Photo-controllable contact angle hysteresis on an artificial Azo-IPN petal

• Published in: Materials letters 2018-05, Vol.219, p.81-84
• Main Authors: Weng, Cheng-Hsi, Lin, Cheng-Chuan, Tsai, Fu-Cheng, Dai, Chi-An, Yang, Fu-Ling, Shih, Wen-Pin, Chang, Pei-Zen
• Format: Article
• Language: English
• Subjects: Biomimetic; Biomimetics; Contact angle; Contact angle hysteresis; Free energy; Hysteresis; Interpenetrating networks; Light; Materials science; POLYMERS; Surface structure; Surfaces
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2018.02.073

•An interpenetration polymer network with tunable contact angle hysteresis is made.•Micron- and nano-scale surface structures of a rose petal are duplicated.•Surface energy is modulated between trans-to-cis azobenzene photo-isomerations. This paper presents a biomimetic rose petal whose contact angle hysteresis can be reversibly tuned by photo-illumination. With azobenzene interpenetrating polymer network, the micron- and nano-scale surface structure of a rose petal was duplicated. By changing the exposure light wavelength, the surface free energy of the artificial petal was modulated between trans-to-cis azobenzene photo-isomerations. The static contact angle of the artificial petal can be tuned to range from 99.2 ± 0.9° to 140.9 ± 1.8°. The contact angle hysteresis between 50.3 ± 0.6° and >84° can be achieved. Comparing to the value measured on a real rose petal, the fabricated counterpart presents more prominent petal effect in terms of larger static contact angle and greater contact angle hysteresis.