A medium electro-wetting digital microfluidic chip and system for deprotection reaction

Abstract

The application discloses a medium electro-wetting digital micro-fluidic chip and system which can be used for deprotection reaction, and the chip adopts a closed structure and comprises a first polar plate, an electrode array, a dielectric layer and a first hydrophobic layer which are sequentially formed on the surface of the first polar plate, a second polar plate, a second hydrophobic layer formed on the surface of the second polar plate, a conductive layer arranged on the second polar plate, and one or more fluid channels, wherein the first polar plate and the second polar plate are oppositely arranged, the first hydrophobic layer and the second hydrophobic layer face each other, and the fluid channel is formed between the first hydrophobic layer and the second hydrophobic layer to enable a liquid drop to move in the fluid channel. The application designs a new digital micro-fluidic chip and system, and realizes the driving of liquid drops of strong acid and strong base by improving the chip structure and parameters, and the chip can be well used in the deprotection reaction process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microfluidic chips, and relates to a medium electrowetting digital microfluidic chip and system for deprotection reaction. BACKGROUND

[0002] Digital microfluidics (DMF) is a powerful emerging technology that uses precise manipulation of liquid droplets in the microliter to nanoliter range to achieve complex laboratory analyses. By combining and repeating multiple operations in a series of steps at a series of levels, complex experimental procedures can be achieved. Compared with other methods, DMF involves much smaller volumes of liquid, and its process is highly automated. It is called chip laboratory technology and has many advantages in the field of life science research, including high potential in portability and significant reduction in consumption of (rare or expensive) reagents or samples.

[0003] Chip droplet driving methods mainly include dielectric wetting driving, thermal capillary tube driving, light induction driving, surface acoustic wave driving and magnetic driving. As the mainstream of chip droplet control technology, the planar droplet driving technology based on electrowetting on dielectric (EWOD) has obvious advantages in the high integration of devices and the convenience of operation with the integration of electronic technology. The droplet control technology based on EWOD is usually called digital microfluidic (DMF). DMF exhibits high flexibility in droplet control ability and the ability to perform multiple parallel biochemical reactions, which has attracted great interest of researchers.

[0004] However, while classic digital microfluidic chips based on electrowetting on dielectric (EWOD) exhibit excellent performance when actuating aqueous droplets, their durability is significantly reduced when actuating droplets in strong acids and bases due to their highly corrosive properties, making them incapable of long-term droplet actuation. Furthermore, factors such as the solution properties, surface tension, and droplet viscosity often affect actuation performance. Adjusting parameters such as voltage and frequency can lead to excessive voltage breakdown, potentially preventing actuation. In biochemistry, BOC (tert-butyloxycarbonyl) is a commonly used protecting group used to protect amino groups in amino acids. During peptide synthesis, BOC protecting groups must be removed to expose the amino groups for further reactions. Several commonly used BOC deprotection methods are listed below: 1. Acidic deprotection: A peptide containing a BOC protecting group is exposed to acidic conditions using a 10%-20% hydrobromic acid (HBr) or hydrochloric acid (HCl) solution to remove the BOC protecting group. This method is fast and has a high yield, but it is necessary to control the acid concentration and reaction time to avoid hydrolysis of the peptide chain caused by excessive acid hydrolysis. 2. Alkaline deprotection: Use a 10%-20% sodium hydroxide (NaOH) or potassium hydroxide (KOH) solution to expose the peptide containing the BOC protecting group to alkaline conditions to remove the BOC protecting group. Compared with acidic deprotection, this method has a lower yield, but is milder and suitable for peptides with poor stability. Chemical deprotection often involves acid-catalyzed or base-catalyzed hydrolysis: it is suitable for the removal of ester and amide protecting groups, and is completed by acid-base reagents such as sulfuric acid and sodium hydroxide. Therefore, microfluidic chips are often unsuccessful in the face of acid-base reactions and cannot be well used in deprotection chemical reactions. This greatly limits the promotion and application of digital microfluidic technology. Summary of the Invention

[0005] The purpose of the present invention is to develop a dielectric electrowetting digital microfluidic chip and system that can be used for deprotection reactions.

