Light‐Fueled Climbing of Monolithic Torsional Soft Robots via Molecular Engineering

Abstract

Azobenzene‐functionalized liquid crystalline polymer networks (azo‐LCNs) are promising candidates for light‐fueled contactless manipulation of miniaturized soft robots through embedding photoactive molecular switches into alignment‐programmable LCNs. In particular, the 3D helical geometry of azo‐LCNs is reported to achieve rapid photomotility by introducing rolling resistance. However, the maximum height of the obstacle that soft robot can overcome is limited by the helix diameter and the stress–strain responsivity. Herein, the helical diameter per unit length and photogenerated stress through molecular engineering of photoactive molecular switches are maximized. The carbon number of aliphatic spacers in the photoactive molecular switches is varied from two to eight to systematically investigate the structure–property–performance relations by studying the molecular geometry, physical properties of polymers, and photomotility of polymers. Furthermore, a finite‐element analysis simulation is presented to understand the rolling locomotion of helical torsional soft robots. Through molecular engineering, the helix diameter per unit length of 0.2 mg soft robots is maximized, demonstrating high Young's modulus (≈2 GPa) and photogenerated stress (>1 MPa), as well as large velocity per body length, compared with the previously reported soft robots. Finally, the molecularly engineered soft robots successfully climb stairs, which is a key task in robotic systems.

Self‐Sustained Snapping Drives Autonomous Dancing and Motion in Free‐Standing Wavy Rings

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Snapping has enabled diverse unique functionalities, including amplified force and fast response, [15] high-speed motion (crawling, [16] swimming, [16,17] and jumping [18][19][20][21] ), physical intelligence, [22] and mechanical memory operation. [23] Among different soft active materials, anisotropic smart materials such as liquidcrystal polymers (LCPs) [24][25][26] have recently attracted growing interest in untethered actuation and motion [27][28][29][30] due to their two-way shape memory effects. LCPs can reversibly shrink or elongate by shifting between the nematic and the isotropic states in response to thermal, photo-, or chemical stimulations.

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Agile Underwater Swimming of Magnetic Polymeric Microrobots in Viscous Solutions

“…The miniaturized polymeric robots are manipulated through shape morphing of local position in the robots or rotational or translational motion of the whole bodies. [11] Photo-triggered actuation is driven by local shape morphing of photoisomerized liquid crystalline polymers [12,13] and local volumetric changes in hydrogels. [14] Spatiotemporal control of light further allows on-demand shape morphing of photoactive liquid crystalline polymers.…”

Fabrication of a tunable photothermal actuator via in situ oxidative polymerization of polydopamine nanoparticles in hydrogel bilayers

“…Light-responsive actuators have been developed by introducing either light-responsive polymers (e.g., azopolymers 13,14 or azocompound-functionalized liquid crystal elastomers) 15 or temperature-responsive polymers (e.g., hydrogels 16 and liquid crystal elastomers 17 ) into photothermal materials that can convert light into thermal energy through the photothermal effect. In the case of an azopolymer-based actuator, the actuation condition is solely dependent on the intrinsic photoisomerization property of the azocompound.…”