Novel Dielectric Substrate Manufacturing for Stretchable Electronics

Stretchable electronics are being used in numerous applications including wearable electronics, stretchable artificial skin, wearable chip devices for health monitoring, and soft robotics, due to their excellent mechanical conformability through stretching, flexing, twisting, and folding. While many current processes use commercially available substrates for printed applications, their ability to stretch and recover is limited. One of the challenges with on-skin wearable devices is permeation resistance to bodily fluids, water vapor, and gases. This work focuses on manufacturing thin substrates with butyl rubber (IIR) as the base material. Butyl rubber is a good barrier to gas and water vapor and has good stretch and recovery. When compounded with a functional filler such as barium strontium titanate (BST), the dielectric properties can be tailored. Since silver in the ink reacts with sulfur in the conventional cure package for IIR, a non-conventional cure package was investigated and optimized for curing. Print parameters and conditions like cure time, temperature, slump, and minimum line width were optimized for different BST loadings. The effect of BST loading on mechanical properties (maximum elongation, recovery, and effect of cyclic strain) of the substrate was studied. Changes in resistance upon single stretch and multiple stretch cycles with different stretchable inks were also analyzed. These substrates showed the high stretch and excellent recovery, broadening the potential capabilities for stretchable electronics.