Digital light processing of liquid crystal elastomers for self-sensing artificial muscles

Abstract

Artificial muscles based on stimuli-responsive polymers usually exhibit mechanical compliance, versatility, and high power-to-weight ratio, showing great promise to potentially replace conventional rigid motors for next-generation soft robots, wearable electronics, and biomedical devices. In particular, thermomechanical liquid crystal elastomers (LCEs) constitute artificial muscle-like actuators that can be remotely triggered for large stroke, fast response, and highly repeatable actuations. Here, we introduce a digital light processing (DLP)–based additive manufacturing approach that automatically shear aligns mesogenic oligomers, layer-by-layer, to achieve high orientational order in the photocrosslinked structures; this ordering yields high specific work capacity (63 J kg−1) and energy density (0.18 MJ m−3). We demonstrate actuators composed of these DLP printed LCEs’ applications in soft robotics, such as reversible grasping, untethered crawling, and weightlifting. Furthermore, we present an LCE self-sensing system that exploits thermally induced optical transition as an intrinsic option toward feedback control.

Cooling‐Accelerated Nanowire‐Nitinol Hybrid Muscle for Versatile Prosthetic Hand and Biomimetic Retractable Claw

“…Therefore, as summarized in Table S1, Supporting Information, the linear actuation performance of CuNF-SMAc artificial muscle showed high actuation bandwidth with a large stroke among other types of previously reported artificial muscles, while at the same time, preserving the advantageous feature of SMA having high work capacity and power density. [41][42][43][44][45][46][47][48][49] Such cooling-accelerated CuNF-SMAcs were directly applied as artificial muscles for a prosthetic hand in which the CuNF-SMAc artificial muscles were used to bend and straighten individual fingers. Although there have been several interesting prosthetic hands developed based on soft artificial muscles, slow actuation speed of the prosthetic hand was always discussed as must-be-solved issue, especially for those fabricated using artificial muscles that actuate under thermomechanical principle.…”

A Shift from Efficiency to Adaptability: Recent Progress in Biomimetic Interactive Soft Robotics in Wet Environments

“…A typical actuator, also known as artificial muscle, is the work horse of soft robots. [ 34 ] It typically needs external stimuli, such as water, [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ] pH, [ 46 , 47 , 48 , 49 , 50 ] heat, [ 47 , 51 , 52 , 53 , 54 , 55 , 56 , 57 ] light, [ 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 ] electricity, [ 53 , 66 , 67 , 68 , 69 , 70 , 71 ] and magnetic field to perform. [ 27 , 72 , 73 , 74 , 75 ] In recent years, soft actuators can be classified based on materials as elastomeric pneumatic actuator (PA), hydrogel actuator (HA), bio‐hybrid actuator (BHA), actuators made of DE, twisted and coiled yarns (TCY), SMA, liquid crystal elastomers (LCE), and ionic polymer‐metal composites (IPMC).…”

Progress in Utilizing Dynamic Bonds to Fabricate Structurally Adaptive Self‐Healing, Shape Memory, and Liquid Crystal Polymers

“…The use of 3D printing in preparing LCE actuators, including the fabrication of mesogen orientation and macroscopic shape design, has also become a research hotspot in this field. [274][275][276][277][278][279][280][281][282] However, materials suitable for printing are still limited due to the necessary mesogens orientation and rheological property of ink. Therefore, the combination of dynamic LCE network with 3D printing will certainly enrich the variety of LCEs suitable for 3D printing.…”