High energy consuming implants like total artificial hearts or ventricular assist devices require a power cable to penetrate the skin, often causing infections and further complications. Inductive power, like that used to charge electric toothbrushes so that no wires are exposed to water, would be very useful to power implants to prevent complications, but uniformly beaming the energy over an effective distance has been a challenge. Recently, though, scientists at University of Washington have reported building a new system that allows for consistent transmission of energy to a depth equivalent to the diameter of the coil. Using a 4 inch coil to beam down 4 inches into the chest should be sufficient to power most devices in average sized people and larger coils can go deeper.
From a U of Washington announcement:
Smith [Joshua Smith, associate professor of computer science and electrical engineering] and colleagues at UW and Intel devised an inductive system that adjusts the frequency and other parameters as the distance or orientation between the transmitter and receiver coils changes, allowing for flexible yet efficient wireless power over medium distances.
“Most people’s intuition about wireless power is that as the receiver gets further away, you get less power,” Smith said. “But with this technique there’s a regime where the efficiency actually doesn’t change with distance.”
Using the wireless system means no power cord poking through the skin, dramatically reducing the risk of infection and improving the patient’s quality of life. Researchers envision a vest that could hold an external transmitter coil connected to a power cord or battery. A small receiver coil implanted under the patient’s skin would connect to a battery that holds enough power for about two hours, meaning the patient could be completely free for short periods of time to take a bath or go for a swim (current users of heart pumps cannot do either). Longer term, the researchers imagine additional power transmitters placed under a patient’s bed or chair, allowing patients to sleep, work or exercise at home unencumbered.
Results presented at the meeting showed the system could power a commercial heart pump running underwater using a receiver coil as small as 4.3 cm (1.7 inches) across. The power transmitted reliably with an efficiency of about 80 percent. Next the researchers hope to test the system with a heart pump implanted in an animal.