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 degrees 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.