Modeling Flexible Electronics Under Biaxial Strain

Flexible electronic systems are likely to see a combination of uniaxial and biaxial stresses and strains when deployed in real-world applications. The manufacturing community must develop standardized methodologies for evaluating the performance and reliability of emerging flexible electronic materials under these biaxial conditions to supplement established uniaxial testing approaches. Previous work has shown that stretchable conductive inks will fail much sooner under biaxial loading conditions, and that an inflation test system can be used to evaluate the electromechanical behavior of the ink under biaxial strain. The research presented herein seeks to demonstrate the development of a visco-hyperelastic material model and a finite-element model to better understand the electrical and mechanical behavior of stretchable conductors examined through biaxial inflation stretch testing. Numerical predictions for the mechanical response of the substrate-ink system and associated increases in the resistance of the ink conductor show agreement with experimental results. Recommendations are made for application of this modeling approach as a tool to improve the design of more reliable flexible electronic materials.