Computational modelling of collagen-based flexible electronics: assessing the effect of hydration

Collagen substrates in flexible electronics emerged as an alternative to the commonly used stretchable synthetic polymers such as polyethylene terephthalate, polyether sulfone, polydimethylsiloxane etc., thanks to their biocompatibility, flexibility and piezoelectric behaviour. Although researchers were successful in manufacturing these flexible-electronics component, still, the mismatch in the levels of stiffness between a softer polymeric substrate and a stiffer metallic layer (electrodes) might cause interfacial delamination. In use, collagen-based flexible electronics might be exposed to both dry and wet conditions. Experimental analysis showed a drastic change in the mechanical behaviour for these two conditions (the modulus changed by three orders of magnitude); hence, it is essential to investigate the behaviour of polymer-metal interface in both situations. In addition, the effect of geometry and orientation of metallic layers should also be considered; this could help to optimize the design of these electronic devices. In this study, 3D computational models were developed in Abaqus Simulia CAE with dimensions similar to those of elements in collagen-based flexible electronics—collagen (substrate) being the base layer while gold (conductive) and chromium (adhesive) were the top and middle layers, respectively. It was found that delamination in wet collagen was much less pronounced and slower as compared to dry collagen. The effects of geometry and orientation also showed significant differences in the pattern and an area of delamination.