Abstract:
Low sound pressure level and high operating voltage of thermophones had limited its applications in the past. In recent years, utilizing Graphene and Carbon nanotubes 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. Laser Scribed Graphene can generate smooth-spectra sound emission over a wide frequency range by means of thermoacoustic (TA) phenomena. The observed sound pressure levels for Laser Scribed Graphene of 1cm2 area is 35dB (Pin=1W). In this work, a thermophone based on multiwalled Carbon nanotubes intercalated Laser Scribed Graphene is fabricated, which provides high Sound Pressure Level of about 60dB (Pin =1W) due to increment in air gap, decrement in the heat capacity per unit area (HCPUA) and enhancement of surface area. The induced insertion of Carbon nanotubes between layers of Graphene oxide causes a huge increase in surface area of Laser scribed Graphene. More air molecules can interact with sound generating surface, efficiently transferring the generated heat into air which results in increasing the sound pressure level. Sound pressure level of device is compared by using polyimide and paper as substrate materials. Robustness of the device is increased by using a novel technique of transferring the laser scribed device from Polyimide sheet onto an insulation tape. The achieved sound pressure, normalized to the input power, has increased about 25dB by intercalating with Multiwall Carbon nanotubes which entitles the proposed structure as a promising candidate for novel thermophone.
