| Recently, inspired by the electronics band theory of natural crystals, a lot workshave been done on wave propagation of periodic composite materials or structures.Generally, those periodic materials or structures with elastic waves stop bands arephononic crystals. Due to the properties like stop bands, conductive bands and defectszones, phononic crystals can be used in various novel devices. Acoustic manipulation, amicro-scale manipulation technique achieved by applying acoustic waves, has someadvantages including non-contact, penetrability and versatility, without any biochemicaldecorations to particles. However, the acoustic fields generated by conventional systemscannot be redesigned easily, nor can the corresponding acoustic radiation forces bemodulated efficiently. Moreover, any particle with size much smaller than wavelengthcannot be manipulated.This essay focus on the properties of phononic crystals and its applications inacoustic manipulation. Specifically, a novel waveguide structure based onmulti-scattering has been developed. The band structures and transmissions of twonovel phononic crystal strips have been studied. The wave guide of elastic wave withfrequency of2.7MHz can be realized with the combination of two phononic crystalstrips. In addition, fabrication of surface acoustic wave devices based on interdigitaltransducers have been studied, which have been used for1D patterning of microbubblesand cavitation. We also have studied the possibility of acoustic aligning microparticlesnear the surface with the phononic crystal slab, which can excite strong local gradientfields. We have experimentally realized the aligning of micro-particles by a PCS. Sincethe manipulation system is fabricated on a chip, it can be easily integrated with MEMStechnology and combined with other micro-processing technology. We believe thistechnique can be developed to meet the needs of non-contact and precise manipulationof cells and biological particles. |
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