Blind hole microcavity void-free liquid filling method based on Venturi effect

Abstract

The invention discloses a venturi effect-based void-free liquid filling method for a blind hole micro-cavity, and belongs to the technical field of micro-fluidic chips. Firstly, a micro-channel structure of the micro-fluidic chip is designed, the micro-channel structure is composed of branch channels and blind hole micro-cavities and arranged on one side of a main channel at equal intervals, the branch channels are contraction micro-channels, and the blind hole micro-cavities are formed in the tail ends of the branch channels. Secondly, liquid is injected into a liquid storage tank of the micro-fluidic chip, the liquid is driven by centrifugal force to flow along a main channel and enters each blind hole micro-cavity through a branch channel, the flow speed of the liquid is increased through a contraction structure of the branch channel, and gas-liquid two-phase flow is promoted to be converted into gas-liquid layered annular flow from Taylor flow containing a large number of bubbles. And finally, after liquid filling is completed, no bubble remains in the blind hole micro-cavity. According to the invention, the flowing mode of gas-liquid two-phase flow is regulated and controlled by optimizing the geometrical shape of the micro-channel, so that void-free liquid filling of the blind hole micro-cavity is realized; complex surface treatment or external force application is not needed, and the success rate and efficiency of liquid filling are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of microfluidic chips and relates to a void-free liquid filling method for blind hole microchambers in a microfluidic chip. The method is particularly suitable for application scenarios such as biological detection, chemical reaction and PCR where bubble residue needs to be avoided. Background Art

[0002] Microfluidic chips can drive liquid flow through external forces such as centrifugal force and gas pressure. They offer advantages such as ease of operation, high throughput, and high integration, making them widely used in fields such as medical diagnostics, environmental monitoring, and food safety. Chambers within microfluidic chips can be categorized as open microchambers or blind microchambers, depending on the inlet and outlet configurations. Open microchambers have the same inlet and outlet directions and at least two connecting channels, including at least one inlet and one outlet. Blind microchambers have opposite inlet and outlet directions and a single connecting channel, meaning the inlet also functions as an outlet. The multiple ports in open microchambers can negatively impact the integrity of the chamber's seal, requiring additional sealing measures during chip fabrication and use to prevent contamination of the liquid within the microchamber. Blind microchambers, however, eliminate the need for additional sealing, resulting in better sealing performance and reducing the risk of cross-contamination. Furthermore, under similar circumstances, the blind microchamber structure simplifies the operational workflow during microfluidic chip use and improves detection efficiency.

[0003] However, residual bubbles are a common technical challenge during the liquid filling process of blind microcavities. While traditional methods such as adding external treatments (such as vacuum pumping or CO2 pre-filling) or modifying chip structures (such as multi-layer designs) can partially address this problem, they have drawbacks such as complex operation, high costs, and poor compatibility.

[0004] In existing technologies, uniform-diameter microchannel structures are prone to forming Taylor flows containing numerous bubbles during liquid filling, trapping them within the microchamber. Furthermore, bubble collapse and localized resistance at microchannel bends can affect the stability and success rate of liquid filling. Therefore, a simple, efficient, and void-free liquid filling method for blind microchambers without requiring complex external processing is needed. Summary of the Invention

[0005] To address the challenges of existing technologies, this paper proposes a converging microchannel structure based on the Venturi effect. By optimizing the microchannel geometry and regulating the flow pattern of gas-liquid two-phase flow, this method enables void-free liquid filling of blind microcavities. This method requires no complex surface treatment or external force application, significantly improving the success rate and efficiency of liquid filling.

[0006] In order to achieve the above object, the technical solution adopted in the present invention is:

[0007] A method for filling a blind micro-chamber with liquid without voids based on the Venturi effect comprises the following steps:

[0008] (1) Design a microchannel structure of a microfluidic chip. The microchannel structure is evenly spaced on one side of a main channel 1 and consists of branch channels 2 and blind microchambers 3. The microchannel structures are all identical, specifically:

[0009] The main channel 1 is open on one side, with a branch channel 2 located at the opening. This branch channel 2 is a converging microchannel, gradually decreasing in size from the opening to the exit. The two joints between the branch channel 2 and the main channel 1 are provided with rounded corners. A circular blind microchamber 3 is provided at the tail end of the branch channel 2. The blind microchamber 3 communicates with the main channel 1 via the converging microchannel, with the center of the blind microchamber 3 located to the right of the branch channel 2. A liquid reservoir 8 is located to the left of the branch channel 2.

[0010] Furthermore, the ratio of the inlet width 4 to the outlet width 5 of the contraction microchannel is 1.5 to 3:1, preferably 2:1.

