Researchers at the University of Michigan have created the first prototype for a millimeter-scale computing system that can hold up to a week's worth of data when implanted in something as small as a human eye.
The computer, called the Phoenix chip, is just over one cubic millimeter in size and was designed to monitor eye pressure in glaucoma patients.
"This is the first true millimeter-scale complete computing system," Dennis Sylvester, a professor at the school and one of the researchers on the project, said in a statement.
Within the computer is an ultra low-power microprocessor, a pressure sensor, memory, a thin-film battery, a solar cell and a wireless radio with an antenna that can transmit data to an external reader device held near the eye.
The chip uses a power gating architecture with an extreme sleep mode that powers the computer up briefly every 15 minutes to take readings. By remaining in sleep mode most of the time, the chip sips power, averaging 5.3 nanowatts every time it turns on.
The Phoenix chip's photovoltaic system requires 10 hours of indoor light or 1.5 hours of sunlight to fully charge the battery.
The chip's micro radio automatically tunes into whatever wireless frequency is available in order to download data to a reader. The data can then be used as part of an electronic medical record for treatment.
According to researchers, the micro computers and their wireless networks could one day also be used to track pollution, monitor structural integrity, perform surveillance, or make virtually any object smart and trackable.
"Our work is unique in the sense that we're thinking about complete systems in which all the components are low-power and fit on the chip," Sylvester said. "We can collect data, store it and transmit it. The applications for systems of this size are endless."
The researchers presented their papers on the new microcomputers and the networks at the International Solid-State Circuits Conference (ISSCC) in San Francisco. The work is being led by three faculty members in the University of Michigan Department of Electrical Engineering and Computer Science.
University professor David Blaauw said that once the chips reach the nanoscale level, hundreds of the computers could be fitted onto a single silicon wafer to perform multiple monitoring tasks.
The researchers pointed to Bell's Law, which states that there's a new class of smaller, cheaper computers about every decade. With each new class, the volume shrinks by two orders of magnitude and the number of systems per person increases. The law has held from 1960s' mainframes through the '80s' personal computers, the '90s' notebooks and the new millennium's smart phones, they said.
"When you get smaller than hand-held devices, you turn to these monitoring devices," Blaauw said in a statement. "The next big challenge is to achieve millimeter-scale systems, which have a host of new applications for monitoring our bodies, our environment and our buildings."
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