The thumping, high-energy beats associated with hip-hop music often have the effect of getting listeners all charged up. Taking that concept one step further, researchers at Purdue University (West Lafayette, IN) have figured out how to harness the low-frequency vibrations of rap music to power an implantable pressure sensor.
|An implantable pressure sensor created by Purdue researchers is powered by harnessing the low-frequency vibrations of rap music. Image: Birck Nanotechnology Center, Purdue University|
“Power sources have been a problem for many medical devices,” observes Babak Ziaie, a professor of electrical and computer engineering as well as biomedical engineering at Purdue. “Batteries for pacemakers are large and run out, for example. Inductive powering—like a transformer—has very short range and, if your antennas are misaligned, [charges] can drop off.”
Seeking to overcome these issues, Ziaie and his team decided to explore the possibility of using the vibration of music to power an implantable sensor. To their surprise, the researchers found that they were able to achieve a proof of concept in only a couple of months using several commercial components.
Consisting of a piezoelectric cantilever beam, four diodes, a capacitor, and a coil that acts as an antenna, the music-responsive implantable sensor employs the low frequency of rap music to excite an ultrasonic transducer. To do so, the piezoelectric cantilever beam vibrates in response to the low-frequency components of the rap music, thereby generating an electrical charge. The charge next travels to a rectifier that, in turn, generates a dc voltage. The charge is then transferred to a capacitor where it is stored. Once the vibrations cease, the charge is moved from the capacitor into the antenna and transmitted out.
“At those low frequencies of rap, the sensor stores a charge in the capacitor; at other frequencies that are not vibrating, the charge is being transferred to the antenna and sending information out,” Ziaie explains. “So, you’re using one frequency for charging while the music is playing; when [the sensor] is not charging, it sends information out.”
This bare-bones, vibration-harnessing technology offers a simplified approach compared with many passive systems that often require complicated circuitry, Ziaie says. “We thought our [technology] was very cool because you only need a speaker and music for the transmitter, and all you need for the receiver is something [to serve as] an antenna in order to pick up the signal.”
Rap music proved to be ideal for this particular experiment, according to Ziaie, because the thickness and length of the cantilever were easily tunable to the low end of the music’s frequency. However, he notes that future versions of the sensor could respond to other music genres by adjusting the thickness and mechanical design of the component.
If commercialized, the pressure sensor could potentially be implanted in such areas as the bladder, uterus, digestive system, and lung, Ziaie says. “Because of the size—it’s about 3 cm × 5 mm—you can’t put the sensor in the eye or the brain right now. But sensors implanted in the abdomen would be easily accessible to sound.”