Researchers recently unveiled the first complete millimeter-scale computing system – the tiniest fabricated to date, a prototype of an implantable eye pressure monitor for glaucoma patients. In another important development, the unit can also link up with other computers to form wireless sensor networks. A new super-compact radio that needs no tuning to find the right communications frequency enables these computers to speak to each other.
Nearly invisible millimeter-scale systems should usher in ubiquitous computing by following the trajectory of Bell’s Law, a new class of smaller, cheaper computers comes along 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 smartphones.
The new system is targeted toward medical applications, focusing on a pressure monitor designed to be implanted in the eye to conveniently and continuously track the progression of glaucoma, a potentially blinding disease. In a package that’s just over one cubic millimeter, the system fits an extremely 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 that would be held near the eye. “This is the first true millimeter-scale complete computing system” according to Dennis Sylvester, a professor of electrical engineering and computer science at the University of Michigan.
The processor in the eye pressure monitor is the third generation of the researchers’ Phoenix chip, which uses a unique 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 5.3 nanowatts. To keep the battery charged, it requires exposure to 10 hours of indoor light each day or 1.5 hours of sunlight. It can store up to a week’s worth of information.
While this system is minuscule and complete, its radio doesn’t equip it to talk to other devices like it. A step has been taken toward enabling such node-to-node communication, courtesy of a consolidated radio with an on-chip antenna. Researchers can precisely control the antenna’s shape and size and therefore how it can be used for communication.