CN111581896A - Method for improving liquid drop driving efficiency of single-pole plate digital micro-fluidic chip and application thereof - Google Patents

Method for improving liquid drop driving efficiency of single-pole plate digital micro-fluidic chip and application thereof Download PDF

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CN111581896A
CN111581896A CN202010434383.9A CN202010434383A CN111581896A CN 111581896 A CN111581896 A CN 111581896A CN 202010434383 A CN202010434383 A CN 202010434383A CN 111581896 A CN111581896 A CN 111581896A
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张永来
吕品
孙洪波
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Abstract

The invention discloses a method for improving the liquid drop driving efficiency of a single-polar plate digital microfluidic chip and application thereof, belonging to the technical field of digital microfluidic chips. The main principle is to analyze the electrowetting force induced by the interdigitated electrode and the Laplace force generated by the deformation of the liquid drop caused by the electrowetting force, establish a mathematical model for calculating the Laplace pressure difference and finally obtain experimental parameters for improving the liquid drop driving efficiency. According to the invention, through modeling and analyzing the dynamic process of the liquid drop, the movement process of the liquid drop can be accurately analyzed, the electrode structure in the chip can be better optimized and designed, and the time interval of the applied voltage between adjacent electrodes can be obtained.

Description

Method for improving liquid drop driving efficiency of single-pole plate digital micro-fluidic chip and application thereof
Technical Field
The invention belongs to the technical field of digital microfluidic chips, and particularly relates to a method for improving the liquid drop driving efficiency of a unipolar plate digital microfluidic chip and application thereof.
Background
The digital microfluidic chip is a technology for controlling liquid drops on a specially prepared substrate by utilizing a dielectric wetting principle. The generation, transfer, mixing and splitting of liquid drops can be realized on the digital microfluidic chip, and the construction of a general biochemical analysis platform can be realized by controlling the liquid drops with different chemical components and combining the technologies of optics, electrochemistry, immunoreaction and the like. The digital micro-fluidic chip mainly comprises a bipolar plate and a unipolar plate. The unipolar plate digital microfluidic chip is an open type liquid drop control mode. In the unipolar plate digital microfluidic chip, a driving electrode and a zero electrode are integrated on the same substrate. The mechanism of droplet dynamics due to dielectric wetting is not clear. The unipolar plate digital microfluidic chip is faced with the problems that the liquid drop control is not stable enough and the internal power mechanism is lack of quantitative analysis. On the one hand, these problems are at risk of failure in droplet manipulation, and on the other hand, the problems are not favorable for maximizing the manipulation efficiency of droplets, and further research and solution are urgently needed.
Disclosure of Invention
Aiming at the defects of the prior art, the technical problems to be solved by the invention are as follows: the method for improving the liquid drop driving efficiency of the single-polar-plate digital micro-fluidic chip is provided, and further stable control of the liquid drops on the single-polar-plate digital micro-fluidic chip is achieved. According to the invention, a mathematical model is established through analysis of liquid drop control on the unipolar plate digital microfluidic chip, so that the liquid drop control efficiency is improved. Through modeling analysis, an interpolation type driving electrode is designed, and the improvement of the liquid drop driving performance and the stable control of the liquid drop are realized. The main principle is to analyze the electrowetting force induced by the interdigitated electrode and the Laplace force generated by the deformation of the liquid drop caused by the electrowetting force, establish a mathematical model for calculating the Laplace pressure difference and finally obtain experimental parameters for improving the liquid drop driving efficiency.
