title: Facile creation of hierarchical PDMS microstructures with extreme underwater superoleophobicity for anti-oil application in microfluidic channels.
abstract: Composition modification and surface microstructures have been widely utilized in interface science to improve the surface performance. In this paper, we observed a significant improvement of oil contact angle (CA) from 66 ± 2° to 120 ± 4° by introducing a radical silanol group on a flat PDMS surface through oxygen plasma pretreatment. By combining surface microstructures and plasma modification, we produced three kinds of superoleophobic surfaces: 20 μm pitch micropillar arrays, 2.5 μm pitch micropillar arrays and gecko foot-like hierarchical microstructures. Among them, the hierarchical surface with high surface roughness showed extreme underwater superoleophobicity, which featured ultrahigh CA (175 ± 3°) and ultrasmall sliding angle (<1°). Quantitative measurements demonstrated that these superoleophobic surfaces exhibited distinct adhesive behaviors, by which they were interpreted as Wenzel's, Cassie's and the Lotus state, respectively. A microfluidic channel with superoleophobic microstructures was further created by novel curve-assisted imprint lithography, and the characterization based on anti-oil contamination applications was carried out and discussed. We believe that the superoleophobic surfaces will power broad applications in oil microdroplet transportation, anti-oil channels and droplet microfluidic systems.
authors.affiliation: State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun, China.
authors.forename: Dong
authors.initials: D
authors.lastname: Wu
authors.forename: Si-zhu
authors.initials: SZ
authors.lastname: Wu
authors.forename: Qi-Dai
authors.initials: QD
authors.lastname: Chen
authors.forename: Shuai
authors.initials: S
authors.lastname: Zhao
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Jian
authors.initials: J
authors.lastname: Jiao
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Piersol
authors.forename: Jian-Nan
authors.initials: JN
authors.lastname: Wang
authors.forename: Hong-Bo
authors.initials: HB
authors.lastname: Sun
authors.forename: Lei
authors.initials: L
authors.lastname: Jiang