Research On The Integration Of Droplet Driving And Detection Based On Digital Microfluidic Chip

Droplet based digital microfluidic technology is favored by researchers because of its strong configurability,parallel processing of multiple droplets and low consumption rate of reagents.It enables the micro analysis system to be applied to many fields such as analytical chemistry,clinical diagnosis,DNA sequencing and environmental monitoring.However,so far,the precise droplet manipulation technology has been affected by many uncertain factors,such as the driving effect of transparent or invisible droplets cannot be observed by the naked eye,and the driving trajectory of droplets cannot be accurately planned.In order to improve the accuracy of droplet manipulation,This paper discusses the driving principle and detection technology of droplets on digital microfluidic chip,and carries out relevant research on the accurate positioning of droplets and the integration of driving device and detection device.Mainly carried out the research work of digital microfluidic(DMF)chip design,system construction of droplet driving and detection integrated device,droplet position detection and path planning.The specific research contents are as follows:(1)Based on the dielectric wetting effect,the driving of micro droplets in digital microfluidic chip is studied;Based on the principle of electrical detection,the precise control of droplet position in the driving process is realized.From the perspective of electrode graphic design,this paper realizes the electrode reuse of driving and detection circuit,and shares a DMF chip to lay the foundation for the integrated device of driving and detection.In this paper,the orthogonal matrix electrode is designed,and the lead reuse technology is used to reduce the lead density and reduce the difficulty of chip processing.Only 14 leads are used to realize the movement of droplets in 49 positions in the digital microfluidic chip.(2)Build an integrated digital microfluidic(DMF)system.The system is mainly composed of upper computer,lower computer hardware and DMF software.The hardware system of lower computer includes driving circuit and detection circuit.The driving circuit adopts the existing devices in the laboratory,and the lower computer detection system is designed independently,mainly including chip selection circuit,detection circuit,switch circuit and other modules;The upper computer program is compiled by using Visual Studio software to realize the integration of driving control and capacitance detection;DMF chip structure is orthogonal matrix electrode.This design can realize that the driving circuit and detection circuit share the same chip.The whole device can detect the position of the droplet in the droplet driving gap,and then plan its path.The AD7746 capacitance detection chip is used to detect the initial position,the position in the process of traveling and the target position of the droplet.The detected position of the droplet is highlighted in red on the upper computer interface,and the experimental effect is verified by judging the actual position of the droplet observed with the help of the microscope.Through many tests,it is found that the maximum difference of capacitance measured at the place with or without droplets can reach 1.4p F,which is obvious for the threshold capacitance of4.096 p F detected by AD7746 capacitance detection chip.The device can accurately detect the location of droplets on the digital microfluidic chip,and the capacitance error range of49 locations detected each time is kept within 2%,with good reliability,and the accuracy of the location of detected droplets is as high as 100%.(3)Through the previous research,this paper has carried out the application of droplet driven chemical fading reaction based on digital microfluidic chip and zebrafish biological experiment.Chemical fading reaction,the fading reaction experiment of potassium permanganate and vitamin C solution in digital microfluidic chip with double plate orthogonal matrix electrode is designed.The two solutions on digital microfluidic chip are1μL respectively.Compared with the complete fading of purple in the same proportion of potassium permanganate solution under conventional conditions(taking 45s),the fading reaction on the digital microfluidic chip takes only 34 s this phenomenon reflects that the digital microfluidic chip technology shortens the reaction time and reduces the consumption of reagents to a great extent;For zebrafish biological experiment,considering the diameter of zebrafish embryo,in order not to destroy zebrafish embryo cells,the 48 h zebrafish shell breaking experiment is completed with the help of single board square digital microfluidic chip.In the experiment,zebrafish embryos with the same number of 5groups(50)were added 50μL of 1mg/mL、1.25mg/mL、1.5mg/mL、1.75mg/mL、2mg/mL streptozyme protease solutions were added to accelerate the breaking of the shell.The optimum concentration was selected(1.5mg/mL)and measured with the help of microfluidic chip technology When the quantity of streptozyme protease solution is 1μL,it takes about 15 min to complete the shell breaking,and the shell breaking rate is the highest,which does not affect its activity.Compared with the traditional method,it takes at least35 min.It shows that this digital microfluidic chip technology has the characteristics of accurate drug administration,one by one control and accelerating the reaction speed.(4)In this paper,the growth state of zebrafish after shell breaking is monitored.With the help of coplanar interdigital electrode combined with continuous microfluidic technology,AD7746 evaluation plate is used to detect the activity of zebrafish passing through the fixed electrode position,so as to judge its health status,and verify that unipolar plate digital microfluidic chip can assist cells in biological experiments.It can be seen that the integrated research of droplet driving and detection based on digital microfluidic chip shows its unique charm in many applications such as biology and chemistry.The characteristics of low dose and rapid response make this technology develop rapidly and can be widely used in clinical trials.