A team of engineers at the University of Michigan has created a computer small enough to stand on the tip of a grain of rice. With a volume of 0.4 cubic millimeters, it holds the title of the world’s smallest computer, outdoing IBM’s most recent attempt.

Because of its small size, there are limitations on what the device can actually do. But according to Xiao Wu, an Engineering doctorate student who worked on the project, the defining elements of a computer are all present.

“It has basic components of a computer,” Wu said. “It has a microprocessor that’s (a) general purpose processor unit. It’s an Arm patent Cortex-M0+, so it’s a commercial processor. And it’s also got its own memory. So it’s a smaller and simpler version of a computer, but it’s got basic elements of the computer.”

The computer is the product of many years of work, according to David Blaauw, a professor of electrical engineering and computer science who co-led the recent project and has been working on tiny computing since 2005. Throughout the years, his team has found ways to reduce power consumption of computer chips and circuits, enabling the development of smaller computers.

Blaauw said with such low power consumption comes the challenge of figuring out how to make a computer run.

“We consume, in standby mode when the sensor's sort of dormant, a few nanoamps, whereas a cell phone would consume a few milliamps,” Blaauw said. “So it's about a million times less than a cell phone power consumption in the same kind of dormant mode."

Blaauw said another challenge is that the computer can only be handled wirelessly. His team communicates with the computer though light signals, and also uses light to recharge it. Regular-size computers and cell phones are able to charge through wires, but the new computer is too small for any kind of connector.

“We can't just conveniently charge it, it has to charge itself with light or something like that,” Blaauw said. “It can't sort of reprogram itself easily with the wire. You need to do it wirelessly. Everything needs to be done wirelessly; it's very challenging.”

Despite these challenges and limitations, the capabilities of small computers like the University’s are valuable. Larger models previously created by the University’s team can monitor pressure or record images and audio, and the most recent model can sense temperature. These abilities have a number of applications, especially because the computer’s small size allows it to be easily implanted. The device can be implanted in a glaucoma patient’s eye to measure pressure or injected into oil wells to measure the temperature and pressure of the oil.

One of the main collaborators with the project is Gary Luker, a professor of radiology and biomedical engineering at the University, whose team focuses on breast cancer. They have been investigating whether changes in temperature or pressure of tumors can be used to predict the success or failure of chemotherapy. Some studies also speculate cancerous tissue is warmer than normal tissue.

To test their hypotheses, Luker and his team been implanting the tiny computers into mouse tumors to measure temperature and pressure. In an email interview with The Daily, Luker noted the tiny computers are the best way to accomplish this type of research, since other methods, like inserting a needle, are invasive and inconsistent.

“The implanted sensors measure these parameters nearly continuously; store the data; and then transmit on demand,” Luker wrote. “No other technology can accomplish this.”

Luker pointed out how his and Blaauw’s collaboration shows working with different University departments can pave the way to groundbreaking research.

“Working with David’s group is a great example of how interdisciplinary research has the potential to transform patient care,” Luker wrote. “The collaboration capitalizes on strengths of UM as an institution — top flight engineering and medical schools.”

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