Somatosensory actuator based on stretchable conductive photothermally responsive hydrogel

Abstract

Mimicking biological neuromuscular systems’ sensory motion requires the unification of sensing and actuation in a singular artificial muscle material, which must not only actuate but also sense their own motions. These functionalities would be of great value for soft robotics that seek to achieve multifunctionality and local sensing capabilities approaching natural organisms. Here, we report a soft somatosensitive actuating material using an electrically conductive and photothermally responsive hydrogel, which combines the functions of piezoresistive strain/pressure sensing and photo/thermal actuation into a single material. Synthesized through an unconventional ice-templated ultraviolet–cryo-polymerization technique, the homogenous tough conductive hydrogel exhibited a densified conducting network and highly porous microstructure, achieving a unique combination of ultrahigh conductivity (36.8 milisiemens per centimeter, 103-fold enhancement) and mechanical robustness, featuring high stretchability (170%), large volume shrinkage (49%), and 30-fold faster response than conventional hydrogels. With the unique compositional homogeneity of the monolithic material, our hydrogels overcame a limitation of conventional physically integrated sensory actuator systems with interface constraints and predefined functions. The two-in-one functional hydrogel demonstrated both exteroception to perceive the environment and proprioception to kinesthetically sense its deformations in real time, while actuating with near-infinite degrees of freedom. We have demonstrated a variety of light-driven locomotion including contraction, bending, shape recognition, object grasping, and transporting with simultaneous self-monitoring. When connected to a control circuit, the muscle-like material achieved closed-loop feedback controlled, reversible step motion. This material design can also be applied to liquid crystal elastomers.

In-situ-grown silver–polymer framework with coordination complexes for functional artificial tissues

“…In addition to the aforementioned applications, we also explored PANSion's potential as a sensorized pneumatic actuator for soft robotics applications (Supplementary Text 7). It is worth highlighting that our PANSion actuator, benefiting from in-situ-grown AgNPs, is self-sensing, a feature usually absent for previously reported cases, or which requires additional post-treatments to be achieved (e.g., surface conductive coating) 5,12,19 . Fig.…”

A comparative review of artificial muscles for microsystem applications

“…Kouwer et al presented thermoresponsive polyisocyanopeptide hydrogel networks that mimic cytoskeletal proteins 150 . Based on interpenetrating polymer networks, conductive responsive hydrogels have been developed to realize smart hydrogel artificial muscles with sensing functions 151 , 152 . Zhao et al 152 demonstrated a soft somatosensitive actuator using an interpenetrating polymer double-network of poly(N- isopropylacrylamide) (PNIPAAm) and PANI.…”

A self-powered flexible sensing system based on a super-tough, high ionic conductivity supercapacitor and a rapid self-recovering fully physically crosslinked double network hydrogel

“…In recent years, a lot of advanced intelligent electronic devices have emerged, such as electronic skin, [1][2][3] soft robotics, [4][5][6] and flexible sensors. [7][8][9][10][11] Among them, flexible sensors have attracted wide attention in the field of human health and movement monitoring because they transform complex external mechanical forces into electrical signals that can easily be collected.…”