A microfluidic chip for controlling droplet size based on piezoelectric perturbations

Abstract

The present invention discloses a microfluidic chip for controlling the size of droplet generation based on piezoelectric perturbations; the microfluidic chip comprises a chip substrate and a piezoelectric component. A main flow path and a pressure fluctuation flow path are provided on the chip substrate. A droplet generation region is provided on the main flow path; the pressure fluctuation flow path comprises a piezoelectric chamber. Two piezoelectric chambers are respectively connected to two pressure fluctuation points on the main flow path. The two pressure fluctuation points are located on both sides of the droplet generation region. Piezoelectric components are installed in both piezoelectric chambers. The piezoelectric component can change its own volume by adjusting the input voltage, so that the pressure at the two pressure fluctuation points changes. The present invention adds a piezoelectric chamber to the continuous phase flow path in the microfluidic chip for generating droplets, utilizes the periodic motion of the piezoelectric component to apply periodic pressure fluctuations to the continuous phase flow path, and then utilizes the peak of this periodic pressure fluctuation to pinch off the discrete phase liquid in advance, thereby forming smaller discrete phase droplets.

Description

Technical Field

[0001] The present invention relates to the field of microfluidics, and in particular to a microfluidics chip for controlling the size of droplet generation based on piezoelectric perturbations. Background Art

[0002] In traditional passive methods, the droplet size and generation frequency are generally controlled by adjusting the two-phase flow rate. However, this method often has a very slow response speed, and the droplet size control is not accurate, which cannot be adapted to production. The active method has the advantages of fast response speed and high accuracy. It is generally used under high-precision droplet size control conditions.

[0003] In the existing technology, active control of droplet generation is generally exerted by introducing external fields such as electricity, magnetism, light and other external energies to achieve precise regulation of droplets to meet actual needs. However, these drives have special requirements for the properties of the fluid and are not sufficiently compatible with the fluid.

[0004] Because the channels of microfluidic chips are often very small, typically on the micron scale, the disturbances required to control droplets are extremely small and precise. In the field of micro-displacement vibration research, piezoelectric ceramics offer advantages such as small size, fast response, and high load-bearing capacity, making them ideal materials for micro-displacement vibration. Therefore, a microfluidic chip based on piezoelectric perturbations that is simple to manufacture, low in cost, highly integrated, highly fluid compatible, and with adjustable droplet size is under development. Summary of the Invention

[0005] The purpose of the present invention is to address the deficiencies of the existing technology and provide a piezoelectric-assisted microchannel droplet generation device, which drives the piezoelectric ceramic to vibrate and directly transmits the vibration to the continuous phase fluid to achieve control of the droplet generation size and frequency.

[0006] In a first aspect, the present invention provides a microfluidic chip for controlling droplet size based on piezoelectric perturbations, comprising a chip substrate and a piezoelectric component. The chip substrate is provided with a main flow path and a pressure fluctuation flow path. The main flow path is provided with a droplet generation region;

[0007] The pressure fluctuation flow path includes piezoelectric chambers. Two piezoelectric chambers are connected to two pressure fluctuation points on the main flow path, respectively. The two pressure fluctuation points are located on either side of the droplet generation area. A piezoelectric component is installed in each piezoelectric chamber. The piezoelectric component can change its volume by adjusting the input voltage, thereby adjusting the pressure within the piezoelectric chamber, resulting in changes in the pressure at the two pressure fluctuation points.

[0008] Preferably, the piezoelectric assembly includes a mounting tube, an end plate, a piezoelectric ceramic, and a wire. The mounting tube is fixed within the corresponding piezoelectric chamber. The end plate is fixed to one end of the mounting tube. The piezoelectric ceramic is disposed within the mounting tube; one end of the piezoelectric ceramic is fixed to the end plate. Two electrodes of the piezoelectric ceramic are led out via two wires passing through the end plate.

[0009] Preferably, the main flow path includes a continuous phase input port, a discrete phase input port, an annular flow channel, an output flow channel, and an output port. The continuous phase input port is connected to the annular flow channel. The ends of the output flow channel are connected to the discrete phase input port and the output port, respectively. The output flow channel intersects and connects with the annular flow channel. The junction of the output flow channel and the annular flow channel forms a droplet generation region. The two pressure fluctuation points on the main flow path are located on the annular flow channel.

