CN103386332A - Method of transporting liquid drops by micro-fluidic chip - Google Patents

Abstract

The invention discloses a method of transporting liquid drops by a micro-fluidic chip. The method comprises following steps: step one, a micro-fluidic chip is provided, the micro-fluidic chip comprises array-arranged driving electrodes, the driving electrodes are in half-moon shapes, in the fluid drop transportation direction, one edge of each electrode is in a convex arc shape, the other edge of each electrode is in a concave arc shape, and the convex arc is opposite to the concave arc between two neighbored electrodes; step two, an electric potential between 32 V and 60 V is exerted between the neighbored driving electrodes to drive the liquid drops on the driving electrodes to move. The method of transporting liquid drops by a micro-fluidic chip aims to reduce the driving voltage of a digital micro-fluidic chip, so the electric field strength of the chip is reduced, damages to the biological activity organisms contained in the liquid drops are avoided, and the use efficiency of the digital micro-fluidic chip is improved at the same time.

Description

Method for microfluidic chip transport of liquid droplets

technical field

The invention belongs to the technical field of biomedicine, and in particular relates to a method for transporting droplets by a microfluidic chip. the

Background technique

The research on microfluidic chips began in the early 1990s. Manz and Harrison first carried out early research on chip electrophoresis, first proposed basic concepts such as micro-total analysis systems, and positioned microfluidic chips as generally having a thickness of no more than 5 mm, and a planar chip with an area of no more than a dozen square centimeters. Due to its many advantages, the dielectric wetting effect is increasingly used to manipulate micro-droplets in digital microfluidic chips. the

In the past two decades, digital microfluidic chips have shown a vigorous development trend in laboratory research and industrial applications, especially digital microfluidic chips based on micro-droplet manipulation have made great progress. The volume of the manipulated droplets can reach the microliter or even nanoliter level, so that at the microscale, the microliter and nanoliter level droplets can be mixed more precisely, and the chemical reaction inside the droplet is more complete. . In addition, different biochemical reaction processes inside the droplet can be monitored, and the micro-droplet can contain cells and biomolecules, such as proteins and DNA, thus achieving higher throughput monitoring. Among many methods of driving micro-droplets, the traditional method is to realize the generation and control of micro-droplets in micro-channels, but the manufacturing process of micro-channels is very complicated, and micro-channels are easily blocked, and the reusability is not high. Requires complex peripherals to be driven. the

In contrast, the use of electric drive has many advantages, among which, the microfluidic chip based on the dielectric wetting effect has its unique advantages, because the microfluidic chip based on the dielectric wetting effect does not require micropipes, micropumps and For complex devices such as microvalves, the manufacturing process is simple, the heat generation is small, the response is fast, the power consumption is low, and the packaging is simple, etc., so the dielectric wetting effect is used more and more to manipulate micro-droplets in digital microfluidic chips. . The microfluidic core based on the dielectric wetting effect can realize the distribution, separation, transportation and merging of micro-droplets. the

At present, the most outstanding foreign research on digital microfluidic chip systems based on dielectric wetting is the University of California, Los Angeles, Duke University, and Purdue University in the United States; the University of Toronto and the University of British Columbia in Canada; Seoul Korea University in South Korea, Pohang University of Science and Technology; Catholic University of Leuven in Belgium; University of Twente in the Netherlands, etc. the

Contents of the invention

Aiming at the deficiencies of the prior art, the purpose of the present invention is to reduce the driving voltage of the digital microfluidic chip, so as to reduce the electric field strength on the chip, avoid causing damage to the biologically active bodies contained in the liquid droplets, and at the same time improve the digital microfluidic chip. The efficiency of the use of fluidic chips. the

For solving above-mentioned technical problem, technical scheme of the present invention is realized like this:

A method for transporting droplets in a microfluidic chip, comprising:

s1. Provide a microfluidic chip. The microfluidic chip includes drive electrodes arranged in an array. The drive electrodes are half-moon-shaped. In the droplet transport direction, one edge of the drive electrodes is a convex arc shape, the edge on the other side is a concave arc shape, and the concavity and convexity between adjacent electrodes are opposite;

s2. Applying a potential of 32V to 60V between adjacent driving electrodes to drive the movement of the liquid droplets on the driving electrodes. the

