Acoustic waves to power mini pressure sensor in implantable medical devices

We have heard of many medical implants over the years, but those powered by sound waves outside are scarce as of now. A team of researchers at Purdue University has come up with an advanced pressure sensitive micro electromechanical system (MEMS), which works on energy from acoustic waves. The pressure sensor is primarily meant to cure patients with aneurisms or incontinence due to paralysis.

Pressure sensor that works on accoustic energy

It’s a fact that acoustic waves, in music such as jazz, rock or blues, produce little energy. The Purdue researchers hope to make use of this energy to power the medical sensor, which has to be implanted in patients’ body. The device contains a vibrating cantilever, which quivers once the acoustic waves hit the sensor. Because of this vibration, the cantilever produces an electrical charge thanks to piezoelectric process. The cantilever beam is composed of a ceramic material called zirconate titanate.

The cantilever vibrates only when there is a certain range of frequencies, i.e. from 200-500 hertz, says Babak Ziaie, a professor at the Purdue University. The produced power is stored in a capacitor, which powers the medical sensor. The music that comes in correct frequency with a strong bass component powers the sensor, adds Ziaie. On its way, the acoustic power from the music goes through the body tissues of the person who wears the pressure sensor.

As the frequency of the music begins to fall outside the expected range, the cantilever halts vibration. This time, the stored electrical charge will be automatically transferred to the sensor to make a pressure reading and later it produces data as radio signals for monitoring. The music doesn’t have the same frequency every time. Therefore, as the frequency changes, the sensor stores and sends data in alternating intervals.

The sensor is mainly meant to help measure the pressure in a blood vessel affected by an aneurism and in the urinary bladder. The sensor is used to diagnose incontinence in an innovative way. Moreover, it could be used to treat patients, who are suffering with paralysis. The conventional diagnostic method of inserting a probe with a catheter could be avoided with the pressure sensor technology. Monitoring many dangerous diseases can be done quite simply.

The research team will present the paper at the IEEE MEMS conference in Paris. Team members Teimour Maleki, Albert Kim, a doctoral student and Ziaie have written the paper. Mr. Ziaie says that the paper demonstrates the feasibility of the concept. Indeed, the technology will make some revolutionary changes in diagnosing diseases in a more simple way. Ziaie says,

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. It doesn't take long to do the measurement.