A theoretical study of the feasibility of acoustical tweezers: Ray acoustics approach
A theoretical study of the feasibility of acoustical tweezers: Ray acoustics approach
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DOI：
10.1121/1.1886387
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发表时间：
2005-05-01
影响因子：
2.4
通讯作者：
Shung, KK
中科院分区：
文献类型：
--
作者：
Lee, J;Ha, K;Shung, KK
光镊在捕获大分子和细胞等生物医学领域有着广泛的应用。对于捕获机制，轴向光强必须有急剧的空间变化，颗粒尺寸必须远大于波长。在声学中也可能存在类似的现象。进行这项工作的目的是从理论上证明，如果满足某些条件，可以在大部分声能集中的焦点附近声学捕获颗粒。在声束波长远小于颗粒尺寸的射线声学体系中，分析了超声场中作用在流体颗粒上的声力。为了将声镊应用于操纵尺寸在几微米或更小的量级的大分子和细胞，先决条件是超声波波长必须远小于几微米。因此，在本文中，分析的基础上，由一个强聚焦的100 MHz的超声换能器与高斯强度分布所产生的场图案。为了实现声捕获，必须产生负的轴向辐射力以将颗粒拉向焦点。本文中考虑用于声捕获的脂肪颗粒具有1.4MRayls的声阻抗。作为脂肪颗粒的尺寸计算的声轴向辐射力的大小从8λ变化到14λ。此外，还计算了不同位置处的菲涅耳系数，以评估反射和折射的相互作用以及它们对声镊效果的相对贡献。仿真结果表明，声镊的可行性取决于声阻抗失配程度和相对于颗粒尺寸的聚焦程度。© 2005美国声学协会。
The optical tweezer has been found to have many biomedical applications in trapping macromolecules and cells. For the trapping mechanism, there has to be a sharp spatial change in axial optical intensity and the particle size must be much greater than the wavelength. Similar phenomenon may exist in acoustics. This work was undertaken to demonstrate theoretically that it is possible to acoustically trap particles near the focal point where most of the acoustic energy is concentrated if certain conditions are met. Acoustic force exerted on a fluid particle in ultrasonic fields is analyzed in a ray acoustics regime where the wavelength of acoustic beam is much smaller than the size of the particle. In order to apply the acoustical tweezer to manipulating macromolecules and cells whose size is in the order of a few microns or less, a prerequisite is that the ultrasound wavelength has to be much smaller than a few microns. In this paper, the analysis is therefore based on the field pattern produced by a strongly focused 100 MHz ultrasonic transducer with Gaussian intensity distribution. For the realization of acoustic trapping, negative axial radiation force has to be generated to pull a particle towards a focus. The fat particle considered for acoustic trapping in this paper has an acoustic impedance of 1.4 MRayls. The magnitude of the acoustic axial radiation force that has been calculated as the size of the fat particle is varied from 8λ to 14λ. In addition, both Fresnel coefficients at various positions are also calculated to assess the interaction of reflection and refraction and their relative contribution to the effect of the acoustical tweezer. The simulation results show that the feasibility of the acoustical tweezer depends on both the degree of acoustic impedance mismatch and the degree of focusing relative to the particle size. © 2005 Acoustical Society of America.