Thermoacoustic Transduction in Individual Suspended Carbon Nanotubes

Abstract

We report an experimental measurement of the acoustic signal emitted from an individual suspended carbon nanotube (CNT) approximate 2 μm in length, 1 nm in diameter, and 10 À21 kg in mass. This system represents the smallest thermoacoustic system studied to date. By applying an AC voltage of 1.4 V at 8 kHz to the suspended CNT, we are able to detect the acoustic signal using a commercial microphone. The acoustic power detected is found to span a range from 0.1 to 2.4 attoWatts or 0.2 to 1 μPa of sound pressure. This corresponds to thermoacoustic efficiencies ranging from 0.007 to 0.6 Pa/W for the seven devices that were measured in this study. Here, the small lateral dimensions of these devices cause large heat losses due to thermal conduction, which result in the relatively small observed thermoacoustic efficiencies.

Spectroelectrochemistry at free-standing carbon nanotubes electrodes

“…In particular, free-standing CNT electrodes represent an innovative factor for very attractive applications, such as electrochemical sensors [15,16], laser absorber [16], gas flowmeter [16], gas heater [16], supercapacitors [17], in thermoacoustic applications [18] and in batteries [19,20]. Different methods have been developed for the fabrication of free-standing CNT films, the most important routes being CVD [16,21,22] and vacuum-filtration [23,24], although others such as the solvent evaporation method [25] have also been used.…”

Theory and modeling of cylindrical thermo-acoustic transduction

“…More recently, Xiao et al [4] investigated the thermo-acoustic transducer which was fabricated by a carbon nanotubes (CNT) thin-film and the similar studies were also reported by other researchers [5][6][7][8]. Subsequently, a series of thermo-acoustic transductions manufactured from different materials such as CNT assemblies [9], aluminum wires array [10,11], graphene [12], silver nanowires film [13], suspended CNT-yarn array on a substrate [14] and individual CNT [15,16], were successively reported. A practical wideband sound frequency graphene earphone was also designed and tested by Tian et al [17].…”

“…3(a). The experimental data points with different shapes refer to the acoustic pressure for different devices, including both semiconducting and quasi-metallic nanotubes [16]. The experimental data denoted by black squares and green up-triangles slightly deviates from the theoretical prediction, which may be resulted from the difference of heat loss rate β 0 between semiconducting and quasi-metallic nanotubes.…”

“…Mason et al [16] conducted an experiment to measure the acoustic signal emitted from CNT having 2 μm in length and 1 nm in diameter. However, they adopted the theoretical model proposed by Xiao et al [4] which was only suitable for far-field acoustic pressure prediction for thin-film suspended in a free space [19].…”

“…In this letter and to improve the model, the length of the CNT is considered as greatly larger than that of diameter, hence the CNT thermo-acoustic transduction can be modeled as a cylindrical conductor. By using the analytical model proposed here, the comparison of analytical prediction with experiment of Mason et al [16] for different input powers is shown in Fig. 3(a).…”