Development of Ultra-Miniature Pressure Sensors for 1-French Biomedical Applications and Beyond

Evolution of micromachined pressure transducers for cardiovascular applications

“…This size constraint has limited the application of micromachined sensors in the cardiovascular field, with its sub-mm features, and has been a persistent area of focus. Two areas of interest include implantable sensing and more regular use of catheter-tip pressure monitoring during hospitalization [30,31]. Since the 2000s, incremental progress has been made in reducing the overall scale of silicon sensors, in one case down to 230 m × 650 m in area and 150 m in thickness for a gauge sensor for catheter applications [31].…”

“…Two areas of interest include implantable sensing and more regular use of catheter-tip pressure monitoring during hospitalization [30,31]. Since the 2000s, incremental progress has been made in reducing the overall scale of silicon sensors, in one case down to 230 m × 650 m in area and 150 m in thickness for a gauge sensor for catheter applications [31]. Additionally, investigators have explored designing transducers with different materials and structures.…”

“…The silicon fusion method immediately reduced the surface area of transducing chips for reasons related to etching geometry, producing gauge sensors for catheter applications with overall dimensions as low as 400 m × 900 m in area and 150 m in thickness [26,65]. Additionally, SOI wafers, with buried oxide layers which could be used as etch stops during diaphragm formation, facilitated diaphragm fabrication and improved dimensional control [31,66]. The most important emergence for the miniaturization of transducers, however, is the topic of the next section-surface micromachining.…”

“…A recent piezoresistive transducer which demonstrates this strategy used a combination of SOI and DeepReactive-Ion-Etching (DRIE) technologies, the latter of which is a plasma etching technique developed in the 1990s for producing structures with high aspect ratios [31,84]. Fabrication began with an SOI wafer with a 2 m surface layer which overlaid a 0.5 m buried oxide.…”

“…A thin layer of silicone is additionally used to seal the external casing for electrical and chemical isolation of the transducing diaphragm from physiological fluids. Combined, all of these components limit the ultimate scale of catheter-tip sensors, as the highly miniaturized transducer chips become as small as the smallest robust packaging [31,105,106].…”