Authors: Y-T Tsai, C-H Choi, E-H Yang
Affilation: Stevens Institute of Technology, United States
Pages: 476 - 479
Keywords: polypyrrole, contact angle hysteresis, surface wettaility
A wettability switchable surface will be demonstrated to study the contact angle hysteresis of liquid droplet. Manipulation of surface wettability can be applied in the field of biomedical (cell-surface interaction) and fluids dynamics (friction reduction). The surface affinity of Polypyrrole (PPy) film can be switched reversibly between hydrophobic and hydrophilic by reduction and oxidation, which needs very low voltage, e.g. -0.5V to 2V. The experiments show that water droplet has 116.5° and 71.5° contact angle on an oxidized and reduced planar PPy surface respectively. According to Wenzel theory, increase of surface roughness can amplify either hydrophobicity or hydrophilicity, which promotes contact angle hysteresis. In this study, a PPy film is integrated with MEMS techniques to create a patterned 3D structure. The dynamic contact angle of water droplet on the fabricated structure will be measured and discussed in this paper. The impact of pattern geometry and oxidized state of PPy is also conducted in this study.