Preferably, in the above-mentioned method for transporting droplets by a microfluidic chip, the microfluidic chip includes a lower plate and an upper plate oppositely arranged, and the lower plate includes a first substrate and sequentially formed The driving electrode, the dielectric layer and the first water-repellent layer on the first base; the upper plate includes a second base and a second water-repellent layer formed on the second base. the

Preferably, in the above-mentioned method for transporting droplets by a microfluidic chip, the first substrate and the second substrate are ITO glass. the

Preferably, in the above-mentioned method for transporting droplets by a microfluidic chip, the material of the dielectric layer is SU-8. the

Preferably, in the above-mentioned method for transporting droplets by a microfluidic chip, the material of the first water-repellent layer and the second water-repellent layer is Teflon. the

This application also discloses a method for making a microfluidic chip, including:

(a) ITO glass is used as the substrate material of the dielectric wetted microfluidic chip, and the driving electrodes and electrode leads are processed by wet etching technology;

(b) SU-8 was used as the dielectric layer material of the chip by spin-coating;

(c) Using electronic fluorinated liquid as solvent to dilute Teflon solution, obtain a water-repellent layer by spin coating and baking process, and obtain the upper plate;

(d) Spin-coat a layer of Teflon coating on the surface of ITO glass as a water-repellent layer to obtain the upper plate;

(e) Connect the upper and lower plates together with double-sided tape to obtain a microfluidic chip. the

Compared with the prior art, the present invention designs a half-moon-shaped driving electrode digital microfluidic chip. Aiming at the current situation that the driving voltage of the digital microfluidic chip is relatively high, compared with the traditional driving electrode structure, a new type of microfluidic chip is developed. A digital microfluidic chip with half-moon-shaped driving electrodes that reduces the driving voltage. Based on the principle of dielectric wetting, the relationship between the dielectric wetting force on the droplet and the corresponding chord length of the effective three-phase contact line on the contact circle of the droplet is analyzed. The chord length formed by the effective three-phase contact line of droplets on the traditional square and fork-shaped driving electrodes and the new half-moon-shaped driving electrodes was compared and analyzed. It is analyzed that the effective chord length formed by the half-moon-shaped driving electrode is the largest among the three driving electrode structures, and thus the dielectric driving force of the half-moon-shaped driving electrode on the digital microfluidic chip is the largest. The effect of driving droplets was verified experimentally by designing and manufacturing three kinds of driving electrode dielectric wetting chips. The experimental results show that the minimum driving voltage of the developed half-moon-shaped driving electrode digital microfluidic chip is about 37% and 67% lower than that of the square and fork-shaped driving electrode chips. In addition, when the effective driving voltage is 60V The speed of 2 μL deionized water micro-droplets on the half-moon-shaped driving electrode chip is about 10 cm/s, which is 3 times and 2 times of the droplet speed on the square and fork-shaped driving electrode chips, respectively. The obtained experimental data proves that the digital microfluidic chip with half-moon-shaped driving electrodes can well achieve the purpose of reducing the driving voltage of the chip. the

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work. the

Fig. 1 is a schematic cross-sectional view of a microfluidic chip in a specific embodiment of the present invention;

Fig. 2 shows three kinds of driving electrode structure schematic diagrams in the specific embodiment of the present invention;

Fig. 3 shows that in the specific embodiment of the present invention, half-moon drive electrode structure schematic diagram;

Fig. 4 shows that effective three-phase contact line analysis top view in the specific embodiment of the present invention;

Figure 5 shows a schematic diagram of a half-moon drive electrode array in a specific embodiment of the present invention;

Fig. 6 shows droplet volume and effective chord length in the specific embodiment of the present invention;

Figure 7a-7c shows the schematic diagram of the main manufacturing process flow of the lower plate of the chip in the specific embodiment of the present invention;

Fig. 8 shows that in the specific embodiment of the present invention, it is the measured figure of the initial contact angle of the droplet;

