January R&D Round UpJanuary 14, 2011 By: Melanie Martella, Sensors
Happy New Year! Let's get the new year started with some neat and useful research and developments, shall we? This month we've got a single-pixel camera that provides great pictures, RFID tags that act as sensors, and diamond microstructures for nano/micro electromechanical systems (MEMS/NEMS).
A Good Image from a Single Pixel
More pixels in a digital image sensor means better images, yes? Not necessarily! Researchers from the Universitat Jaume I's Optics Research Group (GROC) in Castelló, Spain, have created a single-pixel camera that is capable of providing good quality images. The device does this by using a 1 in. miniature LCD screen to emit "noisy" light; the lone pixel generates an image of an object by sequentially recording the light intensity transmitted or reflected by the object when illuminated by a sequence of noisy light beams. As described in "The Universitat Jaume I develops a new single-pixel photo camera," the technology shows promise, particularly for biomedical imaging of tissues that are hard to photograph because of their transparency or their location deep within the body.
RFID Tags as Multipurpose Sensors
Here's a clever riff on an existing technology. Bob Kauffman, research chemist and Doug Wolf, senior research physicist, from University of Dayton Research Institute have created the SMART (Status and Motion Activated Radiofrequency Tag) sensor to be used in so-called smart clamps to secure aircraft wiring. Because modern aircraft contain so much wiring, and because broken or too-tight clamps can damage the wires that they restrain, and because damaged wires are a very bad and possibly dangerous thing, the FAA wanted clamps that could tell technicians when they were damaged. Kauffman took a normal RFID tag, which sends information on receiving a signal from a reader, and modified it by adding a bypass around the tag's microcontroller so that the tag would only respond to the reader if the bypass were broken. Rather than sifting through a raft of signals from good clamps that are working fine and trying to figure out which clamps aren't responding, clamps using SMART would be silent unless damaged. As Kauffman notes in "A SMART Sensor," "With only minor variations to the design or material of the microchip bypass, SMART sensors could be used to detect and report hidden impact damage, cracks, temperature changes, corrosion or tampering in any number of products and devices." What a useful and elegant solution!
Diamond doesn't just make for sparkly jewelry, it's also durable, strong, has excellent chemical stability, and its thermal and electrical properties make it a great candidate for MEMS/NEMS. However, wrangling single-crystal diamond into structures such as cantilevers has proven difficult. Now, Dr. Meiyong Liao and his colleagues from Japan's National Institute for Materials Science, have succeeded in the batch fabrication of cantilevers and bridges of single-crystal diamond. Not only that, but, they've also fabricated a single-crystal diamond NEMS switch.
Building on a single-crystal diamond substrate, they laid down a sacrificial graphite layer and then grew a diamond epilayer over that. When the graphite was removed what was left was a single-crystal suspended structure. (There are excellent scanning electron microscope images of the structures on the abstract page for the research.) The resulting structures have a number of impressive features, including <10 pW power consumption, high reproducibility and reliability, no surface stiction, very low leakage current, stable operation in temperatures to 250°C, and a Young's modulus of 1100 GPa.
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