Where size matters: New brain implant is as small as a grain of salt

The device, reported November 3 in Nature Electronics, was created by a team at Cornell University and collaborators. 

At roughly 300 microns long and 70 microns wide, it is believed to be the smallest implant ever to both detect and transmit electrical signals inside the brain without the need for wires.

The implant, known as a microscale optoelectronic tetherless electrode (MOTE), was tested in mice and remained functional for more than 12 months, capturing both individual neuron spikes and broader activity patterns while the animals continued normal behavior.

Developers say the size matters as much as the functionality. Conventional brain implants and optical fibers can trigger inflammation and immune reactions because they move against soft tissue. 

The Cornell team argues the MOTE’s footprint is small enough to reduce those effects.

“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,” said electrical engineer Alyosha Molnar, who co-led the project. 

Molnar said the device uses optical communication methods similar to those in satellite systems to send data with minimal power.

The implant is powered by red and infrared light that passes through brain tissue and returns data encoded in light pulses. 

Researchers said the materials and design could eventually allow neural recording during MRI scans — something current implants typically can’t withstand — and could be adapted for spinal or peripheral nerve monitoring.

The project involved engineers, physicists and neuroscientists at Cornell and Nanyang Technological University, with support from the National Institutes of Health and the National Science Foundation.