A fiber-optic silicon pressure sensor for ultra-thin catheters

We have developed a new type of fiber-optic pressure microsensor (sensing-element size: 350 mu m x 350 mu m x 350 mu m) suitable for medical instruments such as catheters and endoscopes. The sensing element consists of a diaphragm structure, glass plate and alignment structure. For the transmitting sourer and signal light, a multimode optical fiber 50/125 mu m (core/clad) in diameter has been used. The sensors have been fabricated using micromachining, for example, anisotropic etching and anodic bonding, Pressure measurement is based on modulation of the intensity of optical reflection by deflection of the diaphragm. Pressure measurements of the sensor with sufficient sensitivity (0.19 mu W MPa(-1) on the average) and accuracy have been obtained.