Surface rippling induced by periodic instabilities on a polymer surface

Year: 2015

Authors: Gnecco E., Pedraz P., Nita P., Dinelli F., Napolitano S., Pingue P.

Autors Affiliation: Campus Univ Cantoblanco, IMDEA Nanociencia, E-28049 Madrid, Spain; Marie Curie Sklodowska Univ, Inst Phys, PL-20031 Lublin, Poland; INO CNR, I-56124 Pisa, Italy; Univ Libre Bruxelles, Fac Sci, Lab Polymer & Soft Matter Dynam, B-1050 Brussels, Belgium; Scuola Normale Super Pisa, Lab NEST, I-56127 Pisa, Italy; CNR, Ist Nanosci, I-56127 Pisa, Italy.

Abstract: When the shear stress on a compliant surface exceeds the yield strength of the material, a periodic wrinkle pattern is often observed. This phenomenon has been also recognized at the nanometer scale on polymers, metals, ionic crystals and semiconductors. In those cases, the mechanical stress can be efficiently provided by a sharp indenter elastically driven at constant velocity along the surface. Here we suggest that the formation of such surface ripples can be explained by the competition between the driving spring force and the plastic response of the substrate. In particular, we show how the ripples are expected to disappear when the indentation rate is below a critical value or, alternatively, when the sliding velocity or the lateral stiffness of the contact are too high. The model results are compared to atomic force microscopy experiments on a solvent-enriched polystyrene surface, where the rippling formation is enhanced at room temperature, compared to bulk melts. A similar approach could be employed to describe rippling phenomena on larger scales.

Journal/Review: NEW JOURNAL OF PHYSICS

Volume: 17      Pages from: 032001-1  to: 032001-9

More Information: The Spanish Ministry of Economy and Competitiveness (Project No. MAT2012-38810) is gratefully acknowledged for financial support. This work is supported in part by COST Action MP1303.
KeyWords: surface patterning; Prandtl-Tomlinson model; polystyrene; ripples; atomic force microscopy
DOI: 10.1088/1367-2630/17/3/032001

Citations: 20
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