Selective Decrosslinking in Liquid Crystal Polymer Actuators for Optical Reconfiguration of Origami and Light‐Fueled Locomotion

Abstract

The ability to optically reconfigure an existing actuator of al iquid crystal polymer network (LCN) so that it can displayan ew actuation behavior or function is highly desired in developing materials for soft robotics applications. Demonstrated here is apowerfulapproach relying on selective polymer chain decrosslinking in aLCN actuator with uniaxial LC alignment. Using an anthracene-containing LCN,spatially controlled optical decrosslinking can be realized through photocleavage of anthracene dimers under 254 nm UV light, which alters the distribution of actuation (crosslinked) and non-actuation (decrosslinked) domains and thus determines the actuation behavior upon order-disorder phase transitions. Based on this mechanism, asingle actuator having aflat shape can be reconfigured in an on-demand manner to exhibit reversible shape transformation such as self-folding into origami three-dimensional structures.M oreover,u sing ad yedoped LCN actuator,alight-fueled microwalker can be optically reconfigured to adopt different locomotion behaviors, changing from moving in the laser scanning direction to moving in the opposite direction.

A Soft Transporter Robot Fueled by Light

“…[27] In recent years, a variety of centimeter-sized light-driven soft robots based on LCNs have been demonstrated, [6] yet design and locomotion freedoms in dry environment remain limited to one dimension, either forward [28][29][30] or forward and backward. [31][32][33][34][35][36] Unidirectional locomotion strategies such as inchworm, [28,37] snail, [34] and Mobile organisms with ability for locomotion and transportation, such as humans and other animals, utilize orchestrated actuation to perform actions. Mimicking these functionalities in synthetic, light-responsive untethered soft-bodied devices remains a challenge.…”

Shining Light on Liquid Crystal Polymer Networks: Preparing, Reconfiguring, and Driving Soft Actuators

“…b) Using selective photo‐decrosslinking to optically reconfigure locomotion of light‐fueled microwalker using a dye‐doped LCN actuator: the walking of an arch‐shaped actuator along the laser scanning direction being reconfigured into the crawling of a wrinkle‐shaped actuator against the laser scanning direction. Reproduced with permission . Copyright 2019, Wiley‐VCH.…”

“…By selectively photo‐decrosslinking a given LCN containing photocleavable cross‐links, our group recently developed an LCN that can realize a series of reversible shape transformations or locomotion on demand through optically reconfiguring the same sample . A given LCN, which was first uniformly cross‐linked based on photodimerization of anthracene groups, was irradiated using 254 nm UV light at room temperature in selected areas to induce local photocleavage of anthracene dimers.…”

“…Most notably is the use of light to prepare the surface alignment layer that orients mesogens and defines the LC director field (referred to as photo‐orientation) and the use of light to cross‐link polymer chains in spatially selected regions (denoted as photopatterning) . Second, several approaches have been demonstrated to enable the use of light to reconfigure an existing actuator so that it can display different shape changes or even different locomotion behaviors upon exposure to an identical stimulus . Third, since the reversible shape change is determined by an order–disorder phase transition and light is a convenient way to induce the order–disorder phase transition, light can also be used to control the shape change or drive the locomotion of an LCN actuator (such as walking, climbing, and swimming) .…”

Viewpoint: Pavlovian Materials—Functional Biomimetics Inspired by Classical Conditioning

“…Unlike shape‐changing materials, classical one‐way shape‐memory materials cannot remember the previous temporary states once recovered. Recently, the borderline between the shape‐changing and shape‐memory materials has been blurred by reconfiguration strategies based on dynamic chemical bonding (or in some cases optical approaches) that allows programmable shape morphing even after the materials have been fabricated, and by two‐way shape‐memory materials capable of reversibly switching between the temporary and permanent shapes . By tuning the chemistry, responsive materials can be designed to be multi‐responsive and to possess even more versatile shape‐shifting capabilities and multiple shape‐memory effects .…”