
Brain-computer interfaces have enabled people with paralysis to move a computer cursor with their mind and reanimate their muscles with their thoughts. But the performance of the technology—how easily and accurately a BCI user’s thoughts move a cursor, for example—is limited by the number of channels communicating with the brain.
Science Corporation, one of the companies working towards commercial brain-computer interfaces (BCIs), is forgoing the traditional method of sticking small metal electrodes into the brain in favor of a biology-based approach to increase the number of communication channels safely. “What can I stick a million of, or what could I stick 10 million of, into the brain that won’t hurt it?” says Alan Mardinly, Science Corp co-founder.
The answer: Neurons.
Science Corp has designed a waffle-like device to house and place a new layer of neurons across the brain’s surface. The company’s researchers tested the device in mice, in which the additional neurons enabled the mice to learn to move left or right only if the device is “on.” The research lays the groundwork for a future interface that does not damage the brain as much as existing BCIs—or at all. The research was shared in a study posted to the bioRxiv preprint server in November.
A Neuron-filled Waffle
BCIs connect neurons within the brain to external computers. During clinical studies at universities across the U.S., roughly three dozen humans have controlled BCI technology using millimeter-scale metal electrodes stuck down into the brain through a coin-sized opening in the skull.
Other research teams have designed thinner, softer, or smaller devices than the traditional metal electrodes in order to electrically connect neurons to computers and avoid damaging the neurons and blood vessels while doing so. Neuralink, for instance, uses bendable polymer electrodes in its BCI.
Instead of sticking anything into the brain, the Science Corps device sits on top of it. But the device isn’t just a board stuck on the brain’s surface—it’s full of neurons. Neurons sit in the wells of a waffle-like device before being stuck to the brain surface, neuron-side down. Neurons grow down into the brain, acting as a glue between the device and the brain’s tissue.
Science Corp’s biohybrid technology aims to integrate biology into the devices implanted into the body. Biohybrid technology is an old idea, Mardinly says. It’s gone in and out of popularity in BCI research—it first showing up in early BCI research in the 1990s and again more recently. But the idea is a complex one because neurons are fragile and BCI technology has generally moved towards sturdier electrodes.
Science Corp, based in Alameda, California, was founded in 2021 by Mardinly and one of Neuralink’s co-founders, Max Hodak. The biohybrid project began soon after the medical technology company’s founding in early 2022, and the work presented in the bioRxiv study took around four or five months to complete, Mardinly says.

Science Corp’s setup implants light-sensitive neurons into a mouse’s brain (left). Three weeks after the device was implanted, roughly half of the light-sensitive neurons were still present.Jennifer Brown, Kara M. Zappitelli et al.
The process of building the biohybrid device begins on the benchtop where neurons—specifically a kind called primary cortical excitatory neurons, which fire off signals to neighboring neurons—are derived from embryonic stem cells taken from the same mouse line as the mouse into which Science Corp’s researchers implanted the device to test it. The neurons are modified to have optogenetic properties, meaning they will fire when hit with light of a certain frequency.
The device looks like a waffle with little dishes called microwells, each 10 micrometers in diameter, mounted on a clear backing. Each microwell holds one neuron, and each device, clocking in at around 5 millimeters square, houses an average of 90,000 neurons. Neurons from the biohybrid device grew into the very top part of the cortex and blood vessels grew into the new neurons.
But just having neurons grow into the brain will not mean that the biohybrid device can change the brain’s function.
So, researchers shined light onto the device through a glass window in the mouse’s skull. The light “turned on” the new neurons, and the researchers turned on the light when the mouse was learning whether to turn left or right to get a treat. Mice learned to move to the left of a cage when the light was shone on the device in order to get their reward; when the light was turned off, mice learned to move to the right to get their reward.
The new light-sensitive neurons helped five of the nine mice learn a new behavior, which to Mardinly suggests that the biohybrid device successfully “modulates output behavior.”
Images of the brain under the implant showed neuronal axons sticking down through the pia matter, the dense cell layer at the very surface of the brain, and into layer 1 of the cortex.
“We haven’t proven that they’re forming synopsis, but it seems extremely likely,” Mardinly says.
A Big Jump for BCIs
By itself, this biohybrid device is not yet an interface, says Jack Judy, professor of electrical engineering at the University of Florida, who was uninvolved in the work. Judy previously led a past neuroprosthesis program funded by the U.S. Defense Advanced Research Projects Agency.
“When I think of an interface—well, there’s information coming out of the device,” says Judy. Instead, it’s a way to prepare tissue for an optical interface by spreading optically active cells across the brain, he says.
Mardinly says the team at Science Corps has already begun building future biohybrid devices with inputs and outputs from the brain. The devices house neurons in trenches instead of wells. One side of the trench has LEDs to deliver light to small groups of the neurons, and the other side will have electrical contacts to record the action potentials from neurons, similar to how many BCI technologies record from neurons already in the brain.
Going from proof of concept to a prototype is a big jump, Mardinly says. It’s an “extremely complicated” design, he says. “Is any of this worth it? And, you know, that remains to be seen, right? That’s on us to move forward and demonstrate.”
The research team acknowledges that it is difficult to pinpoint exactly how integrated the neurons from the graft are into the brain. Optogenetic stimulation requires just a few hundred neurons to work, as seen in past studies, and the biohybrid device adds many more than that to the brain.
The study leaves many unknowns, crucially why four of the nine mice with biohybrid devices with light-activated neurons did not learn the task.
The next major milestone is to develop a biohybrid device with human-engineered cells that records and stimulates, and then test the work in a larger animal.