4:15 PM - *SF14.01.08
4D Elastic Microstructures for Robotics and Integrated Photonics
Sara Nocentini1,2,Daniele Martella1,2,Camilla Parmeggiani3,2,Diederik Wiersma3,2,1
National Institute for Metrological Research1,European Laboratory for Nonlinear Spectroscopy2,University of Florence3
Responsive polymers patterned ad the nanoscale in 3D designs allow for functional microstructures with a wide range of applications in between which micro robotics and tunable photonics will be discussed in this contribute. The reversible shape change and refractive index variation of smart polymer such as liquid crystalline networks (LCNs)1 open for a dynamic operation encoded in the material properties and design. LCNs, also defined as “artificial muscles”, offer the possibility to perform different movements depending on their molecular alignment and, by optically controlling their elastic deformation, a wireless activation of microstructures is attained. The light driven elastic deformation of the LC polymeric nanostructures is characterized by a sub-millisecond dynamics that rules the robot evolution and the timescale of the photonic property change.2
To reach such temporal response, light has been used not only as energy source for activating them but also for patterning microstructures in 3D with nanoscale precision.
While most of the available lithographic techniques give access to 2D geometries, a truly 3D shaping can be achieved by Two photon Direct Laser Writing (TP-DLW).3 Such platform replicates arbitrary computer-aided designs with nanoscale resolution and integrates multiple materials on the same chip. By manufacturing LCNs with TP-DLW, untethered microrobot operation and tunable integrated photonic structures will be described.
We will present as a micro walker is able to advance on different substrates;4 and a micro hand can catch micro objects by an external light control and even autonomously, depending on the target optical properties.5
In the field of polymer photonics, tunable devices such as a 2D grating structure with sub-millisecond time response has been demonstrated for optical beam steering exploiting an optically induced reversible shape-change. By creating a structured material out of LCNs, we will show how it is possible to induce a light-induced mechanical deformation of its periodicity that thus triggers a relevant angular deviation of the diffracted beams.6 Further optical functionalities can be addresses through integrated photonic circuits where single mode waveguides coupled to whispering gallery mode resonators (WGMR) enable dynamic signal manipulation and filtering. Tunability has been obtained following two different strategies: a LCN cylinder acts as a mechanical actuator that slightly and finely changes the shape of the polymeric WGMR, while a LCN ring cavity changes its resonance depending on the external light stimulus.7
The versatility of TP-DLW and responsive shape-changing materials has demonstrated its great potential even if it is still in its infancy. Untethered operation of sensitive nanostructures promises intelligent microstructures able to sense and react both for micro robotic applications and light manipulation through photonic circuits and diffractive surfaces.
 M. Warner, E. Terentjev, in Liquid Crystal Elastomers, (Oxford Univ. 2007).
 Nocentini, S., Parmeggiani, C., Martella, D., Wiersma, D.S., Adv. Opt. Mater. 2018,1800207.
 Deubel, M., Von Freymann, G., Wegener, M., Pereira, S., Busch, K., Soukoulis, C.M., Nat. Mater. 2004, 3, 444.
 Zeng, H., Wasylczyk, P., Parmeggiani, C., Martella, D., Burresi, M., Wiersma, D.S., Adv. Mater. 2015, 27, 3883.
 Martella, D., Nocentini, S., Nuzhdin, D., Parmeggiani, C. and Wiersma, D.S., Adv. Mater. 2017, 29, 1704047.
 Nocentini, S., Martella, D., Parmeggiani, C., Zanotto, S., Wiersma, D.S., Adv. Opt. Mater. 2018, 1800167.
 Nocentini, S., Riboli, F., Burresi, M., Martella, D., Parmeggiani, C., Wiersma, D.S., ACS Photonics 2018, 5, 3222.
The research leading to these results has received funding from Ente Cassa di Risparmio di Firenze (grant 2017/0881 and 2017/0713).