Method For Realizing Electromagnetic Tweezers Based On Large Gradient Microwave Focusing Field

Electromagnetic waves have energy and momentum.Electromagnetic tweezers utilize the conservation of momentum between the microwave focusing field and the substance to achieve the capture of matter.On the one hand,it can break through the requirements of optical tweezers for the transparency of surrounding environmental materials.On the other hand,it can enrich advancing the development of the microwave field.It is expected to achieve a universal,simple,and economical electromagnetic capture and manipulation tool.The space-time focusing characteristic of Time Reversal(TR)in the field control can overcome the diffraction and energy divergence of microwaves and realize the spatial focusing field of the microwave frequency band.TR provides a technical means for the realization of electromagnetic tweezers.This thesis aims to realize the capture of a single particle,multiple rayleigh particles with high refractive index and low refractive index by electromagnetic tweezers.How to improve the single point,multi-point field intensity gradient of focusing field and how to realize the annular large gradient microwave focusing field are deeply studied.Firstly,based on the theoretical derivation and data analysis of the time-reversed focus field gradient,two key factors for improving field intensity gradient of focusing field are obtained.Based on the realization of the single-point focusing field by TR technology,the influence of the wire arrangement on the two factors is explored.Two arrangements to improve field intensity gradient of focusing field are adopted,and two large gradient microwave focusing fields are implemented at the excitation antenna.The effect of the change in the position of the focusing antenna on the large gradient microwave focusing field is investigated.The radiation force of a large gradient microwave focusing field on a single high refractive index particle is studied,which verified electromagnetic tweezers based on large gradient microwave focusing field enable the manipulation of high refractive index rayleigh particle at different locations within the range of-120 mm ?x ?120mm,-120 mm ?y ?120mm,and enable capture multiple high refractive index particle at equilibrium locations.Secondly,with single-point focusing fields as the basic fields,the multi-point focusing field is obtained by combining the linear superposition principle of the field.The field intensity gradient of focusing field is increased by loading metal wires near the excitation antenna.With the optimization algorithm,the equilibrium of the multi-point large gradient focusing field strength distribution is optimized,and the equilibrium of the multi-point focusing field strength gradient distribution is realized.The capture of multiple rayleigh particles by multi-point large gradient focusing field is studied.The results show that the electromagnetic tweezers based on multi-point focusing fields can realize the manipulation of multiple high refractive index rayleigh particles at multiple equilibrium positions.Finally,a method to realize the hollow annular large gradient focusing field is proposed to capture the low refractive index rayleighp articles.The theoretical basis of generating the hollow annular focusing field is explained,and the hollow annular focus field is realized by the omnidirectional antenna.The gradient of the hollow annular focusing field is improved by changing the type of D-TRM elements,increasing the number of elements and increasing the feed power.The capture of rayleigh particles by hollow annular large gradient microwave focusing field is investigated.The electromagnetic tweezers based on the hollow region of the hollow annular focusing field can capture the low refractive index particles while the electromagnetic tweezers based on the non-hollow region can realize the capture of the high refractive index particles.