Fig. 9 shows that in the specific embodiment of the present invention, three kinds of droplet movement videos on the driving electrode chip are top-down view;

Fig. 10 shows that in the specific embodiment of the present invention, droplet volume and minimum drive voltage relation figure;

FIG. 11 shows the relationship between the average velocity of a 2 μL droplet and the driving voltage in a specific embodiment of the present invention. the

Detailed ways

The embodiment of the present invention discloses a method for transporting liquid droplets by a microfluidic chip, including:

s1. Provide a microfluidic chip. The microfluidic chip includes drive electrodes arranged in an array. The drive electrodes are half-moon-shaped. In the droplet transport direction, one edge of the drive electrodes is a convex arc shape, the edge on the other side is a concave arc shape, and the concavity and convexity between adjacent electrodes are opposite;

s2. Applying a potential of 32V to 60V between adjacent driving electrodes to drive the movement of the liquid droplets on the driving electrodes. the

Preferably, in the above-mentioned method for transporting droplets 20 by a microfluidic chip, the microfluidic chip includes a lower pole plate and an upper pole plate oppositely arranged, and the lower pole plate includes a first substrate 11 and The driving electrode 12, the dielectric layer 13 and the first water-repellent layer 14 are sequentially formed on the first substrate; the upper plate includes a second substrate 15 and a The second water-repellent layer 16. the

In the above method for transporting droplets by a microfluidic chip, the first substrate and the second substrate are preferably ITO glass. It should be noted that the material used as the substrate is not fixed, as long as it is insulated, such as quartz, insulating silicon wafer, etc., the first substrate and the second substrate can also be made of different materials. the

In the above-mentioned method for transporting droplets by a microfluidic chip, the driving electrodes can be made of any conductive material, and the size and spacing of the electrodes and the number of specific electrodes are not limited. This specification only uses a certain number and specifications of electrodes as examples. example. The electrode array can be one-dimensional or two-dimensional. the

In the above method for transporting liquid droplets by a microfluidic chip, the material of the dielectric layer is preferably SU-8. It should be noted that the dielectric layer should be an insulating dielectric material, but is not limited thereto, preferably a material with a relatively high dielectric constant and strong breakdown resistance. the

In the above-mentioned method for transporting droplets by a microfluidic chip, the material of the first water-repellent layer and the second water-repellent layer is preferably Teflon. the

The embodiment of the present application also discloses a method for making a microfluidic chip, including:

(a) ITO glass is used as the substrate material of the dielectric wetted microfluidic chip, and the driving electrodes and electrode leads are processed by wet etching technology;

(b) SU-8 was used as the dielectric layer material of the chip by spin-coating;

(c) Using electronic fluorinated liquid as solvent to dilute Teflon solution, obtain a water-repellent layer by spin coating and baking process, and obtain the upper plate;

(d) Spin-coat a layer of Teflon coating on the surface of ITO glass as a water-repellent layer to obtain the upper plate;

(e) Connect the upper and lower plates together with double-sided tape to obtain a microfluidic chip. the

The technical solutions in the embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention. the

As shown in FIG. 1 , the driving electrode array is located under the water-repellent layer and the dielectric layer, and the number of driving electrodes is two on the left and the right. When the right driving electrode is powered on, the capacitive effect between the solid-liquid interface causes the contact angle of the micro-droplet to change, thereby generating a pressure difference inside it to drive the micro-droplet, and the micro-droplet will move from the left electrode to the right. On the side electrodes, powering up the control electrodes in turn can drive the micro-droplets to move along the preset path, and realize various manipulations of the micro-droplets. The relationship between the driving voltage and the contact angle can be described by the Yang-Lipmann equation, as shown in formula (1):

$\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; V</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; LG</span>}}\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In formula (1), θ _V and θ ₀ represent the initial contact angle when no driving voltage is applied and the contact angle when driving voltage V is applied, ε _r represents the relative permittivity of the dielectric layer, and ε ₀ represents the dielectric constant of the vacuum Electrical constant, γ _LG represents the "liquid-gas" surface tension, V represents the applied voltage, and d represents the thickness of the dielectric layer.

