Rapid response of thermo-sensitive hydrogels with porous structures

Poly(N-isopropylacrylamide)(PNIPAAm) hydrogel is thermo-sensitive, and undergoes a volume phase transition from a swollen state to a shrunken state. Typically, after immersing poly(N-isopropylacrylamide) hydrogels into hot water above the critical temperature, they undergo a two-step shrinking process, which leads to very slow dynamics. However, potential applications, including soft actuators, drug delivery systems, and cell cultures, demand a quick response. Herein, we synthesize chemically crosslinked PNIPAAm porous hydrogels made of nanofiber mats. Our hydrogels rapidly shrink without the two-step shrinking. The response of this porous gel is over 100 times faster than that of the typical gel.