Rap music powers rhythmic action of medical sensor

January 26, 2012

This graphic illustrates the principles behind the operation of a new type of miniature medical sensor powered by acoustic waves, including those found in music such as rap, blues, jazz and rock. The device, a pressure sensor, might ultimately help to treat people stricken with aneurisms or incontinence due to paralysis. (Birck Nanotechnology Center, Purdue University)

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WEST LAFAYETTE, Ind. – The driving bass rhythm of rap music can be harnessed to power a new type of miniature medical sensor designed to be implanted in the body.

Acoustic waves from music, particularly rap, were found to effectively recharge the pressure sensor. Such a device might ultimately help to treat people stricken with aneurisms or incontinence due to paralysis.


"The music reaches the correct frequency only at certain times, for example, when there is a strong bass component," he said. "The acoustic energy from the music can pass through body tissue, causing the cantilever to vibrate."


"You would only need to do this for a couple of minutes every hour or so to monitor either blood pressure or pressure of urine in the bladder," Ziaie said. "It doesn't take long to do the measurement."



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"This paper demonstrates the feasibility of the concept," he said.

The device is an example of a microelectromechanical system, or MEMS, and was created in the Birck Nanotechnology Center at the university's Discovery Park. The cantilever beam is made from a ceramic material called lead zirconate titanate, or PZT, which is piezoelectric, meaning it generates electricity when compressed. The sensor is about 2 centimeters long. Researchers tested the device in a water-filled balloon.






"A wireless implantable device could be inserted and left in place, allowing the patient to go home while the pressure is monitored," Ziaie said.


A patent application has been filed for the design.  


Source: Babak Ziaie, 765-494-0725, bziaie@purdue.edu

Note to Journalists: An electronic copy of one of the papers is available from Emil Venere, Purdue News Service, at 765-494-4709, venere@purdue.edu


A Novel Electromechanical Interrogation Scheme for Implantable Passive Transponders

A. Kim, T. Maleki, and B. Ziaie  

This paper presents design, fabrication and implementation of a novel electromechanical energy scavenging and wireless interrogation scheme using low-frequency components of musical vibrations to overcome challenges associated with previously reported passive transponders such as: short transmission range, misalignment sensitivity and complicated receiver circuitry. The transponder has two phases of operation: 1) mechanical vibration phase, in which an acoustic receiver (a piezoelectric cantilever) converts the sound vibration into electrical power and charges a capacitor; and 2) electrical radiation phase, in which the stored charge is dumped into an LC tank, forcing it to oscillate at its natural resonance frequency and emitting the energy to an outside receiver. In a pressure-sensing configuration, the distance between a planar coil and a ferrite core is modulated by the pressure, thus changing the inductance and, in turn, inducing a change in the frequency of the emitted signal. A prototype transponder was built and tested using a PZT cantilever with a mechanical resonant frequency of 435 Hz encapsulated in a glass capsule (length=40 mm, diameter=8 mm) along with a rectifier circuitry and a storage capacitor. The inductive pressure sensor located outside the capsule had a sensitivity of 2.5k Hz/kPa. We were able to easily pick up the transmitted RF pulses at distances of up to 7 cm without the tight requirement on alignment between the receiver and the transponder coils.