Stretchable gold conductors embedded in PDMS and patterned by photolithography: fabrication and electromechanical characterization

Stretchable gold conductors embedded in polydimethylsiloxane (PDMS) films were successfully prepared using standard photolithography. The minimum feature sizes patterned in the metal film and PDMS encapsulation are 10 mu m and 20 mu m, respectively. The micro-patterned conductors are robust to uni-axial (1D) and radial (2D) stretching with applied strains of tens of percent. The electrical response of the conductors follows a nonlinear increase with strain, and is reversible. The extensive stretchability of the conductors relies on a randomly and independently distributed network of micro-cracks (similar to 100 nm long) in the metal film on PDMS. The micro-cracks elongate to a few microns length both in the stretching and normal directions in 1D stretching but during 2D stretching, the micro-cracks grow and form 'dry mud' islands leaving the gold microstructure inside the islands intact. Patterning metallic thin films directly onto elastomeric substrates opens a promising route for microelectrodes and interconnects for soft and ultra-compliant MEMS and electronic devices.