Researchers at the University of Wisconsin-Madison have developed an injectable flexible electrode that can aid in neuromodulation therapy, potentially replacing more rigid electrodes that do not mesh well with soft tissues. The injectable material consists of a silicone gel and small metal particles, and it forms a flexible bolus when injected around a target nerve. The nerve can then be electrically stimulated from the surface of the skin using a basic transcutaneous electrical nerve stimulation (TENS) unit. The approach could pave the way for effective neuromodulation therapy for a large variety of diseases.
Neuromodulation, where neurons in the body are stimulated to produce a therapeutic effect, has huge potential for many diseases and conditions, including chronic pain, epileptic seizures, and depression. However, one of the major hurdles to achieving this is the cost and limitations of current implantable devices intended to stimulate neurons. These include expensive implantable devices that are difficult to insert in the body. Moreover, such devices are typically rigid and therefore are not very compatible with the tissues they’re implanted inside.
The University of Wisconsin-Madison team developed a low-cost alternative to traditional implantable neuromodulation devices. This consists of an injectable liquid that forms a semi-solid bolus near a nerve. “You can inject the liquid around the nerve, and it cures in the body to create a wired contact,” said Kip Ludwig, a researcher involved in the study. “Typical implants are really stiff, 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 percent to 200 percent without losing its conductivity.”
The injectable gel is silicone-based, and it contains metal particles so that it is electrically conductive. By injecting the material around a nerve and then up to the surface of the body, under the skin, the researchers can use a common TENS device to stimulate deep nerves from the surface.
“We’re making a bypass from the surface of the skin to the location we want to stimulate,” said Ludwig. “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.”
So far, the researchers have used the system to stimulate the vagus nerve in pigs, and were able to change their heart rate. This suggests that the material might have potential in helping to treat cardiac issues, such as heart failure, arrhythmias, and hypertension.
See a video about the technology below:
Study in Advanced Healthcare Materials: An Injectable Neural Stimulation Electrode Made from an In‐Body Curing Polymer/Metal Composite