Pressure and flow sensor for use in catheters

摘要

The small size and possible low cost of micromachined sensors make them attractive for some medical applications. Minimally invasive therapy aims to reduce the damage done to healthy tissue by reaching the affected area through existing pathways through the body. However, information is scarce as direct view or touch is lacking. Small sensors are needed on catheters inside the blood vessels to gather the data such as blood pressure and flow. To this end a combined pressure and flow sensor is fabricated in an epi-poly process that uses a 4 micrometer thick polysilicon membrane grown during epitaxial growth, to form the diaphragm of the pressure sensor and the thermal insulation of the thermal flow sensor. Using RIE etching of holes through the membrane, sacrificial etching and closing of the etch holes by oxide depositions, a closed reference chamber is formed for an absolute pressure sensor. The process is compatible with standard bipolar electronics to enable integration of signal conditioning, multiplexing, etc. Measurements of the two sensors show that fabrication of flow and pressure sensors using epi-micromachining is possible and that the sensors have the required measurement range, but drift necessitates calibration before use.