The invention is realized by the following technical scheme:
a method for improving the liquid drop driving efficiency of a unipolar plate digital microfluidic chip comprises the following specific steps:
(1) initializing device setting, including selecting electrode shape and size, determining dielectric layer thickness and liquid drop contact angle variation range delta theta:
specifically, the droplet contact angle variation range Δ θ ═ θA-θBWherein an interdigitated electrode array is used as the driving electrode array, thetaB、θASatisfies the equation cos theta of poplar-LippmannB＝cos θA+0 rV2/2dγlg，θAAnd thetaBThe contact angles of the liquid drops before and after the external voltage V is applied are respectively,0andrthe dielectric constants of the vacuum and dielectric layer materials, respectively, and d is the thickness of the dielectric layer; when the liquid drop is placed on the hydrophobic substrate of the unipolar plate digital microfluidic chip before the external voltage is not applied, the contact angle theta of the liquid drop isASatisfies the Young's equation cos thetaA＝(γsg–γsl)/γlgWherein γ issg、γsl、γlgGas-solid interfacial tension, solid-liquid interfacial tension and gas-liquid interfacial tension respectively;
(2) establishing a liquid drop dynamic model and obtaining experimental parameters:
the method comprises the following specific steps: when voltage is applied to a group of electrode units, the contact angle of the liquid drop is reduced due to electrowetting, the contact angles of the left side and the right side of the liquid drop are unequal, namely Laplace pressure difference is generated inside the liquid drop, and therefore calculation of the liquid drop driving force F is establishedactThe formula (c) of (a):
Fact＝ΔPA·SA·cos βA–ΔPB·SB·cos βB
wherein, Δ PAAnd Δ PBRespectively, the Laplace force, S, of the interface generated by the inconsistent deformation of the left and right sides of the liquid dropAAnd SBThe cross-sectional areas of the spherical surfaces on the left and right sides of the droplet, β respectivelyAAnd βBAre respectively Delta PAAnd Δ PBAn included angle formed with the horizontal direction;
viscous drag F experienced by a droplet on a devicehCan be calculated according to the following formula:
Fh＝3γlg·Rb·(cos θB–cos θA)
wherein，γlgIs the gas-liquid interfacial tension; rbA base radius indicating the solid-liquid interface; thetaBAnd thetaAIs the contact angle of the left and right sides of the drop;
furthermore, according to the dynamics law, F is equal toact–Fh＝m·a，
Wherein m is the drop mass and a is the acceleration of the drop as the contact angle changes;
size parameter L of bonding electrode is 2at2The time t required by the movement of the liquid drop on the two adjacent finger-inserting type electrodes can be calculated; according to the calculated time required by the movement of the liquid drop, the time interval of the voltage applied to the electrode can be controlled through programming; through parameter selection and iteration by utilizing the mathematical model, the optimal device performance can be optimized, and the maximization of the liquid drop driving force is realized;
(3) a method for controlling liquid drops by using the unipolar plate digital microfluidic chip;
the method comprises the following specific steps: and (3) completing initialization of device setting by using the analysis method in the step (1), and programming and inputting the time parameters obtained by using the calculation method in the step (2) into the controller.
Further, the device setup initialization in the step (1) includes that the side length of the selected square insertion finger type electrode unit is 1-4mm, the metal layer material of the unipolar plate digital microfluidic chip is indium tin oxide with the thickness of 150-300nm, the dielectric layer material is aluminum oxide with the thickness of 80-150nm, the hydrophobic layer material is Teflon with the thickness of 100 nm. By calculation, a curve of the contact angle of the liquid drop on the square unit along with the increase of the voltage is obtained, and since the contact angle is saturated due to dielectric wetting, theoretical calculation is combined with experimental tests, and finally the change range delta theta of the maximum contact angle of the liquid drop is 0-40 degrees.
