A study on viscoelastic contact behaviors of polymer for transfer printing applications

Abstract

This study is concerned with a multiscale computation of decohesion or debonding in transfer printing between silica and cross-linked poly-dimethlysiloxane (PDMS). A cohesive zone model is established for the interface between the silica and the PDMS, which is characterized by non-bonded atomic interaction of Morse type. Fracture toughness of the interface between the PDMS and the silica is considered to be conserved over time so that the interfacial cohesive zone model is considered to be rate-independent. For analysis of adhesion at macroscale, coarse-graining is conducted for the interfacial cohesive zone model derived from the atomic interaction. The coarse-graining of the cohesive zone at the interface of an amorphous material is established. The coarse-grained cohesive zone model is obtained with the aid of homogenization and relaxation method. The amorphous material in atomic scale is homogenized and the effect of its domain volume upon homogenization is investigated through molecular dynamics (MD). The homogenized amorphous material is then utilized for coarse-graining at the interface. The coarse-graining leads to an increase of opening displacement and a decrease of decohesion traction while fracture toughness of the interface is conserved. A numerical simulation is implemented for adhesion between the PDMS and the silica through finite elements method (FEM). With the aid of the coarse-grained interfacial cohesive zone model, pull-out force is observed to be dependent on transfer velocity. Viscoelasticity of the bulk PDMS used for the transfer printing is found to have a substantial effect on the rate-dependent pull-out force.