[0011] Furthermore, the rounded corner structure provided at the junction of the main channel 1 and the branch channel 2 includes a first rounded corner structure 6 and a second rounded corner structure 7, wherein the first rounded corner structure 6 is located on the side where the center of the blind hole microchamber 3 is located; the rounded corner radii of the first rounded corner structure 6 and the second rounded corner structure 7 are 0.2-0.8 mm and 1-2 mm, respectively, to reduce bubble rupture and local resistance.

[0012] (2) Liquid is injected into the liquid reservoir 8 of the microfluidic chip, and the liquid is driven by centrifugal force to flow along the main channel 1 and enter each blind hole microchamber 3 through the branch channel 2. The contraction structure of the branch channel 2 increases the fluid flow rate, prompting the gas-liquid two-phase flow to transform from a Taylor flow containing a large number of bubbles to an annular flow with gas-liquid stratification, ensuring that the gas is discharged smoothly to complete the liquid filling.

[0013] Furthermore, the angular velocity of the centrifugal force should be 38π to 60π rad / s, and the working time of the centrifuge should be 30 to 120 s.

[0014] Furthermore, the microfluidic chip is made of common polymer materials.

[0015] Furthermore, the volume of the blind hole microchamber is 5 μL and the depth is 0.6 mm.

[0016] Furthermore, the width of the main channel is 0.7 mm and the depth is 0.2 mm.

[0017] Furthermore, the inlet width of the branch channel may be 0.7-1.4 mm, and the outlet width may be 0.35-0.7 mm.

[0018] Furthermore, the liquid is deionized water or a solution containing a dye, which is used to visualize the filling process.

[0019] (3) After the liquid filling is completed, no bubbles remain in the blind hole micro-chamber 3.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) Through the design of the contraction microchannel structure, the Venturi effect is used to increase the fluid flow rate, which promotes the transformation of the gas-liquid two-phase flow from Taylor flow to annular flow, effectively avoiding bubble residue;

[0022] (2) Setting rounded corners at the microchannel turns reduces bubble bursting and local resistance, thereby improving the stability of liquid filling;

[0023] (3) No need for complex external treatment or surface modification, which simplifies the operation process and reduces costs;

[0024] (4) The liquid filling time was shortened by 60.58% and the fluid stability was improved by 66.67%, which significantly improved the performance and reliability of the microfluidic chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the structure of the blind hole microchamber and the contraction microchannel;

[0026] Figure 2 Schematic diagram of the four main forms of gas-liquid two-phase flow in microchannels; Figure 2 (a) Bubble flow morphology; Figure 2 (b) is the Taylor flow form; Figure 2 (c) is the Taylor-annular flow morphology; Figure 2 (d) is the annular flow pattern;

[0027] Figure 3 This is a comparison chart of the liquid filling effects of a uniform diameter microchannel structure, a contraction microchannel structure, and a rounded contraction microchannel structure; Figure 3 (a) shows the filling effect of the microchannel structure with uniform diameter; Figure 3 (b) shows the filling effect of the contraction microchannel structure; Figure 3 (c) shows the filling effect of the rounded contraction microchannel structure;

[0028] Figure 4 This is a schematic diagram of the liquid filling process of the rounded contraction microchannel structure;

[0029] In the figure: 1 main channel, 2 branch channels, 3 blind hole microchamber, 4 contraction microchannel inlet, 5 contraction microchannel outlet width, 6 first rounded corner structure, 7 second rounded corner structure, 8 microfluidic chip liquid reservoir. DETAILED DESCRIPTION

[0030] The embodiments of the present invention are described in detail below in conjunction with the technical solutions and drawings.

[0031] A method for filling a blind micro-chamber with liquid without voids based on the Venturi effect comprises the following steps:

[0032] Step 1: An opening is made on one side of the main channel 1 as the entrance to the branch channel 2. A branch channel 2 is set at the opening. The branch channel 2 is a contraction-type microchannel, and its size gradually decreases from 1.4mm to 0.7mm from the opening to the exit. Rounded corners are set at the two joints between the branch channel 2 and the main channel 1. A circular blind hole microchamber 3 with a volume of 5μL and a depth of 0.6mm is provided at the tail end of the branch channel 2. The blind hole microchamber 3 is connected to the main channel 1 through the contraction-type microchannel, and the center of the blind hole microchamber 3 is located on the right side of the branch channel 2.

[0033] In this embodiment, the rounded corner structure provided at the junction of the main channel 1 and the branch channel 2 includes a first rounded corner structure 6 and a second rounded corner structure 7, wherein the first rounded corner structure 6 is located on the side where the center of the blind hole microchamber 3 is located; the rounded corner radii of the first rounded corner structure 6 and the second rounded corner structure 7 are 0.5 mm and 1 mm respectively.