Further, the step (2) of calculating Δ P in the laplace pressure difference formula of the liquid dropAAnd Δ PB，SAAnd SBAnd βAAnd βBDerived from a mathematical model of droplet wetting; when the volume is V0When the liquid drop is placed on a solid hydrophobic substrate, the liquid drop is connectedThe antenna is theta and the drop can be regarded as a sphere sigma (x)2+y2+z2＝R2) Quilt plane x2+(y-h)2＝b2Intercepting the remaining part;
droplet volume V0Then write to:
Figure BDA0002501681550000031
Figure BDA0002501681550000032
further obtaining the radius R of the ball corresponding to the liquid drop at the moment,
Figure BDA0002501681550000033
further obtaining the radius b and the chord height h of the contact base circle of the solid-liquid interface according to the triangular relation
b＝Rsin(π-θ)
h＝Rcos(π-θ)
According to the vector relation, the included angle beta of the laplace pressure difference along the horizontal direction satisfies the following conditions:
Figure BDA0002501681550000034
Figure BDA0002501681550000035
wherein, thetaAAnd thetaBShowing the left and right contact angles when the liquid drop is deformed; r1And R2Is the radius of the corresponding hemisphere on the left and right sides, h, when the droplet is deformed1And h2Corresponding to the chord height;
cross-sectional area corresponding to laplace pressure on the left and right sides of the droplet:
Figure BDA0002501681550000036
Figure BDA0002501681550000037
for spherical droplets with radius r, the laplace pressure at the interface Δ P ═ 2 γlgAnd/r, the laplace pressures corresponding to the left and right when the droplet deforms are respectively:
Figure BDA0002501681550000041
Figure BDA0002501681550000042
wherein, γlgIs the interfacial tension between the droplet and the air, i.e. the surface tension of water is 72 mN/m.
Further, the droplet driving force F in the step (2)actThe range of (1) is 100-150 mu N, and the acceleration of the liquid drop at the maximum deformation is 30-70mm/s2The time required for the droplet to travel over the square interdigitated electrode unit is 0.1-1.5 s.
Further, the voltage application mode in step (2) is that positive and negative voltages are alternately applied in sequence, the voltage is an alternating voltage, and the voltage range is 50-200V.
The invention also provides application of the method for improving the liquid drop driving efficiency of the unipolar plate digital microfluidic chip in liquid drop control and cargo transportation.
Compared with the prior art, the invention has the following advantages:
(1) by modeling and analyzing the dynamic process of the liquid drop, the movement process of the liquid drop can be accurately analyzed, the electrode structure in the chip can be better optimized and designed, and the time interval of applied voltage between adjacent electrodes can be obtained, so that compared with the traditional experimental test method, the driving efficiency of the liquid drop is improved, and the simplification of the operation and control steps of the liquid drop is realized;
(2) the finger-inserting type electrode is used as the driving electrode of the liquid drop, the driving voltage of the liquid drop is reduced, the stable control of the liquid drop on the single-polar plate digital micro-fluidic chip is realized, and the foundation is laid for the practicability of the single-polar plate digital micro-fluidic chip.
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Fig. 1 is a schematic diagram of a droplet stress analysis of a method for improving droplet driving efficiency of a unipolar plate digital microfluidic chip according to the present invention;
wherein: (a) surface tension distribution during static equilibrium of the liquid drop, (b) Laplacian pressure difference generated during deformation of the liquid drop, (c) and (d) liquid drop mathematical model schematic diagrams;
FIG. 2 is a comparison graph of system energy of a method for improving droplet driving efficiency of a unipolar plate digital microfluidic chip according to the present invention and system energy of a chip in a conventional manner;
FIG. 3 is a schematic view of the structure of the finger-inserted electrode unit of the present invention;
fig. 4 is a cross-sectional view (multi-layer) of a unipolar plate digital microfluidic chip of the present invention;
FIG. 5 is a diagram of a unipolar digital microfluidic chip according to the present invention;
FIG. 6 is a partially enlarged scanning electron microscope of the digital microfluidic chip with unipolar plates according to the present invention;
FIG. 7 is a system schematic of the unipolar plate digital microfluidic chip of the present invention;
FIG. 8 is a process diagram of a method for improving droplet driving efficiency of a unipolar plate digital microfluidic chip according to the present invention for stable droplet manipulation;
wherein (1) - (12) represent the positions of the liquid drops at different moments, and the time of each step is the calculated time interval.
Fig. 9 is a process diagram of the method for improving the droplet driving efficiency of the unipolar plate digital microfluidic chip according to the present invention for droplet cargo transportation;
wherein (1) - (10) represent the positions of the liquid drop and the polyethylene terephthalate globule at different time, and the time of each step is the calculated time interval.
Detailed Description
The following embodiments are only used for illustrating the technical solutions of the present invention more clearly, and therefore, the following embodiments are only used as examples, and the protection scope of the present invention is not limited thereby.