Figure 2 shows square, fork-shaped and half-moon-shaped driving electrodes from left to right, and the outer contours of the electrodes are all 1.4×1.4mm. the

FIG. 3 is a schematic diagram of the structure of the half-moon-shaped driving electrodes. the

As shown in Figure 4, the droplet is located on the left electrode, and the right electrode is turned on. The dotted circle represents the contact circle of the droplet. The radius of the droplet contact circle is the same under the three driving electrodes in Figure 4. When the right electrode conducts When connected, the dielectric wetting force generated in the horizontal direction by the effective three-phase contact line on the droplet contact circle above the electrode can be expressed as formula (2):

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; er</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; cV</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; LG</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; sv</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; sl</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; c</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In formula (3), c represents the capacitance per unit area, γ _LG represents the gas-liquid surface tension, and V represents the driving voltage. It can be seen from the first figure on the left in Figure 2 that the total dielectric force acting on the effective three-phase contact line in the X-axis direction can be obtained by integrating along the three-phase contact line, expressed as formula (4).

In Equation (4), L represents the effective chord length formed by the effective three-phase contact line, and the angle Φ is shown in Figure 4. From Equation (4), the dielectric wetting force along the X-axis direction and the applied driving force can be obtained The magnitude of the square of the voltage is proportional to the chord length L formed by the effective three-phase contact line. Therefore, under the same driving voltage, the greater the chord length L formed by the effective three-phase contact line, the greater the effect on the droplet The greater the dielectric wetting force. Therefore, under the premise of increasing the chord length, the ideal dielectric driving force can be obtained at a lower driving voltage, thereby achieving the purpose of reducing the driving voltage of the digital microfluidic chip. the

When the other physical parameters of the chip are constant, the change of the droplet contact angle is affected by the driving voltage applied to the chip. The greater the voltage, the greater the change of the contact angle will be until the contact angle of the droplet reaches saturation. Conversely, when the driving voltage is constant, the change of droplet contact angle will be affected by other physical parameters on the dielectric wetting chip, such as the thickness of the dielectric layer and the size of the dielectric constant, the shape of the driving electrode, etc., among which The shape of the driving electrode is a very important structural parameter in the chip based on the dielectric wetting effect, because the shape of the driving electrode will affect the distribution of the electric field in the chip, and the distribution of the electric field will affect the change of the droplet contact angle, and the droplet contact angle The amount of change is an important criterion for measuring the size of the dielectric wetting force. In order to obtain a large amount of change in the contact angle, there are certain requirements on the shape of the driving electrodes on the dielectric wetting chip. The driving electrodes usually used in early research are square. The first figure on the left in Figure 2 shows a single square driving electrode, and the middle electrode in Figure 2 is the more commonly used fork-shaped driving electrode. the

Aiming at the deficiencies in the manufacture and use of square and fork-shaped driving electrodes, a new half-moon-shaped driving electrode is proposed. Its structure is shown in Figure 3. The shape of the half-moon-shaped driving electrode on the right side of the horizontal direction is The circle is consistent with the projection of the droplet in the horizontal direction (the cross-sectional circle of the droplet). In this way, there will be a relatively uniform distance between the front part of the droplet and the driving electrode when the droplet starts to move, and the force on the droplet will be relatively evenly. When the three kinds of driving electrodes in Figure 2 are arranged and combined in a certain order, an array electrode chip can be formed. The droplet driving effect of using these three kinds of driving electrodes at the same time is not within the scope of this paper. This embodiment only considers these Droplet driving effect when the three electrodes are individually combined and arranged. the

