Design of nano- and micro-structured molecule-responsive hydrogels

Stimuli-responsive hydrogels have attracted considerable attention for use as smart materials, such as in molecular sensors and drug delivery systems. With a focus on their crosslinking density, we have prepared various molecule-responsive hydrogels that undergo volume changes in response to target molecules based on the association/dissociation of molecular complexes that act as crosslinkers. Recent developments in polymerization techniques enabled us to design various types of polymer nanomaterials. This focus review provides a short overview of our recent studies on thenano- and micro-structured molecule-responsive hydrogels prepared using various polymerization techniques, such as photopolymerization, surface-initiated atom transfer radical polymerization, andsoap-free emulsion polymerization. The nano- and micro-structured molecule-responsive hydrogels showed not only rapid swelling/shrinkage in response to a target molecule owing to their large surface area but also smart functions, such as autonomous molecule-responsive microchannel flowregulation and highly sensitive detection of a target molecule. The smart functions of nano- and micro-structured molecule-responsive hydrogels can provide tools for constructing, for example, sensors, microdevices and smart biomaterials.This work was partially supported by JSPS KAKENHI grant number 15K17912from MEXT Japan, the Kansai University Subsidy for Supporting YoungScholars, 2013, and the Kao Foundation for Arts and Sciences, 2015