[0010] Preferably, during operation, a periodically changing voltage signal is input into the piezoelectric component, causing pressure fluctuations in the continuous phase liquid passing through two pressure fluctuation points, so that the droplet generation area continuously generates droplets of discrete phase liquid corresponding to the frequency and voltage amplitude of the voltage signal.

[0011] Preferably, the two piezoelectric chambers are symmetrically arranged on both sides of the output flow channel.

[0012] Preferably, the output flow channel is provided with a serpentine section; the serpentine section is arranged between the droplet generation area and the output port.

[0013] Preferably, a bottom film is provided on the chip substrate; the bottom film is used to seal the continuous phase input port, discrete phase input port, annular flow channel, output flow channel, output port, initial input port, bifurcated flow channel and openings of the piezoelectric chamber on the bottom surface of the chip substrate.

[0014] Preferably, the pressure fluctuation flow path further includes an initial input port and a bifurcated flow channel. The initial input port communicates with the two piezoelectric chambers via the bifurcated flow channel. The initial input port and the bifurcated flow channel are used to fill the two piezoelectric chambers with a continuous phase liquid before use of the microfluidic chip. During use of the microfluidic chip, the initial input port is closed.

[0015] Preferably, the two pressure fluctuation points are symmetrically arranged with respect to the droplet generation region.

[0016] In a second aspect, a droplet generation method is provided, using the aforementioned microfluidic chip; the droplet generation method comprises the following steps:

[0017] Step 1: introduce the continuous phase liquid into the two piezoelectric chambers so that the two piezoelectric chambers are filled with the mobile phase liquid.

[0018] Step 2: continuously input the continuous phase liquid into the continuous phase input port; continuously input the discrete phase liquid into the discrete phase input port.

[0019] Step three: a periodic voltage signal is applied to the piezoelectric component to cause the piezoelectric component to deform periodically; the pressure at the two pressure fluctuation points fluctuates periodically; as the pressure at the two pressure fluctuation points increases, the continuous phase liquid on both sides of the droplet generation area tends to pinch off the discrete phase liquid in the droplet generation area, thereby changing the size of the discrete phase droplets generated in the droplet generation area.

[0020] Step 4: Adjust the frequency of the voltage signal input to the piezoelectric component so that the size of the generated discrete phase droplets is adjusted to the target value.

[0021] Preferably, in step 4, the relationship between the frequency of the voltage signal and the size of the generated discrete phase droplets is obtained by pre-calibration.

[0022] Preferably, the continuous phase liquid is a hydrophobic liquid; and the dispersed phase liquid is a hydrophilic liquid.

[0023] The present invention has the following beneficial effects:

[0024] 1. The present invention adds a piezoelectric chamber to the continuous phase flow channel in the microfluidic chip that generates droplets. The periodic motion of the piezoelectric component is used to apply periodic pressure fluctuations to the continuous phase flow channel. The peak of this periodic pressure fluctuation is then used to pinch off the discrete phase liquid in advance, forming smaller discrete phase droplets, thereby achieving the purpose of reducing the output droplet size of the microfluidic chip.

[0025] 2. The present invention can change the pressure fluctuation frequency of the continuous phase flow channel by changing the frequency of the voltage signal input to the piezoelectric component, thereby adjusting the size of the output droplets of the microfluidic chip, thereby making the output droplet size of the microfluidic chip flexible and adjustable.

[0026] 3. The present invention integrates the piezoelectric component on the chip substrate and arranges the pressure fluctuation point directly in the main flow path, which improves the integration of the microfluidic chip. While reducing the size of the device, it helps to improve the response speed of the microfluidic chip when the input voltage signal changes.

