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MEMS based lighting control optimises road illumination By OChristoph Hammerschmidt n the basis of its laser spot high-beam headlight, Audi is developing a system that automatically adjusts the illumination for the speed of the vehicle. The new technology utilises only a single MEMS mirror to deflect the laser beam. The laser spot technology for the high beam went into series production for the first time in 2014, in the Audi R8 LMX sports car. Progress in the field of laser light generation now made it possible to integrate the projector technology in a compact yet powerful headlight assembly. The latest iteration uses a single but fast-moving micro mirror that deflects the laser beam. At low speeds, the light is distributed widely across a large area. At higher speed, the aperture angle gets smaller; the intensity as well as the luminous range of the beam is increased. This is of benefit in particular during high-speed rides on motorways. The technology also allows controlling the distribution of the light. Thus, the beam can illuminate specific sections of the illuminated area, resulting in a highly dynamic and variable overall illumination and, likewise, shading. Another achievement is the intelligent, lighting-fast switching of the laser diodes depending on the mirror position. Similar to today’s matrix LED headlights, the new dynamic laser headlight always illuminates the road at high intensity without dazzling other traffic participants. The decisive diffe-rence to matrix LED headlamps is that the matrix laser offers a significantly higher resolution and thus a higher utilisation which improves traffic safety. In addition, this technology enables innovative lighting assistance functions. The new technology employs blue laser diodes (provider: Osram) that feature a light wavelength of 450 nm. The light is directed towards a fast moving mirror with a diameter of 3 mm which deflects the blue light to a converter which generates white light and projects it to the road. The micro mirror is implemented as a silicon MEMs device (provider: Bosch). The same MEMS is used for acceleration sensors and for electronic stability control (ESP) gear. The development of this intelligent lighting system takes place in the iLaS project along with research partners Karlsruhe Institute of Technology (KIT), Bosch and Osram. NFC tags check food freshness LBy Julien Happich ate last year, researchers at the Massachusetts Institute of Technology (MIT) had designed simple gas sensors relying on nanotubes-based chemiresistors (electrical circuits whose resistance changes when exposed to a particular chemical). In their implementation, the carbon nanotubes were chemically modified so that their ability to carry an electric current changed in the presence of a particular gas. This chemiresistive property was then integrated into the powering circuit of commercial near-field communication (NFC) tags. The team first disrupted the electronic circuit by punching a hole in it before reconnecting the circuit with a linker made of the modified carbon nanotubes. Hence, the modified NFC tags could only remain operational and could only be read if the chemiresistors conducted normally, that is without the target chemical in sight. Now, the researchers have modified the carbon nanotubes with metal-containing compounds called metalloporphyrins, known to be very good at binding to nitrogen-containing compounds such as amines. Of particular interest to the researchers were the so-called biogenic amines, such as putrescine and cadaverine, which are produced by decaying meat. When the cobalt-containing porphyrin binds to any of these amines, it increases the electrical resistance of the carbon nanotube, which can be easily measured. The researchers tested the sensor on four types of meat: pork, chicken, cod, and salmon. They found that when refrigerated, all four types stayed fresh over four days. Left unrefrigerated, the samples all decayed, but at varying rates. Designed within NFC-readable RFID labels, the sensors could allow consumers to determine whether the meat in their grocery store or refrigerator is safe to eat. Such sensors could be designed in “smart packaging” that would offer much more accurate safety information than the expiration date on the package, according to Timothy Swager, the John D. MacArthur Professor of Chemistry at MIT who had already proven similar sensors to detect ethylene, a gas that signals ripeness in fruit. “People are constantly throwing things out that probably aren’t bad,” says Swager, who is the senior author of a paper describing the new sensor this week in the journal Angewandte Chemie. “There are several potential advantages in having an inexpensive sensor for measuring, in real time, the freshness of meat and fish products, including preventing foodborne illness, increasing overall customer satisfaction, and reducing food waste at grocery stores and in consumers’ homes,” says Roberto Forloni, a senior science fellow at Sealed Air, a major supplier of food packaging, who was not part of the research team. The researchers have filed for a patent on the technology and hope to license it for commercial development. The research was funded by the National Science Foundation and the Army Research Office through MIT’s Institute for Soldier Nanotechnologies. www.electronics-eetimes.com Electronic Engineering Times Europe May 2015 15


EETE MAY 2015
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