University of Michigan (U-M) researchers are the latest scientists to claim the title of “the world’s smallest computer.” Each side of the new device measures 0.3 mm, which is 1/10 the size the previous titleholder—IBM.
The tiny computer features RAM, photovoltaics, processors, wireless transmitters, and receivers. It’s so small that traditional radio antennae aren’t an option to send and transmit data. Designers thus turned to visible light to take on the role, where a base station receives data, and provides light for programming and power.
Running at low power was key to create such a small design. Electric currents can be induced from the base station’s light and from the device’s transmission LED. Designers also exchanged diodes for switched capacitors.
“We basically had to invent new ways of approaching circuit design that would be equally low power but could also tolerate light,” says David Blaauw, a professor of electrical and computer engineering, who led the development of the new system.
How did the system achieve high accuracy as it ran on low power? The microdevice was developed as a precision temperature sensor, converting temperatures into time intervals guided by electronic pulses.
“The intervals are measured on-chip against a steady time interval sent by the base station and then converted into a temperature. As a result, the computer can report temperatures in minuscule regions—such as a cluster of cells—with an error of about 0.1 degrees Celsius,” according to U-M.
Claiming to have developed the world’s smallest computer is a contentious honor, since the definition of a computer itself is up for debate. For example, U-M and IBM both created systems that lose all previous programming and data once they lose power.
“We are not sure if they should be called computers or not. It’s more of a matter of opinion whether they have the minimum functionality required,” says Blaauw.
Whatever the label may be, the microdevices can help in a number of fields, including internal eye pressure sensing for glaucoma diagnosis, audio and visual surveillance, oil reserve and biochemical process monitoring, and tiny snail studies.
The research paper, “A 0.04mm3 16nW Wireless and Batteryless Sensor System with Integrated Cortex-M0+ Processor and Optical Communication for Cellular Temperature Measurement,” was presented June 21 at the 2018 Symposia on VLSI Technology and Circuits.
Take a look at the image below, which compares the U-M computer (right) to a grain of rice (left).