[0027] 4. The present invention directly fixes the piezoelectric ceramic into the mounting tube, and then buries the entire piezoelectric component into the chip substrate for packaging. The production process is simple and the production cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0029] Figure 2 It is a bottom view schematic diagram of the present invention;

[0030] Figure 3 It is a step cross-sectional schematic diagram of the present invention (along Figure 2(obtained by step-by-step sectioning of the AA path);

[0031] Figure 4 A three-dimensional diagram of the chip substrate 1 of the present invention;

[0032] Figure 5 is a three-dimensional diagram of the piezoelectric component 2 of the present invention;

[0033] Figure 6 is a cross-sectional schematic diagram of the piezoelectric component 2 of the present invention;

[0034] Figure 7 A comparison chart of droplet generation changes of the microfluidic chip provided by the present invention under piezoelectric frequencies of 0 Hz-200 Hz;

[0035] Figure 8 A line graph showing the change in droplet generation frequency of the microfluidic chip provided by the present invention at a piezoelectric frequency of 0 Hz to 200 Hz;

[0036] Figure 9 A comparison chart of droplet generation changes of the microfluidic chip provided by the present invention at a voltage frequency of 36 Hz and voltage amplitudes of 30 V, 50 V, and 80 V;

[0037] Figure 10 A discrete point diagram showing the relationship between droplet generation frequency and voltage input frequency at different voltage amplitudes and voltage input frequencies for the microfluidic chip provided by the present invention;

[0038] Figure 11 This is a graph showing the response speed test results of the microfluidic chip provided by this paper. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the accompanying drawings.

[0040] Example 1

[0041] A microfluidic chip for controlling droplet size based on piezoelectric perturbations comprises a chip substrate 1 and a piezoelectric component 2. The chip substrate 1 is provided with a main flow path and a pressure fluctuation flow path. The main flow path includes a continuous phase input port 3, a discrete phase input port 4, an annular flow channel 5, an output flow channel 6, and an output port 7. The annular flow channel 5 and the output flow channel 6 are provided on the bottom surface of the chip substrate 1. The continuous phase input port 3, the discrete phase input port 4, and the output port 7 are all through-hole structures.

[0042] The continuous phase inlet 3 is connected to the annular flow channel 5 via a flow channel. The ends of the output flow channel 6 are connected to the discrete phase inlet 4 and the output channel 7, respectively. The output flow channel 6 intersects and connects with the annular flow channel 5. The junction of the output flow channel 6 and the annular flow channel 5 forms a droplet generation region. The output flow channel 6 is provided with a serpentine section to extend the flow channel length; this serpentine section is located between the droplet generation region and the output channel 7.

[0043] The pressure fluctuation flow path includes an initial input port 8, a bifurcated flow channel 9 and a piezoelectric chamber 10. The two piezoelectric chambers 10 are symmetrically arranged on both sides of the output flow channel 6. The initial input port 8 is connected to the two piezoelectric chambers 10 through the bifurcated flow channel 9; the two piezoelectric chambers 10 are respectively connected to the two pressure fluctuation points on the annular flow channel 5; the two pressure fluctuation points on the annular flow channel 5 are symmetrically arranged about the droplet generation area. The initial input port 8 and the bifurcated flow channel 9 are used to pass the continuous phase liquid into the two piezoelectric chambers 10 before droplet generation. After the piezoelectric chamber 10 is filled with the continuous phase liquid, the initial input port 8 needs to be sealed with a sealing plug.

[0044] Both piezoelectric chambers 10 contain piezoelectric assemblies 2. These assemblies expand or contract in response to changes in input voltage, resulting in changes in volume. Except for the connections to the bifurcated flow channel 9 and the annular flow channel 5, the piezoelectric chambers 10 are sealed, allowing the expansion and contraction of the piezoelectric assemblies 2 to generate pressure fluctuations by altering the volume within the chambers 10.

[0045] The piezoelectric assembly 2 includes a mounting tube 2-1, an end plate 2-2, wires 2-3, and a piezoelectric ceramic 2-4. The mounting tube 2-1 is fixed within the corresponding piezoelectric chamber 10. The end plate 2-2 is fixed to one end of the mounting tube 2-1. The piezoelectric ceramic 2-4 is an elongated strip and is positioned within the mounting tube 2-1. One end of the piezoelectric ceramic 2-4 is fixed to the end plate 2-2. The two electrodes of the piezoelectric ceramic 2-4 are connected by two wires 2-3 that pass through the end plate 2-2.

[0046] In this embodiment, the piezoelectric chamber 10 is a through-hole structure, the top of which is closed by an end plate 2 - 2 and sealed by silicone.

