Research On Small Cylindrical Single Beam Acoustic Radiation Force Particles

We can manipulate micro-particles (such as atoms, organelles, DNA, etc) using acoustic radiation force. Acoustic tweezers which was made according to this principle have important values in the applications of life sciences, medicine, materials science, chemistry and many other fields. The research on acoustic radiation force of micro-particles plays an important role in the development and improvement of acoustic tweezers. For the cylindrical particle is a very typical particle in practice, we study the acoustic radiation force of a cylindrical micro-particle immersed in water incidented by a single ultrasonic beam. This paper mainly includes the following aspects:1. The acoustic scattering characteristics of cylindrical particles incidented by the plane wave are given.Starting from the basic acoustic wave theory, the scattering characteristics of the plane waves scattered by elastic cylinders, fluid cylinders, rigid cylinders, vacuum cylinders in liquid mediums and elastic mediums are studied. Under different boundary conditions, the expressions and the scattering coefficient are given step by step. This will give the foundation of further study to the acoustic radiation force.2. The values and the variation rules of the acoustic radiation force which acting on cylindrical objects immersed in fluid mediums are calculated and analyzed detail for plane wave incidence.After obtaining the sound pressure expression which contains the second tiny amount, we derived the expression of the acoustic radiation force acting on a cylindrical object in a liquid medium which was incidented by a plane wave. The acoustic radiation force acting on a rigid cylinder, a fluid cylinder and some elastic cylinders is simulated and calculated. The curve of the radiation force function is draw. The simulation results show that the acoustic radiation force function of the rigid cylinder gradually tends to a stable value with the increasing of ka while the elastic cylinder has obvious resonance characteristics and shows a certain peak and valley values. Values of the fluid cylinder’s acoustic radiation force function are smaller, but they show a more uniform periodic changes.3. We derived and obtained the expression of the Gaussian beam factor, then calculated and analyzed the acoustic radiation force acting on a cylindrical object immersed in a liquid medium by a Gaussian beam.Based on the finite series method, we obtained the expression of the Gaussian beam factor. According to the acoustic radiation force theory, we derived the expression of the acoustic radiation force, which is experienced by cylindrical particles immersed in ideal liquid and placed in the center of a Gaussian beam. We calculated the acoustic radiation force acting on the cylinders made from different materials. The curve of the acoustic radiation force function shows that, the radiation force caused by a Gaussian beam was influenced by the waist radius of the Gaussian beam. The larger the waist radius is, the larger the radiation force is. When the waist radius is far larger than the wavelength of the Gaussian beam, the value of the radiation force function of the Gaussian beam is almost the same as that of the plane wave.