A Novel Ultra-miniature catheter tip pressure sensor fabricated using silicon and glass thinning techniques
- PDF / 174,107 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 27 Downloads / 235 Views
A Novel Ultra-miniature catheter tip pressure sensor fabricated using silicon and glass thinning techniques Henry Allen1, Kamrul Ramzan1, Jim Knutti1, and Stan Withers2 1 Silicon Microstructures Incorporated, 46583 Fremont Boulevard, Fremont, CA 94538 2 Jomed Inc, 2870 Kilgore Road, Rancho Cordova, CA 95670 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. INTRODUCTION One of the challenges of invasive monitoring of the body is in making parts small enough to allow them to fit into the targeted environment. One such application is in the small arteries of the heart. Here the arteries start at 2 to 3 mm external diameter and rapidly bifurcate into progressively smaller arteries in the sub-millimeter range. A catheter that occupies more than 1/2 the area of the vessel under study will have detrimental impact on accuracy of the measurement. Because of these concerns, a pressure sensor has been fabricated in a guide-wire to allow accurate measurements of pressure in the Coronary arteries. The guide wire is 0.355 mm in diameter and requires a sensing element that can be housed with lead-outs, housing, and encapsulation in that diameter. The completed guide-wire is shown in Figure 1. The diaphragm size is 280 microns X 130 microns. The wire is constructed with a helical sheath for flexibility except at the tip and around the sensor itself. Here a stainless-steal housing with a machined-in lumen for the sensor is used. Three 25 micron leads are connected to the sensor to allow measurements from 2 piezoresistivesensing elements. A simplified cross-section of top-view of the device is shown in Figure 2.
I7.4.1
Figure 1. Completed SmartWire Guidewire Pressure Transducer
900 µm
Bond pad
Piezoresis
Data Loading...
