SmithsonianMag published a piece on a new development in medical implants. Researchers at Stanford have found a way for electronic medical implants to charge wirelessly while inside the body, including in such vital organs as the brain and heart:
The team’s charging system is a riff on the technology used to power electric toothbrushes, smartphones and other small devices. In those setups, electricity passes through a coil in a power source, creating an electromagnetic field. A corresponding coil in the device itself collects energy from that field, which induces a current that can power the device or charge a battery. This type of wave, known as “near-field,” however, can’t travel very far or pass through tissue.
While there is room for a pacemaker with a battery pack near the heart, other parts of the body provide less area to work with. In the brain, for instance, there isn’t room for an implant to sit right at a treatment site. Instead, doctors would need to place it where there’s a relatively open area, such as the back of the neck, and use wires to reach the target site.
“We’re by no means the first people to do wireless powering for medical implants,” explains John Ho, a graduate student who co-authored the study. “[Implants are] used for things like cochlear implants, but the [power source] itself has to be fairly large and the implant has to be very shallow. They can’t reach the important places in the body, like the heart or the brain.”
That’s why Poon’s work aims to explore how to use “biological tissue to transport energy,” she says. Her 2-mm-by-3-mm electronic implant is powered through the body with a credit-card-sized source (charged independently) outside it.
Her team found a unique method to manipulate the waves so that they propagate and pass through live tissue. The power source generates near-field electromagnetic waves of a specific pattern. As the pulses hit and interact with live tissue, they become a new type of wave, called “mid-field.” “When you place [our power source] over the body, the properties of your tissue actually convert the waves,” she explains.