Karakterisering av en mikrosensorsnål för mätning av syrehalt och konduktivitet

Sammanfattning: This report focuses on the characterization of an acupuncture needle microsensor, designed tomeasure the conductivity and oxygen saturation of tissues in the body, in particular musculartissues. The device is intended to help the practitioner localize and treat sources of chronicneuromuscular pain in patients. Acupuncture is shown in some cases to lower pain in patients.The specific aim of this project was to characterize the functional properties of the microsensor.Oxygen sensing is accomplished using the phosphorescent indicator dye platinum tetraphenyltetrabenzoporphyrin (PtTPTBPF) placed on the tip of an optical fiber placed in the lumen oflong, thin needle, while conductivity sensing is accomplished with a gold-sputtered electrodearrangement at the tip of the needle. The end goal is to get the microsensor needle classified asa medical device. Preclinical tests that are required for the needle to get the approval arediscussed in this report. To determine the needle’s accuracy and precision when measuringconductivity and oxygen saturation, an experimental setup was created in which an in-vitromaterial for the simulation of muscular tissue was utilized. The in-vitro test material wascomprised of a cellulose gel containing different nitrate salts producing a material with similarstiffness to soft tissues in the human body. Different concentrations of the nitrate salts produceddifferent conductivities in the tissue model gels that covered the conductivity span of humantissues. To create different levels of oxygen saturation, the tissue model gels were placed in aplastic bag filled with oxygen or nitrogen. Performance characterizations of individual devicescan be used to calibrate individual devices, which provides data for the technical file used in theapproval of the device as a medical device. However, none of the sensors where able tomeasure the true value of conductivity in the calibration liquids. The oxygen sensor where alsoto slow to get to the true value of the sample. The tests proved that the needle has potential tomeasure the physiochemical properties of oxygen saturation and conductivity in body tissues,but as there is a large variation in measured values between devices, an improvement in devicedesign or manufacturing is likely required in a final medical product.