Stress analysis of stretchable conductive polymer for electronics circuit application

Abstract Because of the lack of information regarding the reliability of stretchable electronic circuits (SECs), this chapter presents the stress analysis of these circuits using a polymer material of polydimethylsiloxane (PDMS) as the substrate and a new formulated Ag flakes blends with PDMS (Ag-PDMS) conductive ink. The mechanical properties were characterized using the Neo-Hookean model for substrate and the multilinear plastic model for conductive ink. Different geometries of an SEC such as rectangular, zigzag, and horseshoe shape were modeled and analyzed under static structural analysis in simulation. The structural analyses were conducted on a real prototype of a thermal sensor circuit application. The structural integrity of the circuit under different geometries, loadings, and materials was assessed by investigating the deformation behavior of the circuit. The obtained results show that the critical area for stress concentration depends on the loading direction either parallel or perpendicular to the circuit printing. The high stress concentration produced at the inner side of the crest and through for both horseshoe and zigzag design. The yield stress for the conductive ink was 0.20 MPa. The stress–strain results of the entire model showed that the maximum equivalent stress was below the yield stress for a simple circuit that was limited to 10% strain applied at 0.19 MPa. However, the maximum equivalent stresses for a thermal sensor circuit exceed the yield stress for uniaxial vertical and biaxial loading at 8% strain and 1.3% strain plastic deformation, respectively. The horizontal loading gives no plastic deformation for a thermal sensor circuit at maximum equivalent stress 0.16 MPa.