It is to be noted that, unless otherwise specified, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art to which the invention pertains.
Example 1
A method for improving the liquid drop driving efficiency of a single-pole plate digital micro-fluidic chip and application thereof are disclosed. Meanwhile, the single-edition digital microfluidic chip selected based on the parameters is verified to have the performance of stably controlling the liquid drops through the minimum energy comparison calculation of the system. The acquisition of the parameters has guiding significance for the subsequent liquid drop flooding experiment.
A method for improving the liquid drop driving efficiency of a unipolar plate digital microfluidic chip comprises the following specific steps:
(1) device setup initialization
The method comprises the following specific steps: the square interdigitated electrode unit shown in fig. 3 was selected as the drive electrode and zero electrode array unit, and the side length of the square was set to 3 mm. The metal layer material of the unipolar plate digital microfluidic chip is indium tin oxide with the thickness of 200nm, the dielectric layer material is aluminum oxide with the thickness of 120nm, and the hydrophobic layer material is Teflon with the thickness of 100 nm. It can be found from experiments that the contact angle of the liquid drop on the flat teflon substrate is about 105 degrees. For a liquid drop with a contact angle of 105 degrees, the solid-liquid contact area of the liquid drop is to completely cover a square electrode unit with the thickness of 3mm, the volume of the liquid drop needs to be less than 27 muL, and 25 muL of the liquid drop is selected for calculation in the example. According to the poplar-Lippmann equation cos thetaB＝cos θA+0 rV2/2dγlgIt can be seen that the variation range of the droplet contact angle is 20 to 105 degrees when the voltage is increased from 0V to 200V. Based on a device comprising the above-mentioned interdigitated electrodes, a dielectric layer and a hydrophobic layerThe electrowetting experiment of the device shows that the contact angle saturation of the liquid drop occurs at about 85 degrees, namely the contact angle variation range of the actual liquid drop is 85 degrees to 105 degrees. The maximum contact angle variation range Δ θ of the droplets is 0 to 20.
(2) Substituting the initial parameters into the model to obtain experimental parameters
For 25 μ L of droplets, according to the formula
Figure BDA0002501681550000061
The radius R of the sphere corresponding to the droplet can be calculated, and the radius b and the chord height h of the contact base circle of the solid-liquid interface can be obtained from b ═ Rsin (pi-theta) and h ═ Rcos (pi-theta) by combining the initial contact angle 105 ° of the droplet. Substituting the acquired three parameters of R, b and h into
Figure BDA0002501681550000062
And
Figure BDA0002501681550000063
(θA＝80°，θB105 deg.), the included angle between the laplace force in two directions and the horizontal direction can be obtained.
At this time, since the radius R of the sphere corresponding to the droplet is already obtained, the result is substituted into
Figure BDA0002501681550000064
And
Figure BDA0002501681550000065
the cross-sectional area corresponding to the laplace pressure on the left and right sides of the droplet can be obtained. Substitution into
Figure BDA0002501681550000066
And
Figure BDA0002501681550000067
the laplace pressures corresponding to the left and right sides of the droplet when deformed can be obtained.
The cross-sectional area S of the spherical surfaces at the left and right sides of the liquid dropAAnd SBContact angle β between left and right sides of dropletAAnd βBAnd in the liquid dropletPartially generating a laplace pressure difference Δ PAAnd Δ PBRespectively substituted into FactThe formula of (a):
Fact＝ΔPA·SA·cos βA–ΔPB·SB·cos βB
the laplace pressure difference formed by the deformation of the liquid drop, namely the driving force of the liquid drop, namely the maximum driving force 120.78 mu N can be obtained.
At this time, since the range of change of the contact angle is known, the viscous resistance F is substitutedh＝3γlg·Rb·(cos θB–cos θA) The viscous resistance of 105.78 μ N was obtained.
Combining sigma F ═ Fact–FhM.a and L2 at2The time required for a droplet to travel over two adjacent interdigitated electrodes can be directly calculated to be 0.85 s.
