability drastically by dislocation annihilation and crack tip blunting near nanoholes. However, the fabrication processes for these new structures are quite complicated and have relatively low productivity. On the other hand, ink-jet printing is one of the most promising processes to fabricate flexible devices because it is possible to write directly any pattern and it can be implemented into a roll to roll process for high productivity. The main problem of ink-jet printing is pore formation during particle or grain growth because it degrades the mechanical and electrical properties of the printed film. In this study, we used ink-jet printing to fabricate optimized nanoporous Ag films and have investigated their fatigue behavior. The results are compared to conventional, thermally evaporated Ag films.
Cyclic bending/sliding tests were performed with 1.1% tensile strain at 5 Hz frequency, and a sliding distance of 10 mm. The electrical resistance of the conventional Ag film started to increase after 15,000 cycles, and the final resistance increased up to 100% due to crack formation along extrusions formed by dislocation motion. In contrast, the electrical resistance of the nanoporous Ag film annealed at above decomposition temperature increased only 60%. In addition, the samples annealed below decomposition temperature showed almost no resistance change. This implies that the fatigue resistance can be improved by controlling the nanoporous structure of inkjet-printed film. The microstructure was controlled by different post heat treatment, and the effect of porosity and the optimum nanoporous structure against fatigue damage will be discussed.

During the last decade inkjet printing has been evolved to a mature technology for the deposition of color inks on flexible and rigid substrate materials. Nowadays, the usage of inkjet technology is widespread from cheap small-office home-office desktop printers to industrial roll-to-roll systems. However, in recent years inkjet technology has been increasingly applied as advanced deposition method for various materials in the field of chemistry, biology and electronics. Numerous publications can be found about inkjet-printed electronics. Most of them rely on laboratory inkjet equipment for the manufacturing. Laboratory inkjet equipment is characterized by using single nozzle systems or small printheads with up to 16 nozzles only. The manufacturing speed and the number of printed devices is usually very low. In comparison to laboratory printheads, the layers printed with industrial printheads are considered as more homogeneous due to a more continuous deposition of the ink. In addition, the usage of industrial printheads also allow the consideration of yield for printed layers and devices which is difficult when using small printheads due to the slow printing process. Both aspects - the transfer from laboratory to industrial equipment and the consideration of yield - are key factors towards commercialization of printed electronics. Despite of the importance of these aspects, they are underrepresented in literature.
Our work focuses on sheet-fed inkjet printing of hundreds or even thousands of electronic components such as resistors, capacitors, and transistors. Basic morphological and functional properties of the fully inkjet-printed layers and the manufactured electrical devices are studied. Depending on the complexity of the printed devices, yields of up to 100 % were obtained (e.g. for resistors). With increasing complexity of the devices, also the requirements for the inkjet printing process increase and thus the yield decreases. Yields of about 80 % were achieved for all inkjet-printed transistors with state-of-the-art performance. We provide a detailed identification and analysis of the origins of the failures responsible for the decreasing yields and introduce concepts to overcome them.

Flat panel display is one of major display products these days. This has been developed based on rigid and flat glass substrates. Glass substrates have enabled many applications as like mobile phones, tablets, laptops, monitors, TVs and large formatted displays for which existing CRT display is not applicable. But glass substrate has several shortcomings. These are brittleness, thick panel and heavy weight compared with flexible substrate as like plastics.
Flexible displays are alternatives of present displays. And it comes up as next generation displays. They are light weight, slim, flexible and can enable a variety of shapes, applications and form factors. For past few years, outstanding achievements have been made on flexible displays especially on process, materials and device area. Process developments and low cost are important for flexible applications and products. For developing flexible displays, LG Display has developed soluble TFT, printing and Roll-to-Roll technology for many years. For high performance product with low cost, combining of each elements of technology is very important.
In this paper, the status of development on flexible display backplane is introduced. For enabling variety of designs and reducing investment/material cost, process directly on flexible films by Roll to roll will be discussed.