Bruce Alphenaar is Chair, and Professor of the Electrical and Computer Engineering at the University of Louisville with the distinction of Research Scholar in Nanotechnology. He received his Ph.D. in Applied Physics from Yale University in 1991, after which he worked as a research scientist for Philips Research Laboratories (The Netherlands), and for Hitachi Research Laboratory, based at the University of Cambridge, England. There he was presented with the Hitachi Manager Director's award for his research on spin electronic devices and circuitry. He joined the University of Louisville in 2000, where his recent research focus includes energy scavenging and high efficiency photovoltaic devices. He has published over 50 peer reviewed journal articles, holds 8 US and European patents, and has been invited to speak on his work at numerous international symposia. Since joining the University of Louisville, he has been PI or co-PI on over $35 M in research funding. His work is currently funded by the National Science Foundation, the Department of Energy, and the Department of Defense.
- Ph.D. in Applied Physics, Yale University, 1991
- M.S. in Applied Physics, Yale University, 1986
- B.S. in Physics, Trinity College, 1984
The strain induced resistance change is compared for asymmetric, symmetric and diffused piezoresistive elements. Finite element analysis is used to simulate the performance of a T-shaped piezoresistive MEMS cantilever, including a lumped parameter model to show the effect of geometric asymmetry on the piezoresistor sensitivity. Asymmetric piezoresistors are found to be much more sensitive to applied load than the typical symmetric design producing about two orders of magnitude higher resistance change. This is shown to be due to the difference in the stress distribution in the symmetric and asymmetric geometries resulting in less resistance change cancellation in the asymmetric design. Although still less sensitive than diffused piezoresistors, asymmetric piezoresistors are sensitive enough for many applications, and are much easier to fabricate and integrate into MEMS devices.