[0006] The technical solutions of the present invention are as follows:

[0007] A dielectric electrowetting digital microfluidic chip for deprotection reaction, which adopts a closed structure and includes:

[0008] A first electrode plate, on the surface of which an electrode array, a dielectric layer and a first hydrophobic layer are sequentially formed;

[0009] A second electrode plate, having a second hydrophobic layer formed on the surface of the second electrode plate; and a conductive layer provided on the second electrode plate;

[0010] One or more fluid channels, the first electrode plate and the second electrode plate are arranged opposite to each other, so that the first hydrophobic layer and the second hydrophobic layer face each other, and the fluid channel is formed therebetween for the liquid droplets to move therein.

[0011] In the technical solution, further, the electrode array has an electrode area of no more than 2mm*2mm, the gap between the first electrode plate and the second electrode plate is 0.2-0.3mm, and the droplet size is controlled to be 3-5ul.

[0012] Further, the electrode array is made of chromium and has a thickness of 200-300nm.

[0013] Further, the medium layer is made of Parylene C and has a thickness of 400-500nm.

[0014] Further, the first hydrophobic layer and the second hydrophobic layer are both Teflon AF solutions containing fluorides with a concentration of 2% and a thickness of 400-500nm.

[0015] A digital microfluidic chip system that can be used for deprotection reaction, comprising the microfluidic chip, further comprising a control circuit board, a driving and heating circuit is designed on the control circuit board, the positive electrode of the power supply of the driving and heating circuit is connected with the electrode array of the first electrode plate, and the negative electrode of the power supply is connected with the conductive layer of the second electrode plate.

[0016] Further, the control circuit board is further provided with a chip inlay plate for fixing the microfluidic chip, and the pins arranged on the chip inlay plate correspond to the four sides of the microfluidic chip, and the circuit on the control circuit board is connected.

[0017] Further, the system further comprises:

[0018] a computer, which sends a control command to the control circuit board to control the driving and heating circuit of the control circuit board;

[0019] a multimeter, which is used for monitoring the real-time voltage of the electrodes in the second electrode plate;

[0020] a three-axis mechanical arm, which is used for controlling the pipette to transfer the droplets to the channel of the microfluidic chip.

[0021] The beneficial effects of the present application are:

[0022] The present application aims at the problem that the current digital microfluidic chip is mostly used for driving the droplets of salt, organic reagent and the like, but lacks a microfluidic chip for use in the driving and the like in the deprotection reaction related to strong acid and strong base, and a new digital microfluidic chip is designed and proposed, the driving of the droplets of strong acid and strong base is realized through improving the chip structure and parameters, and the chip can be well used in the deprotection reaction process. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the microfluidic chip of the present application.

[0024] Figure 2 A schematic diagram of the structure of the system in the present application;

[0025] Figure 3 A schematic diagram of a specific microfluidic chip flow channel design in the present application;

[0026] In the figure: 1, personal computer, 2, pipette, 3, three-axis mechanical arm, 4, multimeter, 5, control circuit board, 6, chip inlay plate, 7, microfluidic chip, 71, second electrode plate, 72, droplet, 73, dielectric layer, 74, electrode array, 75, first electrode plate, 76, second hydrophobic layer. DETAILED DESCRIPTION

[0027] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to specific embodiments of the present application and in conjunction with the accompanying drawings.

[0028] According to a specific example of the present application, the present application provides a medium electro-wetting deprotection reaction digital microfluidic chip, as shown in Figure 1 The microfluidic chip provided by the present application adopts a closed structure composed of an upper plate and a lower plate, and contains:

[0029] The first electrode plate structure has a first electrode plate surface;

[0030] The second electrode plate structure has a second electrode plate surface;

[0031] The second electrode plate surface faces the first electrode plate surface and is spaced apart from the first electrode plate surface to form a plurality of fluid channels for one or more droplets between the first electrode plate structure and the second electrode plate structure.

