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Authors Glatz, B.A. ; Fery, A.
Title The influence of plasma treatment on the elasticity of the in situ oxidized gradient layer in PDMS: towards crack-free wrinkling
Date 01.01.2019
Number 56037
Abstract Controlled surface wrinkling is widely applied for structuring surfaces in the micro- and nano-range. The formation of cracks in the wrinkling process is however limiting applications, and developing approaches towards crack-free wrinkles is therefore vital. To understand crack-formation, we systematically characterized the thickness and mechanics of thin layers formed by O2-plasma-oxidation of polydimethyl siloxane (PDMS) as a function of plasma power and pressure using Atomic Force Microscopy Quantitative Nano-mechanical Mapping (AFM-QNM). We found a nearly constant layer thickness with simultaneously changing Youngs moduli for both power and pressure screenings. We determined the respective crack densities, revealing conditions for crack-free wrinkling. Thus we could identify correlations between the intensity of plasma treatment and the cracking behavior. The primary cause for crack-suppression is a continuous elasticity gradient starting within the soft bulk PDMS, and rising up to several hundred MPa at the oxidized layers surface. With mechanical simulations via the Finite Elements Method (FEM) we were able to demonstrate a noticeable difference in maximal stress intensity smax between a comparable, but theoretical single layer and a gradient interface. A threshold in tensile stress of scrit = 14 MPa distinguishes between intact and cracked layers.
Publisher Soft Matter
Wikidata
Citation Soft Matter 15 (2019) 65-72
DOI https://doi.org/10.1039/C8SM01910J
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