Graphene-Based Thermoacoustic Sound Source.

Thermoacoustic (TA) effect has been discovered for more than 130 years. However, limited by the material characteristics, the performance of TA sound source could not be compared with magnetoelectric and piezoelectric loudspeaker. Recently, graphene, a two-dimensional material with the lowest heat capacity per unit area (HCPUA) was discovered to have a good TA performance. Compared with traditional sound source, graphene TA sound source (GTASS) have many advantages, such as small volume, no diaphragm vibration, wide frequency range, high transparency, good flexibility, and high sound pressure level (SPL). Therefore, graphene has a great potential for the next-generation sound source. Besides, photoacoustic (PA) imaging can be applied to the diagnosis and treatment of diseases using the photo-thermo-acoustic (PTA) effect. Therefore, in this review, we will first introduce the history of TA devices. Then, the theory and simulation model of TA will be analyzed in detail. After that, we will talk about the graphene synthesis method. To improve the performance of GTASS, many strategies such as lowering the thickness, and using porous or suspended structures will be introduced. With good PTA effect and large specific area, graphene PA imaging and drug delivery has promising prospect in the cancer treatment. Finally, the challenges and prospects of GTASS will be discussed.