"A Method to Enhance Transducer Coupling Coefficients"

Inventors: G.A. Lesieutre and C.L. Davis

PSU Invention Disclosure No.95-1502

Licensing Contact: Matthew D. Smith

Issued U.S. Patent No. 6,236,143

This invention provides a method which allows actuator and sensor designers to achieve device coupling coefficients and energy conversion effectiveness higher than currently believed possible. This will improve device sensitivity and performance while reducing weight and power requirements. Using this invention, it is possible, in principle, to achieve device coupling coefficients higher than material coupling coefficients, and to more than double energy conversion effectiveness relative to state-of-the-art transducers. Penn State researchers have validated the physical principles underlying the invention in experiments with a piezoelectric bimorph device.

A coupling coefficient is a measure of the effectiveness with which a shape-changing material converts the energy in an imposed signal to useful mechanical energy (or the converse). Devices made using such materials are also said to have coupling coefficients. There are different kinds of material and device coupling coefficients, corresponding to different modes of excitation and response. Device coupling coefficients are properties of the device and, although related to the material coupling coefficients, are generally different from them. It has been commonly held that a device coupling coefficient cannot be greater than some corresponding coupling coefficient of the material used in the device.

This invention has application to a variety of actuator and sensor devices, and will be especially valuable when there are payoffs for increasing device sensitivity and decreasing device size and power requirements. Potential transducers for which the invention will be useful include hydrophones, medical transducers, ultrasonic NDE transducers, structural positioning and control actuators, and piezoelectric bender-type devices. In addition, an important future field of application is Micro-Electro-Mechanical Systems (MEMS); in MEMS devices, efficiency will be critical and the invention could play an important role.