Research On Digital Microfluidic Chip Based On Droplet Generation And Control Technology

Microfluidic chip droplet technology,as a new technology for manipulating tiny volumes of liquid,can not only realize the generation and control of high-throughput microscopic samples,but also control the independent droplets.The dispersed micro-droplet unit can be used as an ideal micro-reactor,and has shown great application potential in the fields of physics,chemistry,biology,drug screening,material screening,and high value-added micro-particle material synthesis.Microfluidic chip droplet technology has shown great advantages and development potential,but so far there is still some uncertainty in the precise control of microdroplets,such as: how to achieve precise control of droplet size and number,how Simplify device packaging,how to shorten the response time to obtain effective droplets;how to more accurately guide droplets in the downstream environment,selectively capture and detect droplets;or how to effectively improve the driving efficiency of droplets on array electrodes,Accurately realize droplet distribution,separation,fusion and other operations.Therefore,this paper mainly conducts research on the droplet generation mechanism and control technology of the microfluidic chip,and conducts related research work on precise droplet control and device simplification;this paper mainly develops the design and manufacture of droplet generation devices,Digital microfluidic(DMF)chip design,system construction and droplet drive control and other research work.(1)The research and analysis of the droplet generation mechanism of two-phase flow and the existing droplet generation technology.To deal with the problem of the complex structure of the two-phase flow injection and the large external packaging volume in the traditional confocal flow method,this article uses commercial T-tubes,A new method of co-current focusing droplet generation—T-type cocurrent focusing method is proposed.In addition,in order to optimize the taper angle and diameter of the outlet of the embedded capillary,a capillary ring heating stretching method was also proposed.In the research of droplet size control,it was found that the ratio of droplet size to the flow rate of continuous and discrete phases has obvious regularity.As the flow rate ratio increases,the droplet size decreases accordingly;There is an approximately inverse relationship between the sizes.As the droplet size decreases,the frequency of droplet generation will increase.In the study of the uniformity of droplets,this paper obtains the best parameter of the uniformity of droplets,that is the cone angle 4 by orthogonal test and intuitive analysis,The flow rate ratio is 190: 1,the outlet pipe diameter is 72?m,the average volume of the generated droplets is 8.3nL,the generation frequency is 0.7Hz,and the uniformity is 0.011.(2)In this paper,the efficiency of droplet control on DMF chips is improved from the perspective of electrode pattern design.The design of a curved quadrilateral combined electrode is proposed.The edge of the electrode pattern can maintain a greater degree of coincidence with the droplet and can provide a greater initial driving force.Finally,this article uses the soft lithography system to process the electrode.(3)Build a DMF control system.The system mainly includes the lower computer hardware system and the upper computer software system;this paper firstly designs the lower computer hardware system.The hardware system mainly includes the power module,DC boost module,switch circuit and other modules,and draws the PCB board.In addition,this paper uses C# language to develop the DMF host computer control software.The host computer software mainly realizes the control of the lower computer,gives the corresponding control commands and is executed by the main computer control chip to complete the corresponding droplet control.(4)In this paper,the droplet driving control on the single-plate DMF chip is studied,and the droplet motion state in the air domain of the single-plate is discussed and analyzed.In addition,the driving of the droplets in the single-plate oil bath was also tested.The average movement speed of the droplets in the air bath was 25?m/s,and the average movement speed of the droplets in the oil bath was 260?m/s.The movement speed of the medium droplet is significantly faster.The difference between the droplet driving in the two environments is mainly due to the small resistance of the droplet in the oil bath.(5)on the principle of droplet driving based on EWOD,this paper also carried out research on droplet-oriented control in microfluidic chips,proposed the graphic design of crescent-shaped droplet-oriented electrodes,and fabricated droplet-oriented microfluidic chips.In this paper,the guided droplets are introduced into the droplet guiding microfluidic chip from the outside by a T-type cocurrent focusing droplet generating device.In the droplet guiding test research,this paper studies the droplet guiding process,and by analyzing the trajectory of the guided droplet,the estimated minimum deflection angle of the successful droplet guiding is 27~?.