Autonomic Hydrogels through Postfunctionalization of Gelatin

Autonomic systems in biology, such as the circulatory system, function independently without an external stimulus. Materials that mimic this behavior hold promise for energy and medical technologies in the form of sensors, energy conversion units, and versatile micrometer scale machinery. Self-oscillating hydrogels driven by the Belousov–Zhabotinsky (BZ) reaction are one class of autonomic materials that convert chemical energy to mechanical swell–deswell motion. Effective feedback control techniques, as well as materials and processing options, are key challenges in making these materials technologically relevant. To address these challenges we have expanded BZ hydrogel materials options, by utilizing a flexible water-based succinimide–amine coupling reaction for functionalizing bio- and synthetic polymers containing primary amines for use in BZ devices. Herein we characterize the chemomechanical behavior of homogeneous BZ gelatin gels and determine the range of periods and strains attainable. We highlight the two most distinctive, and technologically relevant, features of BZ-gelatin, specifically, its ability to be postfunctionalized with Ru(sbpy) after gel formation and its ability to be patterned into compositionally heterogeneous composites via physical solidification through the thermal reversibility of its melt-gel transition.