Imagine a device so incredibly tiny, it could rest comfortably on a grain of salt, yet it's capable of revolutionizing how we understand the human brain! That's the reality thanks to a groundbreaking neural implant developed by researchers at Cornell University and their collaborators. This marvel of micro-engineering can wirelessly transmit brain activity data in a living animal for over a year.
This incredible feat, detailed in the journal Nature Electronics on November 3rd, showcases the potential of microelectronic systems to function at an unprecedentedly small scale. This opens up exciting new possibilities for neural monitoring, bio-integrated sensing, and many other applications we haven't even dreamed of yet.
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 began working on the technology as a postdoctoral associate in Molnar’s lab.
So, how does this tiny marvel work? The MOTE is powered by red and infrared laser beams that 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, built using the same semiconductor technology found in everyday microchips.
The MOTE itself is remarkably small, measuring 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 explained. "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 first in cell cultures and then implanted it into the barrel cortex of mice – the brain region responsible for processing sensory information from whiskers. Over a year, the implant successfully recorded electrical activity spikes from neurons and broader patterns of synaptic activity. And the best part? The mice remained healthy and active throughout the entire process.
"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 really interesting: Molnar suggests that the MOTE's material composition could allow for electrical recordings from the brain during MRI scans, which is largely impossible with current implants. The technology could also be adapted for use in other tissues, such as the spinal cord.
Molnar first conceived of the MOTE 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.
This technology promises to change the future of neuroscience. What do you think about the potential of these tiny implants? Could this technology lead to breakthroughs in treating neurological disorders, or are there ethical concerns we should be discussing? Share your thoughts in the comments below!
