Droplet separation device and method based on digital microfluidic chip

Abstract

The droplet separation device and method based on a digital microfluidic chip provided in this application include a square electrode array disposed on the digital microfluidic chip and an interdigital electrode assembly disposed on the square electrode array. When a droplet containing a droplet moves to the interdigital electrode on which a high-frequency dielectrophoresis signal is applied, the droplet is subjected to the resultant force of the dielectrophoresis force and the fluid drag force, causing the droplet to align in a certain direction to achieve the tearing of the droplet, resulting in sub-droplets with a more uniform droplet distribution. This solves the problem of more controllable and uniform droplet sorting and separation on a digital microfluidic platform, and can make the existing droplet separation based on digital microfluidic chips more reliable.

Description

Technical Field

[0001] This application belongs to the field of microfluidics technology, specifically relating to a droplet separation device and method based on a digital microfluidic chip. Background Technology

[0002] Dielectric wetting refers to the phenomenon where changing the voltage between insulating substrates causes a change in surface energy due to the accumulation of surface charge on the droplets, thus altering the contact angle. Digital microfluidic chips based on the principle of dielectric wetting apply voltage in a specific sequence to an electrode array between parallel substrates, allowing surface tension to drive droplet movement. Building upon droplet movement, digital microfluidics is increasingly being applied to droplet separation and sorting within droplets, and further, to separation at the single droplet level.

[0003] Dielectrophoresis is the phenomenon where matter aligns itself in the direction of an applied electric field due to polarization. The dielectric constant of a material often changes with the frequency of the applied electric field; and the applied voltage and dielectric constant ultimately affect the dielectric force. By changing the voltage frequency and magnitude, this property is widely used in the manipulation of liquid droplets.

[0004] Existing microfluidic-based dielectrophoretic manipulation methods for droplets are commonly found in channel-type microfluidics. Liquid is continuously pumped in from the inlet, and potentials are spaced above the channel. The electric field direction forms a specific angle with the liquid flow velocity direction, causing the resultant force of the dielectrophoretic force and fluid drag on the droplets to be in a specific tilted direction, thus causing them to move uniformly in that direction. In another approach, a pair of interdigitated electrodes with a specific tilt angle are placed below the channel. With the electric field tilted, the resultant force on the droplets is aligned with the flow direction, resulting in a uniform row, thus eliminating the need for a tilted channel.

[0005] Current droplet separation on digital microfluidic chips mainly relies on droplet movement and tearing mechanisms, resulting in significant randomness in the separation of droplets into sub-droplets and low precision. While existing droplet manipulation methods based on dielectrophoresis can precisely control the direction of droplets along the fluid flow, they cannot flexibly obtain discrete droplets containing other droplets. Summary of the Invention

[0006] Therefore, it is necessary to provide a droplet separation device that can achieve discrete and uniform droplet sorting, addressing the shortcomings of existing technologies.

[0007] To solve the above problems, this application adopts the following technical solution:

[0008] One of the objectives of this application is to provide a droplet separation device based on a digital microfluidic chip, including a square electrode array disposed on the digital microfluidic chip and an interdigital electrode assembly disposed on the square electrode array. The square electrode array includes a plurality of ordinary electrodes, and the interdigital electrode assembly includes a plurality of interdigital electrodes arranged at intervals.

[0009] In some embodiments, the ordinary electrode adjacent to the interdigitated electrode is the same size.

[0010] In some embodiments, the angles of the several interdigitated electrodes arranged at intervals are different.

[0011] In some embodiments, the tilt angle can be obtained based on the size parameters of the digital microfluidic chip and the properties of the droplet.

[0012] The second objective of this application is to provide a separation method for a droplet separation device, comprising the following steps:

[0013] A high-frequency dielectrophoresis signal and a low-frequency electrowetting signal are applied to both sides of any one of the interdigitated electrodes, respectively.

[0014] Move the droplet to the position of the interdigitated electrode;

[0015] The interdigitated electrodes are de-energized, and a low-frequency electrowetting signal is applied to both sides of any one of the ordinary electrodes to achieve tearing of the droplet.

[0016] In some embodiments, the following step is also included: directing the droplet to a smaller electrode region for graded tearing.

[0017] In some embodiments, the droplets comprise microbeads, bacteria, or cells.

[0018] In some embodiments, the side length ratio of the multiple sets of interdigitated electrode dimensions is 1:2:4:…N to achieve a dichotomous tearing of the droplet.

