Study Of Self Assembly Of Particles Using The Resonance Characteristics Of The Two Dimensional Phononic Crystal Slabs

An object insonified by a sound field can be experienced a steady force that iscalled the acoustic radiation force. The acoustic radiation force is caused by a changein the energy density of an incident acoustic wave and is used to manipulate particles.The acoustic manipulation has characteristics of non-contact, non-damage andpenetrability. It is one of physical researches to manipulate, separate and captureMicro/Nano-particle. The research about the acoustic force on spherical particles,columnar particles in plane wave field, standing wave field and Bessel bind field hasstudied by the scholars of every country. While up to now, there are few studies aboutthe manipulation in complex acoustic field (non-analysis acoustic field). The acousticradiation force is affected by the form of acoustic field. So it is critical to designoptimizing acoustic field to realize diversification acoustic manipulation.The phononic crystal is a kind of material or the structure with periodicdistributed elastic constant and density. It has all kinds of band gap because of thecombined effect of Bragg scatter and single Mie’s scatter. The particular energy bandowned by the phononic crystal can be used to control the acoustic waves or elasticwaves effectively.In this work, the problem of controlling the particle based on the resonancecharacteristics of two-dimensional phononic crystal slab is studied, acoustic radiationforce which exists nearby the two-dimensional phononic crystal slab is calculated byFinite-Difference Time-Domain (FDTD), and the patterns and rules of controlling theparticle using the resonance characteristics of two-dimensional phononic crystal slabis discussed. Specific contents are as follows:Firstly, I study the resonance of two-dimensional phononic crystal slab by themethod of Finite-Difference Time-Domain. The result indicates that the phononiccrystal slab exhibits sharp resonant features superimposed upon a smoothly varyingbackground. The research of the particle manipulation can be carried on by the factthat the phonon crystal board can have the resonating peak in the specific frequency value and produce the resonant mode.Then, acoustic radiation force exerted on particle above the phononic crystal slabis studied by the method of Finite-Difference Time-Domain combined withmomentum-flux tensor theory. The result shows that there is a resonantly-enhanced,stably trapped acoustic radiation force on the particle.Finally, I study the trapping patterns, and acoustic radiation force dependent onthe wavelength, particle size, and particle material respectively. It shows that the forcedecreases as the radius of the particle decreases. And when the material of particlechanges, the attraction from phononic crystal slab still exists. And with the distancebetween the particle and the hole increase, the acoustic radiation force exerted on theparticle decrease. It is shown that tuning the wavelength of incident acoustic wavemay thus allow the formation and reconfiguration of patterns.In conclusion, I study the acoustic radiation force on particles above PCSnumerically. The results show that this system may thus allow realizing screen andself-assembly particles by tuning the frequency.