Fitness trackers have become some of the more popular types of wearable technology in recent years, but engineers at the University of California, Berkeley want to take the concept one step further by developing miniscule, wireless sensors to monitor a person’s internal health.

These devices would be approximately the same size as a grain of dust and would be implanted into a person’s body, where they would provide real-time monitoring of organs, muscles, and/or nerves, the researchers explained in the August 3 edition of the journal Neuron.

Furthermore, the sensors don’t use batteries and could be used to stimulate nerves and muscles, thus providing a potentialnew way to treat disorders such as epilepsy or to activate a person’s immune system. The devices, which have already been implanted in the muscles and peripheral nerves of rats, use ultrasound both as a source of power and as a way to read the collected data.

Dubbed “neural dust,” the sensors have already been reduced down to a one millimeter cube and contain a piezoelectric crystal. The crystal converts ultrasound vibrations emanating from outside a person’s body into electricity, which is used to power a tiny transistor on the device which is in direct contact with a nerve or muscle fiber, the study authors explained.

Devices could also be used to power prosthetics, researchers claim

Voltage spikes in the fiber causes changes to the circuit and the vibration of the crystal, which in turn changes the echo detected by the ultrasound receiver (which in the majority of instances will also be the source of the vibrations). Since ultrasound technology is common in hospitals and the vibrations can penetrate most parts of the body, it seemed like a natural fit.

Furthermore, as co-lead author Michel Maharbiz, an associate professor of electrical engineering and computer sciences at UC-Berkley, noted in a statement, “I think the long-term prospects for neural dust are not only within nerves and the brain, but much broader.”

“Having access to in-body telemetry has never been possible because there has been no way to put something supertiny superdeep,” Maharbiz, who co-authored the study along with colleague and UC-Berkley neuroscientist Jose Carmena, explained. “But now I can take a speck of nothing and park it next to a nerve or organ, your GI tract or a muscle, and read out the data.”

In order to test out their devices, Maharbiz and Carmena powered up the sensors using six 540-nanosecond ultrasound pulses delivered once every 100 microseconds. This provided them with continual readouts from the device in real-time. So far, the experiments have been limited to just the peripheral nervous system and muscles, but the researchers are confident that they could also be effective in the brain and central nervous system and brain, and could even be used to control prosthetic devices eventually.

“The original goal of the neural dust project was to imagine the next generation of brain-machine interfaces, and to make it a viable clinical technology,” said neuroscience graduate student Ryan Neely. “If a paraplegic wants to control a computer or a robotic arm, you would just implant this electrode in the brain and it would last essentially a lifetime.”

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Image credit: Stephen McNally and Roxanne Makasdjian, UC Berkeley

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