A new cellular electret sensor-actuator

The new form of electret, EFoam, has a high degree of sensitivity, and can be manufactured with varying stiffness and shape. Initial investigations indicate sensitivity comparable to that of other commercially available piezoelectric polymers. Further work is needed to explore the maximum sensitivity attainable. Due to the nature of manufacture, EFoam can be made both in conventional sheet form, and bulk, three-dimensional shapes. The molding procedure used, combined with some post-processing, could confer EFoam with complex shapes, endowing different areas of the structure with heterogeneous and controllable mechanical properties. Finally, the resonant behavior (and so stiffness) of EFoam can be altered as a function of a dc-offset voltage applied.