Tuning response amplitude in nanoimprinted thermoresponsive polymer blend

We demonstrate the potential of thermoresponsive poly N‐(isopropylacrylamide) (PNIPAM) based surfaces in achieving a low‐energy approach to modulate surface wetting for applications such as fog harvesting and anti‐fogging. Alternative to grafting methods, we use a two‐step approach for tuning the response amplitude. First, we blend PNIPAM with a chemically non‐reactive poly (vinylidene fluoride), PVDF (1/3, 1/1, 3/1 by weight). Second, thermal nanoimprint lithography is used to create micro (3, 5, 10, and 20 μm) and nano‐scale (100 and 200 nm) pillars. Nano‐patterned surfaces show a response amplitude of ~30°–50° compared to ~15°–30°, observed for the micro‐patterned surface. X‐ray photo‐electron spectroscopy and energy dispersive X‐ray analysis confirms the reduction of polyvinylidene fluoride phase domains and enrichment of PNIPAM on the nano‐patterned surface. A real‐time dynamic mist condensation study showed that the nano‐patterned blend exhibited a lower temperature range (34/41°C) for on/off (wetting/drying) state compared to an unpatterned blend (37/50°C).