An electret touch sensor

In the research presented here we have examined the response of an electret transducer to forces applied over a localized area of the transducer face. The electret is modeled as a membrane under tension suspended above a flat back electrode. The air between the back electrode and the electret foil communicates with the environment through holes in the back electrode. The electret foil is described by a mesh of nodes, and standard finite difference techniques are used to find the deflection of the membrane in response to pressures applied at selected nodes. Static and dynamic analyses of this model have correlated well with the analytical solution for a uniform pressure on the transducer face. The device has been built and its response to impulses at various locations measured. Experimental results and theoretical predictions are in good agreement. Applications for this force-sensing device are expected to be primarily in the area of robotics.