Generation of Radiation Pressure in Thermally Induced Ultrasonic Emitter Based on Nanocrystalline Silicon

Abstract

To confirm the applicability of thermally induced ultrasonic emission from nanocrystalline silicon (nc-Si) devices as radiation pressure generators, the dynamic response has been investigated under a pulse operation mode. The nc-Si emitter is fabricated on a p-type Si wafer by conventional electrochemical anodization with subsequent formation of the surface electrode. Due to the flat nature of the frequency response of this emitter, the device emits an acoustic wave with little distortion under the pulse-drive condition. It is shown that a significant radiation pressure of 34.5 Pa is generated by a concentrated burst-like electrical input, and that a beam located at a distance can be levitated as a result of the mechanical loading effect. This siliconbased emitter is attractive for applications to integrated nano-or micro-electromechanical systems.

Solution for acoustic field of thermo-acoustic emission from arbitrary source

“…4(a)-4(f) at a frequency of 120 kHz and a radial distance of 60 mm from the centre of TA emitter with power input q 0 = 1 W/cm 2 . Moreover, by Fourier series expansion of applied heat flux and spectral decomposition and synthesis of sound, the acoustic pressure field of impulse-driven TA emitter 5,6,23 can also be depicted by virtue of Eq. (11).…”

“…1 Many experimental investigations on this phenomenon and its application were carried out, regarding various aspects of TA ultrasound, such as characteristics, intensification, radiation pressure, three-dimensional image sensing, phased array and impulse operation, and sound reproduction, which show that thermo-acoustic ultrasound has lots of advantages over traditional electric-acoustic ultrasound due to its unique nature −− wideband flat frequency response: larger frequency bandwidth and acoustic pressure, lesser reverberation and distortion, higher sensing accuracy and spatial resolution, easily integrated in MEMs and sound signal self-demodulation, and availability and controllability for finely structured phase arrays operation. [2][3][4][5][6][7][8][9][10][11][12][13] However, theoretical investigation of TA emission seriously lags behind the experimental one due to comparatively fewer efforts. Currently, alomast all the formulas for calculating TA emission so far are one-dimensional, 1,[14][15][16][17]19,22 taking advantage of the plane-wave solution based on the pressure-temperature coupled equations in a fluid given by F. A. McDonald and G. C. Wetsel, Jr., 18 and the problems of near-and far-field TA emission need to be dealt with seperately.…”

Characteristics of thermally induced acoustic emission from nanoporous silicon device under full digital operation

“…[24][25][26] Due to the compatibility with the impulse drive, the PS emitter is also applicable to the probe for the 3-dimentional object sensing in air 27 and the acoustic pressure generator for noncontact actuation of a beam. 28 The present paper reports the underlying physics and characteristics of the PS emitter under full digital drive mode in a frequency range from the audio to ultrasonic band (0.3À40 kHz). The specific frequency responses observed in the open space and closed one are discussed in relation to the emission mechanism.…”

Model for thermoacoustic emission from solids

“…All of these attractive merits are mainly attributed to its unique nature-constant ͑flat͒ amplitude-frequency response over a wide frequency range. [2][3][4][5][6][7][8][9] However, compared with lots of experimental studies, theoretical investigations of this characteristic are very few. After Shinoda et al presented a formula for PS thermal-ultrasonic emission by utilizing the fundamental equations of McDonald and Wetsel's photoacoustic model, Boullosa and Santillán also derived an expression from thermal piston model for ultrasound radiation from TA transducer.…”