Stretchable Capacitive Strain Sensors Based on a Novel Polymer Composite Blend

Wearable sensors, capable of detecting various motions of the human body, present unique opportunities for the development of advanced electronic interfaces. Such sensors have widespread applications in robotics, medicine, and electronic gaming. Capacitive sensors have numerous advantages. They are physically robust, can be constructed from a variety of materials in different shapes and sizes, and have the potential of be manufactured at low cost. Here, we present two a capacitive strain gauges based on a novel silver-polymer composite material. The first sensor utilized an interdigitated finger pattern, which changed capacitance during tensile strain. The silver-polymer composite was used as the conductive filler material while the commercially available silicone elastomer Ecoflex® served as both the dielectric material and substrate. The silver-polymer composite was prepared by dispersing silver flakes into a mixture of polyvinyl alcohol, poly(3,4-ethyl-ene-dioxythiophene) (PEDOT): Poly(styrene sulfonic acid) (PSS), and phosphoric acid. The second sensor utilized a parallel plate capacitor configuration with the silver-polymer composite serving as the conducting plates and urethane adhesive (Ure-Bond®) as the dielectric material. Mechanical and electrical performance of both sensors, along with fabrication techniques, will be discussed.