Needle-Access Power Outlet for Implants Survives 100 Insertions

A soft, spongy implantable power outlet survived more than 100 needle insertions without losing electrical performance or insulation, according to engineers at the University of California, Irvine. The device, described 8 July in Science Advances, is intended to charge and read out implanted bioelectronics — including neural interface devices — through a needle jab rather than through a permanent socket or a bulky wireless antenna.

"It is intended to serve as a general access point that could be integrated with many existing implantable bioelectronic devices, including sensors, neural interfaces, stimulators, and battery-powered systems," said Dion Khodagholy, associate professor of electrical engineering and computer science at UC Irvine.

How the device works

The implantable bioelectric outlet is built from a porous plastic sponge with pores roughly 150 micrometers wide — about the diameter of a very fine needle. The fabrication is a three-step dip process:

• The sponge is dipped in a conductive polymer, coating each pore with a layer 100 to 200 nanometers thick.
• A silicone rubber solution forms a protective, electrically insulating jacket around the exterior.
• Several jacketed layers are sandwiched between unmodified sponge layers and the whole stack is sealed in silicone rubber.

Because the jacketed layers are conductive throughout, the needle does not need to strike one precise point to make a connection. That is a practical improvement over pin-and-socket designs that demand accurate alignment.

"With our approach, the device remains completely under the skin," said Hyung Joon Shim, a postdoctoral scholar in electrical engineering at UC Irvine. "A needle is inserted only when electrical access is needed and is removed afterward."

What did the animal studies show?

This is animal work, not clinical data, and readers should hold it to that standard. The evidence comes from three species:

• In mice and rats, the team coupled the outlets to neural interface devices. Needle insertion recharged implant batteries and pulled data at the implants' maximum transfer speed of nearly 16 megabits per second.
• In pigs, the outlets supported electrical stimulation implants previously shown to aid nerve healing, delivering 20-microampere pulses of 100 milliseconds each over extended periods.
• Outlets implanted in mice for more than one year showed no degradation and no visible adverse effects.

The porous structure resisted crack propagation when punctured with needles ranging from 30 gauge (0.1 millimeters) to 18 gauge (1.5 millimeters). "In our laboratory tests, the device maintained its electrical performance and insulation after more than 100 insertions," Khodagholy said.

"Long-term safety and stability are among the most important requirements for any implantable technology," said Jennifer Gelinas, associate professor of pediatrics and anatomy and neurobiology at UC Irvine.

What does this change for implanted neural interfaces?

For now, nothing in clinical practice. The device is investigational, animal-stage, and its anesthetized-subject protocol sidesteps the problem of a moving, awake patient. Gelinas noted that in an awake subject the needle and wire would need securing to the skin with medical tape or an adhesive dressing, much like an IV line.

The realistic promise is hybrid: routine wireless operation, with needle access reserved for fast charging, bulk data downloads, firmware updates, or maintenance. "An implant might use wireless communication for routine operation, and use the implantable bioelectric outlet only when direct access is more useful," Shim said.

The road from rodent to reading room

Discomfort is expected to resemble an injection or a small IV needle. Future versions could use thinner needles — the outlet probe needs no hollow fluid channel, so it could be slimmer than a conventional injection needle — plus topical anesthetics or coatings that reduce pain and inflammation.

The fabrication relies on readily available materials, which Shim said could make manufacturing and translation more practical. Gelinas was blunt about the remaining gaps: pain, skin irritation, infection risk, tissue response, and electrical performance across many access sessions all require evaluation before any patient use.

For clinicians who follow implantable neurotechnology, the work is worth tracking rather than acting on. A percutaneous access point that tolerates repeated punctures would ease the power and data bottlenecks that limit long-term implanted systems, but the first human validation studies remain ahead.