A Novel Ultra-miniature catheter tip pressure sensor fabricated using silicon and glass thinning techniques

Abstract

A novel subminiature pressure sensor for blood pressure measurement has been fabricated. The device is only 250 microns wide and 70 microns thick. It is 1.1 mm in length. The sensor is housed in a guide-wire lead for use in measuring coronary artery blood pressure. The device has a 5 micron thick silicon diaphragm and senses pressure using a 1/2 bridge piezoresistive network. Glass is processed to provide depressions above the sensing area as well as above the connection area of the device. A full-thickness silicon wafer is processed using standard micromachining techniques. V-Groove notches are micro-machined on the top surface of the silicon to provide locators/guides for the lead-wires. Diaphragm windows are patterned on the back of the silicon wafer and the wafer is etched down to form the 5 micron diaphragm, using electro-chemical etch-stop techniques. The Glass and Silicon wafers are aggressively cleaned prior to bond. The glass and silicon wafers are then precisely aligned to better than 10 microns and bonded using anodic bonding techniques.The glass/silicon wafer sandwich then has the silicon thinned from 400 microns to 37 microns using both grinding and polishing. Then the full-thickness glass wafer is etched in HF to a thickness of 37 microns as well, for a composite 74-micron thick structure. The wafer is then diced to form the micro-mechanical structure.

Novel miniature MRI-compatible fiber-optic force sensor for cardiac catheterization procedures

“…These sensors were used for different kinds of measurements, such as blood pressure, oxygen level, blood flow, blood velocity and others. They make use of several sensing principles, such as strain-gauges [8], piezoresistivity [9], PVDF films [1] and fibre-optic technology [10], [11], [15]. However, only a small number of sensors were developed for the detection of contact forces between the catheter and tissue [12], [13].…”

Blood Pressure Sensors: Materials, Fabrication Methods, Performance Evaluations and Future Perspectives

“…The cannula is connected to an infusion tube, and the catheter-tip is the pressure sensing component in the transducer assembly. The transducer assembly conventionally utilizes MEMS technology to convert pressure waves into electrical signals [60,61] using silicon-based [62] and non-silicon based MEMS, such as Ti/Pt metallic wire coated with PI/SU [63], PEDOT: PSS with a Ag protective layer on a flexible PDMS substrate [64] and PVF 2 [65]. Other non-catheter-based pressure sensors include a capacitive-based bioresorbable POMaC/PGS/Mg on a (PHB/PHV) substrate sensor [66].…”

Precision in harsh environments

“…Silicon sensors were able to meet the space restrictions of this application and, with the correct coating/packaging, were able to withstand the environment and avoid generation of any unwanted reaction from the host. A pressure sensor that uses a membrane was a simple device that met all requirements and has been a successful commercial product for many years 99 . Companies such as NovaSensors (Buellton, CA, USA), Braun (Frankfurt, Germany), Edwards, Yilson Medical Technology, and Cook Medical (Bloomington, IN, USA) have pressure-monitoring catheters in the market, and many more companies are currently producing these types of devices.…”