Development of Conductive Surface on Polyurethane Foam Using In Situ Polymerization of Pyrrole for Capacitive Pressure Sensing

Capacitive pressure sensors have always held a significant place in engineering applications. In this letter, we present the electrophysico-chemical characterization of an ultrasoft and highly compressible capacitive pressure sensor based on polyurethane foam with top and bottom surfaces coated with thin films of conductive polypyrrole. An in-situ chemical oxidative method was used to effectively synthesize a promising conducting polypyrrole foam capacitor. We synthesized the polypyrrole thin films as two parallel electrodes on the polyurethane foam. The foam was cut into cuboids of dimensions 2 cm x 2 cm x 0.5 cm. Different concentrations of pyrrole and FeCl3 were prepared to compare and obtain the best sensitivity. We observed that high sensitivity was achieved when the molar ratio of the monomer and oxidant was 1, with the value being 1.01 kPa(-1), at 25 kPa pressure. We also performed finite element method (FEM) simulations, which verified the mechanical deformation along with changes in space charge density for applied pressure. The sensor can be fabricated in different shapes and sizes for various applications of free-form electronics, such as soft robotics, wearable, biomedical, and so on.