Digital microfluidic chip, pixel driving method thereof, and constant temperature amplification method

Abstract

The present application relates to the technical field of microfluidics, and provides a digital microfluidic chip, which comprises an electrode array, a driving module and a top cover arranged above the electrode array, a gap for accommodating small droplets is formed between the top cover and the electrode array, the electrode array comprises a plurality of rows of electrode array groups, each row of the electrode array groups comprises a plurality of electrodes, the driving module controls each electrode in each row of the electrode array groups to be opened in turn, and the size of the small droplets is regulated by adjusting the gap and the electrodes in the electrode array. A pixel driving method of the digital microfluidic chip is also provided. A constant temperature amplification method is also provided, which adopts the pixel driving method of the digital microfluidic chip. The GOA and MUX circuit combination design is adopted, the driving signal complexity of the electrode matrix can be greatly reduced, the stability is improved, and simple and flexible electrode driving is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microfluidic technology, in particular to a digital microfluidic chip, a pixel driving method thereof, and a constant temperature amplification method. BACKGROUND

[0002] How to uniformly decompose a certain volume of liquid into a large number of microdroplets with uniform volume is one of the key problems to be solved in microfluidic technology, and is a key link in many application fields including digital polymerase chain reaction (ddPCR), digital loop-mediated isothermal amplification (dLAMP), digital enzyme-linked immunoassay (dELISA), and single-cell omics. At present, the technical means for generating nanoliter droplets with high throughput mainly include microdroplet microfluidic technology and micro-well microfluidic technology. The representative of microdroplet microfluidic technology includes Bio-Rad and 10XGenomics. The characteristic of this technology is to control oil with high-precision micro-pump, and to continuously extrude the sample liquid with a cross-shaped structure to generate a large number of small droplets with a volume of picoliters to nanoliters. The representative of micro-well microfluidic technology is Thermo Fisher. The characteristic of this technology is to use mechanical force to coat the sample solution on the micro-well array, so that the sample is evenly distributed to each micro-well to form small droplets with a volume of picoliters to nanoliters. Digital microfluidics has the ability to independently control each microdroplet, making it another technical means for high-throughput generation of microdroplets.

[0003] The method of generating nanoliter droplets with high throughput based on microdroplet microfluidic technology relies on the precise control of the pressure of high-precision micro-pump and the high-precision chip processing technology based on MEMS. The generated microdroplets are still saved together in the same container, and each droplet needs to be detected one by one through the microfluidic channel. The equipment cost is high, and the system is complex. The technology based on micro-well microfluidic technology usually needs to use mechanical force to uniformly coat the reagent on the surface of the micro-well array, and then fill the upper and lower surfaces of the micro-well with inert medium liquid. The disadvantage of this method is that the operation process is relatively complex, the degree of automation is low, the experimental throughput is low, and the sample preparation time is long. The method of generating nanoliter droplets with high throughput based on digital microfluidic technology can continuously separate a large droplet into a large number of small droplets and then transfer the small droplets to the corresponding position. The main disadvantage of this method is that the traditional digital microfluidic circuit has high complexity, and a higher density of electrodes means poorer chip stability and higher cost. SUMMARY

[0004] The purpose of the present application is to provide a digital microfluidic chip, a pixel driving method thereof, and a constant temperature amplification method, which can at least solve some of the defects in the prior art.

[0005] To achieve the above object, the embodiment of the present application provides the following technical scheme: a digital microfluidic chip, comprising an electrode array, a driving module and a top cover arranged above the electrode array, the top cover and the electrode array have a gap for accommodating a small droplet, the electrode array comprises a plurality of rows of electrode array groups, each row of the electrode array groups comprises a plurality of electrodes; the driving module controls each electrode in each row of the electrode array groups to be sequentially turned on, and the size of the small droplet is regulated by adjusting the gap and the electrodes in the electrode array.

[0006] Further, the driving module comprises N channels and N switch control circuits, each of the channels is correspondingly arranged with each of the switch control circuits, each of the channels outputs a data signal to the corresponding switch control circuit; each of the switch control circuits comprises a plurality of switches, each of the switches is correspondingly arranged with each of the electrodes in each row of the electrode array groups, and each switch controls the corresponding electrode to be turned on.

