A highly sensitive modular elastomer-based capacitive pressure sensor for respiration monitoring

Sleep Apnea (SA) is one of the most prevalent but yet underreported public health issues all around the world. The diagnosis of SA requires sleep monitoring or polysomnography (PSG), which is recording several bio-physiological signals during sleep, including respiration. The state of the art for respiration monitoring is measuring the nasal or oral airflow by means of a pressure sensor, placed on the chest of the patient and connected to a long nasal/oral cannula (tube) that is placed in front the nose/mouth. This long tube in many cases is a source of discomfort for the patient. In this work, an elastomer-based flexible capacitive pressure sensor is presented that mounts on the upper lip of the patient. The sensor structure has a novel modular design that gives freedom to make the sensor smaller or larger with the same relative sensitivity . The sensor is designed for the low pressure range from -50 to 100 Pa suitable for the intended application with a high absolute and relative sensitivity of 0.52 pF/Pa and 2.064 kPa-¹, respectively, and capability to withstand overpressure up to 2 kPa without permanent damage. The sensor prototype has low non-linearity and hysteresis errors of less than 12%FS a resolution of 1.7 Pa.