Fixing you from within

Scientists are developing dust-sized wireless-sensor implants to track neural activity in real time to monitor or treat conditions such as epilepsy and control next-generation prosthetics.

The tiny devices have worked in rats and could be tested in people within two years, researchers say.

"You can almost think of it as sort of an internal, deep-tissue Fitbit, where you would be collecting a lot of data that today we think of as hard to access," said Michel Maharbiz, an associate professor of electrical engineering and computer science at the University of California, Berkeley.

Fitbit Inc sells wearable fitness devices that monitor heart rate, quality of sleep, steps walked, stairs climbed and more.

Current medical technologies employ a range of wired electrodes attached to parts of the body to monitor and treat conditions ranging from heart arrhythmia to epilepsy. The idea, according to Maharbiz, is to make those technologies wireless.

The new sensors do not need wires or batteries. They use ultrasound waves for power and to retrieve data from the nervous system.

The sensors, which the scientists call motes, are about the size of a grain of sand.

According to findings published recently in the journal Neuron, the scientists used motes to monitor in real time rats' peripheral nervous systems - the part of the body's nervous system that lies outside the brain and spinal cord.

The sensors consist of components called piezoelectric crystals that convert ultrasound waves into electricity, which powers tiny transistors in contact with nerve cells in the body. The transistors record neural activity and, using the same ultrasound wave signal, send the data outside the body to a receiver.

The researchers said such wireless sensors might be able to give human amputees or quadriplegics a more efficient means of controlling future prosthetic devices.

"It's a meaningful advancement in recording data from inside the body," said Dr Eric Leuthardt, a professor of neurosurgery at Washington University in St Louis.

"Demonstrations of capability are one thing, but making something for clinical use, to be used as a medical device, is still going to have to be worked out."

Before implanting wireless sensors into the brain, the science of understanding how the brain processes and shares information needs to advance further, he said.

To deliver motes, currently one millimetre in size, in the brain, the researchers would need to miniaturise the sensors further to about 50 microns, about the width of a human hair.

"It's not impossible," Maharbiz said. "The math is there."