Micro-Machined Stent-Type Flow Sensor for Evaluation of Nasal Respiration

We present a thermal flow sensor that is suitable for measuring nasal respiration. To fix the flow sensor inside the nasal passage, we integrated it onto a stent structure, which is normally used as a medical device. The sensor was monolithically integrated on the Ti substrate by applying photolithography and wet etching processes. The developed fabrication has advantage that it is able to fabricate the both of the cavity for the thermal isolation and the stent structure during the same process. We mounted the flow sensor onto the inner surface of the silicone tube by inflating the balloon tube. The mechanical strength of the cylindrical stent under the compression condition was also studied, and it showed an elastic deformation when the force was less than 0.08 N. The developed flow sensor could detect the flow direction at the flow range of 0-2000 ccm. A response time of less than 260 msec was obtained by forming a cavity under the sensor.