SWANS Implants Communicate Through Tissue With Long Battery Life

SWANS implants use passive components to consume very little power while listening. Their battery life is more than 15 times longer than that of Bluetooth and NFC devices. The complete implant, including its battery, measures 3 × 1.1 × 17 millimeters and fits through a 6-gauge needle.

Testing SWANS Implants in Tissue and Living Rats

To test the system, Abramson and his colleagues placed the implants on chicken breasts, skin-on and bone-in pork belly, and live rats.

“Pork belly has a very thick, uneven texture,” Abramson says. The signal had to pass through fat, muscle, bone, and skin. A single 10-volt pulse produced a detectable voltage gradient extending more than 30 centimeters across the tissue and up to 14 centimeters in depth. That is more than 10 times the coverage of Bluetooth or NFC.

In living rats, the signals reached subcutaneous, intraperitoneal, and intragastric implants. Placement had little effect on performance. “We put the wearable on the rat’s abdomen and were able to activate it on the rat’s back,” Abramson said.

Implants Trigger Targeted Nerve Stimulation

In the most advanced experiments, the researchers attached strain sensors across the front legs of rats. When the sensors detected movement in the left or right forelimb, a hub sent a limb-specific pulse into the body. The signal reached the corresponding implant in the hindlimb, stimulating the sciatic nerve and causing that paw to twitch.

The researchers also built an inter-implant relay. It passed a signal to a second implant only when a temperature sensor detected a fever of 40°C (104°F) or higher.

Two-Month Rat Study Found No Major Safety Signals

Abramson said the researchers did not anticipate significant safety issues because pacemakers and nerve stimulators already use similar voltages and pulse lengths.

During a two-month study in rats, scar tissue up to 1 millimeter thick formed around the implants. However, the team continued to communicate with the devices by increasing the voltage within safe limits.

The pulses did not stimulate nerves other than the targeted nerves, alter the heart’s electrical activity, or cause cell death or oxidative stress compared with non-energized needles or implants.