Chemomechanical self-oscillating gels driven by redox oscillations of terpyridine-based iron complexes as materials for soft actuators

Abstract

Self-oscillating chemomechanical redox-responsive poly(N-isopropylacrylamide) gels containing terpyridine-iron complexes were developed. Two types of gels containing the complexes as pendant groups or as cross-linking agents were designed and prepared. All the obtained gels exhibited pronounced chemomechanical oscillations resulting from the Belousov–Zhabotinsky reaction within their structure. They periodically swelled and contracted upon oxidation and reduction of the terpyridine–iron complex under mild conditions and at low mineral acid concentrations. The periodic changes in linear dimensions of the gels reached 17%. It was found that the propagating chemical wave moved along the cylindrical gel causing autonomous peristaltic motion due to local swelling. Based on the obtained gel, a lever-type actuator was created demonstrating periodic lifting of the lever. The gels were characterized through scanning electron microscopy, and the dependence of their structure and chemomechanical properties on the catalyst concentration was investigated. These gels hold great promise for creating soft and self-moving muscle-like actuators, devices capable of transmitting and interpreting signals through traveling chemical waves, and sensor systems that respond to changes in oxidation-reduction states.

Graphical abstract

Keywords

chemomechanical self-oscillating gel / actuator / terpyridine-based iron complex / Belousov–Zhabotinsky reaction

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