Micro-Fabricated Skin-Like AlN/Polyimide/PDMS Sensor for Obstructive Sleep Apnea Monitoring

In this study, micro-fabricated skin-like aluminum nitride (AlN)/Polyimide (PI)/Polydimethylsiloxane (PDMS) sensors were developed via an 8-inch wafer process for obstructive sleep apnea monitoring. Unlike the conventional transfer printing process, for the first time, our study allows patterned piezoelectric AlN sensing elements to integrated with PI layer and PDMS substrate for mass production. The PDMS layer in the sensor provides benefits, such as more convenience to handle the sensor, skin-like properties, comfortable and intimate sensorlskin interface. Polyimide serves as not only the encapsulation layer to insulate and protect AlN sensing element, but also the barrier layer to alleviate the stress and mechanical mismatch between AlN and PDMS layers. After being worn on the chest, the flexible AlN/PI/PDMS sensor enables the accurate respiratory rate and heartbeat monitoring which are validated by a commercial wearable device. In sleep pattern tests, obstructive sleep apnea (OSA) is obviously identified from the respiratory waveform recorded by the AlN/PI/PDMS sensor. Therefore, our study paves an alternative way to determine OSA via flexible, light ( $28.28\pm 0.07\ \text{mg}$ ), skin-like sensor in a home environment.