New Wireless Sensor Uses Light to Run Nearly Perpetually

1 mm thick sensor could be used in medical and building applications.

2 min read
New Wireless Sensor Uses Light to Run Nearly Perpetually

The race to create tiny wireless sensors that could monitor anything from pressure in the eyes and brain to the stability of bridges appears to be heating up. Earlier this month, IEEE Spectrum reported on two approaches to creating an almost-indefinitely-running sensor using piezoelectric systems to convert tiny vibrations into power. Now, another team from the University of Michigan has created an alternative approach that uses solar power to keep the sensor running autonomously for many years.

The new sensor checks in at less than 9 mm3, and utilizes an ARM Cortex-M3 core processor. The system allows the sensor to consume only about 100 picowatts when in sleep mode, and only 2.1 µw upon waking up to take sensor measurements. The average power consumption comes out to less than 1 nanowatt. To provide that power, the sensor has a thin-film lithium-ion battery and two 1 mm2 solar cells. It need only be exposed to even mild lighting conditions periodically; in fact, one of the researchers, professor of electrical and computer engineering David Blaauw, said in a press release that it can even be indoor lighting to power the sensor.

The U of M researchers, who presented their work at the International Solid State Circuits Conference in San Francisco last week, said they are working with doctors to come up with potential medical applications for their device. Such internal versions of their sensor could be modified to harvest power from heat or movement, much like the microelectromechanical systems described above. They could be used to monitor pressure in the eyes or brain, or even inside tumors in cancer patients. Blaauw said in a phone call that the intraocular pressure monitoring application could actually still use solar power even when implanted within the eye.

"There is one piece that's missing from our system, and that's the communication," Blaauw said. "That still needs to be added, but we have some prototypes." He said the communications system will not substantially change the sensor's size. Other systems that incorporate a real microprocessor clock in at around 1 cm3, Blaauw said. "Ours is almost 100x smaller."

Image credit: Daeyeon Kim, University of Michigan

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This Implant Turns Brain Waves Into Words

A brain-computer interface deciphers commands intended for the vocal tract

10 min read
A man using an interface, looking at a screen with words on it.

A paralyzed man who hasn’t spoken in 15 years uses a brain-computer interface that decodes his intended speech, one word at a time.

University of California, San Francisco
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A computer screen shows the question “Would you like some water?” Underneath, three dots blink, followed by words that appear, one at a time: “No I am not thirsty.”

It was brain activity that made those words materialize—the brain of a man who has not spoken for more than 15 years, ever since a stroke damaged the connection between his brain and the rest of his body, leaving him mostly paralyzed. He has used many other technologies to communicate; most recently, he used a pointer attached to his baseball cap to tap out words on a touchscreen, a method that was effective but slow. He volunteered for my research group’s clinical trial at the University of California, San Francisco in hopes of pioneering a faster method. So far, he has used the brain-to-text system only during research sessions, but he wants to help develop the technology into something that people like himself could use in their everyday lives.

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