Implantable medical devices are usually powered with batteries. But now there’s one powered by rap music.
The device is a small pressure sensor. The power comes from a tiny cantilever, made of a ceramic material that it generates current when it is compressed. The material, known as piezoelectric material, is pretty common. They already exist in push-start gas grills or in some models of electric-acoustic guitars. The sensor is outlined in a paper by doctoral student Albert Kim and two research scientists, Teimour Maleki and Babak Ziaie, at Purdue University.
When vibrations between 200 and 500 hertz hit the cantilever, it sends current to the sensor. The charge is stored in a tiny capacitor. Once the vibrations fall outside of that range, the capacitor discharges and the sensor sends a radio signal with the pressure data. The frequencies also happen to be in the same range as a lot of rap music — largely the driving bass rhythm. That bass sound can penetrate human body tissue more easily (think of the thumping feeling in your chest when that guy with the massive sound system drives by).
Ziaie said in a statement that rap seemed to be the best because it uses a lot of bass rhythm, but other genres would do it — thumping dance club music, for instance. But why design a sensor this way? Ziaie noted that a simple tone would also do the job, but that would be annoying to listen to for more than a minute or so.
The pressure sensor was tested on a water-filled balloon, but it could be used for conditions such as treating incontinence or aneurisms. In the former, one needs to check bladder pressure and then stimulate the nerves that close the sphincter muscles, and this kind of device could do that. In the latter, knowing the pressure on blood vessels is key to making sure further damage doesn’t occur.
A big advantage to powering any medical device this way is that it can be deeper inside the body. Many medical devices are powered via induction with a battery outside the body. But the device then has to be pretty close to the surface, usually no more than a centimeter or so. That limits the options for placing it. The sound-powered sensor doesn’t have that problem.
The team will be presenting their findings during an IEEE conference this week in Paris.
Image: Terrence Jennings/Retna Ltd./Corbis