[0034] Step 2: Inject 300 μL of a 1 mg / mL amaranth solution into reservoir 8 of a microfluidic chip made of polymethyl methacrylate (PMMA). Centrifugal force drives the liquid along main channel 1. Set the centrifuge angular velocity to 40πrad / s and the single centrifugation time to 60 seconds. Start the centrifuge to drive the liquid flow. The liquid enters blind microchamber 3 through the constricted microchannel. The constriction of branch channel 2 increases the fluid velocity, transforming the gas-liquid two-phase flow from Taylor flow containing numerous bubbles to annular flow with gas-liquid stratification, ensuring smooth gas discharge and completing liquid filling.

[0035] In this embodiment, the volume of the blind hole microchamber is 5 μL and the depth is 0.6 mm.

[0036] In this embodiment, the width of the main channel 1 is 0.7 mm and the depth is 0.2 mm.

[0037] In this embodiment, the inlet width 4 of the branch channel 2 is 1.4 mm, and the outlet width 5 is 0.7 mm.

[0038] Step 3: After the liquid filling is completed, no bubbles remain in the blind hole micro-chamber 3, and the liquid filling time is 2.03 seconds.

[0039] The above-described embodiments merely express the implementation methods of the present invention, but should not be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A method for filling a blind micro-chamber with liquid without gaps based on the Venturi effect, characterized in that: The blind micro-chamber void-free liquid filling method comprises the following steps: The first step is to design a microchannel structure of a microfluidic chip. The microchannel structure is evenly spaced on one side of a main channel (1) and consists of branch channels (2) and blind hole microchambers (3), wherein the branch channels (2) are contraction microchannels. The main channel (1) is open on one side, and a branch channel (2) is provided at the opening, and the size gradually decreases from the opening to the outlet; a circular blind hole micro-chamber (3) is provided at the tail end of the branch channel (2); In the second step, liquid is injected into the liquid reservoir 8 of the microfluidic chip. The liquid is driven by centrifugal force to flow along the main channel (1) and enter each blind hole microchamber (3) through the branch channel (2). The contraction structure of the branch channel (2) increases the fluid flow rate, completing the liquid filling, and no bubbles remain in the blind hole microchamber (3).

2. The method for filling a blind micro-chamber with liquid without gaps based on the Venturi effect according to claim 1, characterized in that: Rounded corner structures are provided at the two connecting points between the branch channel (2) and the main channel (1).

3. The method for filling a blind micro-chamber with liquid without gaps based on the Venturi effect according to claim 2, characterized in that: The fillet structure provided at the junction of the main channel (1) and the branch channel (2) comprises a first fillet structure (6) and a second fillet structure (7), wherein the first fillet structure (6) is located on the side where the center of the blind hole microchamber (3) is located; and the fillet radii of the first fillet structure (6) and the second fillet structure (7) are 0.2-0.8 mm and 1-2 mm, respectively.

4. The method for filling a blind micro-chamber with liquid without gaps based on the Venturi effect according to claim 1, characterized in that: The center of the blind hole microchamber (3) is located on the right side of the branch channel (2), and the liquid storage tank 8 is located on the left side of the branch channel (2).

5. The method for filling a blind micro-chamber with liquid without gaps based on the Venturi effect according to claim 1, characterized in that: The inlet width of the branch channel (2) is 0.7-1.4 mm, and the outlet width is 0.35-0.7 mm.

6. The method for filling a blind micro-chamber with liquid without gaps based on the Venturi effect according to claim 1, characterized in that: The ratio of the inlet width (4) to the outlet width (5) of the branch channel (2) is preferably 2:

1.

7. The method for filling a blind micro-chamber with liquid without gaps based on the Venturi effect according to claim 1, characterized in that: The angular velocity of the centrifugal force should be 38π~60πrad / s, and the working time of the centrifuge should be 30~120s.

8. The method for filling a blind micro-chamber with liquid without gaps based on the Venturi effect according to claim 1, characterized in that: The material of the microfluidic chip is a common polymer material; the liquid is deionized water or a solution containing a dye.

9. The method for filling a blind micro-chamber with liquid without gaps based on the Venturi effect according to claim 1, characterized in that: The volume of the blind hole microchamber (3) is 5 μL and the depth is 0.6 mm.

10. The method for filling a blind micro-chamber with liquid without gaps based on the Venturi effect according to claim 1, characterized in that: The main channel (1) has a width of 0.7 mm and a depth of 0.2 mm.

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