Researchers have developed a needle-thin, flexible brain implant less than half a millimeter wide that can record electrical activity, deliver drugs, and stimulate nerve cells using light across multiple brain layers simultaneously. Developed by a cross-institutional team, the mAxialtrode marks a shift from rigid silicon devices to softer, tissue-friendly polymers.
Traditional brain research tools often rely on rigid silicon components or basic, flat-ended optical fibers that interact with neural tissue only at their very tip. These conventional glass or plastic fibers permit scientists to monitor or stimulate just one location at a time, creating a blind spot when studying complex neurological processes that require communication across several distinct brain layers. To overcome those physical and functional limits, a collaborative team of investigators has engineered a much more versatile instrument known as the microfluidic Axialtrode, or mAxialtrode.
The project brings together researchers from DTU, the University of Copenhagen, University College London, and other institutions. Rather than forcing scientists to choose between recording electrical signals, delivering liquid medication, or applying optical stimulation with separate hardware, the new device packs all three capabilities into a single polymer fiber.
Engineering the Needle-Thin mAxialtrode
Manufacturing the mAxialtrode starts with a larger polymer rod. Researchers heat this material and draw it down into an ultra-thin strand, comparable to pulling a fine thread of sugar with extreme precision. The resulting fiber measures less than half a millimeter across.
Running through the center of this flexible fiber is a dedicated light-conducting core designed for optogenetics, a method that uses light to activate specific nerve cells. Surrounding the optical core are eight microscopic channels capable of transporting liquids. These same internal pathways also house microscopic metal wires dedicated to measuring electrical activity.
Kunyang Sui stated that most current brain implants are based on hard materials such as silicon, which can irritate the brain and trigger inflammatory reactions in the tissue.
Because the device is constructed from soft, plastic-like polymers rather than rigid silicon, it flexes and moves naturally alongside brain tissue rather than pressing stiffly against it over extended periods.
Testing in Living Mice and Potential Therapeutic Horizons
The research team put the system through its paces during in vivo experiments on living mice, connecting the implanted electrodes to recording gear, light sources, and miniature fluid pumps. The trials confirmed that the single lightweight fiber allowed the test animals to move about without obvious discomfort while researchers stimulated nerve cells using both blue and red light.
At the same time, the team recorded electrical activity simultaneously across shallow and deeper structures, including both the hippocampus and the cerebral cortex. The device also successfully injected distinct chemical substances at separate depths, with delivery points spaced nearly three millimeters apart along a single insertion.
While the technology functions primarily as a sophisticated research apparatus for investigating memory, decision-making, and signal pathways involved in conditions like epilepsy, its creators envision broader future applications. Over the long term, developers suggest the mAxialtrode could combine precise drug delivery with concurrent electrical or light stimulation inside targeted regions of the brain.
Clinical Realities and Next Steps for the Platform
Despite the versatility demonstrated in laboratory mice, investigators emphasize that routine clinical use remains a distant prospect. Transforming the experimental device into a therapy for human patients will demand extensive additional development, rigorous safety testing, and formal regulatory approvals.
The underlying neurophysiological validation and in vivo experiments were advanced through close collaboration involving Associate Professor Rune W. Berg at the University of Copenhagen and Associate Professor Rob C. Wykes at University College London, alongside the concept’s developers, Kunyang Sui and Associate Professor Christos Markos. As development continues, the platform points toward a future where a single, tissue-compatible fiber can listen to and influence the brain on multiple fronts at once.