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March 2nd, 2012
Distinguished Lecture
"Vacuum Nanosystems for Energy Conversion"
Dr. Roger Howe
William E. Ayer Professor of Engineering
Electrical Engineering Department
Stanford University
When: Friday, March 2nd, 2012 at 3:05 p.m.
Where: Warnock 2250
Refreshments served at 2:45 p.m. The lecture is open to the public.
Abstract
Micro and nano-fabricated sensors (e.g., accelerometers and gyroscopes) and actuators (e.g., light valve chips for projection and cell-phone displays) have become commonplace in recent years. Some of these devices must operate in a hermetically sealed, low-pressure ambient, a need that motivated the development of low-cost, wafer-scale vacuum encapsulation technologies. In this talk, I’ll identify a promising direction for nanotechnology, in which vacuum is more than simply the ambient surrounding a microstructure, but rather is a critical element in device operation.
Thermionic energy converters were conceived in 1915, demonstrated in 1939, and were the focus of astronomical investments during the space race by NASA and the Soviet Union. A 6 kW thermionic converter, fabricated using precision machining and vacuum-tube technology, was flown in the late 1980s by the Soviets. Thermionic converters can be fabricated using extensions of MEMS technology, in which advances in materials, micromachining, and vacuum encapsulation processes can be used to enhance performance and reduce fabrication costs. Potential commercial applications include topping cycles in small-scale co-generation. Recently, a new conversion concept has been demonstrated at Stanford, in which a semiconductor photocathode replaces the conventional metal cathode. This photon-enhanced thermionic energy (PETE) converter harvests photon energies above the bandgap, as well as broad-spectrum radiation through heating of the photocathode. It is attractive as the high-temperature topping cycle for solar-thermal power stations. Micro- and nano-structured, high-temperature materials and micromachining processes are also essential to fabricating wafer-scale, cost-effective PETE converters. I will conclude by summarizing the research directions that are needed to bring thermionic and PETE conversions into the mix of energy conversion options.
Frontiers in Engineering Innovation: The Judd Distinguished Lectures
The Frontiers in Engineering Innovation lecture series brings leaders in engineering fields to campus to share their groundbreaking ideas with with our students, faculty, and community.
Selection as a Judd Lecturer is one of the highest honors bestowed by the ECE Department, and is the result of a comprehensive process including nomination and selection by a faculty committee. Selection criteria are based upon significant contributions in science and technology relating to ECE.
Speaker Biography
Roger T. Howe is the William E. Ayer Professor in the Department of Electrical Engineering at Stanford University, as well as the Faculty Director of the Stanford Nanofabrication Facility. He earned a B.S. degree in physics from Harvey Mudd College, Claremont, California and an M.S. and Ph.D. in electrical engineering from the University of California, Berkeley in 1981 and 1984. After faculty positions at Carnegie-Mellon University in 1984-1985 and the Massachusetts Institute of Technology from 1985-1987, he returned to Berkeley where he was a Professor until 2005.
His research interests include micro electromechanical system (MEMS) design, micro/nanomachining processes, and self-assembly processes. A major focus of his research from the early 1980s until recently was technologies for integrated microsystems, which incorporate both silicon integrated circuits and micromechanical structrures. Recently, his research has shifted to nano electromechanical systems (NEMS), for applications ranging from chemical sensors to relays and logic devices. Prof. Howe has made contributions to the design of MEMS accelerometers, gyroscopes, electrostatic actuators, and microresonators. He was elected an IEEE Fellow in 1996, was co-recipient of the 1998 IEEE Cledo Brunetti Award, and was elected to the U.S. National Academy of Engineering in 2005 for his contributions to MEMS processes, devices, and systems. He was a co-founder of Silicon Clocks, Inc., a start-up company that commercialized poly-SiGe integrated MEMS-on-CMOS for timing applications, which was acquired by Silicon Laboratories, Inc., in April 2010.
In December 2009, he became the Faculty Director of the Stanford Nanofabrication Facility. In February 2011, became the Stanford Site Director of the National Nanotechnology Infrastructure Network (NNIN) and in September 2011, he became Director of the NNIN.