Determination of relevant material behavior for use in stretchable electronics

Stretchable electronics getting more and more in focus for medical applications (e.g. skin wearable body-monitoring systems or sensitivs implants). Typically, electronic components and metal conductor paths are embedded in elastomeric substrates. These material combinations of highly elastic behavior of the substrate (strains up to ~ 150 %) and the relatively stiff metal components with a typical elastic stretchability (Cu <; 1 %) cause a problem regarding the mechanical reliability. The important factor for reliability assessment by FEM is not only the material properties of individual components, but also the behavior of metal-polymer interfaces. Accurate prediction of component behavior requires both, suitable material models and accurate material properties data. In this paper, we present our results of an adapted approach to assess material properties by mechanical test methods under plane stress conditions, under tensile loads and equi-biaxial tension experiments using an uniaxial testing machine. These results were used for the modelling of hyper-elastic material properties under multi-axial states of stress. This study is part of very important research to develop new simulation techniques and testing methods to be able to use hyper-elastic modelling approaches for industrial applications.