Imagine a world where we can peek directly into the brain, understanding its intricate workings with unprecedented clarity. Well, that world is getting closer, thanks to a groundbreaking innovation: a neural implant so incredibly tiny, it could comfortably sit on a grain of salt! This remarkable device, developed by Cornell University researchers and their collaborators, can wirelessly transmit brain activity data in a living animal for over a year.
This incredible feat, detailed in Nature Electronics on November 3rd, showcases the potential of microelectronic systems operating at an unbelievably small scale. This opens doors to a new era of neural monitoring, bio-integrated sensing, and a host of other applications we can only begin to imagine.
The device, known as a microscale optoelectronic tetherless electrode, or MOTE, was co-led by Alyosha Molnar, the Ilda and Charles Lee Professor in the School of Electrical and Computer Engineering, and Sunwoo Lee, an assistant professor at Nanyang Technological University. Lee initially started working on this technology during his postdoctoral work in Molnar’s lab.
So, how does this tiny marvel work? The MOTE is powered by red and infrared laser beams, which pass harmlessly through brain tissue. It then transmits data 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. This is supported by a low-noise amplifier and optical encoder, all built using the same semiconductor technology found in everyday microchips.
To give you a sense of scale, the MOTE is only 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 explains. "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.”
The researchers tested the MOTE in cell cultures and then implanted it into the barrel cortex of mice, the brain region that processes sensory information from whiskers. Over a year, the implant successfully recorded electrical activity spikes from neurons and broader patterns of synaptic activity – all while the mice remained healthy and active.
"One of the motivations for doing this is that traditional electrodes and optical fibers can irritate the brain," Molnar noted. "The tissue moves around the implant and can trigger an immune response. Our goal was to make the device small enough to minimize that disruption while still capturing brain activity faster than imaging systems, and without the need to genetically modify the neurons for imaging.”
But here's where it gets controversial... Molnar believes the MOTE's material composition could allow for electrical recordings during MRI scans, which is largely impossible with current implants. This opens exciting possibilities for combining different brain imaging techniques. The technology could also be adapted for use in other tissues, such as the spinal cord, and even integrated with future innovations like opto-electronics embedded in artificial skull plates.
Molnar first conceived of the MOTE back in 2001, but the research gained momentum about a decade ago when he began discussing the idea with members of Cornell Neurotech. Co-authors of the paper include Chris Xu, Paul McEuen, Jesse Goldberg, and Jan Lammerding.
What do you think? Could this technology revolutionize how we understand the brain? Are there any ethical concerns that should be addressed? Share your thoughts in the comments below!
