Wireless Recharging Of Implant Batteries Via Ultrasound

Researchers are working on technology to recharge medical implants over a wireless connection.

When the battery dies in an implanted medical device, surgery is typically required to replace it. However, a group of researchers is working on technology to change that, according to the scientific organization Acoustical Society of America, which held a conference this month where the research was first presented. 

"To keep our bionic body parts from powering down, [a group of] researchers is developing a safe, noninvasive, and efficient means of wireless power transmission through body tissue," the society said in an announcement. 

"Currents of 300 milliamperes (mA) have been delivered across tissue depths of up to 1.5 centimeters. At depths of 5 centimeters, 20 mA were delivered. Currents such as these can service most medical-grade rechargeable batteries,” lead researcher Leon Radziemski of Tucson-based Piezo Energy Technologies said in the release.

The technology is based on piezoelectric generation of ultrasound. "In piezoelectrical systems, materials are squeezed or stressed to produce a voltage. In turn, applied voltages can cause compression or extension," the announcement said. 

The group has tested the technology on pigs, demonstrating "safe charging over several hours of ultrasound exposure," the release said. 

Medical device implants are critical to patients with a growing set of conditions such as chronic pain, Parkinson's disease, deep brain tremors, arrhythmias, and nerve and muscle disorders.

For instance, just last month the FDA approved a new medical device implant used to treat epilepsy: the RNS Stimulator.

This device "consists of a small neurostimulator [which] is connected to one or two wires (called electrodes) that are placed where the seizures are suspected to originate within the brain or on the surface of the brain," FDA said in a release.

As NPR described it, "Imagine a tiny computer embedded under your scalp that's constantly tracking your brain activity and zapping you when it senses something awry."

But power presents difficulties with this hopeful new technology. 

"The most common problems in clinical tests of the device were infections at the implant site and batteries that ran down too soon," NPR said.