Pioneers in pain relief: UF-led research team test injectable, battery-free neural implants

A team led by University of Florida researchers is developing an injectable implant to stimulate nerves without batteries or wires. The research stands to improve treatment for chronic pain and neurological disorders. 

The implant is injected into the body and powered wirelessly by a small, wearable — and removable — transmitter worn outside the body that transmits energy through the tissue.  

“In our study, we demonstrated that the implant could be placed next to the sciatic nerve in rats and wirelessly activate the nerve and produce muscle responses. We also found that it remained in position with minimal visible tissue response during the study,” said project lead Adam Khalifa, Ph.D., the Dean Wayne Chen Faculty Fellow and an assistant professor in UF's Department of Electrical & Computer Engineering, known as ECE. 

These tiny stimulators are injected into the body with a needle. The wearable transmitter, in turn, is smaller than a baseball card and is affixed to the skin near the implant with an adhesive. The battery is in the transmitter, which takes advantage of the fact that the body’s tissues naturally conduct electricity to send energy through the tissue and power the tiny implant. 

Another benefit: Patients can wear the transmitter as they need it. If the device is treating pain, for example, patients can remove the transmitter, like a patch, when the pain is gone. 

Existing spinal or peripheral nerve stimulators require surgical implantation to accurately position leads on millimeter-scale nerves. Those stimulators are powered by bulky batteries with long electrodes that are surgically implanted under the skin.  

This new wireless device makes procedures much more appealing to patients, who go home that day without the discomfort — and cost — of a more invasive procedure. 

The team also includes UF’s Nelms Rising Star Endowed Professor Baibhab Chatterjee, Ph.D., UF Instructional Associate Professor Erin Patrick, Ph.D., and Shriya Srinivasan, Ph.D., director of the BIONICs Lab at Harvard University. They detailed the research in a paper published this month in the journal Advanced Science. 

In her lab at Harvard, Srinivasan and her team are developing treatments through a single needle point a few millimeters in size. The smaller the better, as implementation is scar-free and can be performed by a procedural specialist, not a neurosurgeon. 

“I am building many technologies for clinical scale,” said Srinivasan, who serves as an assistant professor of bioengineering at Harvard. “All the projects in our lab are supposed to be in the clinic between five and 10 years from now. And in that sense, having mechanisms that allow us to miniaturize is super critical.” 

Srinivasan took interest in the project after she and Khalifa met at a conference. Her lab works with implantable and ingestible devices for neuromodulation across the body. A major challenge, she said, is power and coupling.  

UF Health neurosurgeon Serban Negoita, MD, has been collaborating with Khalifa and sees broader potential for using injectable devices to interact with the nervous system. 

“I think the clinical applications are widespread and robust, from epilepsy to detection of ischemia/stroke after traumatic brain injury or subarachnoid hemorrhage to treating disorders of consciousness,” said Negoita, 

Battery-less, injectable stimulators hold tremendous promise for pain relief, and the next step is testing the device in humans or large animals. 

“We are working to reduce its size by half for testing in humans, but that is still a work in progress," Khalifa said, 

This research evolved after the National Institutes of Health awarded Khalifa a $1.5 million grant in 2024 to develop minimally invasive implants. At the time, he said the “ultimate goal is to develop devices that are battery-free, injectable microchips that can be deployed anywhere in the body.” 

 The new study is an important step toward that vision, and the team is seeking additional grants to further the research.  

“The long-term vision,” Khalifa said, “is to make electrical stimulation therapies smaller, less invasive and easier to deploy throughout the body, potentially opening new approaches for conditions such as chronic pain, nerve injuries and other neurological disorders.”