[0047] The dispersed phase liquid can carry target components such as drugs.

[0048] In this embodiment, the structure of the flow channel is a cross-focusing flow channel, the depth and width of which are both 200 microns, and the fluid inlet and outlet are both holes with a diameter of 6 mm. The selected piezoelectric ceramic is a rectangular stacked piezoelectric ceramic with a length, width and height of 1.65mm*1.65mm*5mm, a maximum driving voltage of 90V, and a maximum output displacement of 4 microns.

[0049] A bottom film 11 is provided on the bottom surface of the chip substrate 1; the bottom film 11 is used to seal the bottom of the continuous phase input port 3, the discrete phase input port 4, the annular flow channel 5, the output flow channel 6, the output port 7, the initial input port 8, the bifurcated flow channel 9 and the piezoelectric chamber 10.

[0050] During operation, the same periodically varying voltage signal is applied to the two piezoelectric components 2, causing the pressure within the two piezoelectric chambers 10 to fluctuate periodically. This, in turn, causes the pressure at the two pressure fluctuation points on the annular flow channel 5 to fluctuate periodically. When the pressure at these two pressure fluctuation points on the annular flow channel 5 increases, the discrete phase fluid is pinched off prematurely to produce droplets of a specified size. By varying the frequency of the voltage signal within a certain frequency range, the output droplet size can be controllably varied.

[0051] Example 2

[0052] The test process of the droplet output characteristics of the aforementioned microfluidic chip as a function of the voltage signal input frequency:

[0053] In this embodiment, the dispersed phase liquid is pure water, and the continuous phase liquid is paraffin oil (CAS No. 8042-37-5); the flow rate of both is set to 0.7 ml / h; no piezoelectric vibration excitation is applied, and the voltage signal input frequency is 10 Hz, 15 Hz, 20 Hz, 30 Hz, 35 Hz, 40 Hz, 45 Hz, 50 Hz, 60 Hz, 70 Hz, 80 Hz, 120 Hz, and 200 Hz. The droplet generation process is photographed and observed with a high-speed camera, and the droplet size and the frequency of droplet generation are measured with the aid of measurement software. The comparison of droplets generated under different conditions is shown in Figure 2. Figure 7 and 8 The above voltage signal adopts a sine signal with an amplitude of 80V.

[0054] Among them, when no piezoelectric vibration excitation is applied, the average equivalent diameter of the droplets is 149 microns, and the average droplet generation frequency is 15Hz. When 10Hz piezoelectric vibration excitation is applied, the average equivalent diameter of the droplets is 166 microns, and the average droplet generation frequency is 10Hz. When 15Hz piezoelectric vibration excitation is applied, the average equivalent diameter of the droplets is 145 microns, and the average droplet generation frequency is 15Hz. When 20Hz piezoelectric vibration excitation is applied, the average equivalent diameter of the droplets is 132 microns, and the average droplet generation frequency is 20Hz. When 25Hz piezoelectric vibration excitation is applied, the average equivalent diameter of the droplets is 122 microns, and the average droplet generation frequency is 25Hz. When 30Hz piezoelectric vibration excitation is applied, the average equivalent diameter of the droplets is 115 microns, and the average droplet generation frequency is 30Hz. When 35Hz piezoelectric vibration excitation is applied, the average equivalent diameter of the droplets is 109 microns, and the average droplet generation frequency is 35Hz. When 45Hz piezoelectric vibration excitation is applied, the average equivalent diameter of the droplets is The average equivalent diameter of the droplets is 128 microns, and the average droplet generation frequency is 22.5Hz. When 50Hz piezoelectric vibration excitation is applied, the average equivalent diameter of the droplets is 122 microns, and the average droplet generation frequency is 25Hz. When 60Hz piezoelectric vibration excitation is applied, the average equivalent diameter of the droplets is 152 microns, and the average droplet generation frequency is 15Hz. When 70Hz piezoelectric vibration excitation is applied, the average equivalent diameter of the droplets is 151 microns, and the average droplet generation frequency is 14Hz. When 80Hz piezoelectric vibration excitation is applied, the average equivalent diameter of the droplets is 154 microns, and the average droplet generation frequency is 13Hz. When 120Hz piezoelectric vibration excitation is applied, the average equivalent diameter of the droplets is 150 microns, and the average droplet generation frequency is 13Hz. When 200Hz piezoelectric vibration excitation is applied, the average equivalent diameter of the droplets is 153 microns, and the average droplet generation frequency is 13Hz. After testing, it was found that when the piezoelectric frequency was less than 10Hz, the droplet generation was unstable or the droplet size changed periodically; when the piezoelectric frequency was between 10Hz-38Hz, the droplet generation was stable, the generation frequency was synchronized with the piezoelectric ceramic vibration frequency, and the droplet size changed significantly.

