The Influence of Surface Topography and Surface Chemistry on the Anti-Adhesive Performance of Nanoporous Monoliths

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• 作者：Anna Eichler-Volf ; Longjian Xue ; Gregor Dornberg ; He Chen ; Alexander Kovalev ; Dirk Enke ; Yong Wang ; Elena V. Gorb ; Stanislav N. Gorb ; Martin Steinhart
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：August 31, 2016
• 年：2016
• 卷：8
• 期：34
• 页码：22593-22604
• 全文大小：599K
• 年卷期：0
• ISSN：1944-8252

文摘

We designed spongy monoliths allowing liquid delivery to their surfaces through continuous nanopore systems (mean pore diameter ∼40 nm). These nanoporous monoliths were flat or patterned with microspherical structures a few tens of microns in diameter, and their surfaces consisted of aprotic polymer or of TiO₂ coatings. Liquid may reduce adhesion forces F_Ad; possible reasons include screening of solid–solid interactions and poroelastic effects. Softening-induced deformation of flat polymeric monoliths upon contact formation in the presence of liquids enhanced the work of separation W_Se. On flat TiO₂-coated monoliths, W_Se was smaller under wet conditions than under dry conditions, possibly because of liquid-induced screening of solid–solid interactions. Under dry conditions, W_Se is larger on flat TiO₂-coated monoliths than on flat monoliths with a polymeric surface. However, under wet conditions, liquid-induced softening results in larger W_Se on flat monoliths with a polymeric surface than on flat monoliths with an oxidic surface. Monolithic microsphere arrays show antiadhesive properties; F_Ad and W_Se are reduced by at least 1 order of magnitude as compared to flat nanoporous counterparts. On nanoporous monolithic microsphere arrays, capillarity (W_Se is larger under wet than under dry conditions) and solid–solid interactions (W_Se is larger on oxide than on polymer) dominate contact mechanics. Thus, the microsphere topography reduces the impact of softening-induced surface deformation and screening of solid–solid interactions associated with liquid supply. Overall, simple modifications of surface topography and chemistry combined with delivery of liquid to the contact interface allow adjusting W_Se and F_Ad over at least 1 order of magnitude. Adhesion management with spongy monoliths exploiting deployment (or drainage) of interfacial liquids as well as induction or prevention of liquid-induced softening of the monoliths may pave the way for the design of artificial surfaces with tailored contact mechanics. Moreover, the results reported here may contribute to better understanding of the contact mechanics of biological surfaces.