Development of integrated optic pressure sensor to be incorporated into a catheter for blood pressure measurement

本研究的目的是开发一种集成的光学压力传感器，可以插入到导管测量血压。该传感器由作为压力敏感结构的膜片和穿过膜片的直单模波导组成。首先，我们从理论上研究了相对于波导位置和膜片尺寸的传感器灵敏度。根据理论结果，只要边长比和特征长度保持不变，即使膜片尺寸减小，灵敏度也保持不变。接下来，使用具有相同边长比和相同特征长度的三个制造的传感器来实验检查这样的尺度减小规则。传感器的精确尺寸为2.0mm× 10 mm ×35μm、2.5mm×12.5mm×49μm和3.0mm× 15 mm ×64μm。三种传感器的测量灵敏度与理论预测的非常相似。最后，我们使用比6 F导管大10倍的模拟导管制造了第一个原型版本。由于传感器预期插入20 mm长、直径为20 mm的模拟导管中，因此其尺寸设置为10 mm × 20 mm ×420μm，膜片尺寸为1.5 mm × 7.5 mm ×23μm。传感器灵敏度为81 mrad/kPa，足以测量血压。尽管所制造的传感器仍然相当大，但是通过基于比例缩小规则减小隔膜尺寸，可以预期实现可以插入导管中的小型化传感器。

The purpose of this study is to develop an integrated optic pressure sensor that can be inserted into a catheter to measure blood pressure. The sensor consists of a diaphragm as a pressure-sensitive structure and a straight single-mode waveguide across the diaphragm.First, we theoretically examined sensor sensitivity with respect to waveguide position and diaphragm dimensions. According to the theoretical results, sensitivity remains constant even if the diaphragm dimensions are reduced as long as both the side length ratio and the characteristic length remain constant. Next, such a scale-reduction rule was experimentally examined using three fabricated sensors with the same side length ratio and the same characteristic length. The exact dimensions of the sensors were 2.0mm×10mm×35μm, 2.5mm×12.5mm×49μm, and 3.0mm×15mm×64μm. The measured sensitivities of the three sensors were quite similar to each other as theoretically predicted.Finally, we fabricated the first prototype version using a mimic catheter ten times larger than a 6F catheter. Since the sensor was intended to be inserted into a 20mm-long mimic catheter with a diameter of 20mm, its dimensions were set to be 10mm×20mm×420μm, with the diaphragm dimensions of 1.5mm×7.5mm×23μm. The sensor sensitivity was 81mrad/kPa, which is sufficient to measure blood pressure. Although the fabricated sensor is still quite large, by reducing the diaphragm dimensions based on the scale-reduction rule, the realization of a miniaturized sensor that can be inserted into the catheter can be expected.