Figure 4 is a schematic diagram of the arrangement and combination of droplet cross-section circle (dotted circle) and 2 square, 2 fork-shaped and 2 half-moon-shaped driving electrodes. As shown in Fig. 4(a), most of the droplet cross-section circle is located on the left electrode, and the size of the square electrode is 1.4×1.4mm; in Fig. 4(b), the outer contour of the fork-shaped electrode is 1.4× 1.4mm, the length of the fork is 200μm, and the height is 157μm; the outer contour of the half-moon electrode in (c) of Figure 4 is 1.4×1.4mm, and the arc radius of the half-moon driving electrode is 800μm. The initial position of the droplet is the same for the three driving electrodes in Figure 4, and most of the droplet is located on the left electrode; the initial position of the left driving electrode is also the same, and the right side is square, fork-shaped and half-moon. The driving electrodes are turned on; the thick solid line in Figure 4 represents the effective three-phase contact line formed by the contact circle of the droplet. The effective three-phase contact line is a segment of the arc of the droplet contact circle above the conductive driving electrode, which is formed by contacting the water-repellent layer and the air medium. As mentioned above, when the right driving electrode is turned on, the dielectric wetting force per unit length along the X-axis (the direction of droplet movement) on the effective three-phase contact line is expressed as formula (2), and each The expression of the total dielectric wetting force acting on the droplet can be obtained by integrating the dielectric wetting force per unit length along the effective three-phase contact line, as shown in formula (4). the

Figure 5 shows a schematic diagram of a half-moon-shaped drive electrode array, the number of electrodes in the array is 5, and the distance between drive electrodes is 50 μm. the

In order to make the inference of the magnitude of the dielectric wetting force at the initial moment of the droplet in the case of three kinds of driving electrodes general, this embodiment calculates the corresponding values of different droplet volumes according to the range of the droplet volume that the chip can drive. The length of the chord length L corresponding to the effective three-phase contact line, the calculation results are summarized in Figure 6. It can be seen from Figure 6 that when the droplet volume increases from 1.89 μL to 4.79 μL, the chord length L formed on the square driving electrode structure gradually increases from zero to the maximum value of 1400 μm. When the droplet volume is 1.89 μL, the chord length L on the fork-shaped driving electrode is 471 μm. When the chord length on the square and half-moon-shaped driving electrodes is zero, the droplet can be driven, but the fork-tooth-shaped driving electrode The fabrication of the electrode is complicated, and due to the existence of the fork structure, when the electrode is turned on, the electric field strength on the tip is relatively large and the chip is easy to be damaged. In addition, the maximum effective chord length L on the fork-tooth-shaped driving electrode structure is 1298 μm, which is smaller than the square and fork-tooth-shaped driving electrodes. The change of the chord length L on the half-moon-shaped driving electrode is that when the volume of the droplet is the smallest, the cross-sectional circle of the droplet is tangent to the arc of the conductive driving electrode on the right, and no effective three-phase contact line is formed. At this time, the chord length L is zero ; When the droplet volume increases from the smallest to the largest, the chord length L can always remain at 1400μm. The chord length L on the three driving electrode structures in Figure 6 will increase with the increase of the droplet volume. Among them, as long as the volume of the droplet is larger than the minimum volume that the chip can drive the droplet, the half-moon-shaped driving electrode will increase. The largest range. In addition, when the volume of the droplet is greater than the minimum volume that the chip can drive, the effective chord length that can be formed on the half-moon-shaped drive electrode can be obtained when the volume of the droplet on the three drive electrode chips is the same through the analysis of Figure 6 It is the largest among the three kinds of driving electrodes, which means that the dielectric driving force is the largest when the semi-moon-shaped driving electrode is used to drive the droplets of the same volume, and the large dielectric driving force can well ensure the continuity of the droplet movement on the chip . the

As shown in Figure 7a, ITO glass is used as the base material of the dielectrically wetted microfluidic chip, and three shapes of driving electrodes and electrode leads are processed by wet etching technology. As shown in FIG. 7b, SU-8 is used as the dielectric layer material of the chip by spin-coating SU-8, and the dielectric constant of SU-8 is 3.2. A layer of SU-8 with a thickness of 1 μm is evenly coated on the ITO glass with electrodes engraved as the dielectric layer of the chip. Figure 7c shows that the Teflon solution of DuPont Company is diluted with electronic fluorinated liquid as a solvent, and a water-repellent layer with a thickness of about 50 nanometers is obtained by spin coating, baking and other processes. The upper plate of the chip is directly spin-coated with a layer of Teflon coating on the surface of the ITO glass as the water-repellent layer, and the manufacturing process is the same as that of the water-repellent layer of the lower plate. Then use double-sided tape as the upper and lower plates to connect together, and the distance between the upper and lower plates is H=300μm. the

