Smart surfaces: reversible switching of a polymeric hydrogel topography

Patterns imprinted on smart surfaces are fabricated by direct laser interference patterning (DLIP) of thick films based on poly(N-isopropylacrylamide) (PNIPAM) doped with suitable dyes. Optical and atomic force (AFM) microscopy images reveal that the pattern imprinted on the dry hydrogel film (line-arrays) becomes flat due to swelling of the hydrogel upon immersion in water. The pattern re-emerges after drying the hydrogel. Heating the hydrogel above the phase transition temperature of PNIPAM (ca. 32 °C) also restores the pattern by hydrogel volume collapse. This behaviour suggests that this patterning technique would allow us to produce surfaces useful for technological application.