Simple Synthesis of Elastomeric Photomechanical Switches That Self‐Heal

Abstract

This article introduces a simple two‐stage method to synthesize and program a photomechanical elastomer (PME) for light‐driven artificial muscle‐like actuations in soft robotics. First, photochromic azobenzene molecules are covalently attached to a polyurethane backbone via a two‐part step‐growth polymerization. Next, mechanical alignment is applied to induce anisotropic deformations in the PME‐actuating films. Cross‐linked through dynamic hydrogen bonds, the PMEs also possess autonomic self‐healing properties without external energy input. This self‐healing allows for a single alignment step of the PME film and subsequent “cut and paste” assembly for multi‐axis actuation of a self‐folded soft‐robotic gripper from a single degree of freedom optical input.

Bio‐inspired Design and Additive Manufacturing of Soft Materials, Machines, Robots, and Haptic Interfaces

“…[39,40] Light as apower source can be remotely applied at room temperature and controlled by rapid modulation, which makes light-driven soft actuating materials advantageous for potential applications in untethered micro-and macroscale soft robots. [41] Ap revious review by Ikeda et al explicitly introduced the photomechanical effect in polymers,w ith an emphasis on light-driven LCEs. [42] Similar to photoregulated biological processes caused by phototropins in many plants, [43] photoresponsive properties can be introduced into apolymer matrix by covalently incorporating photochromic molecules, such as azobenzene.U pon irradiation with ultraviolet (UV) or visible light, this molecule can effectively absorb light energy and reversibly experience trans-cis isomerization, thereby inducing as ignificant change in the free volume.…”

“…Theg reat straining polymer networks via fluids grippers, [9] [15] mobile soft robots, [16,19,20] biomimetics [8] simple fabrication,r apid actuation/require tethered power source (DIW,S LA) electricallyd riven (dielectric elastomer actuators) electroactive polymers (e.g. acrylic elastomers, silicones, polyurethanes), compliant electrodes electrostatic pressures by large electric fields artificialm uscles, [22-26, 28, 29] biomimetics [27] rapid actuation/require high voltage and may suffer electrical breakdowns thermally driven (liquid-crystalline elastomers) liquid-crystal mesogens in polymer network reversible anisotropic-toisotropic phase transition biomimetics, [38] artificial muscles [39,40] rapid, wireless actuation/ high temperature, may require complex synthesis or processing (DIW) light-driven (azobenzene-containing LCEs) azobenzene LC mesogens in polymer network UV-triggered trans-cis isomerizationo fazobenzene and room-temperature phase transition gripper, [41] biomimetics, [45,46] mobile soft robots, [47][48][49] wireless, rapid, room-temperature actuation, 3D movement/low energy efficiency,l ow force magnetically driven magnetic fillers embedded in polymer network magnetic force or torque caused alignment microrobots or mobile soft robots, [50,52,[55][56][57] biomimetics, [51,53] biomedical devices [54] wireless, rapid actuation/ require programmed domains (DIW) chemicallyr esponsive (osmotic-based actuators/animal dermis) hydrogels mass transport of solvent caused swelling biomimetics, [63] grippers, [64,65] artificial muscles [66,67] combinablew ith other actuation schemes/low speed, require aqueous environment (DIW,S LA) permeability of most environments allows it further to be used in confined space,such as bio-inspired microrobots, [53][54]…”

“…Light as a power source can be remotely applied at room temperature and controlled by rapid modulation, which makes light‐driven soft actuating materials advantageous for potential applications in untethered micro‐ and macroscale soft robots . A previous review by Ikeda et al explicitly introduced the photomechanical effect in polymers, with an emphasis on light‐driven LCEs .…”

Bioinspiriertes Design und additive Fertigung von weichen Materialien, Maschinen, Robotern und haptischen Schnittstellen

“…Licht als Energiequelle kann bei Raumtemperatur aus der Ferne angewendet und bei schneller Modulation gesteuert werden, was lichtgesteuerte weiche Aktuatormaterialien vorteilhaft für mögliche Anwendungen in netzunabhängigen weichen Robotern im Mikro‐ und Makromaßstab macht . Ein früherer Übersichtsartikel von Ikeda et al.…”

Solar‐Driven Soft Robots

“…[ 5 ] While these materials offer some forms of actuation for small scale devices, they operate with high energy photons in the UV spectrum or high intensity infrared light generating temperatures >150 °C making them not suitable for driving soft robots to perform untethered manipulation or locomotion at larger scales. Other types of nonthermal light‐induced actuation mechanisms such as photostriction, [ 5 ] cis – trans photoisomerization in azobenzenes, [ 5 ] photomechanical elastomers, [ 26 ] and photoreversible [2+2] cycloaddition reactions in polymers containing cinnamic groups exist. [ 27 ] Nonetheless, they operate with UV light—with exposure time of more than an hour, exhibit slow response time and small strain/stress not sufficient for realization in high performance soft robotic embodiments.…”