This equation computes the equivalent mechanical pressure generated by electrostatic pressure created when a electroactive polymer has a voltage applied across it.
Dielectric elastomers (DEs) are smart materials that can produce large strains. They belong to the group of electroactive polymers (EAP). Actuators created from EAPs -- DE actuators (DEA) -- transform electric energy into mechanical work. They are lightweight and have a high elastic energy density. See the image below (from https://en.wikipedia.org/wiki/Dielectric_elastomers)