Almost all inflammatory diseases of the middle ear are ascribed to a dysfunction of the Eustachian tube, which regulates the middle ear pressure with respect to ambient pressure and allows for the drainage of middle ear secretion. Currently, no method exists for the testing of the tube function under physiological circumstances. We are working on a new tube operation measurement technique, where the in- or outward movements of the eardrum caused by pressure-compensating tube openings are analyzed. These movements are detected by a specially designed strain gauge (figure 1) and generate characteristic signals during tube openings.
Furthermore, the cure of a chronic inflammation of the middle ear often requires surgery, possibly including rearrangement of the ossicle chain and restoration of the eardrum. For the subsequent healing process, the auditory canal must remain sealed for approx. three weeks, which makes visual control of the healing progress impossible. An alternative surveillance is desirable in order to confront potential complications. This can be done through impedance spectroscopy, which enables distinction between different tissues and their physiological and pathological condition.
The aim of this project is to unite both the strain gauge and the electrode for impedance spectroscopy on one thin film, characterize their measuring performance of tube operation and the wound healing progress and build an analysis system for mobile application. After surgery, the film is placed on the eardrum in order to monitor the healing process and tube operability. Long-term measurements of the tube operation are expected to serve the appraisal of professional pilots and scuba divers or enable an adaption of the surgical intervention method to the tube’s operability previous to ear surgery.
The strain gauge is fabricated using lithography and wet chemical etching on a highly flexible PET-film coated with a Cu/Ni/Mn-alloy. High flexibility is demanded for painless application on the extremely sensitive eardrum. The sensor metallization is isolated using a thin spin-coated layer of silicone. The strain gauge design takes into account the anatomy of the eardrum. Separation is carried out using laser cutting in cooperation with Sartorius, Hamburg. The integration of the electrode is intended on the back-side of the film.
