Neural implant smaller than salt grain wirelessly tracks brain

ITHACA, N.Y. – Cornell University researchers and collaborators have developed a neural implant so small that it can rest on a grain of salt, yet it can wirelessly transmit brain activity data in a living animal for more than a year.

The breakthrough, detailed Nov. 3 in Nature Electronics, demonstrates that microelectronic systems can function at an unprecedentedly small scale, opening new possibilities for neural monitoring, bio-integrated sensing and other applications.

Development of the device, called a microscale optoelectronic tetherless electrode, or MOTE, was co-led by Alyosha Molnar, professor in the school of electrical and computer engineering, and Sunwoo Lee, an assistant professor at Nanyang Technological University who first began working on the technology as a postdoctoral associate in Molnar’s lab.

Powered by red and infrared laser beams that pass harmlessly through brain tissue, the MOTE transmits data back using tiny pulses of infrared light, which encode the brain’s electrical signals. A semiconductor diode made of aluminum gallium arsenide captures light energy to power the circuit and emits light to communicate the data. Supporting this is a low-noise amplifier and optical encoder built using the same semiconductor technology in everyday microchips.

The MOTE is about 300 microns long and 70 microns wide.

“As far as we know, this is the smallest neural implant that will measure electrical activity in the brain and then report it out wirelessly,” Molnar said. “By using pulse position modulation for the code – the same code used in optical communications for satellites, for example – we can use very, very little power to communicate and still successfully get the data back out optically.”

Molnar said the MOTE’s material composition could make it possible to collect electrical recordings from the brain during MRI scans, which is largely not feasible with current implants. The technology could also be adapted for use in other tissues, such as the spinal cord, and even paired with future innovations like opto-electronics embedded in artificial skull plates.

For additional information, see this Cornell Chronicle story.

Media note: Pictures can be viewed and downloaded here: https://cornell.box.com/v/neuralimplant

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