Thermal-responsive hydrogel surface: tunable wettability and adhesion to oil at the water/solid interface

We present a thermal-responsive poly(N-isopropylacrylamide) (PNIPAM) hydrogel, which can responsively and reversibly control the wettability and adhesion to oil at water/solid interface. The hydrogel surface can switch from a superoleophobic and low adhesive state below the PNIPAM lower critical solution temperature (LCST, similar to 32 degrees C) to an oleophobic and high adhesive state above its LCST. Moreover, the thermal-responsive wettability and adhesion to oil at the water/solid interface can be tailored by designing and constructing ordered micro-structures on the surface. We demonstrated the thermal-responsive changing of the topography on PNIPAM hydrogel surface by atomic force microscopy and proposed a mechanism of inter-molecular to intra-molecular hydrogen binding transitions. We believe the reported material has promising utilizations in micro fluidics, control of bio-relevant adhesion and under-water antifouling materials.