Tutorial SM03—Introduction to Flexible, Stretchable Biointegrated Electric Devices and Related Mechanics

Instructors: John A. Rogers, Northwestern University; Yonggang Huang, Northwestern University; Tae-Woo Lee, Seoul National University; Keon Jae Lee, Korea Advanced Institute of Science and Technology

The tutorial is aimed at providing introductory courses to the fundamentals of flexible, stretchable biointegrated materials. The session presents various devices including skin-integrated electronics, bioinspired soft electronics and self-powered electronics.    

8:30 am
An Overview of Materials and Design Principles for Skin-Integrated, Stretchable Electronic and Microfluidic Devices in Medicine and Sports
John A. Rogers, Northwestern University

Biological systems are mechanically soft, with complex, time-dependent 3D curvilinear shapes; modern electronic and microfluidic technologies are rigid, with simple, static 2D layouts.  Eliminating this profound mismatch in physical properties will create vast opportunities in man-made systems that can intimately integrate with the human body, for diagnostic, therapeutic or surgical function with important, unique capabilities in fitness/wellness, sports performance and clinical health care. Over the last decade, a convergence of new concepts in materials science, mechanical engineering, electrical engineering and advanced manufacturing has led to the emergence of diverse, novel classes of "biocompatible" electronic and microfluidic systems with skin-like physical properties. This talk describes the key ideas and presents some of the most recent device examples, including wireless, battery-free electronic "tattoos" with applications in continuous monitoring of vital signs in neonatal and pediatric intensive care; and microfluidic/electronic platforms that can capture, manipulate and perform biomarker analysis on microliter volumes of sweat, with applications in sports and fitness. 

10:00 am BREAK

10:30 am
Mechanics of Stretchable and Flexible Electronics
Yonggang Huang, Northwestern University

Recent advances in mechanics and materials provide routes to integrated circuits that can offer the electrical properties of conventional, rigid wafer-based technologies but with the ability to be stretched, compressed, twisted, bent and deformed into arbitrary shapes. Inorganic electronic materials in micro/nanostructured forms, intimately integrated with elastomeric substrates, offer particularly attractive characteristics in such systems, with realistic pathways to sophisticated embodiments. Mechanics plays a key role in this development by identifying the underlying mechanism and providing analytical solutions to guide design and fabrication. This talk focuses on the design, modeling, simulation and optimization of stretchable and flexible electronics.

1:30 pm
Flexible, Stretchable Bioinspired Artificial Nervous Systems
Tae-Woo Lee, Seoul National University

Living organisms have evolved to efficiently developing their functions and structures. For adopting their superior characteristics in many latest technologies, bioinspired electronics have been extensively developed. Particularly, artificial nervous systems are one of the bioinspired electronics to replicate the functions and operating principles of biological nervous systems. Here, bioinspired artificial nervous systems were demonstrated by using flexible and stretchable organic electronics. For the artificial mechanoreceptor nervous systems, pressure sensors (artificial mechanoreceptors), organic ring oscillators (artificial nerve fibers) and synaptic transistors (artificial synapses) were integrated like biological counterparts. The applicability for neural prostheses of this artificial sensory nerve was verified by connecting the artificial sensory nerve to the biological motor nerves in a detached inset leg, and successfully actuating the biological motor nerves depending on external pressure information. In addition, an organic nanowire-based artificial sensorimotor nervous system was developed by employing a self-powered photodetector (an artificial light-sensory organ), a stretchable artificial synapse and a polymer actuator (an artificial muscle). The voltage pulses of a self-powered photodetector triggered by optical signals drove the stretchable synaptic transistor, and synaptic outputs were used for actuation of an artificial muscle fiber in the same way that a biological muscle fiber contracts. Lastly, an organic artificial synapse was integrated with a triboelectric sensor for demonstrating an artificial auditory system. The morphology of organic semiconductors of the artificial synapses was modulated to emulate the facilitation recover time of biological synapses. Our bioinspired artificial nervous systems based on flexible and stretchable organic electronics would be a platform for developing bioinspired soft electronics, neuroinspired robots and electronic prostheses.

3:00 pm BREAK

3:30 pm
Self-Powered Flexible Electronics Beyond Thermal Limit
Keon Jae Lee, Korea Advanced Institute of Science and Technology

This seminar introduces three areas of recent progress in self-powered flexible electronic systems beyond thermal limits. The first part will introduce self-powered systems for IoT sensors and flexible energy source. A flexible nanogenerator converts external biomechanical movement into electrical energy for self-powered IoT and biomedical devices such as a pacemaker and transportation. In addition, flexible piezoelectric materials detect the minute vibration of membrane or human skin that expands the application of a self-powered acoustic sensor and healthcare monitor. The second part will introduce laser–material interaction for flexible applications. Laser technology of ultra-short pulse duration becomes important for future flexible electronics since a high-temperature process can be adopted on plastic substrates, which is essential for high-performance electronics. Exciting results of flexible laser material interaction will be explored from both material and device perspectives including nanomaterial synthesis, inorganic laser liftoff and plasmonic material reaction. The third part will discuss flexible large scale integration (f-LSI) for flexible CPU and high density memory. Flexible LSI is an essential part of future electronics for data processing, storage and radio-frequency (RF) communication. To fabricate f-LSI, we integrated an 0.18 CMOS process of single-crystal silicon nano-transistors with flexible electronics. Simultaneous roll transfer and interconnection of flexible NAND Flash memory was achieved using anisotropic conductive film (ACF). Finally, we introduce the highly efficient and long-term stable flexible vertical micro LED (f-VLED) for full color displays, wearable and biomedical applications. Using optogenetic mouse models, f-VLED stimulated motor neurons deep below layer III from the brain surface and induced mouse behavior changes. These f-VLED can also be used as tools for skin research and phototherapy.