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A team led by Deblina Sarkar at the MIT Media Lab has developed a radically new kind of brain implant that is smaller than a cell, powered by near-infrared light, and can be delivered to the brain through a simple injection, rather than open-brain surgery. The study, published recently, describes “circulatronics”—tiny photovoltaic chips that can generate electrical pulses once inside the brain, potentially transforming how neurological disorders are treated.
Traditional brain implants restore functions like movement or speech, but their use is limited by the need for invasive surgery and bulky hardware. Sarkar’s team overcame these barriers by building microchips just 10 microns wide—flexible, biocompatible devices that act like miniature solar panels. The challenge was delivering them into the brain without disrupting the protective blood–brain barrier. The researchers solved this using a clever “Trojan horse” strategy: attaching the chips to monocytes, immune cells that naturally travel into inflamed brain regions. Using click chemistry, the chips latch onto monocytes like detachable Velcro.
In mouse experiments, the injected hybrid cell-chip implants navigated the bloodstream, crossed the intact blood–brain barrier, and accumulated precisely at artificially inflamed brain sites. When stimulated with pulses of near-infrared light—easily penetrating skull and tissue—the chips triggered neuronal activity comparable to that produced by conventional implants. Importantly, the devices did not disturb normal behaviour, cognition, or organ function over six months.
The approach could one day enable non-surgical treatment for conditions such as Alzheimer’s, depression, stroke, and brain tumours. Because the chips can be engineered to dissolve, they may also offer a way to record brain activity in healthy people over time. Sarkar’s team, through their spinoff Cahira Technologies, aims to begin clinical trials within three years, with the long-term goal of deploying injectable bio-electronic devices throughout the body to monitor or modulate disease.
