A uniform droplet generation device based on a microfluidic feedback valve

Abstract

The application discloses a kind of uniform droplet generation devices based on microfluidic feedback valve, comprising: the inlet pipeline made of hydrophobic material, multichannel microfluidic chip, outlet pipeline, super-hydrophobic plate;One end of inlet pipeline is communicated with fluid input port, and the other end is communicated with chip inlet;Chip inlet is communicated with chip outlet by fluid channel, fluid channel is provided with n level bifurcation, finally with chip outlet one-to-one correspondence;Feedback valve is set on each fluid channel of each level bifurcation;One end of outlet pipeline is communicated with chip outlet, and the other end is communicated with the through-hole of capillary structure on super-hydrophobic plate;Super-hydrophobic plate is fixed on adjustable tilt table, control end controls motor movement, and then drives adjustable tilt table to rotate.The application generates droplet automatically on super-hydrophobic surface using gravity, and makes system flow resistance concentrate in multichannel microfluidic chip, reduces the unevenness of flow resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microfluidics, in particular to a uniform droplet generation device based on a microfluidic feedback valve. BACKGROUND

[0002] Generating uniform droplets in air has important applications in droplet power generation, agricultural drip irrigation, chemical industry, etc. Currently, the methods for generating droplets in air include: using a single vertical thin tube to continuously generate single-size uniform droplets under the action of gravity and surface tension, which cannot change the droplet size without replacing the thin tube; the existing patents propose to use centrifugal and vibration type micro-droplet generation devices, which have the problem of low efficiency; if a multi-channel simultaneous droplet generation or multi-droplet generation mode is used, the efficiency of droplet generation can be improved, such as the patent proposes to generate droplets by bubble breaking, but there is a problem of large droplet size dispersion, and the device needs an additional air pressure power source, which is relatively complex.

[0003] In view of the above problems, there are three main schemes for the multi-channel microfluidic design scheme: (1) adopting a tree branch-shaped bifurcated flow channel design; (2) using a stepped distributor, a tapered inlet, etc. to regulate the geometric parameters of the microfluidic chip; (3) using a perforated baffle and other auxiliary devices. For example, the patent proposes a laminated multi-channel droplet microfluidic chip design, but the above devices have the problems of complex design, poor flow uniformity between multiple channels, and complex device design, etc., and the principle generally uses oil phase shearing to form droplets in the oil phase, which is difficult to directly generate droplets with uniform size in air. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application proposes a uniform droplet generation device based on a microfluidic feedback valve.

[0005] The specific technical solutions are as follows:

[0006] A uniform droplet generation device based on a microfluidic feedback valve, comprising: an inlet pipeline made of a hydrophobic material, a multi-channel microfluidic chip, an outlet pipeline, and a super-hydrophobic plate; the multi-channel microfluidic chip comprises: a chip inlet, a fluid channel, a feedback valve, and a chip outlet;

[0007] One end of the inlet pipeline is in communication with a fluid input port, and the other end is in communication with the chip inlet; the chip inlet and the chip outlet are in communication through the fluid channel, and the fluid channel is provided with n levels of bifurcations, and the fluid channel after the final bifurcation corresponds to the chip outlet one by one; a feedback valve is arranged on each fluid channel of each bifurcation level;

[0008] One end of the outlet pipeline is communicated with the chip outlet, and the other end is communicated with the through hole of the super-hydrophobic plate capillary structure; the height difference between the through hole of the super-hydrophobic plate and the multi-channel microfluidic chip is less than the height difference from the fluid inlet to the multi-channel microfluidic chip.

[0009] The uniform droplet generation device based on the microfluidic feedback valve further comprises an adjustable tilting table, a motor and a control end; the super-hydrophobic plate is fixed on the adjustable tilting table, and the control end controls the movement of the motor to drive the rotation of the adjustable tilting table.

[0010] Further, the hydrophobic material is selected from polydimethylsiloxane.

[0011] Further, the diameter d of the through hole on the super-hydrophobic plate c <1.3mm, each bifurcation divides the fluid channel into two paths, and the flow resistance in the multi-channel microfluidic chip and the total flow resistance of the device satisfy the following expression:

[0012]

[0013] In the formula, l is the length of each fluid channel, k is the distance between the adjacent two chip outlets, d0 is the diameter of the inlet pipeline and the outlet pipeline, d e is the equivalent diameter of each fluid channel, l0 is the length of the inlet pipeline, and l6 is the length of the outlet pipeline.

[0014] Further, the inlet pipeline and the chip inlet, the outlet pipeline and the chip outlet, and the outlet pipeline and the super-hydrophobic plate are connected by interference fit.

[0015] Further, the distance from the through hole on the super-hydrophobic plate to the plane of the multi-channel microfluidic chip is less than the distance from the fluid inlet to the horizontal plane of the multi-channel microfluidic chip.

[0016] The beneficial effects of the present application are:

[0017] (1) The present application efficiently generates a large number of uniform-sized droplets through the multi-channel microfluidic chip and the super-hydrophobic effect, and the flow resistance is concentrated in the multi-channel microfluidic chip, thereby avoiding the influence of the size error of the pipeline on the uniformity of the droplet size, and the design of the feedback valve can reduce the influence of environmental disturbance, thereby solving the problem of size difference of the droplets in the parallel design.

