Controlled Bi-Axial Buckling and Postbuckling of Thin Films Suspended on a Stretchable Substrate with Square Prism Relief Structures

Stretchable electronics have spurred rapid developments from curvilinear devices to bio-integrated diagnostic and therapeutic devices. The wavy configuration in the device components on a stretchable elastomeric substrate surface plays a prominent role in simultaneously achieving high areal coverage and stretchability without compromising the electric performance, resulting in unique applications in stretchable and flexible light-emitting diodes (LEDs), batteries, supercapacitors, and photovoltaics. In this study, we investigate the buckling behaviors of stiff thin films on the top surface of a biaxially pre-strained elastomeric substrate with square prism micro-patterned structures. Based on energy minimization, a theoretical model is established to study the buckling profiles and the maximum strain for different pre-strain levels along two directions, which agrees reasonably well with those obtained by the finite element analysis (FEA). After revealing the effect of the center-To-center distance in micro-patterned structures and the interfacial contact width between the film and substrate on the buckling behavior, the elastic stretchability of the system is studied.