On the Dynamics of a Capacitive Microplate for Blood Pressure Sensing Based on Korotkoff Sounds

Hypertension is known as one of the common heart diseases and accordingly accurate measurement of blood pressure is of great significance. The impetus of the present study is to propose a Micro-Electro-Mechanical-Systems (MEMS) -based capacitive pressure sensor for blood pressure sensing based on Korotkoff sounds. Although the operating frequency of the MEMS pressure meters is inherently much more than the mean blood pressure, we have tuned the operating frequency of the pressure meter, thanks to the presentation of softening electrostatic voltage. Electrostatic voltage decreases the resonance frequency of the resonator so that the operating frequency is shifted to the desired region. Having studied the Korotkoff sounds in the brachial artery, the appropriate dimensions of the circular microplate to use in the sphygmomanometer were determined. The motion equations were discretized and numerically integrated over time to capture the time response. The frequency response of the resonator in the vicinity of the primary resonance along with the bandwidth of the Korotkoff sounds on the frequency domain are presented. The resonance region is fitted within the bandwidth of the Korotkoff sounds by softening the microplate which accordingly pushes the resonance region leftward on the frequency domain. The capacitance variation as a function of the applied pressure is also determined.