Synthesis and electromechanical actuation of a temperature, pH, and electrically responsive hydrogel

Abstract

Hydrogels that are capable of responding to electrical stimuli, pH, and temperature are of great interest for developing artificial muscles, biosensors, drug release devices, etc. This study reports on the synthesis, characterization, and performance of a responsive conducting hydrogel, designed and prepared to be part of an artificial muscle system. This hydrogel was obtained using two basic components: (1) poly(isopropyl acrylamide–co–acrylic acid) and (2) polyaniline. The samples were homogeneous and well-integrated, characterized by FTIR and swelling assays. Additionally, the capacity of the hydrogel’s actuation, i.e., the capacity to generate stress, through controlled changes in the temperature and using an electrical stimulus was also tested. The hydrogels proved to be temperature sensitive and were able to generate a contraction stress when a temperature change was applied over a wide range of values, which include the low critical solution temperature (LCST) of poly(N-isopropylacrylamide). The application of an electric field enabled the production of a contraction stress other than that generated by thermosensitivity. Regarding the hydrogel pH sensitivity, the hydrogels showed lower levels of swelling when in contact with low pH solutions.