Actuation of Hydrogel Architectures Prepared by Electrophoretic Adhesion of Thermoresponsive Microgels

Owing to their unique properties, hydrogels may be used for preparing soft actuators. Soft actuators are expected to respond quickly; however, the response speed of gels is slow. To study this issue and overcome it, thermoresponsive soft actuators were prepared by the electrophoretic adhesion of cationic and anionic thermoresponsive microgels, comprising poly(diallyldimethylammonium chloride) and poly(styrenesulfonate) sodium salt, respectively. The kinetics of the prepared hydrogel architectures in response to temperature depended on the microgel diameter instead of the architecture size. We also prepared bilayered hydrogel architectures by adhesion of thermoresponsive and/or nonthermoresponsive microgels. These bent rapidly in response to temperature because these architectures consisted of microgel assemblies. In addition, specific bending motion was demonstrated by the adhesion of microgel layers of different sizes. The present study provides not only a guideline for the design of hydrogel actuators with quick response but also presents a method for the free-form fabrication of functional hydrogel materials that undergo complex motions in response to stimuli.