Miniaturized sound generators are attractive to realize intriguing functions. Thermoacoustic device’s application is seriously limited due to the frequency-doubling phenomenon. To address this issue, photoacoustic sound generator is considered as a promising alternative. Here, based on vertical single-wall carbon nanotubes (CNTs) array, we introduce a photoacoustic sound generator with internal nano-Helmholtz cavity. Different from traditional device that generates sound by periodically heating up the open space air around material, this sound generator produces an audio signal by forming a forced vibration of the air inside the CNTs. Interestingly, anomalous photoacoustic behavior is observed that the sound pressure level (SPL) curve has a resonance peak, the corresponding frequency of which is inversely proportional to the CNTs array’s height. Furthermore, the energy conversion efficiency of this photoacoustic device is 1.64 times as large as that of a graphene sponge-based photoacoustic device. Most importantly, this device can be employed for music playing, bringing a new clew for the development of musical instruments in the future.

Three main ambipolar compact models for Two-Dimensional (2D) materials based Field-Effect Transistors (2D-FETs) are reviewed: (1) Landauer model, (2) 2D Pao-Sah model, and (3) virtual Source Emission-Diffusion (VSED) model. For the Landauer model, the Gauss quadrature method is applied, and it summarizes all kinds of variants, exhibiting its state-of-art. For the 2D Pao-Sah model, the aspects of its theoretical fundamentals are rederived, and the electrostatic potentials of electrons and holes are clarified. A brief development history is compiled for the VSED model. In summary, the Landauer model is naturally appropriate for the ballistic transport of short channels, and the 2D Pao-Sah model is applicable to long-channel devices. By contrast, the VSED model offers a smooth transition between ultimate cases. These three models cover a fairly completed channel length range, which enables researchers to choose the appropriate compact model for their works.