[0007] Further, when the number of the switches is halved, the size of the electrodes is doubled compared with the size of the electrodes before the reduction; when the number of the switches is reduced by one fourth, the size of the electrodes is tripled compared with the size of the electrodes before the reduction.

[0008] Further, the electrode array further comprises a dielectric layer covering the electrodes and a first hydrophobic layer covering the dielectric layer, and the first hydrophobic layer and the top cover have the gap therebetween.

[0009] Further, the top cover and the electrode array have the gap therebetween.

[0010] Further, the top cover comprises a second hydrophobic layer, a conductive layer covering the second hydrophobic layer and an upper cover arranged on the conductive layer, and the second hydrophobic layer and the electrode array have the gap therebetween.

[0011] The embodiment of the present application provides another technical scheme: a pixel driving method of a digital microfluidic chip, which is used for the above-mentioned digital microfluidic chip, and the method comprises the following steps: first, a channel outputs a data signal to a switch control circuit to control the on-off state of a switch of the switch control circuit, and then the on-off of the switch is controlled according to a time sequence to control the array corresponding to the switch in each row of electrode array groups of an electrode array to be turned on.

[0012] Further, the time sequence control specifically comprises:

[0013] S1, first, T0, T1, T2, T3, T4 and Tn time points are sequentially set;

[0014] S2, wherein T0 is the initial state of one row of electrode array groups, at this time, each switch of one of the switch control circuits is open, at this time, no signal is output to the electrode corresponding to each switch, and all electrodes are closed; at T1, the first switch of one of the switch control circuits is closed, and the other switches are open, the data signal of the channel corresponding to the switch control circuit is written into the electrode corresponding to the closed switch, and the electrode is opened; at T2, the second switch of one of the switch control circuits is closed, and the other switches are open, the data signal of the channel corresponding to the switch control circuit is written into the electrode corresponding to the closed switch, and the electrode is opened; at T3, the third switch of one of the switch control circuits is closed, and the other switches are open, the data signal of the channel corresponding to the switch control circuit is written into the electrode corresponding to the closed switch, and the electrode is opened; at T4, the fourth switch of one of the switch control circuits is closed, and the other switches are open, the data signal of the channel corresponding to the switch control circuit is written into the electrode corresponding to the closed switch, and the electrode is opened; until at Tn, the nth switch of one of the switch control circuits is closed, and the other switches are open, the data signal of the channel corresponding to the switch control circuit is written into the electrode corresponding to the closed switch, and the electrode is opened;

[0015] S3, thus completing the control of each electrode of one row of electrode array groups;

[0016] S4, then repeating the timing control of the S2 step to complete the control of each electrode of the remaining rows of electrode array groups to output signals to the entire electrode array.

[0017] Further, the number of switches in the switch control circuit is halved, and the size of the electrode is increased by one time compared with the size of the electrode before reduction; the number of switches in the switch control circuit is reduced by one fourth, and the size of the electrode is increased by three times compared with the size of the electrode before reduction.

[0018] The embodiment of the application provides another technical scheme: a constant temperature amplification method adopting the pixel driving method of the digital microfluidic chip.

[0019] Compared with the prior art, the application has the following beneficial effects:

[0020] 1. The GOA and MUX circuit combination design can greatly reduce the driving signal complexity of the electrode matrix, improve stability, and realize simple and flexible electrode driving.

[0021] 2. The MUX switch module can be controlled to adjust the electrode combination, control the minimum reaction system, and improve the droplet generation efficiency.

[0022] 3, The volume of the small droplet is accurately controlled by adjusting the gap and the electrode combination, and the on-chip experiment can be performed after the small droplet separation is completed.

[0023] 4, Any droplet can be selected for screening or individual experiment.

[0024] 5, The electrode shape can be any shape or combination of any shape.

[0025] 6, No high-precision micro-pump and other equipment is needed, and the system cost is reduced.

[0026] 7, Strong expansion capability, the pixel scale and driving capability of the chip can be improved by optimizing the timing and upgrading the MUX circuit.

