Silicone rubber is chosen as the main substrate because of following reasons. Changing the proportions of silicone elastomer and PDMS which is mentioned in fabrication process allows different elasticity for the sensor.
- first, it acts as a dielectric with a highly negative triboelectric polarity. Human skin is highly electropositive. Thus, while it get into contact with sensor for any manipulation, it highly increase the magnitude of the self-powered current generated by mechanical deformation.
- Second, the elastic properties of silicone rubber allows a wide varieties of gestural input and human interactions. It can be easily squeezed, stretched, twisted or twirled, and then return to original shape. Such properties provide many opportunities for many use cases in different contexts.
Copper and Silver coated Nylon are chosen as electrodes for following reasons:
- Coiling conductive threads around the silicone rubber improves mechanical strength and charge flow. Such spiral structure of electrode coils allows manipulation of sensor while reducing the silicone punctures and tensile failures when sensor is stretched.
- The inner electrode copper wire has high conductivity and very low resistivity, about 1.7 * 10^2 Ohm * m^ -1.
- The outer electrode silver-coated nylon is conductive (< 1 Ohm* m^-1) and has specific physical properties like high tensile strength, high elongation tolerance, high tear strength, and high puncture resistance. Such properties support silicone rubber cord under applied loads.
- Tight winding of coils and having no gap between two successive turn of electrodes maximize the structural reinforcement and also maximize the contact area between dielectric layers of the silicone rubber and the PVA. such contact area maximization improve the triboelectric charging and the amount of harvesting power.