[0019] The technical solution adopted in this application has the following effects:

[0020] The droplet separation device and method based on a digital microfluidic chip provided in this application include a square electrode array disposed on the digital microfluidic chip and an interdigital electrode assembly disposed on the square electrode array. When a droplet containing a droplet moves to the interdigital electrode on which a high-frequency dielectrophoresis signal is applied, the droplet is subjected to the resultant force of the dielectrophoresis force and the fluid drag force, causing the droplet to align in a certain direction to achieve the tearing of the droplet, resulting in sub-droplets with a more uniform droplet distribution. This solves the problem of more controllable and uniform droplet sorting and separation on a digital microfluidic platform, and can make the existing droplet separation based on digital microfluidic chips more reliable. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The droplet separation device for the digital microfluidic chip provided in Embodiment 1 of this application.

[0023] Figure 2 This is a design layout of the digital microfluidic chip provided in Embodiment 1 of this application.

[0024] Figure 3 This is a flowchart illustrating the steps of the separation method of the droplet separation device provided in Embodiment 2 of this application.

[0025] Figure 4 This is a force diagram of a droplet provided in Embodiment 2 of this application.

[0026] Figure 5 This is a simulation diagram of the flow field of droplet movement on a square digital microfluidic chip provided in Embodiment 2 of this application. Detailed Implementation

[0027] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0028] In the description of this application, it should be understood that the terms "upper", "lower", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0030] Example 1

[0031] Please see Figure 1 This is a schematic diagram of the structure of a droplet separation device based on a digital microfluidic chip provided in an embodiment of this application. It includes: a square electrode array 110 disposed on the digital microfluidic chip and an interdigital electrode assembly 120 disposed on the square electrode array 110. The square electrode array 110 includes a plurality of ordinary electrodes 111, and the interdigital electrode assembly 120 includes a plurality of interdigital electrodes 121 arranged at intervals.

[0032] In some embodiments, the tilt angles of the several interdigitated electrodes 121 arranged at intervals are different.

[0033] It is understood that the tilt angle can be calculated based on the size parameters of the digital microfluidic chip and the properties of the droplet.

[0034] In this embodiment, the interdigitated electrodes 121 are spaced out at three angles: 15°, 10°, and 7.5°. Each angled interdigitated electrode 121 has three sizes, all in a 2:1 ratio, with dimensions of 400 / 200 / 100 μm. The tooth widths of each interdigitate finger are 45 / 20 / 6 μm. Due to the influence of the machining process linewidth, the tooth pitch is 6 μm. Please refer to [link to documentation]. Figure 2 The electrodes in regions 1, 2, and 3 have side lengths of 400, 200, and 100 μm, respectively. The interdigitated tilt angles of region 2 from left to right and region 3 from bottom to top are 15°, 10°, and 7.5°, respectively.

[0035] It is understandable that the dimensional parameters (tilt angle, tooth width, tooth pitch) of the interdigital electrode 121 can vary depending on the signal (frequency, magnitude) and chip size (electrode size, plate gap).

[0036] In some embodiments, the ordinary electrode 111 adjacent to the interdigitated electrode 121 is the same size.

[0037] It is understandable that each electrode arrangement design has multiple sizes to facilitate sequential operation in stages.

[0038] The droplet separation device based on a digital microfluidic chip provided in Embodiment 1 above arranges ordinary square electrodes and interdigitated electrodes on the digital microfluidic chip in a certain order. When a high-frequency dielectric electrophoresis signal and a low-frequency electrowetting signal are respectively connected to both sides of the interdigitated electrodes, and a low-frequency electrowetting signal is applied to the ordinary electrode, when the droplet containing the droplet passes through the interdigitated electrode at a certain speed, the droplet, which originally moves with the flow field, can be arranged in the droplet according to a specific law. Through a certain electrode switching sequence, the droplet is further torn apart.

[0039] The droplet separation device provided in Embodiment 1 above can flexibly obtain discrete droplets containing droplets through a digital microfluidic platform, which is superior to the traditional channel-type continuous fluid.

[0040] Example 2

[0041] Please see Figure 3 The flowchart below shows the steps of the separation method of the droplet separation device provided in Embodiment 2, which includes the following steps:

[0042] Step S110: Apply a high-frequency dielectric electrophoresis signal and a low-frequency electrowetting signal to both sides of any one of the interdigitated electrodes 121.

