Liquid‐Crystalline Soft Actuators with Switchable Thermal Reprogrammability

Abstract

Thermal reprogrammability is essential for new‐generation large dry soft actuators, but the realization sacrifices the favored actuation performance. The contradiction between thermal reprogrammability and stability hampers efforts to design high‐performance soft actuators to be robust and thermally adaptable. Now, a strategy has been developed that relies on repeatedly switching on/off thermal reprogrammability in liquid‐crystalline elastomer (LCE) actuators to resolve this problem. By post‐synthesis swelling, a latent siloxane exchange reaction can be induced in the common siloxane LCEs (switching on), enabling reprogramming into on‐demand 3D‐shaped actuators; by switching off the dynamic network by heating, actuation stability is guaranteed even at high temperature (180 °C). Using partially black‐ink‐patterned LCEs, selectively switching off reprogrammability allows integration of completely different actuation modes in one monolithic actuator for more delicate and elaborate tasks.

Smart Polymers for Microscale Machines

“…Using this method, helical shape transformation can be obtained by stretching the film around a cylindrical object ( Figure a). [ 129,132,158 ] For example, a helical transformation was obtained by an exchangeable liquid crystalline epoxy thermoset. [ 132 ] The mesogens were aligned by mechanical stretching around a cylindrical object and fixed at a high T V of 180 °C.…”

“…Reproduced with permission. [ 158 ] Copyright 2020, Wiley–VCH. b) Shape‐morphing obtained by selected polymerization for a mechanical stretched strip with mono‐ and polydomains.…”

“…This strategy obtaining 3D to planar transformation has also been used by other groups. [ 127,132,158 ] This 3D to planar transformation can also be achieved by crosslinking the LCE at a temperature higher than the operation temperature to create residual stress during photopolymerization. [ 128a,133,165 ]…”

“…[ 155a ] Black ink was also found to be sufficient for NIR absorption as demonstrated by a LCE hook with black ink coated on the surface of the hook. [ 158 ]…”

A New Strategy of Discretionarily Reconfigurable Actuators Based on Self‐Healing Elastomers for Diverse Soft Robots

“…The process of reconfiguring a single actuator to exhibit multiple actuation modes promotes optimum utilization of resources, and sustainability. [ 29 ] Reconfiguration is also expected to be the key to developing a new generation of adaptive soft actuators with advanced tunable deformation capabilities. [ 29,30 ]…”