The driving efficiency of a droplet is also related to the driving stability of the droplet, which can be measured by the system energy. While calculating the system energy E of the droplet moving on the finger-type electrodeew，
Eew＝At·(0·r)·d–1·[χ(1–χ)·(Vh–Vd)2]/2
Wherein At is the area of the block-shaped interdigitated electrode;0andrthe dielectric constants of the vacuum and dielectric layer materials, respectively; χ ═ ar/(Ah+Ar)，AhAnd ArAn electrode area for applying a driving voltage and an electrode area for applying a reference voltage representing droplet coverage; vhAnd VdIs the drive electrode voltage and the voltage on the droplet.
At the same time, the system energy formula E is utilizedew＝At·(0·r)·d–1·[χ(1–χ)·(Vh–Vd)2]The system energy as the droplet moves over the interdigitated electrodes was calculated and compared to the conventional scheme. As a result, as shown in fig. 2, the minimum energy principle shows that the system becomes more stable as the system energy becomes smaller. According to the calculation, the above-mentioned interpolationWhen the finger-type electrode is used for driving liquid drops, the system energy is 215 nanojoules, which is 210 nanojoules lower than that of the conventional electrode with the same size when the liquid drops are driven; moreover, when the interdigital electrode is used for driving liquid drops, the fluctuation quantity of the system energy is 20 nanojoules, and when the traditional square electrode with the same size is used for driving the liquid drops, the system energy variation quantity is 115 nanojoules, which is more than 5 times of the scheme.
(3) A method for controlling liquid drops by using the unipolar plate digital microfluidic chip;
the method comprises the following specific steps: the voltage application mode is that positive and negative voltages are alternately applied in sequence, the voltage is alternating current voltage, and the voltage range is 50-200V. And (3) inputting the time interval t of applying voltage between the adjacent electrodes, which is calculated in the step (1) and the step (2), into the controller by programming the program, wherein the time interval t is 0.85 s.
As can be seen from fig. 1, laplace pressure difference exists between the left and right sides of the deformed droplet, and the dynamics of the droplet can be analyzed by the analysis method, so as to obtain the optimal parameters for droplet manipulation. This analysis is of great significance for stable driving of the subsequent droplets.
As can be seen from fig. 3, one block driving unit is formed by combining two independent finger-inserted electrodes, and the size of the electrode structure can be adjusted according to the size of the droplet to be controlled.
Example 2
A method for improving the liquid drop driving efficiency of a unipolar plate digital microfluidic chip is used for stable liquid drop control and cargo transportation, and comprises the following specific steps:
the procedures (1), (2) and (3) are the same as those in example 1.
(4) And preparing the unipolar plate digital microfluidic chip according to the shape and size parameters of the electrode unit and the thicknesses of the dielectric layer material and the hydrophobic layer material in device initialization, wherein the preparation process is as follows.
The method comprises the following specific steps: (1) and (3) cleaning the indium tin oxide glass by using toluene, acetone, ethanol and deionized water under the ultrasonic condition, and drying. (2) The cleaned substrate was coated with a layer of SU-8 photoresist having a thickness of about 80 μm by spin coating, and was baked in an oven at 95 ℃ for 6 minutes, and subjected to photolithography and development. And then, placing the substrate covered with the SU-8 masking layer into aqua regia (nitric acid, hydrochloric acid and deionized water in a volume ratio of 1:3:6) at the temperature of 50 ℃ for etching to prepare the finger-inserting type electrode array. (3) And then the etched substrate is placed into SU-8 degumming liquid to be soaked for 30 minutes, the SU-8 masking layer is removed, and then deionized water is used for cleaning and drying. (4) And evaporating a layer of aluminum oxide as a dielectric layer on the substrate containing the electrode array by using electron beam evaporation. (5) And finally, spin-coating a Teflon hydrophobic material on the dielectric layer. The unipolar plate digital microfluidic chip preparation is completed as shown in fig. 4, 5 and 6.
(5) The prepared unipolar plate digital microfluidic chip is connected with a peripheral control circuit, and the connection mode of the circuit is shown in fig. 7. And the system is used to manipulate the droplets as shown in figure 8. The droplets are moved in sequence at calculated time intervals.
