Fabrication of biomimetic device with PS-b-PNIPAAm copolymer pillars mimicking a gecko foot pad

Inspired by the climbing aptitude of geckos, a gecko's foot pad can alternately attach to and detach from almost any kind of surface. We firstly fabricated a multi-layer thin film with electrodes as a thermal device that could adjust the surface temperature by applying voltage. We sequentially used very-large-scale integration (VLSI) process and atom-transfer radical-polymerization (ATRP) process to generate well-defined pillar patterns of polymerized styrene as seta analogues and successively grafted n-isopropylacrylamide (NIPAAm) as thermally responsive terminating of the pillars to mimic the configuration of a real gecko's foot pad. Our fabrication strategy exploits surface textures of polystyrene (PS) and thermally responsive terminating of PNIPAAm, which could generate alternately ca. 88.1 and 11.3 nN of adhesive force at 0.2 and 2 V of applying voltage, respectively. The results indicate that the adjustable adhesive ability of the copolymer brushes could approach the climbing aptitude of a gecko much more closely through voltage tuning. The advantage of the processing strategy described here is the potential to fabricate a device of an artificial foot pad to mimic the climbing aptitude of geckos vividly.