During the experiment, a deionized water droplet of a certain volume was placed on the two driving electrodes adjacent to the lower plate of the chip with a micro-injector. Due to the presence of a Teflon water-repellent layer on the chip surface, the initial contact of the droplet The angle θ ₀ can reach about 120°, as shown in Figure 8, and then use 300μm thick double-sided tape to combine the upper plate and the lower plate to form a "sandwich" structure. The signal voltage generated by the signal generator is amplified by the piezoelectric ceramic drive power supply to generate the voltage required to drive the droplets. The frequency is fixed at 100Hz, and the motion of the deionized water droplets is recorded by a CCD camera.

The video screenshot of the movement of 2 μL deionized water droplets is shown in Figure 9. Because the driving electrodes are obtained by etching ITO glass, and ITO glass has light transmission; in addition, a white SU-8 dielectric layer is coated on the top of the driving electrodes; deionized water is colorless and transparent, so for better Show the relative position of the driving electrode and the liquid droplet. According to the actual shape and position of the driving electrode and the actual position and outer contour of the liquid droplet in this embodiment, the driving electrode and the liquid droplet are connected by dotted lines in (a) and (b) in Figure 9. The outline of the droplet is shown, and the shape of the droplet in (c) in Fig. 9 is not shown by a dotted line, and its outline is its actual shape. In Figure 9, the droplet is at the initial moment of being driven in Figure A, Figure E and I, Figures B, C and D; F, G and H; Figures J, K and L respectively give the drive electrode 1 in time sequence, 2 and 3 power up. the

It can be seen from Figure 9 that when the driving voltage V _RM3 =32V, the droplet on the square driving electrode in Figure 9(a) and the fork-shaped driving electrode in Figure 9(b) cannot be driven, and the position of the droplet is not change. The droplets in plots I, J, K, and L in Fig. 9(c) were successfully driven, and the droplets moved to the right. In the half-moon-shaped driving electrode dielectric wetted chip in Fig. 9(c), as mentioned in the analysis of the driving electrode design scheme, the chord length formed by the effective three-phase contact line is relatively long. When the droplet is driven, the first half of the droplet movement is semicircular, which is equal to the arc distance of the left outer contour of the adjacent right half-moon-shaped driving electrode. When the right half of the droplet is semicircular, the droplet All parts of the front are evenly stressed, and the droplet can be successfully driven and moved to the right.

The relationship between the minimum driving voltage of the digital microfluidic chip with square, fork-shaped and half-moon electrodes and the droplet volume is shown in Figure 10. It can be seen from Figure 10 that when the droplet volume is the smallest 1.89μL, only the fork-shaped electrode can drive the droplet with a voltage of about 38V, which is mainly because the special structure of the fork-teeth design will reduce the The relative distance between two adjacent electrodes is shortened, so that the effective chord length of a certain size is 471 μm. It can be seen from Figure 9 that with the increase of the droplet volume, the minimum driving voltage of the three driving electrode shapes that can drive the droplet movement will increase, but the increase of the traditional square and fork-shaped driving electrodes is significantly greater than that of the half-moon shape. When the droplet volume reaches the maximum of 4.79 μL, the driving voltages of the square and fork-shaped electrodes are 85V and 90V respectively, while the minimum driving voltage of the half-moon-shaped driving electrode is 51V. It can be seen from Figure 10 that, in addition to the minimum volume, the minimum driving voltage on the half-moon-shaped driving electrode chip is about 37% lower than the minimum driving voltage on the fork-shaped driving electrode chip, and it is lower than the minimum driving voltage on the square driving electrode chip. About 67%, so, compared with the square and fork-shaped driving electrode chips, the half-moon-shaped driving electrode chip can obtain the same dielectric driving force with a lower driving voltage. the