[0043] Please combine Figure 1 Because the voltage and frequency range required for dielectrophoresis and dielectric wetting differ significantly—for example, dielectrophoresis-driven dielectric droplets (such as PS microspheres) often require AC frequencies in the MHz range, while the commonly used signal frequencies for dielectric wetting are no more than the kHz range—the two types of signals are connected separately. To maintain the droplet-moving capability of the interdigital electrodes, the two electrodes on either side of the interdigital fingers are connected to a high-frequency dielectrophoresis (DEP) signal and a normal passive drive (PM) signal (i.e., a low-frequency electrowetting signal), respectively.

[0044] Step S120: Move the droplet to the position of the interdigitated electrode.

[0045] It is understandable that during the process of moving the droplet to the position of the interdigitated electrode 121, the droplet has a certain moving speed, and at the same time, the direction of the force on the droplet is perpendicular to the direction of the droplet velocity, so it tends to align longitudinally. Please refer to [link / reference needed]. Figure 4 , is a force diagram of the droplet.

[0046] Please see Figure 5 The simulation of the droplet movement flow field on the square digital microfluidic chip provided in this embodiment shows that the droplet movement velocity is concentrated at the front end.

[0047] Step S130: The interdigitated electrode 121 is de-energized, and a low-frequency electrowetting signal is applied to both sides of any one of the ordinary electrodes 111 to achieve tearing of the droplet.

[0048] It is understandable that, since the droplet arrangement direction is the same as the tearing direction, the number of droplets in the two sub-droplets obtained at this time is more even than that in ordinary tearing.

[0049] In some embodiments, the following steps are also included:

[0050] Step S140: The droplet is directed to a smaller electrode area for graded tearing.

[0051] In some embodiments, the side length ratio of the multiple sets of interdigitated electrode dimensions is 1:2:4:…N to achieve a dichotomous tearing of the droplet.

[0052] It is understandable that, compared to tearing droplets containing liquid on ordinary electrodes and then subjecting them to graded tearing, the uniformity of droplet separation on digital microfluidic chips is improved.

[0053] In some embodiments, the droplets comprise microbeads, bacteria, or cells.

[0054] The droplet separation method based on a digital microfluidic chip provided in this embodiment involves a droplet containing droplets moving to an interdigital electrode to which a high-frequency dielectrophoresis signal is applied. The resultant force of the dielectrophoresis force and the fluid drag force causes the droplets to align in a certain direction to achieve tearing of the droplets, resulting in sub-droplets with a more even distribution. This solves the problem of more controllable and uniform droplet sorting and separation on a digital microfluidic platform, making existing droplet separation based on digital microfluidic chips more reliable.

[0055] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A droplet separation device based on a digital microfluidic chip, characterized in that, The chip includes a square electrode array disposed on the digital microfluidic chip and an interdigital electrode assembly disposed on the square electrode array. The square electrode array includes a plurality of ordinary electrodes, and the interdigital electrode assembly includes a plurality of interdigital electrodes arranged at intervals. A high-frequency dielectrophoresis signal and a low-frequency electrowetting signal are connected to both sides of the interdigitated electrode, respectively. A low-frequency electrowetting signal is applied to the ordinary electrode. When a droplet containing particles passes through the interdigitated electrode, the droplet is further torn apart by the electrode switching sequence.

2. The droplet separation device according to claim 1, characterized in that, The ordinary electrode adjacent to the interdigitated electrode has the same size.

3. The droplet separation device according to claim 1, characterized in that, The tilt angles of the several interdigitated electrodes arranged at intervals are different.

4. The droplet separation device according to claim 3, characterized in that, The tilt angle is obtained based on the size parameters of the digital microfluidic chip and the properties of the droplet.

5. A separation method for the droplet separation device according to claim 1, characterized in that, Includes the following steps: A high-frequency dielectrophoresis signal and a low-frequency electrowetting signal are applied to both sides of any one of the interdigitated electrodes, respectively. Move the droplet to the position of the interdigitated electrode; The interdigitated electrodes are de-energized, and a low-frequency electrowetting signal is applied to the adjacent ordinary electrodes perpendicular to the droplet's direction of motion to achieve the tearing of the droplet.

6. The separation method of the droplet separation device according to claim 5, characterized in that, It also includes the following steps: moving the droplet to a smaller electrode region for graded tearing.

7. The separation method of the droplet separation device according to claim 6, characterized in that, The droplets may include microbeads, bacteria, or cells.

8. The separation method of the droplet separation device according to claim 6, characterized in that, The side length ratio of the multiple sets of interdigitated electrodes is 1:2:4:…N to achieve the bisection tearing of droplets.

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