[0027] 8, It can be applied to various micro-droplet-based biochemical applications. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A schematic diagram of a driving module of a pixel driving method of a digital microfluidic chip provided by the embodiment of the present application;

[0029] Figure 2 A signal timing diagram of a driving module of a pixel driving method of a digital microfluidic chip provided by the embodiment of the present application;

[0030] Figure 3 A schematic diagram of a driving module of a pixel driving method of a digital microfluidic chip provided by the embodiment of the present application after merging half of the pixels;

[0031] Figure 4 A schematic diagram of a driving module of a pixel driving method of a digital microfluidic chip provided by the embodiment of the present application after merging all the pixels;

[0032] Figure 5 A schematic diagram of a digital microfluidic chip provided by the embodiment of the present application;

[0033] In the drawing marks: 3-small droplet; 5-upper cover; 6-conductive layer; 7-second hydrophobic layer; 8-gap; 9-first hydrophobic layer; 10-dielectric layer; 11-electrode. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0035] Please refer to Figure 5The embodiment of the present application provides a digital microfluidic chip, which comprises an electrode array, a driving module and a top cover arranged above the electrode array, wherein a gap 8 for arranging a small droplet 3 is arranged between the top cover and the electrode array, the electrode array comprises a plurality of electrode array groups, each of the electrode array groups comprises a plurality of electrodes 11, the driving module controls each electrode 11 in each electrode array group to be opened in sequence, and the size of the small droplet 3 is regulated by adjusting the gap 8 and the electrodes 11 in the electrode array. Preferably, the electrode array further comprises a dielectric layer 10 arranged on the electrodes 11 and a first hydrophobic layer 9 arranged on the dielectric layer 10, and the gap 8 is arranged between the first hydrophobic layer 9 and the top cover. The chip further comprises a top cover arranged above the electrode array, and the gap 8 is arranged between the top cover and the electrode array. The top cover comprises a second hydrophobic layer 7, a conductive layer 6 arranged on the second hydrophobic layer 7 and an upper cover 5 arranged on the conductive layer 6, and the gap 8 is arranged between the second hydrophobic layer 7 and the electrode array. In the embodiment, the small droplet 3 is arranged between the top cover composed of the upper cover 5, the conductive layer 6 and the second hydrophobic layer 7 and the electrode array composed of the first hydrophobic layer 9, the dielectric layer 10 and the electrodes 11, and the volume of the small droplet 3 can be accurately regulated between picoliters and microliters by adjusting the gap 8 and the size of the electrodes 11. After high-throughput nanoliter droplet separation is completed, corresponding experiments and detection can be performed on the digital microfluidic chip, such as ddPCR, dLAMP, dELISA single-cell experiment and the like. Meanwhile, any small droplet 3 on the chip can be screened or independently experimented, and more small droplets 3 or multiple samples can be separated by expanding the size of the chip. Specifically, the size of the gap 8 and the electrodes 11 can be controlled by the driving module by using a specific time sequence to open the electrodes 11, so that the movement and separation of the injected liquid are realized, and a large number of small droplets 3 are rapidly and massively generated depending on appropriate path control. A large amount of liquid is injected into the digital microfluidic electrode array developed by combining the GOA technology, and based on the GOA technology and the MUX (data selector) circuit design, the number of signal lines can be greatly reduced, the pixel circuit structure can be simplified, the pixel combination can be flexibly performed according to different application scenes, and the system expandability and stability can be improved.

