Research On Controllable Adjustment Of Concentration Gradients Of Nanoscale Fluid Based On Droplet Microfluidic

Concentration gradients refer to the distribution of solute concentration in a certain area with increasing or decreasing law.This concept has important significance in the field of biomedicine and chemistry.Especially with the deepening of protein screening,enzyme kinetic analysis and cell biology research,the analog analysis of samples with different concentrations is an important part of the experiment.At present,samples of different concentrations mainly rely on the traditional manual preparation method,which is time-consuming and labor-intensive.After the development of robot technology,the robot operation can combine different reagents,but the reagent preparation takes a long time,the consumption is large,and the gradient accuracy is low.In recent years,with the development of microfluidic technology,screening experiments for different concentration conditions are usually carried out in microfluidic chips.Therefore,based on the droplet microfluidic technology,the traditional method of preparing concentration gradient solutions is cumbersome and the gradients are inaccurate,this paper develops a microfluidic chip which is simple,easy to operate,and can quickly generate stable and high-precision concentration gradients.First,it comprehensively elaborates the research status of droplet generation technology and concentration gradients at home and abroad.Through theoretical and simulation analysis,it deeply explores the fluid flow and droplet formation mechanism in the micro channel,and obtains the factors that affect the droplet generation process.And comprehensively analyze the state of droplet formation in the coaxial flow channel.Then,based on the co-flow method,a W/O water-in-oil droplet generation model is established to simulate the droplet formation process of the two-phase flow in the microchannel,the factors such as surface tension,viscous force,and flow velocity of various phases related to the size of droplets are simulated and analyzed to provide guidance for subsequent experiments.Secondly,the theoretical and simulation analysis of fluid mixing and static concentration gradient generation in the microchannel are carried out.Based on the convection-diffusion effect,analyze the mixing fluid and the factors affecting the concentration in the microchannel;In the static concentration gradient simulation part,by adjusting the ratio of the two droplets to simulate the mixing process of the two-phase flow in different ratios,it provides a theoretical analysis for the concentration gradient generation in the microfluidic chip.Thirdly,the design and processing of concentration gradient droplet microfluidic chip is introduced.Combined with the previous theory and simulation analysis,the design of the chip is discussed,including the technical and structural aspects.The equipment and materials required for chip processing are selected for the design,and the production process of the chip is systematically organized.The key issues in processing are explained,and finally the required chip objects are developed using glass capillaries.Finally,the developed chip is used to conduct concentration gradient droplet generation experiment.First,build an experimental system and prepare the materials needed for the experiment,and conduct a single emulsion droplet formation experiment.The single emulsion droplets are composed of two-phase aqueous solution,and the monodispersity is good.The relationship between the droplet size of single emulsion and the flow rate of each phase is explored through experiments,and the previous simulation results are verified.Afterwards,a concentration gradient droplet generation experiment is carried out to prepare concentration gradient droplets in the order of 103-104 with nanoscale fluids,which achieves the research goal of generating high-order concentration gradient microdroplets with a simple chip structure,effectively reducing the cost of samples,improving the preparation efficiency of concentration gradient reagents.