(6) The small ball (the size is equivalent to that of a liquid drop, the diameter is about 3mm) prepared by using the polyethylene terephthalate is locally modified by polydimethylsiloxane, and the local hydrophilicity can be obtained.
(7) And (3) putting the local hydrophilic polyethylene glycol terephthalate pellets obtained in the step (4) on the liquid drops in the device subjected to the steps (1) and (2), so that the liquid drops can be tightly adhered to the polyethylene glycol terephthalate pellets.
(8) And (5) driving the polyethylene terephthalate pellets on the chip based on the liquid drops according to the test method in the step (5). As shown in fig. 9, the liquid drop can still move stably on the designed unipolar plate digital microfluidic chip without increasing the time interval and with a certain load. This indicates that the designed chip and the chosen experimental parameters can stably realize the driving of the liquid drop. And the liquid drop can be controlled by real-time motion according to a pre-designed path.
As can be seen from fig. 4, the unipolar plate digital microfluidic chip has three layers in total, namely, a metal electrode layer, a dielectric layer, and a hydrophobic layer. Moreover, the thickness of each layer can be precisely controlled by the fabrication process, which is critical to its function.
As can be seen from fig. 5, the designed unipolar plate digital microfluidic chip can be successfully prepared according to the above process parameters, and the reconfigurability of the chip can be realized by the ordered arrangement of the driving units.
As can be seen from FIG. 6, the hydrophobic layer of the unipolar plate digital microfluidic chip has a smooth and flat surface and no defects.
Fig. 7 shows a testing system of the digital microfluidic chip.
As can be seen from fig. 8, the droplet control can be successfully realized by using the unipolar plate digital microfluidic chip of the present invention.
As can be seen from fig. 9, the driving of the droplet-based polyethylene terephthalate pellets can be successfully achieved by using the unipolar plate digital microfluidic chip of the present invention.
The preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims (7)

1. The method for improving the liquid drop driving efficiency of the unipolar plate digital microfluidic chip is characterized by comprising the following specific steps of:
(1) initializing device setting, including selecting electrode shape and size, determining dielectric layer thickness and liquid drop contact angle variation range delta theta:
specifically, the droplet contact angle variation range Δ θ ═ θA-θBWherein an interdigitated electrode array is used as the driving electrode array, thetaB、θASatisfies the equation cos theta of poplar-LippmannB＝cosθA+0 rV2/2dγlg，θAAnd thetaBThe contact angles of the liquid drops before and after the external voltage V is applied are respectively,0andrthe dielectric constants of the vacuum and dielectric layer materials, respectively, and d is the thickness of the dielectric layer; when the liquid drop is placed on the hydrophobic substrate of the unipolar plate digital microfluidic chip before the external voltage is not applied, the contact angle theta of the liquid drop isASatisfies the Young's equation cos thetaA＝(γsg–γsl)/γlgWherein γ issg、γsl、γlgGas-solid interfacial tension, solid-liquid interfacial tension and gas-liquid interfacial tension respectively;
(2) establishing a liquid drop dynamic model and obtaining experimental parameters:
the method comprises the following specific steps: when voltage is applied to a group of electrode units, the contact angle of the liquid drop is reduced due to electrowetting, the contact angles of the left side and the right side of the liquid drop are unequal, namely Laplace pressure difference is generated inside the liquid drop, and therefore calculation of the liquid drop driving force F is establishedactThe formula (c) of (a):
Fact＝ΔPA·SA·cosβA–ΔPB·SB·cosβB
wherein, Δ PAAnd Δ PBRespectively, the Laplace force, S, of the interface generated by the inconsistent deformation of the left and right sides of the liquid dropAAnd SBThe cross-sectional areas of the spherical surfaces on the left and right sides of the droplet, β respectivelyAAnd βBAre respectively Delta PAAnd Δ PBAn included angle formed with the horizontal direction;
viscous drag F experienced by a droplet on a devicehCan be calculated according to the following formula:
Fh＝3γlg·Rb·(cosθB–cosθA)
wherein, γlgIs the gas-liquid interfacial tension; rbA base radius indicating the solid-liquid interface; thetaBAnd thetaAIs the contact angle of the left and right sides of the drop;
furthermore, according to the dynamics law, F is equal toact–Fh＝m·a，
Wherein m is the drop mass and a is the acceleration of the drop as the contact angle changes;
size parameter L of bonding electrode is 2at2The time t required by the movement of the liquid drop on the two adjacent finger-inserting type electrodes can be calculated; according to the calculated time required by the movement of the liquid drop, the time interval of the voltage applied to the electrode can be controlled through programming;
(3) a method for controlling liquid drops by using the unipolar plate digital microfluidic chip;
the method comprises the following specific steps: and (3) completing initialization of device setting by using the analysis method in the step (1), and programming and inputting the time parameters obtained by using the calculation method in the step (2) into the controller.
