Strain-Insensitive, Stretchable Thermoacoustic Loudspeaker with Entangled Carbon Nanotubes

This paper reports on a strain-insensitive, stretchable loudspeaker composed of a carbon nanotube (CNT) array partially embedded in a stretchable elastomer substrate. This loudspeaker operates by thermoacoustic transduction, where air vibrations are generated through heat transfer, thereby inducing a sound wave. CNT array has a low heat capacity per unit area, and the high aspect ratio of the CNT structure provides a large effective surface area, enabling efficient heat transfer to the surrounding air. This feature does not necessitate the usage of an extremely thin substrate, as required by other thermoacoustic loudspeakers to minimize heat capacity, thereby enhancing the mechanical stability of the loudspeaker. Furthermore, the entangled CNT strands maintain a stable electrical connection even when stretched. Given these excellent characteristics, the loudspeaker achieves a high sound pressure level (SPL) exceeding 60 dB with only a 4.37 dB variation even over 150% strain.