Researchers at the University of Michigan, makers of the world's smallest computer before IBM took the title, have devised a computer smaller than a grain of rice.
The new microdevice measures 0.3 mm x 0.3 mm, which is nearly a tenth of the most recent record-holder by IBM, a computer presented at the Think conference in March 2018.
In new research presented at the 2018 Symposia on VLSI Technology and Circuits in Honolulu, Hawaii, the team presented the new device, which runs on its own processors, RAM, and solar cells for power generation.
A Microdevice That Runs On Light
One of the challenges in making a computer this tiny is figuring out how to run on very low power. Because it is too small to have a radio antenna like conventional computers, the microdevice runs on visible light that is received from a base station. This light, and also light that comes from transmitters, can generate electric currents within the computer's small circuits.
"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, professor of computer and electrical engineering.
The researchers say the microdevice is flexible enough to fit a variety of applications. For instance, the Michigan Micro Mote, the world's smallest computer before being topped by IBM's device, was used for a wide range of applications in the medical field. These include testing eye pressure for glaucoma patients, monitoring of biochemical processes, and cancer research. The Micro Mote was also useful in checking oil reservoirs, audio and visual surveillance, and snail research.
For the microdevice, the researchers chose to test it first in oncological applications, specifically in diagnosing tumors and evaluating new forms of cancer treatment.
Previous studies have shown that tumors may be hotter than their surrounding tissue, which means they could potentially be detected by measuring the temperature of cells and comparing it with the surrounding tissue.
The microdevice has proven to have a very high accuracy in temperature measurements. Using a precision sensor that can convert temperature into time intervals, which are then compared to a steady interval sent by the base station, it can detect temperature even in the tiniest of spaces, such as a clump of tumorous cells, with an offset of 0.1 degree Celsius, and compare it with its neighboring cells.
"Since the temperature sensor is small and biocompatible, we can implant it into a mouse and cancer cells grow around it," says Gary Luker, biomechanical engineer and radiologist who has been working with the team.
The researchers, however, are actually wary about calling their microdevice a computer. The Micro Mote, which used solar cells to harness ambient light to power the battery, could run in rooms without sunlight and retain programming and data even after it being shut down.
The microdevice, along with IBM's tiny computer, on the other hand, will lose all programming once someone shuts it down.
"We are not sure if they should be called computers or not," Blaauw admits. "It's more of a matter of opinion whether they have the minimum functionality required."