Kip Ludwig, a UW–Madison professor of biomedical engineering and neurological surgery, holds a syringe filled with “injectrode” material. [Image from University of Wisconsin-Madison]
The researchers’s new type of electrode can be injected as a liquid and cure within the body. Traditional neuromodulation treatments require surgically implanted devices that can cost up to six figures. They require complex procedures for installation and can fail because they’re rigid devices that are attempting to mesh with soft biological tissues.
“You can inject the liquid around the nerve, and it cures in the body to create a wired contact,” Kip Ludwig, professor of biomedical engineering and neurological surgery, said in a news release. “Typical implants are really stuff, and so as the body moves, they wear and tear and break down. Our liquid cures, and the result is much closer to the normal elasticity of tissue. You can actually stretch it and increase its size 150% to 200% without losing its conductivity.”
The “injectrode” was created using a mixture of a silicone base, like surgical glue, and small metal particles to make the liquid conductive. The device was then put through a number of FDA preclinical tests and used it to induce heart rate changes in pigs by stimulating the vagus nerve.
“We essentially went through the standard repertoire of electrochemical tests to show this acts like a standard wire electrode that could be used to stimulate the nerve,” James Trevathan, first author on the study, said.
The research team is part of a multi-institution team that received a $2.1 million grant from the National Institutes of Health to develop a system to stimulate spinal nerves as a non-opioid pain treatment alternative. As a part of the grant, the University of Wisconsin-Madison researchers are testing a method in which they inject the fluid around the nerve, then extrude a thin insulated string of material back to underneath the surface of the skin. Then, the researchers inject more composite material and use a basic transcutaneous electrical nerve stimulation unit to stimulate the nerve from the surface of the skin.
“We’re making a bypass from the surface of the skin to the location we want to stimulate,” Ludwig said. “As we learn more and more about how to interface with the nervous system, we’re not limited to what we’ve implanted through an invasive surgical procedure. We can actually change how we stimulate how we talk to the nerve because we’re essentially just routing our connection to this deep nerve back to the surface of the skin.”
The researchers hope to use the device in a robotic surgical system in a procedure that would be similar to getting a tattoo.
The research was published in the Advanced Healthcare Materials journal and was supported by the Defense Advanced Research Projects Agency, National Science Foundation and the NIH.
