Liquid Crystal Networks on Thermoplastics: Reprogrammable Photo‐Responsive Actuators

Abstract

Arbitrary shape (re)programming is appealing for fabricating untethered shape‐morphing photo‐actuators with intricate configurations and features. We present re‐programmable light‐responsive thermoplastic actuators with arbitrary initial shapes through spray‐coating of polyethylene terephthalate (PET) with an azobenzene‐doped light‐responsive liquid crystal network (LCN). The initial geometry of the actuator is controlled by thermally shaping and fixing the thermoplastic PET, allowing arbitrary shapes, including origami‐like folds and left‐ and right‐handed helicity within a single sample. The thermally fixed geometries can be reversibly actuated through light exposure, with fast, reversible area‐specific actuation such as winding, unwinding and unfolding. By shape re‐programming, the same sample can be re‐designed and light‐actuated again. The strategy presented here demonstrates easy fabrication of mechanically robust, recyclable, photo‐responsive actuators with highly tuneable geometries and actuation modes.

Light Tracking and Light Guiding Fiber Arrays by Adjusting the Location of Photoresponsive Azobenzene in Liquid Crystal Networks

“…[1][2][3] Among various external energy sources, photon energy provides a promising and versatile platform to construct untethered actuators featured with a high degree of flexibility, accuracy, and programmability. [4][5][6] Heliotropism, the motion of flowers or leaves in response to the position of the sun to maximize energy harvesting, provides inspiration for researchers for the development of light responsive materials and optical light guiding elements. [7] Heliotropismlike actuators have been developed to achieve light tracking in artificial fiber arrays based on a feedback loop involving photothermal effects and the mechanical properties of the polymers employed.…”

Reconfigurable Soft Actuators with Multiple‐Stimuli Responses

“…[ 29 ] Recently, Schenning and co‐workers showed a thermoplastic bilayer actuator consisting of polyethylene terephthalate (PET) and LCN. [ 30 ] Through thermal‐induced shape programming, the actuator can be re‐shaped from folded geometries into more classical bent or helical shape actuators, opening a door to facilely prepare shape‐reconfigurable actuators.…”

“…In addition, for advanced materials, to fabricate composites usually compensate for insufficient on functions for instance bilayer actuators. [ 12,13,30,50,51 ]…”

“…Thermoplastic PET capable of remolding under heating allow it to be reprocessed into any desired permanent shapes. [ 30 ] Meanwhile, PET with high Young's modulus and tensile strength (Table S2, Supporting Information) is suitable to enhance mechanical robustness of soft actuators. [ 30 ] Integrating thermal plasticity and robustness of PET, the bilayer actuator shows a shape reprogrammable characteristic at high temperature.…”

“…[ 30 ] Meanwhile, PET with high Young's modulus and tensile strength (Table S2, Supporting Information) is suitable to enhance mechanical robustness of soft actuators. [ 30 ] Integrating thermal plasticity and robustness of PET, the bilayer actuator shows a shape reprogrammable characteristic at high temperature. Through recyclable shape reconfiguration, we obtained various structural actuators from one sample, such as foldback‐clip‐shaped and Ω‐shaped actuators as shown in Figure 1D.…”