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Tuesday, July 08, 2008 A Picowatt ProcessorA low-power chip could be used for implantable medical sensors. By Kate Greene
Before long, sensors may be implanted in our bodies to do things like measure blood-glucose levels in diabetics or retinal pressure in glaucoma patients. But to be practical, they'll have to both be very small--as tiny as a grain of sand--and use long-lasting batteries of similarly small size, a combination not commercially available today. Now researchers at the University of Michigan have made a processor that takes up just one millimeter square and whose power consumption is so low that emerging thin-film batteries of the same size could power it for 10 years or more, says David Blaauw, professor of electrical engineering and computer science at Michigan and one of the lead researchers on the project. But when this processor, dubbed the Phoenix, is coupled with a battery, the whole package would only be a cubic millimeter in volume. At this scale, Blaauw says, it could be feasible to build the chip into a thick contact lens and use it to monitor pressure in the eye, which would be useful for glaucoma detection. It could also be implanted under the skin to sense glucose levels in subcutaneous fluid. More broadly, this low-power approach to processor design could be used in environmental sensors that monitor pollution, or structural health sensors, for instance. The processer uses only about 30 picowatts (a picowatt is one-millionth of one-millionth of a watt) of power when idle. When active, the processor consumes only 2.8 picojoules of energy per computing cycle. That amount is about a tenth of the energy used by the most energy-efficient chips on the market, says Jan Rabaey, a professor of electrical engineering and computer science at the University of California, Berkeley, who was not involved in the research. The Michigan team's main idea was to design a chip that runs at an extremely low voltage. While microprocessors for personal computers may require two volts of electricity per operation, the Phoenix only needs 500 millivolts, or 75 percent less. At this voltage, parts of the chip don't operate well, explains Blaauw, so his team redesigned the chip's memory, which is smaller than most processor memory, and its internal clock so that it could operate with minimal electrical input. The chip's clock--the timepiece that synchronizes number-crunching operations--has been reduced to an extremely slow rate of 100 kilohertz, as opposed to the gigahertz rates of personal computers. This approach makes sense for sensors, says Blaauw. "If we wanted to monitor pressure in the eye . . . we only need to take readings every few minutes," he says. |
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From the Lab: Information Technology
08/19/2008
Comments
midas on 07/08/2008 at 1:26 AM
1
Kate Greene on 07/08/2008 at 10:03 AM
Information Technology Editor
7
carlii on 07/08/2008 at 6:01 AM
25
b4b2 on 07/08/2008 at 4:02 PM
9
Here is a website that addresses the potential of using the electrolytes in the bloodstream to generate energy.
http://electronics.howstuffworks.com/nanorobot3.htm
Ben
carlii on 08/13/2008 at 3:47 AM
25
GreenPlease on 07/08/2008 at 9:09 AM
7
robin26 on 07/22/2008 at 5:51 PM
8
Within the lung, for example, there is constant ventilation and evaporation, and therefore some cooling takes place. A device embedded within the lung may be able to achieve enough temperature difference between the lung's surface tissue and some deeper tissue in order to generate some small but usable electrical power.
robin26 on 07/22/2008 at 5:28 PM
8
"The processer uses only about 30 picowatts";
"the processor consumes only 2.8 picojoules of energy per computing cycle";
"The chip's clock...has been reduced to...100 kilohertz".
These three statements don't seem to fit together. If the processor consumes 30pW, and the clock frequency is 100kHz, then the energy consumed per clock cycle is 30pW / 100kHz = 300E-18 J, or 300 atto-Joules. If one "computing cycle" means one clock cycle, then one computing cycle consumes 300 aJ, not the 2.8 pJ cited by the article.
smhanson on 07/24/2008 at 8:13 AM
1
robin26 on 07/24/2008 at 9:40 AM
8