Stretching mode deformation analysis for an elastomeric encapsulation-assisted stable flexible electronic substrate

Abstract

The substrate plays an important role in flexible devices and sensors. In this direction, it is observed that elastomeric encapsulation assists the sensor system to deform successfully under stretching. The encapsulation not only makes it flexible but also protects it from environmental factors and mechanical damage. In this paper, a finite element method analysis is used to study the mechanical effects on the encapsulated system, which provides insight into the design of a stretchable substrate for flexible electronic systems. Here, a serpentine silver electrode is designed on a polyethylene terephthalate substrate, which is then encapsulated by polydimethylsiloxane. With the variation in the ratio of top-to-bottom encapsulation thickness i.e. T en1: T en2, the interfacial stress was studied. The mismatch in T en1 and T en2 may result in compressive bending strain, which can be avoided by making T en1 = T en2. It is observed from the simulation that, there is a spike in von-Mises stress at the interface of the substrate and the encapsulation when stretching mode deformation is applied. Also, this maximum stress varies with the variation in encapsulation thickness. For a range of total encapsulation thickness i.e. T EN = T en1 + T en2 = 30 μm to 100 μm, the optimum thickness is found to be 55 μm, for which the spike in interfacial von-Mises stress is minimum.