[0018] (2) The present application generates droplets in an air environment by using gravity, without additional shear, low energy consumption, and has a self-cleaning function. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a structural schematic diagram of the uniform droplet generation device based on the microfluidic feedback valve according to the present application.

[0020] Figure 2 This is a schematic diagram of the structure of the multi-channel microfluidic chip used in this invention, wherein (a) is a front view of the chip and (b) is a schematic diagram of the AA section in (a).

[0021] Figure 3 This is a schematic diagram of droplet generation.

[0022] Figure 4 This is a schematic diagram of the droplet generation process in Embodiment 1 of the present invention.

[0023] Figure 5 This is a graph showing the relationship between flow rate, tilt angle, and droplet volume when the outlet diameter is 0.82 mm in Embodiment 1 of the present invention.

[0024] Figure 6 This is a graph showing the relationship between flow rate, tilt angle, and normalized droplet volume when the outlet diameter is 0.82 mm in Embodiment 1 of the present invention.

[0025] Figure 7 This is a graph showing the relationship between flow rate, tilt angle, and normalized droplet volume when the outlet diameter is 0.51 mm in Embodiment 2 of the present invention.

[0026] In the diagram, valve 1, inlet pipe 2, multi-channel microfluidic chip 3, chip inlet 3-1, fluid channel 3-2, feedback valve 3-3, chip outlet 3-4, outlet pipe 4, adjustable tilting stage 5, superhydrophobic plate 6, motor 7, and control terminal 8. Detailed Implementation

[0027] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. The objectives and effects of the present invention will become clearer as a result. The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0028] like Figure 1 As shown, a uniform droplet generation device based on a microfluidic feedback valve includes: a valve 1, an inlet pipe 2, a multi-channel microfluidic chip 3, an outlet pipe 4, an adjustable tilting stage 5, a superhydrophobic plate 6, a motor 7, and a control terminal 8. The multi-channel microfluidic chip 3 includes: a chip inlet 3-1, a fluid channel 3-2, a feedback valve 3-3, and a chip outlet 3-4. Fluid enters the multi-channel microfluidic chip 3 through the inlet pipe 2 and is divided into multiple streams, which then generate droplets on the surface of the superhydrophobic plate 6 via the outlet pipe 4. The inlet pipe 2, the multi-channel microfluidic chip 3, the outlet pipe 4, and the superhydrophobic plate 6 are all made of hydrophobic materials; in this embodiment, PDMS (polydimethylsiloxane) is used.

[0029] One end of the inlet pipe 2 is in communication with the fluid input port, and a valve 1 is arranged to control the flow rate at the inlet. The other end of the inlet pipe 2 is in communication with the chip inlet 3-1 of the multi-channel microfluidic chip 3 in an interference fit. As shown in Figure 2 , the chip inlet 3-1 is in communication with the chip outlet 3-4 through a fluid channel 3-2, and the fluid channel 3-2 is provided with n levels of bifurcations, each level of bifurcations divides the fluid into two paths, and finally divides the fluid into 2 n paths of fluid, and corresponds to 2 n chip outlets 3-4 one by one, realizing parallel design; a glass slide is used to seal the fluid channel 3-2. A feedback valve 3-3 is arranged on each fluid channel 3-2 of each level of bifurcations, which is used to uniformize the flow resistance of each fluid channel 3-2, and realize uniform distribution of the fluid among the fluid channels 3-2, thereby avoiding the size difference of droplets generated by multiple channels.

[0030] The diameter of the outlet pipe 4 is the same as that of the inlet pipe 2, one end of the outlet pipe 4 is in communication with the chip outlet 3-4 in an interference fit, and corresponds to 2 n chip outlets 3-4, and the outlet pipe 4 has 2 n roots; the other end of the outlet pipe 4 is in communication with 2 n through holes on the super-hydrophobic plate 6 in an interference fit, and the through holes are capillary structures; in this embodiment, the super-hydrophobic plate 6 is made of PDMS (polydimethylsiloxane) with a micro-column structure. The super-hydrophobic plate 6 is fixed on the adjustable tilting table 5, and the tilting angle of the adjustable tilting table 5 is adjusted by driving the motor 7 through the control end 8.

[0031] As shown in Figure 3 , the fluid flows into the through holes on the super-hydrophobic plate 6 through the outlet pipe 4, and when the gravitational force of the fluid is balanced with the surface tension on the surface of the super-hydrophobic plate 6, the fluid breaks near the outlet to generate droplets with uniform size, and the size of the generated droplets can be adjusted by the tilting angle of the adjustable tilting table 5.

[0032] To ensure that the droplets can be generated under the action of gravity, the height difference h1 between the through holes on the super-hydrophobic plate 6 and the multi-channel microfluidic chip 3 needs to be less than the height difference h0 from the fluid input port to the multi-channel microfluidic chip 3, i.e. h0 > h1.