[0055] When the voltage signal amplitude is fixed at 80V and the piezoelectric frequency is further increased to 40Hz, the droplet size changes periodically; when the frequency is increased to 45Hz; the droplet generation frequency is half of the piezoelectric vibration frequency. After continuing to increase the piezoelectric vibration frequency to 120Hz, further increasing the piezoelectric frequency has no obvious effect on the size and frequency of droplet generation.

[0056] Example 3

[0057] The test process of the droplet output characteristics of the aforementioned microfluidic chip as the voltage signal amplitude changes:

[0058] In this embodiment, the test process is the same as that of embodiment 2, except that the frequency of the piezoelectric sinusoidal signal is fixed at 36 Hz; the voltage amplitude is changed to 30 V, 50 V, and 80 V in sequence, and the size of the droplets generated is related to the frequency. Figure 9 shown.

[0059] from Figure 9 It can be seen that when the voltage frequency is fixed at 36 Hz and the voltage amplitude is changed to 30 V, 50 V, and 80 V respectively, the droplet generation frequency is 18 Hz, 18 Hz, and 36 Hz respectively, indicating that the voltage amplitude will also affect the frequency range in which the droplet generation frequency is synchronized with the voltage frequency.

[0060] Using the data obtained in Examples 2 and 3, as well as the droplet generation frequencies under the conditions of multiple voltage amplitudes and input frequencies, a discrete point diagram of the relationship between the droplet generation frequency and the voltage input frequency under different voltage amplitudes and voltage input frequencies is obtained as shown in FIG. Figure 10 As shown; Figure 10 In the figure, the gray dots represent the relationship between the droplet generation frequency fd and the voltage input frequency fp, which is fp / fd=k=1; the red dots represent the relationship between the droplet generation frequency fd and the voltage input frequency fp, which is fp / fd=k=2; and the blue dots represent the relationship between the droplet generation frequency fd and the voltage input frequency fp, which is fp / fd=k=3.

[0061] In the k=1 interval, the amplitude and frequency of the sinusoidal signal of the control signal generator can be calculated according to the formula Control the droplet size; where R is the equivalent radius of the output droplet; f p is the frequency of the sinusoidal signal; Q d is the dispersed phase flow rate.

[0062] Example 4

[0063] The response speed test process of the aforementioned microfluidic chip's output droplet size adjustment is as follows:

[0064] When a voltage signal with an amplitude of 80V and a sinusoidal frequency of 30Hz is temporarily applied to the microfluidic chip without a voltage signal, the changes of the droplets in the channel are as follows: Figure 11 shown; from Figure 11 As can be seen from the figure, the output droplet size switches rapidly, indicating that the response speed of the microfluidic chip provided in Example 1 is very fast.

Claims

1. A microfluidic chip for controlling the size of droplet generation based on piezoelectric perturbations, comprising a chip substrate (1); characterized in that: It also includes a piezoelectric component (2); a main flow path and a pressure fluctuation flow path are provided on the chip substrate (1); a droplet generation area is provided on the main flow path; the pressure fluctuation flow path includes a piezoelectric chamber (10); two piezoelectric chambers (10) are respectively connected to two pressure fluctuation points on the main flow path; the two pressure fluctuation points are respectively located on both sides of the droplet generation area; a piezoelectric component (2) is installed in each of the two piezoelectric chambers (10); the piezoelectric component (2) can change its own volume by adjusting the input voltage, adjust the pressure in the piezoelectric chamber (10), and cause the pressure of the two pressure fluctuation points to change.

