Pressure Transducer for Medical Applications Employing Radial Expansion of a Low-cost Polymer Tube

We present a low-cost pressure transducer for medical applications. It's based on the radial expansion of a liquid filled elastic tube, which is detected by a capacitive measuring principle in a non-contact manner. For optimization we investigated the influence of the number and arrangement of the measurement electrodes, their length as well as the gap separating them. The optimized electrode geometry features a sensitivity of 0.195 fF/103 Pa and a corresponding mean coefficient of variation (CV) of 6.4% considering three individual transducer assemblies. The transducer performance was investigated applying pressures up to 50 x 103 Pa. Due to aviscoelastic behavior of silicone material we determined a hysteresis effect whichimplied a maximum error of 1.13 fF implying a pressure error of 5.8 x 103 Pa.