Anisotropic volume change of poly(N-isopropylacrylamide)-based hydrogels with an aligned dual-network microstructure

A macroscopically anisotropic PEG–PNIPA hydrogel with a novel aligned dual-network microstructure has been fabricated, which displays a unique anisotropic two-dimensional shrinkage in response to a temperature increase. It consists of an aligned porous PEG scaffold as the primary network and PNIPA polymer inside the pores as the second network. The aligned porous PEG scaffold plays a critical role in achieving the anisotropic shrinkage by not only templating formation of the PNIPA microcylinders but also constraining the axial shrinkage of the cylindrical samples.