High Efficiency and Anomalous Photoacoustic Behavior in Vertical CNTs Array

Abstract

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.

A Novel Three-Point Localization Method for Bladder Volume Estimation

“…Ultrasound imaging has gained increasing attention for bladder volume measurement due to its unique advantages, including non-invasiveness, repeatability, and suitability for large-scale applications [ 23 , 24 , 25 , 26 , 27 ]. McLean et al [ 28 ] employed a 2.25 MHz focused transducer for two-dimensional ultrasound gray scale imaging to estimate bladder volume.…”