Case studies Chemical Engineering and Chemistry 2015-2021

Appendix B: Case studies 7 B.2. LIGHT-RESPONSIVE LIQUID-CRYSTAL POLYMERS FOR SOFT ROBOTICS Context Soft robots are currently receiving a lot of attention as the use of compliant materials can improve their safety when working in close contact with fragile objects and humans. In contrast to hard robots, in which stiff segments limit the adaptability and versatility of devices, soft robots are fully comprised of soft materials that better emulate living, soft-bodied organisms and are more suitable for interactions with humans. However, promising applications are limited by the dependence on electrical or pneumatic tethers. To free soft robots from tethering to external or heavy on-board control units, the development and assembly of polymers which undergo macroscopic deformations in response to light is of great importance. Marina Pilz da Cunha’s PhD research in the Stimuli-responsive Functional Materials & Devices group focused on light- responsive liquid crystal polymers. Her thesis reports on three highly innovative advancements related to untethered soft robotics: a fundamental understanding of light-responsive polymers, novel polymer materials and actuator assemblies for making robotic devices. Our research By combining two different stimuli-responsive materials in a single soft robotic device, she demonstrated how assemblies of soft actuators can expand device functionality and allow for the completion of multiple tasks that are not possible for single-component systems. In this part of Marina’s research, collaboration with the Microsystems group of Jaap de Toonder in the Department of Mechanical Engineering was of crucial importance. Collaborating with researchers in the Department of Mechanical Engineering stimulated her immensely in thinking beyond a fundamental understanding and fabricating novel polymer materials, leading to light- driven robotic devices that can perform tasks. For example, sheadvanced the stateof theart in light-drivenuntetheredsoft robotsby reportinga multi-functional robot based on liquid-crystalline polymers employing two different azobenzene derivatives making up the device’s ‘arms’ or ‘legs’. The first fully light-fueled mini-transporter can perform multi-directional locomotion and functions including pick-up, transportation and directional release of a cargo (Figure 1). She further developed an untethered multimodal light-driven aquatic device that integrates two different stimuli-responsive materials, a flexible magnetic polymer stem and a light-responsive azobenzene-doped liquid-crystal network gripper. The independent device segments can be orthogonally controlled to realize different functions: magnetic-driven stirring and light-triggered gripping within the same device. Figure 1: a) Transport mini-robot with light-responsive legs and arms, able to deliver cargo. b) The different appendages have different light-responsive molecules. c, d) The light-driven transporter in action, wirelessly walking and making a turn.