Design of small size and high sensitive less-invasive wireless blood pressure sensor using MEMS technology

This study presents an implantable passive wireless blood pressure sensor using an inductive coupling wireless sensing technique that is designed for long-term monitoring of blood pressure in hypertension patients. This sensor includes a gold tapered square spiral inductor and a circular capacitor with a polyimide diaphragm. The purpose of this study is to minimise the dimension of the sensor due to the limitation of space around the vessel; therefore, a microelectromechanical systems (MEMS) inductor and a capacitor with small dimension and high sensitivity are used. In this structure, the diaphragm is deflected by applied pressure which capacitance and then resonance frequency are changed. These changes are sensed remotely with inductive coupling, which eliminates the need of wires connection for monitoring. In this method, a blood pressure signal can be obtained by measuring the impedance phase dip from the external coil. The distance between two coils is 8 mm. The sensor is designed to provide a resonance frequency range of 282-381 MHz for a pressure range of 0-250 mmHg. Simulation has been done using COMSOL Multiphysics and ADS software. The dimension of the sensor is 2.2 mm x 2.2 mm and the sensitivity of the sensor is 1550. This sensor has a small size and high sensitivity rather than previous works.