[0036] As an optimization scheme of the embodiment of the present application, refer to Figures 1 to 4, the driving module includes N channels and N switch control circuits, each of the channels is one-to-one matched with each of the switch control circuits, each of the channels outputs a data signal for the corresponding switch control circuit; each of the switch control circuits includes a plurality of switches, each of the switches is one-to-one matched with each of the electrodes 11 in each row of the electrode array group, and each switch controls the opening of the corresponding electrode 11. Preferably, when the number of the switches is halved, the size of the electrode 11 is doubled compared with the size of the electrode 11 before the reduction; when the number of the switches is reduced by one fourth, the size of the electrode 11 is tripled compared with the size of the electrode 11 before the reduction. Traditional digital microfluidic chips apply signals to all driving electrodes at the same time, which means that an electrode array with M rows and N columns needs to apply MxN control signals at the same time. A large number of parallel signal transmissions depend on more complex circuit layout and higher processor performance, which increases the possibility of signal interference while increasing the design difficulty and cost. Based on the traditional digital microfluidic chip based on flat panel display technology, the array rows are sequentially opened by the Gate IC, which can simplify the circuit and reduce the cost to a certain extent. The GOA technology further simplifies the opening and closing of the array rows, which no longer depends on the additional Gate IC, but is automatically completed on the chip. In terms of column electrode control, the introduced MUX circuit can integrate a signal output module with A channels and a module containing B independently controllable switches based on the principle of time division multiplexing, further simplifying the number of data signals. The method of this paper optimizes the structure of the digital microfluidic chip based on the GOA technology and the MUX circuit, and maximizes the control ability of the digital microfluidic chip on the liquid, while flexibly and controllably designing the time sequence for the generation and control of microdroplets with a specified volume.Specifically, in the present embodiment, T0, T1, T2, T3, T4 and Tn time points are set in sequence; wherein the T0 time point is the initial state of one row of electrode array groups, at this time, each switch of one of the switch control circuits is open, at this time, no signal is output to the electrode 11 corresponding to each switch, and all electrodes 11 are closed; at the T1 time point, the first switch of one of the switch control circuits is closed, and the other switches are open, the data signal of the channel corresponding to the switch control circuit is written to the electrode 11 corresponding to the closed switch, and the electrode 11 is opened; at the T2 time point, the second switch of one of the switch control circuits is closed, and the other switches are open, the data signal of the channel corresponding to the switch control circuit is written to the electrode 11 corresponding to the closed switch, and the electrode 11 is opened; at the T3 time point, the third switch of one of the switch control circuits is closed, and the other switches are open, the data signal of the channel corresponding to the switch control circuit is written to the electrode 11 corresponding to the closed switch, and the electrode 11 is opened; at the T4 time point, the fourth switch of one of the switch control circuits is closed, and the other switches are open, the data signal of the channel corresponding to the switch control circuit is written to the electrode 11 corresponding to the closed switch, and the electrode 11 is opened; until at the Tn time point, the nth switch of one of the switch control circuits is closed, and the other switches are open, the data signal of the channel corresponding to the switch control circuit is written to the electrode 11 corresponding to the closed switch, and the electrode 11 is opened; in this way, the control of each electrode 11 of one row of electrode array groups is completed; then the time sequence control of the above steps is repeated to complete the control of each electrode 11 of the remaining rows of electrode array groups, so as to output signals to the entire electrode array.

