Nanoporous Monolithic Microsphere Arrays Have Anti-Adhesive Properties Independent of Humidity
by
Anna Eichler-Volf 1
, Longjian Xue 2,*, Alexander Kovalev 3, Elena V. Gorb 3, Stanislav N. Gorb 3,* and Martin Steinhart 1,*
Anna Eichler-Volf 1, Longjian Xue 2,*, Alexander Kovalev 3, Elena V. Gorb 3, Stanislav N. Gorb 3,* and Martin Steinhart 1,*
1
Institut für Chemie neuer Materialien, Universität Osnabrück, Barbarastr. 7, Osnabrück 49069, Germany
2
School of Power and Mechanical Engineering, Wuhan University; Donghu South Road 8, Wuhan 430072, China
3
Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 9, Kiel 24118, Germany
*
Authors to whom correspondence should be addressed.
Academic Editor: Frank A. Müller
Materials 2016, 9(5), 373; https://doi.org/10.3390/ma9050373
Received: 19 April 2016 / Revised: 9 May 2016 / Accepted: 10 May 2016 / Published: 14 May 2016
(This article belongs to the Special Issue Bioinspired and Biomimetic Materials)
Bioinspired artificial surfaces with tailored adhesive properties have attracted significant interest. While fibrillar adhesive pads mimicking gecko feet are optimized for strong reversible adhesion, monolithic microsphere arrays mimicking the slippery zone of the pitchers of carnivorous plants of the genus Nepenthes show anti-adhesive properties even against tacky counterpart surfaces. In contrast to the influence of topography, the influence of relative humidity (RH) on adhesion has been widely neglected. Some previous works deal with the influence of RH on the adhesive performance of fibrillar adhesive pads. Commonly, humidity-induced softening of the fibrils enhances adhesion. However, little is known on the influence of RH on solid anti-adhesive surfaces. We prepared polymeric nanoporous monolithic microsphere arrays (NMMAs) with microsphere diameters of a few 10 µm to test their anti-adhesive properties at RHs of 2% and 90%. Despite the presence of continuous nanopore systems through which the inner nanopore walls were accessible to humid air, the topography-induced anti-adhesive properties of NMMAs on tacky counterpart surfaces were retained even at RH = 90%. This RH-independent robustness of the anti-adhesive properties of NMMAs significantly contrasts the adhesion enhancement by humidity-induced softening on nanoporous fibrillar adhesive pads made of the same material.
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Keywords:
block copolymers; microspheres; monolayers; monoliths; surfaces; adhesion; biomimetics; nanoporous materials
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MDPI and ACS Style
Eichler-Volf, A.; Xue, L.; Kovalev, A.; Gorb, E.V.; Gorb, S.N.; Steinhart, M. Nanoporous Monolithic Microsphere Arrays Have Anti-Adhesive Properties Independent of Humidity. Materials 2016, 9, 373.
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