In a landmark advancement for neurotechnology, researchers have unveiled a brain implant so small it rivals the size of a single grain of rice. Dubbed the microscale optoelectronic tetherless electrode (MOTE), this ultra-miniature device is not only the tiniest neural implant capable of wireless brain activity monitoring, but it also holds promise for use in other delicate tissues of the body.
Measuring roughly the width of a human hair around 300 microns long and 70 microns wide the implant translates neural activity into pulses of infrared light. These light signals can penetrate brain tissue and bone to reach a remote receiver, allowing high-resolution monitoring without physical wires. Alyosha Molnar, an electrical engineer at Cornell University and co-author of the study, remarked, “To our knowledge, this is the smallest device that can record electrical brain activity and transmit it wirelessly.”
The concept for MOTE was first envisioned by Molnar in 2001, but nearly twenty years of development were needed to realize it. Built using a semiconductor diode of aluminium gallium arsenide, the implant is capable of both emitting light to send data and harvesting light energy for its own power. It leverages transmission technologies common to microchips, including pulse position modulation a method also employed in satellite communications paired with an optical encoder and a low-noise amplifier, ensuring highly efficient data transfer with minimal electricity use.
Before animal trials, MOTE was tested in lab-grown cell cultures. Subsequent implantation into the barrel cortex of mice a brain region that processes sensory signals from whiskers showed remarkable results. The device consistently recorded neuronal activity and synaptic patterns over the span of a year, demonstrating reliability in both active and healthy subjects.
Traditional neural implants often face challenges such as interference with MRI scans and tissue irritation caused by electrodes or optical fibers. MOTE addresses these issues through its biocompatible materials and wireless design, minimizing immune reactions while capturing brain signals faster than conventional imaging methods. Molnar emphasized, “We aimed to create a device that is small enough to avoid disrupting brain tissue, yet powerful enough to record activity without the need for genetic modifications.”
While the current focus is on brain monitoring, MOTE’s applications could extend to other sensitive tissues like the spinal cord. Researchers envision integrating the device into synthetic skull plates or adapting it to monitor diverse physiological signals across the body. The study concludes that this technology lays the groundwork for long-term, untethered, and minimally invasive monitoring of vital signals, opening doors to unprecedented insights into neural and bodily functions.