[0037] Please refer to Figures 1 to 5The embodiment of the present application provides a pixel driving method of a digital microfluidic chip, which is used for the digital microfluidic chip and comprises the following steps: first, a channel output data signal is adopted to control the on-off state of switches of a switch control circuit, then the on-off of the switches is controlled according to a time sequence to control the array opening of each row of electrode array groups corresponding to the switches of the electrode array. Preferably, the time sequence control is as follows: S1, first, T0, T1, T2, T3, T4 and Tn time points are sequentially set; S2, the T0 time point is the initial state of one row of electrode array groups, at this time, the switches of one switch control circuit are all turned off, at this time, no signal is output to the electrodes 11 corresponding to each switch, and all the electrodes 11 are turned off; at the T1 time point, the first switch of one switch control circuit is turned on, and the other switches are turned off, the data signal of the channel corresponding to the switch control circuit is written into the electrodes 11 corresponding to the closed switch, and the electrodes 11 are turned on; at the T2 time point, the second switch of one switch control circuit is turned on, and the other switches are turned off, the data signal of the channel corresponding to the switch control circuit is written into the electrodes 11 corresponding to the closed switch, and the electrodes 11 are turned on; at the T3 time point, the third switch of one switch control circuit is turned on, and the other switches are turned off, the data signal of the channel corresponding to the switch control circuit is written into the electrodes 11 corresponding to the closed switch, and the electrodes 11 are turned on; at the T4 time point, the fourth switch of one switch control circuit is turned on, and the other switches are turned off, the data signal of the channel corresponding to the switch control circuit is written into the electrodes 11 corresponding to the closed switch, and the electrodes 11 are turned on; until at the Tn time point, the nth switch of one switch control circuit is turned on, and the other switches are turned off, the data signal of the channel corresponding to the switch control circuit is written into the electrodes 11 corresponding to the closed switch, and the electrodes 11 are turned on; S3, the control of each electrode 11 of one row of electrode array groups is completed in this way; S4, then, the time sequence control of the S2 step is repeated to complete the control of each electrode 11 of the remaining rows of electrode array groups, so that the signal is output to the entire electrode array. The number of switches in the switch control circuit is reduced by half, and the size of the electrode 11 is increased by one time compared with the size of the electrode 11 before the reduction; the number of switches in the switch control circuit is reduced by one fourth, and the size of the electrode 11 is increased by three times compared with the size of the electrode 11 before the reduction. In the embodiment, the small droplet 3 is located between the top cover composed of the upper cover 5, the conductive layer 6 and the second hydrophobic layer 7 and the electrode array composed of the first hydrophobic layer 9, the dielectric layer 10 and the electrode 11, and the volume of the small droplet 3 can be accurately controlled between picoliters and microliters by adjusting the gap 8 and the size of the electrode 11. After the high-throughput nanoliter droplet separation is completed, corresponding experiments and detection can be carried out on the digital microfluidic chip, such as ddPCR, dLAMP, dELISA single cell experiment and the like.Meanwhile, any small droplet 3 on the chip can be screened or independently tested, and more small droplets 3 or multiple groups of samples can be separated by expanding the size of the chip. Specifically, the size of the gap 8 and the electrode 11 can be controlled by the driving module to open the electrode 11 by using a specific timing, so as to realize the movement and separation of the injected liquid, and to rapidly and massively generate small droplets 3 depending on appropriate path control. Injecting a large amount of liquid into a digital microfluidic electrode array developed in combination with the GOA technology, based on the GOA technology and the MUX (data selector) circuit design, the number of signal lines can be greatly reduced, and the pixel circuit structure can be simplified. According to different application scenarios, the pixel combination can be flexibly performed, and the system scalability and stability can be improved.

[0038] Referring to Figures 1 to 5 The embodiment of the present application provides a constant temperature amplification method, which adopts the pixel driving method of the digital microfluidic chip. In the embodiment, the above method can be extended and applied to other nucleic acid detection such as constant temperature amplification.

[0039] The following is a specific implementation, taking a four-switch control circuit as an example:

[0040] The data signal output by the N-channel MUX is output to a certain row, and the EN circuit is a four-switch control circuit (which can simultaneously output the on-off states of four switches). T0 is the initial state, at this time, EN1-EN4 are all disconnected, and no signal is output to the corresponding electrode 11. At T1, EN1 is closed, EN2-EN4 are disconnected, and data is written to all EN1 electrodes 11; at T2, EN2 is closed, EN1, EN3, and EN4 are closed, and data is written to all EN2 electrodes 11; and so on. At T3 and T4, data is written to all EN3 and EN4 electrodes 11, respectively. By repeating the Figure 1 process shown above, the signal can be output to the entire electrode array within the defined time of a frame. The signal timing is as shown in Figure 2 , CLK and CLKB are clock signals of the GOA circuit, STV is a row initialization signal, EN1-EN4 correspond to the aforementioned EN switch signals, and DATA is a voltage signal output to the column. As shown in Figure 2 , within one CLK / CLKB clock signal, data writing to all EN pixels can be completed. Due to the physical properties of the switching of the EN switch, which includes inherent delay time, the switching of the switch can be reduced by merging the pixels without affecting the function. Figure 3 , by merging EN1 and EN2 pixels and merging EN3 and EN4 pixels, the number of switch switching is reduced by half, and the size of the electrode 11 is doubled. Further as Figure 4As shown, if all the EN electrode states are combined, then there is no need to switch the switch state, but the minimum electrode size is enlarged by 3 times. The minimum electrode size determines the minimum droplet size that can be separated. The electrode 11 combination can be flexibly switched according to the reaction system size required by the corresponding function of the chip, and only the corresponding control program needs to be modified, without the need for additional differentiation of the chip.

