Bioinspired Self-Resettable Hydrogel Actuators Powered by a Chemical Fuel

Abstract

The movements of soft living tissues, such as muscle, have sparked a strong interest in the design of hydrogel actuators; however, so far, typical manmade examples still lag behind their biological counterparts, which usually function under nonequilibrium conditions through the consumption of high-energy biomolecules and show highly autonomous behaviors. Here, we report on self-resettable hydrogel actuators that are powered by a chemical fuel and can spontaneously return to their original states over time once the fuels are depleted. Self-resettable actuation originates from a chemical fuel-mediated transient change in the hydrophilicity of the hydrogel networks. The actuation extent and duration can be programmed by the fuel levels, and the self-resettable actuation process is highly recyclable through refueling. Furthermore, various proof-of-concept autonomous soft robots are created, resembling the movements of soft-bodied creatures in nature. This work may serve as a starting point for the development of lifelike soft robots with autonomous behaviors.

Chemical energy assisted self-assembling of a porphyrin-substituted benzoic acid in complex environments

“…3 With the continuously supported compound EDC as the chemical fuel, these anhydrides were able to further assemble into functional transient supramolecular structures, as demonstrated by Boekhoven, Hartley and other groups. 3 b ,4 However, in our present study, we noticed that the reaction between EDC and a porphyrin-substituted benzoic acid ( POR-COOH , Fig. 2b) did not result in the insoluble anhydride intermediate.…”

Temporary Actuation of Bilayer Polymer Hydrogels Mediated by the Enzymatic Reaction

“…To generate a multiple or cyclic response, it is usually necessary to provide multiple stimuli, which limits the development of stimuli-responsive hydrogels as a kind of smart actuators. To overcome this shortcoming, scientists recently coupled stimulus-responsive hydrogels with synthetic chemical reaction networks or pH oscillation devices to achieve the programed or periodic deformation of hydrogels. − These studies highlight the importance and necessity of constructing soft actuators with temporally controlled deformation abilities.…”

Recent progress of fuel-driven temporary materials

“…In 2022, F. Xuan, Y. Wang, and coworkers demonstrated an EDC-driven hydrogel actuator based on poly(acrylic acid) (PAA). [37] As shown in Figure 3c, the addition of the EDC led to the deswelling of the PAA hydrogel, which can self-relax with the slow hydrolysis of the anhydride linkage. The temporary deformation is repeatable by the refueling of the EDC.…”

“…Thus, to avoid the high toxicity, carbodiimide, for example, 1-ethyl-3-(3-(dimethylamino)propyl)-carbodiimide (EDC), was used to replace the iodomethane or dimethyl sulfate to initiate the temporary gelation of precursors containing carboxyl groups. [23,[31][32][33][34][35][36][37] As shown in Figure 3a, D. Haldar and coworkers presented a temporary hydrogel of which the precursor was benzyloxycarbonyl-L-phenylalanine (ZF). [35] Upon the addition of EDC, two ZF molecules rapidly condensed to an anhydride gelator, yielding a self-supporting, translucent gel.…”