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In contrast, the maximum strain on the piezoelectric beam of the conventional structure was only 1.42 × 10 −5 under the same excitation (Fig. In our asymmetric gapped cantilever structure, the amplitude-frequency response showed that the maximum strain on the piezoelectric beam was 1.38 × 10 −4 under 0.11 g excitation (Fig. 2a) was much more significant than that on a conventional structure (Fig. According to theoretical simulation, the strain experienced by the piezoelectric beam on our structure (Fig. Harmonic response analysis of the dynamic model was conducted under different excitation accelerations (from 0.01 g to 0.11 g). We used theoretical simulation to show the advantage of our sensor with an asymmetric gapped cantilever structure compared with conventional structures (Fig. Moreover, the lung and heart sound recorded by our sensors are in good agreement with previous clinical reports, suggesting that our sensor offers a potential alternative for the diagnosis and prognosis of pneumonia or other similar diseases.įull size table Theoretical simulation and characterization of sensor performance From both theoretical simulations and mechanical tests, our sensors show improved sensitivity compared with conventional sensors, making them suitable for monitoring weak heart and lung sounds. Herein, we were motivated to explore more applications of our sound sensors in the assessment of lung and heart states of discharged pneumonia patients. However, none of them have been systematically used to monitor patients with pneumonia. Previously, based on asymmetric gapped cantilever structures, we developed a series of small-sized and ultrasensitive sound sensors for continuous monitoring of heart and lung sounds in healthy subjects 14, 15, 16. Compared with stethoscopy, miniaturized accelerometers can be taped on a person’s chest wall for more convenient and continuous cardiorespiratory monitoring. An alternative approach for detecting lung and heart sounds is based on accelerometer use 12, 13. Conventional stethoscopy is widely used for intermittent auscultation however, stethoscopy has a number of limitations, such as poor wearability due to its bulky size, friction noise during diagnosis, and difficulty in detecting weak acoustic signals including lung sounds. Therefore, the development of novel sensing systems that are time-saving, low cost, highly sensitive, easy to read, instrument-free, and able to achieve on-site continuous monitoring 10, 11 has great potential in the diagnosis and prognosis of pneumonia diseases.Īuscultation of chest wall sounds, including both heart and lung sounds, offers an easy but very effective approach for the clinical diagnosis of cardiovascular and respiratory systems. However, these methods generally require large, sophisticated, and expensive instruments highly trained personnel complex procedures and far less harmless procedures (such as CT and MRI). Meanwhile, heart injury in patients can be revealed by echocardiography (ECG) 7 and cardiac magnetic resonance imaging (MRI) 8, 9. Lung ultrasound also offers a quantitative method to assess the lung state in patients 7. Lung injury in patients can be revealed by abnormal findings based on chest CT images 1, 2, 3, PET/CT 4, and artificial intelligence (AI)-assisted diagnosis 5, 6. Similar content being viewed by othersĪssessment of lung and heart states is critical when evaluating the health condition of patients with pneumonia. This sensor provides a cost-effective alternative approach to the diagnosis and prognosis of pneumonia and has the potential for clinical and home-use health monitoring. Compared with conventional medical instruments, our sensor device provides rapid and highly sensitive detection of lung and heart sounds, which greatly helps in the evaluation of lung and heart states of pneumonia patients. Our observations were in good agreement with clinical reports. Over time, the lung and heart states of the patients gradually improved after discharge. Our sound sensor also successfully tracked the recovery course of the discharged pneumonia patients. For the first time, lung injury, heart injury, and both lung and heart injuries in discharged pneumonia patients were revealed by our sensor device. Our sensor achieves a high sensitivity of 9.2 V/g at frequencies less than 1000 Hz, making it suitable to use to monitor weak physiological signals, including heart and lung sounds. Based on two-stage amplification, which consists of an asymmetric gapped cantilever and a charge amplifier, our accelerometer exhibited an extremely high ratio of sensitivity to noise compared with conventional structures. In this study, we present a small-sized and ultrasensitive accelerometer for continuous monitoring of lung and heart sounds to evaluate the lung and heart states of patients. Assessment of lung and heart states is of critical importance for patients with pneumonia.