Study Of A Flexible Thermoacoustic Device Based On Few-layer Graphene Film

The thermoacoustic(TA)effect refers to the conversion between thermal energy and sound energy under certain circumstances.Sound emission is one of the most common applications for that.There are a couple of advantages for the TA loudspeaker in comparison to the conventional coil loudspeak and the electrostatic loudspeaker,such as simple structure,tiny thickness,and magnet-free.Some TA loudspeakers could also be transparent and flexible.Those merits have attracted reseacher's attention to push back the frontiers of this field.As a result,more and more potential applications of TA device would be realized in the near future.Here in this paper,a flexible TA device based on few-layer graphene film is introduced.The design of the device is completed by using the theory of thermoacoustic effect and the finite element analysis(FEA)method.We have acquired a simple and high-efficient method to fabricate large-area ultrathin graphene flim.Few-layer graphene flakes were exfoliated from high-quality graphite powder.The droplet of ethanol with graphene flakes spreads quickly on the surface of deionized(DI)water owing to the Marangoni effect,forming self-assembled graphene film with large area.Subsequent characterization results show that the thickness of the graphene flake was about 4 nm,whereas the thickness of the self-asembled graphene film was of several microns.High quality of the graphenen film was confirmed by the Raman spectrum.We also patterned metal interdigital electrodes on the surface of the flexible substrate via MEMS processing techniques.The whole fabrication process of our TA device is quite simple and cost-effective by combining the graphene film with the flexible substrates together.The resistance of our TA device could be minimized to about 7 ?,so that our TA device is compatible with the audio amplifying circuit board which is available in the market.To get a better understanding of the acoustic performance of our TA device,a testing platform has been built.Several vivid applications,such as playing music,measuring distance(by using the ultrasonic generated by our TA device),have been successfully achieved.The sound pressure level(SPL)of our TA device could reach to 71.57 d B at 1W power and 1cm distance.We hope that the exploration in this paper could enrich the study and further development of TA devices.