[0032] The first electrode plate is provided with a plurality of independently controllable driving electrodes. The second electrode plate serves as a ground electrode, and the first electrode plate serves as a driving electrode, containing a series of electrode arrays;

[0033] In this example, the first electrode plate and the second electrode plate are both made of conductive glass. The conductive layer of the first electrode plate forms driving electrodes by etching, and then the upper surface is covered with a dielectric layer and a first hydrophobic layer in sequence. The second hydrophobic layer is provided on the conductive layer of the second electrode plate and is opposite to the first hydrophobic layer of the first electrode plate. The space between the first hydrophobic layer and the second hydrophobic layer is the electrode plate gap, forming one or more fluid channels, and an opening and an outlet are designed on the second electrode plate for each fluid channel for the entry and exit of droplets.

[0034] The driving electrode on the first electrode plate and the conductive layer of the second electrode plate constitute a driving electrode group for driving the displacement of the liquid drop, each group of driving electrodes is controlled by an independent driving circuit, and the working principle is that the first electrode plate driving electrode is connected to the positive pole of the power supply, the second electrode plate conductive layer is connected to the negative pole of the power supply, a closed loop can be formed with the liquid drop between the second electrode plate and the first electrode plate, and the contact angle of the micro liquid drop surface is changed according to the basic principle of dielectric wetting after the voltage is applied, and the liquid drop moves according to the planned path by sequentially energizing and de-energizing the adjacent driving circuits.

[0035] Among them, the electrode area in the electrode array is generally not more than 2mm*2mm, the gap between the first electrode plate and the second electrode plate is 0.2-0.3mm, and the liquid drop size is controlled to be 3-5ul.

[0036] The thickness of the electrode array is controlled to be 200-300nm, and the thickness of the dielectric layer should be controlled to be 400-500nm. The thickness of the first hydrophobic layer and the second hydrophobic layer should be controlled to be 400-500nm.

[0037] The digital microfluidic chip provided in the example can effectively realize the driving of the liquid drop of strong acid and strong base by improving the electrode size, the gap between the electrode plates, the liquid drop size, the thickness of the dielectric layer and the hydrophobic layer, and can be used for driving the solution of the deprotection reaction, etc. It has obvious advantages in chemical reaction application, solves the problem that there is no digital microfluidic chip available in the chemical deprotection reaction process, and solves the problem of multiple transfer or preparation in the process involving deprotection reaction in microliter level reaction.

[0038] In addition, as Figure 2 The application also provides a corresponding microfluidic chip system, in addition to the above-mentioned microfluidic chip, further comprising:

[0039] The control circuit board contains single-chip microcomputer, driving circuit and other electronic components, and provides driving signals to control the electrodes of the microfluidic chip and communicates with the power supply. In a specific example of the application, a chip inlay plate for fixing the medium electro-wetting microfluidic chip is arranged above the control circuit board, and the circuit on the control circuit board is connected through the pin array arranged on the chip inlay plate corresponding to the four sides of the microfluidic chip.

[0040] The personal computer sends control commands to the single-chip microcomputer;

[0041] The single-chip microcomputer reads the control commands sent by the personal computer and provides driving signals to the driving circuit;

[0042] The driving circuit provides voltage to the electrodes in the microfluidic chip; the driving circuit contains AND gate array and small relay array;

[0043] The multimeter is used to monitor the real-time voltage of the driving electrode;

[0044] Tri-axial robotic arm for controlling a pipette to transfer droplets onto a microfluidic chip.

