Stretchable piezoelectret electronic stethoscope for phonocardiography and lung sound detection in motion and noise conditions

Real-time and continuous monitoring of phonocardiography (PCG) and lung sound (LS) is an essential and affordable method for cardio-pulmonary disease detection. Herein, a stretchable piezoelectret mechano-acoustic sensor based on the square column array and island-bridge structure is proposed. A prototype consisting of four 10mmx10mm piezoelectret sensor units in 2x2 array with 10mm spacing connected by serpentine interconnects is fabricated and used to measure PCG and LS. The sensor unit has a sensitivity of 491pC/N and achieves a flat frequency response within a frequency range of 30 Hz to 1000 Hz. The proposed stretchable piezoelectret sensor also demonstrates excellent stretching robustness by maintaining a stable output intensity during 10 % bi-axial strain cycles. Experimental results show that this system can effectively detect PCG and LS, and a beat-to-beat comparison to commercial device is conducted. To prove the feasibility in wearable conditions, the proposed sensor is used to monitor PCG in motion condition and noisy environment, showing excellent resistance to the motion artifact and noise interference and clearly reflecting the intensity variation of heart activity.