All-nanofiber–based, ultrasensitive, gas-permeable mechanoacoustic sensors for continuous long-term heart monitoring

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 117; no. 13; pp. 7063 - 7070
• Main Authors: Nayeem, Md Osman Goni, Lee, Sunghoon, Jin, Hanbit, Matsuhisa, Naoji, Jinno, Hiroaki, Miyamoto, Akihito, Yokota, Tomoyuki, Someya, Takao
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 31.03.2020
• Subjects: Acoustic noise; Acoustics; Acoustics - instrumentation; Bending machines; Cardiovascular diseases; Decibels; Electrodes; Heart - physiology; Humans; Monitoring, Physiologic - instrumentation; Nanofibers; Noise levels; Performance degradation; Permeability; Physical Sciences; Sensitivity; Sensors; Signal monitoring; Signal to noise ratio; Sound waves; Vibration; biomedical devices; gas-permeable sensors; mechanoacoustic sensor; wearable electronics
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1920911117

The prolonged and continuous monitoring of mechanoacoustic heart signals is essential for the early diagnosis of cardiovascular diseases. These bodily acoustics have low intensity and low frequency, and measuring them continuously for long periods requires ultrasensitive, lightweight, gas-permeable mechanoacoustic sensors. Here, we present an all-nanofiber mechanoacoustic sensor, which exhibits a sensitivity as high as 10,050.6 mV Pa−1 in the lowfrequency region (<500 Hz). The high sensitivity is achieved by the use of durable and ultrathin (2.5 μm) nanofiber electrode layers enabling a large vibration of the sensor during the application of sound waves. The sensor is ultralightweight, and the overall weight is as small as 5 mg or less. The devices are mechanically robust against bending, and show no degradation in performance even after 1,000- cycle bending. Finally, we demonstrate a continuous long-term (10 h) measurement of heart signals with a signal-to-noise ratio as high as 40.9 decibels (dB).