[0045] In addition, the application provides a preparation method of the first electrode plate in the microfluidic chip, comprising the following steps:

[0046] 1. Electrode processing

[0047] a. Coating. A 200 nm thick chromium film is coated on the glass substrate by magnetron sputtering method;

[0048] b. Pretreatment. The substrate is placed in a special HMDS machine for pretreatment to improve the adhesion of the substrate surface to the photoresist;

[0049] c. Coating. A layer of positive photoresist AZ5214 with a thickness of about 1.4 μm is coated on the aluminum film by spin coating method;

[0050] d. Pre-baking. In order to remove the organic solvent in the photoresist, the substrate is placed on a heating plate at 95°C for 90s;

[0051] e. Exposure. The substrate is exposed to the prepared film mask on the MA6-2 photoetching machine for 6.5s;

[0052] f. Development. The exposed wafer is placed in 3038 developing solution for development, then repeatedly rinsed with deionized water, and finally dried with nitrogen;

[0053] g. Fixing. In order to completely cure the glue film and improve the adhesion of the glue film to the wafer, the substrate needs to be heated on a hot plate at 110°C for 2min;

[0054] h. Etching. Wet etching process is used for etching operation, the substrate is placed in a solution of phosphoric acid, nitric acid, glacial acetic acid and water = 16:1:1:2 for water bath heating at 50°C, and after a proper time, the pattern on the photoresist can be copied to the metal layer;

[0055] i. Removing the remaining photoresist after the electrode array processing is completed. First, the substrate is placed in acetone for 5min of ultrasonic cleaning, then in isopropyl alcohol for 5min of ultrasonic cleaning, and finally rinsed with flowing deionized water and dried with nitrogen;

[0056] 2. Dielectric layer plating. A 500 nm thick Perhydrolit C is sputtered on the ITO surface forming the electrode pattern as a dielectric layer by using a magnetron sputtering instrument;

[0057] 3. Plating a hydrophobic layer. The hydrophobic layer material is selected as a Teflon AF solution with a concentration of 2% fluoride, with a thickness of 500 nm; drying. The glass on which the Teflon is spin-coated is placed in an oven for drying, with a temperature setting of 110°C, and a drying time of about 3 hours, and is removed after cooling.

[0058] The microfluidic chip obtained based on the first electrode plate design is shown in FIG. 1. Figure 3

[0059] The above describes specific embodiments of the present application. It should be understood that the present application is not limited to the specific embodiments described above, and various changes or modifications can be made by those skilled in the art within the scope of the claims, without affecting the essential content of the present application. In the case of no conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.​

Claims

1. A dielectric electrowetting digital microfluidic chip that can be used for deprotection reaction, characterized in that: Adopt closed structure, including: A first electrode plate, on the surface of which an electrode array, a dielectric layer and a first hydrophobic layer are sequentially formed; A second electrode plate, having a second hydrophobic layer formed on the surface of the second electrode plate; and a conductive layer provided on the second electrode plate; One or more fluid channels, wherein the first electrode plate and the second electrode plate are arranged opposite to each other so that the first hydrophobic layer and the second hydrophobic layer face each other, and the fluid channels are formed therebetween for the liquid droplets to move therein; The electrode array has an electrode area of ​​no more than 2 mm x 2 mm, a gap between the first and second plates of 0.2-0.3 mm, and a droplet size of 3-5 μl. The electrode array is made of chromium with a thickness of 200-300 nm. The dielectric layer is made of parylene C with a thickness of 400-500 nm. The first and second hydrophobic layers are both dried from a 2% Teflon AF solution and have a thickness of 400-500 nm.

2. A system comprising the dielectric electrowetting digital microfluidic chip for deprotection reaction according to claim 1, characterized in that: It also includes a control circuit board, on which a driving and heating circuit is designed. The positive pole of the power supply in the driving and heating circuit is connected to the electrode array of the first electrode plate, and the negative pole of the power supply is connected to the conductive layer of the second electrode plate.

3. The system according to claim 2, characterized in that The control circuit board is also provided with a chip inlay plate for fixing the microfluidic chip, which is connected to the circuit on the control circuit board via pins arranged around the microfluidic chip on the chip inlay plate.

4. The system according to claim 2, wherein: The system further comprises: A computer sends a control command to the control circuit board to control the driving and heating circuits of the control circuit board; A multimeter for monitoring the real-time voltage of the electrode in the second plate; A three-axis robotic arm is used to control the pipette to transfer droplets to the channels of the microfluidic chip.

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