Implantable bioelectronics are now often key to assisting or monitoring the heart, brain and other vital organs, but they often lack a safe and reliable way to transmit data to doctors. Now, researchers at Columbia School of Engineering have created a way to augment implantable bioelectronics via simple, high-speed, low-power wireless data links using naturally occurring ions, positively charged or negatively charged atoms in the body.

Implantable bioelectronics is playing an increasingly important role in healthcare. For example, pacemakers can help ensure a patient's heart stays beating in a healthy way, neurointerface devices can help patients with epilepsy and other conditions by stimulating specific brain regions to alleviate neurological symptoms, and even connect a paralyzed person's brain to a robotic limb. However, a major challenge for implanted bioelectronics is how to transmit data through the body to external devices for further analysis and diagnosis by doctors and scientists.

"From brain or muscle activity to hormone concentrations, these data need to be transmitted so that they can be advanced processed and reviewed by experts before medical decisions are made." Said Dionne Hodaghori, associate professor of electrical engineering at Columbia University and co-senior author of the study.

Jennifer Gelinas, assistant professor of neurology at Columbia University Irvine Medical Center, added, "This is especially important for conditions such as epilepsy or movement disorders that can fluctuate greatly over time. An example of this is the neurospace device for epilepsy. Data from the device needs to be downloaded so clinicians can adjust their stimulation regimen to better treat epilepsy."

While cables provide an easy way to quickly transfer data from implants to external machines, the way they penetrate tissue limits their long-term use. At the same time, traditional wireless methods using radio waves or visible light usually cannot penetrate biological tissues.

We still lack secure, effective, long-term wireless communication with implanted devices.

Use the body's ions

One interesting strategy that bioelectronics can use to communicate is one that the human body often uses: ions. Inside the body, cells regularly move ions to communicate with each other.

Now, Hodaghori and his colleagues have developed a way to use human ions to transmit data at megahertz rates, millions of bits per second. Their study, ion Communication in Implantable Bioelectronics, was published April 6 in the journal Science Advances.

The way living tissues are rich in ions means they store electrical potential energy, like a battery. The new technology, called ion communication, takes advantage of this fact to help the implanted bioelectronics exchange data with external devices.

Ion communication involves a pair of electrodes implanted inside the tissue and another pair placed on its surface. Implanted devices encode data in alternating electrical pulses, storing energy in tissues. In turn, ground-based receivers can detect this energy and decode it.

In the new study, the researchers detail what geometric properties determine the depth to which ion communication is likely to reach the body, as well as strategies for establishing multiple parallel communication lines between electrodes. They found that ion communication is able to transmit data across distances, which helps it target a variety of tissue types, from human skin to internal organs.