A Novel Multifunctional BP/Reduced Graphene Oxide Film and Its Applications

As previous studies investigated the acoustic and piezoresistive properties of materials separately, a scalable mixed-solution coating approach for fabricating black phosphorus (BP)/reduced graphene oxide (rGO) composite films is designed with a controlled BP:rGO volume ratio of 1:4 in this work. The acoustic characteristic and the piezoresistive characteristic of this BP/rGO film are studied. Experimental results reveal that the BP/rGO TA speaker outperforms conventional devices, achieving a sound pressure level (SPL) of 79.39 dB at 3.1 kHz and a maximum SPL of 80.82 dB, representing a notable enhancement in acoustic output. The speaker exhibits a peak TA efficiency of 27.6×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> %, a low repeatability error of 0.12%, and stable highfrequency acoustic performance in a broad frequency range (0.2~20 kHz). In addition, this film is employed as sensor to detect pressure from 0 to 9.92 kPa with superior sensitivity (5.95 kPa<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup>, 0~1.24 kPa; 0.32 kPa<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup>, 1.24~9.92 kPa). Therefore, the results underscore the material’s exceptional acoustic and mechanical properties, positioning the BP/rGO film as a promising candidate for applications in smart wearables and health monitoring systems.