Four months later, researchers from the University of Michigan (United States) have managed to reduce its size and even make the IBM device look like a giant. The size barely reaches a millimeter long, it stays at 0.3 mm.

Its size, comparable to that of a grain of rice, allows you to make a short to-do list. It can do calculations, some operations, it has a processor and it also has RAM. « We’re not sure if they should be called a computer or not. It’s more a matter of opinion whether they have the minimum required functionality,” says David Blaauw, professor of electrical and computer engineering at the University of Michigan.

Despite its tiny size, it has a big but: when it is turned off, all the stored information is lost. Also new, engineers at the University of Michigan have managed to make this device work with photovoltaic energy. “We had to invent new ways to approach circuit design that would be equally low-power, but could also tolerate light,” Blaauw points out.

Designed as a precision temperature sensor, the new device converts temperatures into time intervals, defined with electronic pulses. The intervals are measured on-chip against a constant time interval sent by the base station and then converted to a temperature. As a result, the computer can report temperatures in tiny regions, such as a group of cells, with an error of about 0.1ºC.

The system is very flexible and could be reinvented for a variety of purposes, but the team chose precision temperature measurements because of a need in oncology.

Some studies suggest that tumors run hotter than normal tissue, but the data is not strong enough to be confident on the issue. Temperature can also help evaluate cancer treatments.