Stretchable and compressible thin films of stiff materials on compliant wavy substrates

Buckling of stiff thin films on compliant substrates has been investigated extensively for its application in stretchable electronics.  In spite of many attractive features, the buckling process has some disadvantages. First, the control over the geometries or the phases of the waves is limited. Second, the compressive strains in the buckled films yield stretchability at the expense of reduced compressibility. In this paper published in APL (Xiao et al., Appl. Phys. Lett. 93, 013109 (2008)), we presented an alternative design that involves stiff thin films conformally integrated with a compliant wavy substrate, thereby avoiding any initial film strain and thus achieving both high stretchability and compressibility. Furthermore, this approach provides precise control over the wavy geometries. These advantages imply its applications in stretchable electronics and other emerging technologies.

In this paper, the deformation of Au thin films on wavy elastomeric substrates are studied via analytical, numerical and experimental approaches. The maximum film strain is obtained in terms of film and substrate elastic moduli, film thickness, amplitude and wavelength of the wavy profile, and the applied strain. These analytical solutions agree well with both finite element analysis and experimentally measured changes of the sinusoidal profile under small, uniaxial strains. A simple expression for the system stretchability and compressibility is established.