Research On The Manipulation Of Micro-Nano Particles Based On Optofluidic System

With the progress of biochemical and medical research,the requirements for the size and manipulation accuracy of research objects have been continuously improved,which have reached the micron or even nanometer level.The traditional manipulation technology has been unable to meet the existing needs,and the optofluidics technology,which integrates microfluidic chips and optical manipulation,has emerged as the times require.It has high manipulation accuracy,low sample volume requirements,high device integration,and no damage to the target.Its advantages make it widely used in the fields of micro-nano particle trapping and sorting.In this thesis,a novel optofluidic system is proposed to realize multifunctional manipulation of microparticles on a chip.The specific research contents are as follows:(1)The principle of optical manipulation is studied,while a design scheme for sorting microparticles of different sizes is proposed.The optical forces experienced by polystyrene microparticles of different sizes are calculated based on the finite element method.The scattering intensities and spot of polystyrene microparticles of different sizes are measured to distinguish the manipulated objects in the dark field.The fiber optical tweezers are applied to the optofluidic system to simplify the optical setup,which is used to build a microparticle sorting scheme with the optofluidic chips.(2)Aiming at the influence of flow velocity on microparticle manipulation,a method of improving microparticle sorting efficiency by using the colliding flow is proposed.Through simulation and experiments,the effects of hydrodynamic focusing and collision of each inlet fluid under different flow velocity ratios are studied.In addition,the optimal flow velocity parameters are selected.The moving speeds of microparticles with two different sizes in the sorting process are analyzed.Compared with the traditional optofluidic system,the average moving speed of the microparticles during the sorting process is improved,thereby realizing the efficient sorting of the microparticles.(3)Control schemes for trapping and moving microparticles are investigated.By adjusting the inlet of the microparticles and controlling the flow rate,the microparticles are confined to the optical working area by hydrodynamic focusing,which improves the probability of the microparticles being trapped.The moving speeds of the microparticles are analyzed during the trapping process.The optical forces on the microparticles at the equilibrium position are estimated.When the microparticles are stably trapped,the microparticles can be controlled to move back and forth in two fixed positions by adjusting the laser power.The experimental results verify the feasibility of the scheme.In summary,the optofluidic system proposed in this thesis can realize multifunctional manipulation,such as trapping,moving and sorting polystyrene microparticles of different sizes,and improve the sorting efficiency.The system can also be applied to nanoparticles of different shapes and sizes,as well as biological cells.Therefore,the system has great application potentials.