As shown in Fig. 11, it is the relationship diagram between the average speed of 2 μL deionized water droplets on three driving electrode chips and the driving voltage (the driving voltage is an effective value). In order to reduce the error, the driving experiments of the droplets on the three types of chips were carried out 5 times under each driving voltage value, and then according to the moving distance and moving time of the droplets in each video, the droplet’s movement distance at each driving voltage was obtained. average speed. It can be seen from Figure 11 that the greater the driving voltage, the greater the average velocity of the droplets. Under the minimum driving voltage of the three driving electrodes, it can be obtained from the comparison of the average velocity of the droplets when the droplets can be successfully driven that the average velocity of the droplets on the half-moon-shaped driving electrode chip is up to 1.8cm/s, which is significantly larger than that of the square And the average velocity of the droplet on the fork-shaped drive electrode chip is 0.4cm/s and 0.8cm/s. the

In summary, the present invention is based on the Yang-Lipmann equation, and after derivation, the formula of the dielectric driving force on the droplet is obtained. From the force formula on the droplet, it can be known that the larger the effective chord length, the greater the force of the droplet on the chip. The greater the dielectric driving force received. Under certain conditions, the size of the effective chord length related to the droplet contact circle on the square and fork-shaped driving electrodes commonly used in digital microfluidic chips and the half-moon-shaped driving electrode was compared. After analyzing the effective chord length on the half-moon-shaped driving electrode The length is the largest among the three kinds of driving electrodes, so the digital microfluidic chip of the half-moon-shaped driving electrode drives the micro-droplets of the same volume with the largest dielectric driving force. the

It will be apparent to those skilled in the art that the invention is not limited to the details of the above-described exemplary embodiments, but that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Accordingly, the embodiments should be regarded in all points of view as exemplary and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and it is therefore intended that the scope of the invention be defined by the appended claims rather than by the foregoing description. All changes within the meaning and range of equivalents of the elements are embraced in the present invention. Any reference sign in a claim should not be construed as limiting the claim concerned. the

In addition, it should be understood that although this specification is described according to implementation modes, not each implementation mode only contains an independent technical solution, and this description in the specification is only for clarity, and those skilled in the art should take the specification as a whole , the technical solutions in the various embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art. the

Claims (6)

1. a micro-fluidic chip transports the method for drop, it is characterized in that, comprising:

S1, provide a micro-fluidic chip, described micro-fluidic chip to comprise the drive electrode that array arranges, described drive electrode is semilune, on the drop throughput direction, one lateral edges of drive electrode is the arc of convex, and the opposite side edge is the arc of concavity, and is concavo-convex relative between adjacent electrode;

S2, apply the electromotive force of 32V～60V between the adjacent driven electrode, with driving, be positioned at liquid drop movement on drive electrode.

2. micro-fluidic chip according to claim 1 transports the method for drop, it is characterized in that: described micro-fluidic chip comprises bottom crown and the top crown that is oppositely arranged, described bottom crown comprise the first substrate and be formed at successively the described first suprabasil described drive electrode, dielectric layer and first is detested water layer; Described top crown comprises the second substrate and is formed at described second suprabasil second detests water layer.

3. micro-fluidic chip according to claim 2 transports the method for drop, it is characterized in that: described first substrate and second substrate are ito glass.

4. micro-fluidic chip according to claim 2 transports the method for drop, it is characterized in that: the material of described dielectric layer is SU-8.

5. micro-fluidic chip according to claim 2 transports the method for drop, it is characterized in that: described first detests water layer and second, and to detest the material of water layer be Teflon.

6. the preparation method of micro-fluidic chip claimed in claim 2, is characterized in that, comprising:

(a) adopt the base material of ito glass as the moistening micro-fluidic chip of dielectric, by wet etching technique, process drive electrode and contact conductor;

(b) by the dielectric layer material of spin coating SU-8 as chip;

(c) adopt electronics to fluoridize liquid as solvent dilution Teflon solution, by spin coating, baking process, obtain detesting water layer, obtain top crown;

(d) detest water layer in the conduct of ito glass surface spin coating one deck teflon coatings, obtain top crown;

(e) with two-sided tape, upper bottom crown is linked together, obtain micro-fluidic chip.

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