High-precision detection of ordinary sound by electrospun polyacrylonitrile nanofibers

Polyacrylonitrile (PAN) nanofibers show piezoelectric properties and the capability to harvest sound energy for power generation purposes. However, their application as an acoustic sensor to detect sound was not studied. In this paper, we report the novel amazing ability of electrospun PAN nanofibers to precisely detect low-to-middle frequency sound (100-600 Hz) at the middle sound pressure level (60-95 dB), which covers the main sound spectrum in our daily activities. The nanofiber sensor device shows high sensitivity, with a signal-to-noise ratio as high as 57.2 dB and fidelity as high as 0.995. Compared to the acoustic sensor made of electrospun poly(vinylidene fluoride) nanofibers under the same condition, our PAN device has a much wider response bandwidth, larger sensitivity, and higher fidelity, indicating the important role of polymer type in the acoustic detection of electrospun nanofibers. The brilliant detection accuracy originates from the high piezoelectricity and rigidity of PAN nanofibers, facilitating deformation recovery and reduction of the interference from harmonics. To demonstrate the remarkable sound detection ability, we used the PAN device to convert a piece of music into electrical signals and then converted the electrical signals into sound. The playback sound was almost identical to the original sound waves. Electrospun polyacrylonitrile nanofibers may form a novel acoustoelectric transducer for accurate sound detection and other high-tech applications.