December R&D Round UpDecember 5, 2008 By: Melanie Martella, Sensors
This month, superconducting transistors, a radar-based crib monitor, and adapting the way flies hear to aid unmanned aerial vehicles.
A Superconducting Transistor
Microchips may get a serious bump in speed because of research performed by Andrea Caviglia and his colleagues at the University of Geneva. According to the New Scientist article "First superconducting transistor promises PC revolution," the researchers have created a superconducting version of a Field Effect Transistor (FET). While investigating the behavior of a single crystal with strontium titanate and lanthanum aluminate segments, the team found that, at 0.3 K, a layer of free electrons at the interface between the two metal oxides flowed without resistance and the material became superconducting. Applying an electrical field to the strontium titanate side draws the electrons away from the interface and the lanthanum aluminate side stops conducting. In other words, they can turn the superconductivity off and on. Conventional FETs are limited by speed; a superconducting FET removes this limitation. Now all they have to do is figure out how to do a room-temperature version. Can you imagine having to keep your computer at 0.3 K?
Doppler Radar Goes Domestic
Engineering researchers at the University of Florida have designed a prototype baby monitor that uses Doppler radar to sense the motion of the baby's chest while the baby is breathing. The radar unit mounts on the crib while a remote unit elsewhere has lights to show the status of the monitor and can also can sound an alarm if the baby stops breathing or its breathing falls below a preset threshold. Engineering students Changzhi Li, Julie Cummings, Jeffrey Lam, Eric Graves, and Stephanie Jimenez designed the device using the Doppler technology developed by Professor Jenshan Lin. As quoted in the article "Engineers: Wireless crib monitor keeps tabs on baby's breathing", "Future versions could also detect heartbeat, using a higher frequency signal." (Read the article to learn about other applications of Doppler radar for search and rescue and life sign monitors integrated into cell phones.)
From Fly's Ear to UAV
To my shame, I had not realized that flies even had ears. But they do, and their ears are extremely effective at localizing sounds in the 5 kHz range. Which is important if you are Dr. Miao Yu, a professor of mechanical engineering at the University of Maryland, and you are trying to develop miniature acoustic sensors and develop sound localization methods that don't rely on large-scale microphone arrays. And if you are the US Air Force, you would very much like the ability to add these sensors to unmanned aerial vehicles to improve their operational and homing capabilities. According to Dr. Willard Larkin, Air Force Office of Scientific Research program manager, as quoted in "Research into flies' hearing could aid unmanned aerial vehicles," "The key idea of this research is to understand how sound localization is possible in a pair of mechanically-coupled ears separated by only 500 microns, and to test this understanding."
The prototype microphone uses flexible polyamide "eardrums" coupled with a silicon dioxide bridge that mimics the chitin bridge linking the fly's eardrums. This bridge works to amplify the tiny differences in the sound wave that arrive at each ear and, consequently, allows the insect to identify where the sounds are coming from. Yu's prototype has an air-filled cavity surrounding the eardrums and fiber-optic cables in the casing. The fiber-optic cables shine light onto the eardrums, transmitting the reflected light to an optical sensor. As the eardrums flex, the pattern of reflected light changes and the computer uses this data to calculate the angle at which the sound is arriving. (For more on this research, there's an excellent article at New Scientist, "Mic based on fly ear can pinpoint sounds".)
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