双层微球壳流固耦联振动及声散射分析

Analysis on coupling vibration between a micro double-layer spherical shell and fluids and its acoustic scattering

为研究在药物输送中常用包裹药物的双层壳体声散射特性,本文建立了双层微球壳与其内外流体耦联振动模型。通过求解在超声波作用下各层球壳与内外流体的耦合作用方程,得到了球壳径向位移的级数形式解;利用此级数解分析了球壳的材料参数和几何参数对声散射特性的影响。结果表明:散射率曲线的峰值总是出现在耦联系统的固有频率处;内层球壳的密度增大200kg/m3时,第1阶子波的第2个散射率峰值增大了13.9%,但对第0阶子波基本无影响;内层球壳的杨氏模量增大40MPa时,固有频率增加近20%;外层球壳厚度增加0.1μm时,固有频率增大的幅度较小,但各散射率峰值减小幅度均大于9%。这些结果有助于了解双层微球壳声散射特性,从而指导药物包裹体的参数设计。

The double-shell is commonly used to wrap drug in drug delivery.A model of coupling vibration between a micro double-layer spherical shell and liquids is proposed to make clear the acoustic scattering characteristics.The equations,which describe coupling vibration between the two-layer shell and liquids when acted by an ultrasonic wave,are solved.A solution of shell radial displacement with a series form is obtained.The dependence of acoustic scattering characteristics upon spherical shell material parameters and geometry parameters is analyzed by use of the solution.The numerical results indicate that the reflectivity will reach a peak while the forcing frequency is identical to one of the natural frequencies of the coupling system.When the density of inner shell increases 200kg/m3,the second reflectivity peak of the 1st scattered sub-wave will increase 13.9%,however little effect is acted on the 0-th scattered sub-wave.The first natural frequency increases close to 20% when Young's modulus of the inner shell increases 40MPa.Comparing a single layer shell,the double-layer shell with an outer shell of 0.1μm thickness has little higher natural frequencies,but its amplitude peaks of the reflectivity have been lowered more than 9%.All these are helpful to understand acoustic scattering characteristics of the double layer micro-spherical,and to guide the design on parameters of the drug packaging shell.