Researchers unveil first millimetre scale computing system

The implantable eye pressure monitor for glaucoma patients measures slightly more than 1mm³ and features 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 transfer data to an external device held near the eye. "This is the first true millimetre scale complete computing system," said Professor Dennis Sylvester, who led the research alongside David Blaauw and assistant Professor David Wentzloff. "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. We can collect data, store it and transmit it. The applications for systems of this size are endless." According to the Professor, the processor in the eye pressure monitor is the third generation of the researchers' Phoenix chip, which uses a power gating architecture and an extreme sleep mode to achieve ultra low power consumption. The newest system wakes every 15 minutes to take measurements and consumes an average of 5.3nanowatts. To keep the battery charged, it requires exposure to 10 hours of indoor light each day or 1.5 hours of sunlight and can store up to a week's worth of information. "The next step is to allow the device to communicate with others like it," said Sylvester. As such, Prof Wentzloff is working with doctoral student Kuo-Ken Huang to develop a consolidated radio with an on chip antenna that is able to keep time on its own and serve as its own reference. "By integrating the antenna through an advanced cmos process, we can precisely control its shape and size and therefore how it oscillates in response to electrical signals," said Wentzloff. "By designing a circuit to monitor the signal on the antenna and measure how close it is to the antenna's natural resonance, we can lock the transmitted signal to the antenna's resonant frequency. "We believe these millimetre scale systems could enable ubiquitous computing. Because they're so small, hundreds of thousands could be manufactured on one wafer. There could be 10s to 100s of them per person and it's this per capita increase that fuels the semiconductor industry's growth."