World’s Smallest Implantable Brain Stimulator Demonstrated in Human Patient

Implantable devices that deliver electrical stimulation to the central or peripheral nervous system are increasingly employed in the treatment of psychiatric conditions, movement disorders, and pain issues, and for helping to restore mobility after spinal cord injuries. However, the current implantable devices used for brain stimulation depend on comparatively large batteries. These batteries need to be implanted under the skin at a location different from the stimulation device and are connected by long wires. This arrangement requires additional surgeries, increases the risk of hardware complications like wire breakage, and often requires surgeries to replace batteries. Engineers have now developed what is considered the smallest implantable brain stimulator used in a human to date. Utilizing innovative magnetoelectric power transfer technology, this tiny device can be wirelessly powered by an external transmitter and is capable of stimulating the brain through the dura—the protective membrane that lines the base of the skull.

This device, created by engineers at Rice University (Houston, TX, USA) and dubbed the Digitally programmable Over-brain Therapeutic (DOT), could transform the treatment landscape for drug-resistant depression and other psychiatric or neurological disorders. It provides a less invasive alternative compared to existing neurostimulation therapies and other brain-computer interfaces (BCIs), offering greater patient autonomy and easier access. The device utilizes a material that efficiently converts magnetic fields into electrical energy. This conversion is highly efficient even at small dimensions and tolerates alignment errors well, simplifying the activation and control processes. The device itself is 9 millimeters wide and capable of delivering up to 14.5 volts of electrical stimulation.

Image: The first-ever miniaturized brain stimulator has been shown to work in a human patient (Photo courtesy of Rice University)

In initial tests, the device was temporarily implanted in a human patient to stimulate the motor cortex, the brain region that controls movement, successfully eliciting a hand movement. Further tests showed that the device could stably interface with the brain for up to 30 days in pig models. The implant procedure, taking about 30 minutes, involves placing the device within the skull bone, resulting in an almost invisible incision and implant site. Patients would be able to return home on the same day as the procedure. The technology could allow it to be operated comfortably from home. Doctors would prescribe and oversee the treatment, but patients would manage the application themselves.

“In the future, we can place the implant above other parts of the brain, like the prefrontal cortex, where we expect to improve executive functioning in people with depression or other disorders,” said Jacob Robinson, a professor of electrical and computer engineering and of bioengineering at Rice.

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Rice University