[0041] While embodiments of the present application have been shown and described with reference to particular embodiments thereof, it will be understood by those skilled in the art that various changes in form and details can be made therein without departing from the spirit and scope of the application. The scope of the application is defined by the appended claims and their equivalents.

Claims

1. A digital microfluidic chip, characterized in that: The device includes an electrode array, a driving module, and a top cover located above the electrode array. A gap for placing small droplets is provided between the top cover and the electrode array. The electrode array includes multiple rows of electrode array groups, and each row of the electrode array group includes several electrodes. The driving module controls each electrode in each row of the electrode array group to turn on sequentially. The size of the small droplets is adjusted by regulating the gap and the electrodes in the electrode array. The driving module includes N channels and N switch control circuits. Each channel is configured in a one-to-one correspondence with each switch control circuit. Each channel outputs a data signal to its corresponding switch control circuit. Each switch control circuit includes several switches. Each switch is configured in a one-to-one correspondence with each electrode in each row of the electrode array. Each switch controls the opening of its corresponding electrode. When the number of switches is halved, the size of the electrode is doubled compared to the size of the electrode before the reduction; when the number of switches is reduced by one-quarter, the size of the electrode is tripled compared to the size of the electrode before the reduction.

2. The digital microfluidic chip as described in claim 1, characterized in that: The electrode array further includes a dielectric layer covering the electrodes and a first hydrophobic layer covering the dielectric layer, with the gap between the first hydrophobic layer and the top cover.

3. The digital microfluidic chip as described in claim 1, characterized in that: It also includes a top cover located above the electrode array, with the gap between the top cover and the electrode array.

4. The digital microfluidic chip as described in claim 3, characterized in that: The top cover includes a second hydrophobic layer, a conductive layer covering the second hydrophobic layer, and an upper cover covering the conductive layer, with the gap between the second hydrophobic layer and the electrode array.

5. A pixel driving method for a digital microfluidic chip, characterized in that, For use in a digital microfluidic chip as described in any one of claims 1-4, the method includes the following steps: first, outputting a data signal to a switch control circuit via a channel to control the on / off state of the switch control circuit; then, controlling the on / off state of the switch according to a timing sequence to control the array corresponding to the switch in each row of the electrode array to be turned on.

6. The pixel driving method for a digital microfluidic chip as described in claim 5, characterized in that: The specific timing control is as follows: S1, first set T0, T1, T2, T3, T4 up to Tn time points in sequence; S2, where T0 is the initial state of one row of electrode array groups, at which time all switches of one of the switch control circuits are open, no signal is output to the electrode corresponding to each switch, and all electrodes are closed; at T1, the first switch of one of the switch control circuits is closed, the other switches are open, and the data signal of the channel corresponding to the switch control circuit is written to the electrode corresponding to the closed switch, and the electrode is turned on. At time T2, the second switch of one of the switch control circuits closes, the other switches open, and the data signal of the channel corresponding to the switch control circuit is written to the electrode corresponding to the closed switch, thus turning the electrode on. At time T3, the third switch of one of the switch control circuits closes, the other switches open, and the data signal of the channel corresponding to the switch control circuit is written to the electrode corresponding to the closed switch, thus turning the electrode on. At time T4, the fourth switch of one of the switch control circuits closes, the other switches open, and the data signal of the channel corresponding to the switch control circuit is written to the electrode corresponding to the closed switch, thus turning the electrode on. Until time Tn, when the nth switch of one of the switch control circuits is closed and the other switches are open, the data signal of the channel corresponding to the switch control circuit is written to the electrode corresponding to the closed switch, and the electrode is turned on. S3, thus completing the control of each electrode in one row of the electrode array group; S4, then repeat the timing control of step S2 to complete the control of each electrode in the remaining rows of electrode array groups, so as to output the signal to the entire electrode array.

7. The pixel driving method for a digital microfluidic chip as described in claim 6, characterized in that: The number of switches in the switch control circuit is halved, and the size of the electrode is doubled compared to the size of the electrode before the reduction; the number of switches in the switch control circuit is reduced by one-quarter, and the size of the electrode is tripled compared to the size of the electrode before the reduction.

8. An isothermal amplification method, characterized in that: The pixel driving method of the digital microfluidic chip as described in any one of claims 5-7 is adopted.

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