Research Of Obstructive Sleepapnea Monitoring Sensor Based On Thin Film Thermocouple

Obstructive sleep apnea syndrome（OSAHS）is a very common sleep respiratory disease.Snoring,poor sleep quality and daytime sleepiness are the main symptoms.It is found that OSAHS is related to stroke,coronary heart disease and other diseases,which is harmful to health.For this disease,standard polysomnography is widely used as a detection method in clinic,but its disadvantage is that it requires high cost and will cause psychological burden to patients.In recent years,portable sleep breathing monitoring equipment has become the main development direction in this field.In this paper,based on the Seebeck effect of thermocouple,an obstructive apnea monitoring sensor based on flexible substrate is designed to monitor the respiratory signal by measuring the temperature change during breathing.The advantages of the sensor are easy to carry,good economy,friendly to human body and no psychological burden.The sensor was designed based on Seebeck effect and heat transfer theory.The structure of the sensor isolates the temperature of the hot end and the cold end of the thermocouple.The hot end of the thermocouple extends into the nasal cavity to monitor the changes of hot and cold airflow during breathing.The cold end is led out through the electrode pin to maintain the ambient temperature.The temperature difference forms the thermoelectromotive force,which can be converted into respiratory signal through the circuit.Then,the physical model of the sensor was built.Through the finite element simulation,the performance of the sensor with different thermocouple thickness and flexible film thickness was compared.Combined with the actual process,the structure of the sensor was optimized.Finally,the sensor was fabricated by MEMS technology,and the detection circuit was designed to get the actual signal.The measured data indicate that there is a significant difference between normal breathing curve and apnea curve.During normal breathing,the voltage signal measured by the sensor increases in the expiratory phase,and decreases in the inspiratory phase.The curve as a whole will show a wave shape of rising and falling.When apnea occurs,the voltage signal will decrease by more than 90% and show a disordered fluctuation state.According to the change of voltage signal,the breathing state can be judged.Therefore,it can be concluded that the design of sensor in this paper can complete the preliminary diagnosis of obstructive sleep apnea hypopnea syndrome syndrome.