UntetheredMay 3, 2007 By: Melanie Martella, Sensors
On one of my rambles around the Web this week, I happened upon the story "Plastic sheet delivers wireless power" on Nature's news feed. Japanese researchers have created a thin plastic sheet capable of supplying up to 40 W of power to products on or near to it. Sure, the products need to have a special receiving coil to accept the power from the sheet, but it's still immensely clever.
This material relies on an organic molecule with controllable conductivity that's layered with copper coils and MEMS switches. Intrigued? How about this comment from the article, "The researchers say the transmission of power happens with 81.4% efficiency—compared to 93% efficiency in the wired grid network as a whole—with a "quite low" level of leaked electromagnetic radiation. As a demonstration of the product's safety, the paper shows it powering an LED at the bottom of a bowl containing water and a live fish."
The final Wow! factor is that this sheet was created by printing the various layers. Because it uses organic transistors rather than silicon ones, the researchers didn't have to use traditional semiconductor manufacturing techniques which are difficult, expensive, and tend to use an array of really toxic chemicals.
If you've been reading Sensors for a while, you know we've been following the development of wireless sensor networks (WSN) for several years. Right now, the limiting factor to shrinking the size of the sensor nodes appears to be the battery or power source. The silicon just keeps getting smaller and smaller but the batteries aren't shrinking at the same rate, so people are keeping their eyes open for better batteries or alternative sources of energy, such as energy harvesting.
If you're interested in this, here are a couple of relevant stories and Web sites. The first, from PhysOrg.com, talks of a research development for increasing the efficiency of solar energy harvesting by using nanoscale coaxial cables. You can read the full article, "Nanoscale 'Coaxial Cables' for Solar Energy Harvesting" here. The researchers—Yong Zhang, Lin-Wang Wang, and Angelo Mascarenhas—who found the novel nanowires work at the National Renewable Energy Laboratory and Lawrence Berkeley National Laboratory (LBNL). In fact, BP just funded a $500 million dollar research effort into renewable and sustainable energy sources with LBNL, the University of California at Berkeley, and the University of Illinois at Urbana-Champaign. The Energy Biosciences Institute, according to the full press release, will initially concentrate on biofuels but will also study alternative energy sources and ways to mitigate our sadly deleterious affect on the environment, at least as far as energy consumption goes.
Finally, there's EnergyHarvesting.net which acts as a forum for information on energy harvesting for WSN and control systems. This is both an interesting and increasingly important topic, so keep your eyes peeled. If you've got something to add, please scroll WAY down to the bottom of the page to post your comment.
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