Northwestern University implant activates neurons with micro-LED array

16 Dec 2025

Patterned bursts of light could help rehabilitation and pain relief.

A project at Northwestern University (NU) has developed a new implant for activating the neurons of mouse subjects with light.

The soft and flexible device sits under the scalp but on top of the skull, delivering patterns of LED light through the bone to trigger genetically modified neurons across the cortex.

Developed in the NU lab of John Rogers and soon to be described in Nature Neuroscience, the implant could offer new routes to modulating pain perception, stimulating vision or hearing prostheses, and enhancing rehabilitation.

"Our brains are constantly turning electrical activity into experiences, and this technology gives us a way to tap into that process directly,” said NU neurobiologist Yevgenia Kozorovitskiy.

"This platform lets us create entirely new signals and see how the brain learns to use them. It brings us just a little bit closer to restoring lost senses after injuries or disease while offering a window into the basic principles that allow us to perceive the world."

In 2021 the Rogers Group developed what was said to be the first fully implantable, programmable, wireless, battery-free device capable of controlling neurons with light, in which illumination from a single micro-LED light source was used to stimulate genetically modified neurons.

The new device goes further, featuring not just one but a programmable array of up to 64 micro-LEDs. This means researchers can send complex sequences to the brain that may resemble the distributed activity that occurs during natural sensations. Because real sensory experiences activate distributed cortical networks, not tiny localized groups of neurons, the multi-region design mimics more natural patterns of brain activity.

Addressing health challenges in humans

The implant is also less invasive, noted the NU team. Instead of extending into the brain through a tiny cranial defect, the new soft flexible device conforms to the surface of the skull and shines light through the bone.

"Developing this device required rethinking how to deliver patterned stimulation to the brain in a format that is both minimally invasive and fully implantable," commented John Rogers.

"By integrating a soft, conformable array of micro-LEDs with a wirelessly powered control module, we created a system that can be programmed in real time while remaining completely beneath the skin, without any measurable effect on natural behaviors of the animals."

In trials, the project studied mice given the task of visiting a specific port in a chamber in order to receive a reward. The implant was programmed to deliver dozens of alternative stimulation patterns to the animal's brain, and the team associated one of those patterns with the choice that yielded a reward; a connection the mice quickly learned, consistently choosing correctly when stimulated.

The next steps will be to test more complex patterns, to see how many distinct stimulations the brain can learn. Future iterations might include more LEDs, narrower spacing between LEDs, larger arrays covering more of the cortex and wavelengths of light that penetrate deeper into the brain.

"The system represents a significant step forward in building devices that can interface with the brain without the need for burdensome wires or bulky external hardware," said Rogers. "It's valuable both in the immediate term for basic neuroscience research and in the longer term for addressing health challenges in humans."