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Engineers have created the first “active matrix” display using a new class of transparent transistors and circuits, a step toward realizing applications such as e-paper, flexible color monitors and “heads-up” displays in car windshields.

The transistors are made of “nanowires,” tiny cylindrical structures that are assembled on glass or thin films of flexible plastic. The researchers used nanowires as small as 20 nanometers - a thousand times thinner than a human hair - to create a display containing organic light emitting diodes, or OLEDS. The OLEDS are devices that rival the brightness of conventional pixels in flat-panel television sets, computer monitors and displays in consumer electronics.

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r. Yu-Chong Tai, professor of electrical engineering and bioengineering at the California Institute of Technology in Pasadena, is an electrical engineer whose early work pioneered a new direction that is now called, “microelectromechanical systems” (MEMS). He has published on just about every facet of MEMS, from shear-stress sensors to micromachining to thermal sensors to lab-on-a-chip. His recent research forays are leading him into studies of biological systems at the micro level. According to our Special Topics analysis of MEMS research over the past decade, Dr. Tai’s work ranks at #5, with 27 qualifying papers cited a total of 272 times. In the ISI Essential Science Indicators Web product, Dr. Tai’s record includes 41 papers cited a total of 383 times to date. Dr. Tai points to some of his earlier papers and presentations, which are outside of the range of our database, as very important in the field. Among these is a presentation report (Fan L.S., Tai Y.C., Muller R.S., “IC-processed electrostatic micromotors,” Tech. Digest, IEEE International Electron Device Meeting [IEDM ’88], San Francisco, Calif., Dec. 11-14, 1988, pp.666-669; and Fan L.S., Tai Y.C., Muller R.S., “Integrated movable micromechanical structures for sensors and actuators,” IEEE Trans. On Electron Devices ED-35:724-730, 1988). Dr. Tai is a graduate of National Taiwan University and received his master’s and Ph.D. in electrical engineering and computer sciences from University of California, Berkeley. He took a faculty appoint at the California Institute of Technology in 1989.

Your work is in microelectromechanical systems (MEMS). Could you explain what this field is?

The name MEMS didn’t even exist in the ‘80s while I was in graduate school. My major was integrated circuits (IC) then. I learned solid-state devices and IC technology. So I know how to make these devices. It all started with an interesting question. We knew that the IC industry was really big in the 1980s. People had already invested billions, if not trillions, of dollars in IC technology. The question was: can we do something with the IC technology for applications other than IC? In other words, IC technology is a huge investment, could something else benefit from it? Here, IC is really only electrical devices. What devices, other than electrical devices, could we build? From an academic point of view, this whole world is either electrical or mechanical. For example, even biology and its fundamental science are all electrical or mechanical. Similarly, chemistry is no different.

Continue reading ‘MEMS: An INTERVIEW with Dr. Yu-Chong Tai’ »

It’s one of those everyday annoyances, finding yourself with a flat battery in any one of the gadgets we carry around constantly now. I would love the option of charging your phone or your ipod while you’re out and about. And it looks like that may be possible soon, with a recent report in Nature on power production from nanotextiles (watch me carefully avoid the use of the pun ‘power dressing’!) The textiles consist of zinc oxide nanowires which generate electricity by the piezoelectric effect, in other words, produce electricity when under mechanical stress. The zinc oxide nanowires are embedded around a Kevlar fibre to produce something looking like a bottle-brush. Some are then coated in a nanolayer of gold, to act as an electrode. These are aligned and the ‘bristles’ rub past each other, creating the electrical current (see picture). Once optimised, this nanotextile should provide a simple and cheap way to convert energy of walking into electrical energy. This report follows an earlier report of a knee brace designed to harvest energy from walking. Maybe one day we will be able to throw our old chargers out and simply plug in and go for a stroll!

Forty years ago, mathematician Mark Kac asked the theoretical question, “Can one hear the shape of a drum?”

If drums of different shapes always produce their own unique sound spectrum, then it should be possible to identify the shape of a specific drum merely by studying its spectrum, thus “hearing” the drum’s shape (a procedure analogous to spectroscopy, the way scientists detect the composition of a faraway star by studying its light spectrum).

But what if two drums of different shapes could emit exactly the same sound? If so, it would be impossible to work backward from the spectrum and uniquely surmise the physical structure of the drum, because there would be more than one correct answer to the question.

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Bypassing decades-old conventions in making computer chips, Princeton engineers developed a novel way to replace silicon with carbon on large surfaces, clearing the way for new generations of faster, more powerful cell phones, computers and other electronics.

The electronics industry has pushed the capabilities of silicon — the material at the heart of all computer chips — to its limit, and one intriguing replacement has been carbon, said Stephen Chou, professor of electrical engineering. A material called graphene — a single layer of carbon atoms arranged in a honeycomb lattice — could allow electronics to process information and produce radio transmissions 10 times better than silicon-based devices.

Until now, however, switching from silicon to carbon has not been possible because technologists believed they needed graphene material in the same form as the silicon used to make chips: a single crystal of material 8 or 12 inches wide. The largest single-crystal graphene sheets made to date have been no wider than a couple millimeters, not big enough for a single chip. Chou and researchers in his lab realized that a big graphene wafer is not necessary, as long they could place small crystals of graphene only in the active areas of the chip. They developed a novel method to achieve this goal and demonstrated it by making high-performance working graphene transistors. 

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