This 2-cm-long device, designed to be implanted in patients, an example of a microelectromechanical system, or MEMS. The heart of the sensor is a vibrating cantilever, a thin beam attached at one end like a miniature diving board. The beam is made from a piezoelectric material called lead zirconate titanate, or PZT, that generates electricity when compressed. Music within a certain range of frequencies, from 200-500 hertz, causes the cantilever to vibrate, generating electricity and storing a charge in a capacitor.
When the frequency falls outside of the proper range, the cantilever stops vibrating, automatically sending the electrical charge to the sensor, which takes a pressure reading and transmits data as radio signals. Because the frequency is continually changing according to the rhythm of a musical composition, the sensor can be induced to repeatedly alternate intervals of storing charge and transmitting data.
A receiver that picks up the data from the sensor could be placed several inches from the patient. The sensor is capable of monitoring pressure in the urinary bladder and in the sack of a blood vessel damaged by an aneurysm. Such a technology could be used in a system for treating incontinence in people with paralysis by checking bladder pressure and stimulating the spinal cord to close the sphincter that controls urine flow from the bladder. More immediately, it could be used to diagnose incontinence. The conventional diagnostic method now is to insert a probe with a catheter, which must be in place for several hours while the patient remains at the hospital.
Also: A Georgia Tech spinoff is pioneering a new class of MEMS heart monitoring devices.