2. The method according to claim 1, wherein the initialization of the device setup in step (1) includes setting the side length of the selected square finger-inserted electrode unit to be 1-4mm, setting the metal layer of the unipolar plate digital microfluidic chip to be indium tin oxide with a thickness of 150-300nm, the dielectric layer to be aluminum oxide with a thickness of 80-150nm, and the hydrophobic layer to be Teflon with a thickness of 100 nm.
3. The method for improving the drop driving efficiency of the unipolar plate digital microfluidic chip according to claim 1, wherein the drop contact angle varies from 0 ° to 40 °.
4. The method for improving the droplet driving efficiency of the unipolar plate digital microfluidic chip according to claim 1, wherein the meter in the step (2)Calculating Δ P in Laplace pressure difference formula of liquid dropAAnd Δ PB，SAAnd SBAnd βAAnd βBDerived from a mathematical model of droplet wetting; when the volume is V0When the liquid drop of (2) is placed on a solid hydrophobic substrate, the contact angle of the liquid drop is theta, and the liquid drop can be regarded as a sphere sigma (x)2+y2+z2＝R2) Quilt plane x2+(y-h)2＝b2Intercepting the remaining part;
droplet volume V0Then write to:
Figure FDA0002501681540000021
Figure FDA0002501681540000022
further obtaining the radius R of the ball corresponding to the liquid drop at the moment,
Figure FDA0002501681540000023
further obtaining the radius b and the chord height h of the contact base circle of the solid-liquid interface according to the triangular relation
b＝Rsin(π-θ)
h＝Rcos(π-θ)
According to the vector relation, the included angle beta of the laplace pressure difference along the horizontal direction satisfies the following conditions:
Figure FDA0002501681540000024
Figure FDA0002501681540000025
wherein, thetaAAnd thetaBShowing the left and right contact angles when the liquid drop is deformed; r1And R2Is the radius of the corresponding hemisphere on the left and right sides, h, when the droplet is deformed1And h2Corresponding to the chord height;
cross-sectional area corresponding to laplace pressure on the left and right sides of the droplet:
Figure FDA0002501681540000031
Figure FDA0002501681540000032
for spherical droplets with radius r, the laplace pressure at the interface Δ P ═ 2 γlgAnd/r, the laplace pressures corresponding to the left and right when the droplet deforms are respectively:
Figure FDA0002501681540000033
Figure FDA0002501681540000034
wherein, γlgIs the interfacial tension between the droplet and the air, i.e. the surface tension of water is 72 mN/m.
5. The method for improving the droplet driving efficiency of the unipolar plate digital microfluidic chip according to claim 1, wherein the droplet driving force F in the step (2)actThe range of (1) is 100-150 mu N, and the acceleration of the liquid drop at the maximum deformation is 30-70mm/s2The time required for the droplet to travel over the square interdigitated electrode unit is 0.1-1.5 s.
6. The method for improving the droplet driving efficiency of the unipolar plate digital microfluidic chip according to claim 1, wherein the voltage application manner in the step (2) is that positive and negative voltages are alternately applied in sequence, and the voltage is an alternating voltage and is in a range of 50-200V.
7. The method for improving the droplet driving efficiency of the unipolar plate digital microfluidic chip as claimed in claim 1, wherein the method is applied to droplet manipulation and cargo transportation.
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