中文摘要：

随着生物医学和工业领域对纳米粒子的非接触式操控需求的日益强烈,对新型声镊子的设计提出更高的要求.在忽略球粒子所在液体的粘滞力和声损耗的前提下,利用球散射法计算了环状换能器对轴向球粒子的声辐射力,在理论上发现环状换能器捕获轴向上球粒子的可能性.球散射法既可以应用于远大于波长的粒子,也可以用于远小于波长的粒子,具有普遍适用性.根据理论结果发现声辐射力受球粒子与换能器之间的距离,环状换能器内外半径大小,球粒子的大小以及材料特性等因素的影响.而且环状换能器的近场区存在着一些声辐射拉力区.声辐射拉力区随着环状换能器外半径,内半径的改变而发生相应变化.环状活塞换能器对轴向球状粒子的声辐射力特性可以用来设计新式声镊子装置,其中空位置可以用来放置监控设备来监控操纵粒子,或者安装机械操控装置以改变换能器的位置和方向.这些理论和计算结果对单声源声镊子的实现具有指导意义.

英文摘要：

With the demand for non-contact manipulation of nano-size particles becomes more urgent in biomedical and industrial field,it has higher request for the design of new acoustic tweezers devices which use the forces of ultrasonic radiation to trap and manipulate particulate matters.Neglecting the fluid＇s viscosity where the sphere is immersed and acoustic losses,the acoustic radiation force are calculated by scattering theory for a middle hollow ring-shaped piston exhibited on the sphere which is located on the axial line of the ring-shaped piston in the paper.The calculation theoretically demonstrates the possibility to trap a sphere with a single-beam ring-shaped piston transducer.The scattering theory,which surmounts the restriction to the long-wavelength（Rayleigh）or the short-wavelength（ray）regimes,can be applied in almost all kinds of circumstances.The calculation result reveals that the radiation force are effected by the following facts as the distance separating the sphere from the center of piston source,the outer and inner radius of the circular ring-shaped transducer,the radius of the sphere particle and the material properties of the sphere.In addition,the simulations demonstrate that there are some pulling force areas in the near field of the ringshaped transducer,and the pulling force areas varies along with the outer and inner radius of the ring-shape transduc-er.Such radiation force feathers on a sphere of ring-shaped transducer may theoretically help induce new acoustic tweezer applications whose middle hollow region can be used to install photography facilities to monitor the particle manipulating procedure or control linkage to change position and direction of the transducer.The theory and calculation result may also help design new beam-forming equipment or manufacture new efficient single beam acoustic trapping devices.