Bio-compatible micro-sensor for blood pressure measurement using SiC technology

摘要

A monolithic SiC pressure sensor for blood pressure measurement has been investigated. For the implantable blood pressure measurement sensor, the sensor is wireless, biocompatible and linear. The SiC is used for its superior physical, chemical and mechanical characteristics. The sensor uses a wireless telemetry system that can be implanted in patient's body and coupled with an external inductor. The resonant peak method is used for sensing the changes in pressure. The sensor is made with planar inductor and a variable capacitance sensor. Together they make a resonant circuit, which loosely couples with an external inductor. This sensor gives the continuous, real-time measurement of the blood pressure. There is strong evidence that SiC material is biocompatible when used as a coating on vascular stents [1]. The sensor must function optimally in the pressure range between 50-250 mmHg. The paper discusses the design, layout, modeling, fabrication and characterization of the blood pressure measurement sensor. The layout and modeling of the sensor is done using FEA (finite element analysis) software Coventor and Tanners L-Edit. The simulation for membrane deflection, stress analysis and electro-mechanical analysis were performed. Various fabrication techniques for fabricating the planar inductor and the capacitor are detailed. The fabricated planar inductor gives a value of 1.43μH at 13MHz. 3C-SiC has a Young's Modulus of about twice that of silicon (SiC =488-700 GPa) and is chemical inert. A larger Young's Modulus improves the sensitivity of the pressure sensor in this case. The real-time analysis for electromechanical characteristics of this sensor is done in a simulated laboratory set up. The changes in resonant peak frequency w.r.t. pressure are recorded.