Disclosed is an apparatus for sensing a force, comprising an actuator having a conductive deformable surface, a substrate having a first conductive trace and a second conductive trace, a housing coupled to the actuator and to the substrate, holding the actuator in proximity to the substrate, and a circuit...http://www.google.com/patents/US7721609?utm_source=gb-gplus-sharePatent US7721609 - Method and apparatus for sensing the force with which a button is pressed