[0033] To ensure the uniformity of the droplets, the diameter d c of the through holes on the super-hydrophobic plate 6 needs to be less than 1.3 mm, and at the same time, the flow resistance in the multi-channel microfluidic chip 3 and the total flow resistance of the entire device need to meet the following conditions:

[0034]

[0035] In the formula, l is the length of each fluid channel 3-2, k is the distance between two adjacent chip outlets 3-4, d0 is the diameter of the inlet pipe 2 and the outlet pipe 4, and d e l0 is the equivalent diameter of each fluid channel 3-2, l0 is the length of the inlet pipe 2, and l6 is the length of the outlet pipe 4.

[0036] Example 1

[0037] In this embodiment, d is taken as c =0.82mm, using deionized water as the fluid, it is input into a uniform droplet generation device based on a microfluidic feedback valve. A high-speed camera is used to capture the droplet formation and falling process. Figure 4 As shown, d c A schematic diagram of the droplet generation process when the droplet diameter is 0.82 mm, the tilt angle of the adjustable tilting stage 5 is 45°, and the input flow rate is 3 ml / min.

[0038] Change the tilt angle and input flow rate, and calculate the resulting droplet size based on the captured image. For example... Figure 5 As shown, it reflects d c The relationship between input flow rate, tilt angle, and droplet volume when the droplet diameter is 0.82 mm; from... Figure 5 It can be seen that the larger the tilt angle, the larger the droplet volume generated at the outlet under the same flow rate. For example... Figure 6 As shown, it reflects d c When the droplet size is 0.82 mm, and a superhydrophobic PDMS surface is present at the outlet, the droplet size remains relatively stable in the flow rate range of 1-9 ml / min for the curves -60P, -45P, -30P, -15P, and 0P (i.e., droplet outlet tilt angles upward at 15°, 30°, 45°, and 60°). However, for the bare outlet without PDMS and the outlet with a superhydrophobic PDMS surface pointing vertically downward, the droplet size changes more significantly with the flow rate, and it is impossible to maintain a stable droplet size.

[0039] Example 2

[0040] In this embodiment, d is taken as c =0.51mm, and the other conditions are the same as in Example 1. The result is as follows: Figure 7 The graph shows the relationship between flow rate, tilt angle, and normalized droplet volume. As can be seen from the graph, at d... c When the droplet size is 0.51 mm, the droplet size curves for -60P, -45P, -30P, -15P, and 0P (i.e., droplet outlet tilt angles upwards at 15°, 30°, 45°, and 60°) remain relatively stable within a flow rate range of 1-9 ml / min. However, the droplet size produced by the bare outlet without PDMS and the vertically downward droplet outlet with PDMS shows significant changes with flow rate. Figure 790P, 0L curves in FIG. 6.

[0041] Those skilled in the art can understand that the above description is only preferred examples of the application and is not used to limit the application. Although the application has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples, or make equivalent replacements to some of the technical features. Any modifications, equivalent replacements, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A uniform droplet generation device based on a microfluidic feedback valve, characterized in that, include: The system comprises an inlet pipe, a multi-channel microfluidic chip, an outlet pipe, and a superhydrophobic plate, all made of hydrophobic materials. The multi-channel microfluidic chip includes a chip inlet, a fluid channel, a feedback valve, and a chip outlet. One end of the inlet pipe is connected to the fluid inlet, and the other end is connected to the chip inlet; the chip inlet and the chip outlet are connected through a fluid channel, which has n levels of branching, and the final branched fluid channel corresponds one-to-one with the chip outlet; a feedback valve is installed on each fluid channel of each branch. One end of the outlet pipe is connected to the chip outlet, and the other end is connected to the through hole of the capillary structure on the superhydrophobic plate; the height difference between the through hole on the superhydrophobic plate and the multi-channel microfluidic chip is less than the height difference between the fluid inlet and the multi-channel microfluidic chip. The uniform droplet generation device based on a microfluidic feedback valve further includes: an adjustable tilting stage, a motor, and a control terminal; the superhydrophobic plate is fixedly connected to the adjustable tilting stage, and the control terminal controls the movement of the motor, thereby driving the adjustable tilting stage to rotate; The diameter of the through holes on the superhydrophobic plate d c <1.3mm, each stage of bifurcation divides the fluid channel into two paths, and the flow resistance within the multi-channel microfluidic chip and the total flow resistance of the device satisfy the following expression: ； In the formula, l The length of each fluid channel segment, k This represents the distance between the outlets of two adjacent chips. d 0 represents the diameter of both the inlet and outlet pipes. d e This is the equivalent diameter of each fluid channel segment. l 0 represents the length of the inlet pipe. l 6 represents the length of the outlet pipeline.

2. The uniform droplet generation device based on a microfluidic feedback valve according to claim 1, characterized in that, The hydrophobic material is polydimethylsiloxane.

3. The uniform droplet generation device based on a microfluidic feedback valve according to claim 1, characterized in that, The inlet pipe is connected to the chip inlet, the outlet pipe is connected to the chip outlet, and the outlet pipe is connected to the superhydrophobic plate by an interference fit.

Images