Fabrication and investigation of a thermoacoustic loudspeaker based on carbon nanotube coated laser-scribed graphene

In spite of being known since a century ago, high operational voltage and low sound pressure level have limited wide applications of thermophones. In recent years, utilizing graphene in thermophones has been proposed as an attractive solution, which is benefiting from high electrical and thermal conductivity and inherent high surface area, to enhance the heat transfer and lowering the required electrical input power. In this paper, a laser-scribed graphene (LSG) layer is utilized to realize graphene-based thermophones, which provide a considerably high sound pressure level of about 80 dB (Pin = 0.6 W). Furthermore, a layer of carbon nanotubes (CNTs) is incorporated on the prepared LSG sheets, which benefits from both randomly oriented CNTs over the surface of reduced graphene oxide (rGO) sheets and suspended CNTs, which act like heat exchanger nano-fins on rGO sheets and efficient heat generators, respectively. The input voltage for CNT/LSG based thermophones is measured 7 times lower than the prepared LSG samples, in order to generate the same sound pressure level (75 dB). The achieved sound pressure, normalized to the input power, has increased about 80 dB by incorporating CNTs which entitles the proposed structure as a promising candidate for novel thermophones.