2. A microfluidic chip for controlling droplet size based on piezoelectric perturbation according to claim 1, characterized in that: The piezoelectric component (2) includes a mounting tube (2-1), an end plate (2-2), a wire (2-3) and a piezoelectric ceramic (2-4); the mounting tube (2-1) is fixed in a corresponding piezoelectric chamber (10); the end plate (2-2) is fixed to one end of the mounting tube (2-1); the piezoelectric ceramic (2-4) is arranged in the mounting tube (2-1); one end of the piezoelectric ceramic (2-4) is fixed to the end plate (2-2); and two electrodes of the piezoelectric ceramic (2-4) are led out through two wires (2-3) passing through the end plate (2-2).

3. The microfluidic chip for controlling droplet size based on piezoelectric perturbation according to claim 1, characterized in that: The main flow path includes a continuous phase input port (3), a discrete phase input port (4), an annular flow channel (5), an output flow channel (6) and an output port (7); the continuous phase input port (3) is connected to the annular flow channel (5); both ends of the output flow channel (6) are connected to the discrete phase input port (4) and the output port (7), respectively; the output flow channel (6) and the annular flow channel (5) intersect and are connected; the connection between the output flow channel (6) and the annular flow channel (5) forms a droplet generation area; the two pressure fluctuation points on the main flow path are located on the annular flow channel (5).

4. The microfluidic chip for controlling droplet size based on piezoelectric perturbation according to claim 3, characterized in that: During operation, a periodically changing voltage signal is input to the piezoelectric component (2), causing the continuous phase liquid passing through two pressure fluctuation points to generate pressure fluctuations, so that the droplet generation area continuously generates droplets of the discrete phase liquid corresponding to the frequency and voltage amplitude of the voltage signal.

5. The microfluidic chip for controlling droplet size based on piezoelectric perturbation according to claim 3, characterized in that: The output flow channel (6) is provided with a serpentine section; the serpentine section is arranged between the droplet generation area and the output port (7).

6. The microfluidic chip for controlling droplet size based on piezoelectric perturbation according to claim 3, characterized in that: A base film (11) is provided on the chip substrate (1); the base film (11) is used to seal the openings of the continuous phase input port (3), the discrete phase input port (4), the annular flow channel (5), the output flow channel (6), the output port (7), the initial input port (8), the bifurcated flow channel (9) and the piezoelectric chamber (10) on the bottom surface of the chip substrate (1).

7. The microfluidic chip for controlling droplet size based on piezoelectric perturbation according to claim 1, characterized in that: The pressure fluctuation flow path further comprises an initial input port (8) and a bifurcated flow channel (9); the initial input port (8) is connected to the two piezoelectric chambers (10) via the bifurcated flow channel (9); the initial input port (8) and the bifurcated flow channel (9) are used to fill the two piezoelectric chambers (10) with a continuous phase liquid before the microfluidic chip is used; during the use of the microfluidic chip, the initial input port (8) is closed.

8. The microfluidic chip for controlling droplet size based on piezoelectric perturbation according to claim 1, characterized in that: The two pressure fluctuation points are symmetrically arranged with respect to the droplet generation region.

9. A droplet generation method, characterized in that: A microfluidic chip according to any one of claims 1 to 8 is used; the droplet generation method comprises the following steps: Step 1: introducing a continuous phase liquid into the two piezoelectric chambers (10) so that the two piezoelectric chambers (10) are filled with the mobile phase liquid; Step 2: continuously inputting the continuous phase liquid into the continuous phase input port (3); continuously inputting the discrete phase liquid into the discrete phase input port (4); Step 3: a periodic voltage signal is applied to the piezoelectric component (2), causing the piezoelectric component (2) to deform periodically; the pressures at the two pressure fluctuation points fluctuate periodically; during the process of increasing the pressures at the two pressure fluctuation points, the continuous phase liquid on both sides of the droplet generation region tends to pinch off the discrete phase liquid in the droplet generation region, thereby changing the size of the discrete phase droplets generated in the droplet generation region; Step 4: Adjust the frequency of the voltage signal passed into the piezoelectric component (2) so that the size of the generated discrete phase droplets is adjusted to the target value.

10. A droplet generation method according to claim 9, characterized in that: In step 4, the relationship between the frequency of the voltage signal and the size of the generated discrete phase droplets is obtained by pre-calibration.

Images