CN114199629A

CN114199629A - A kind of microfluidic automatic quantitative sampling method and system

Info

Publication number: CN114199629A
Application number: CN202111388204.3A
Authority: CN
Inventors: 夏焕明; 茅成跃; 周严
Original assignee: Nanjing University of Science and Technology
Current assignee: Nanjing University of Science and Technology
Priority date: 2021-11-22
Filing date: 2021-11-22
Publication date: 2022-03-18

Abstract

The invention discloses a microfluid automatic quantitative sampling method and a system, wherein the system comprises a capacitance metering chip, a capacitance signal acquisition module, a driving and controlling module and a liquid supply and driving unit; the capacitance signal acquisition module is used for acquiring capacitance signals of the metering chip and transmitting the capacitance signals to the driving and control module; the driving and controlling module is used for obtaining a reagent with a set volume according to the capacitance of the capacitive metering chip and controlling the on-off of the liquid supply and driving unit so as to control the volume of the reagent entering the capacitive metering chip and push out the reagent to obtain a measured reagent; and the liquid supply and drive unit is used for supplying the reagent into the capacitive metering chip and pushing the measured reagent out of the sampling chamber. The method realizes the automatic calibration function of different sampling media, and further automatically samples the different sampling media according to the set value.

Description

Automatic quantitative sampling method and system for microfluid

Technical Field

The invention belongs to the technical field of microfluidics and chip experiments, and particularly relates to an automatic quantitative sampling method and system for microfluidics.

Background

With the continuous development of the application of the microfluidic technology in various fields, the metering requirement for fluid sample injection is higher and higher. The accuracy of the sampling quantity often directly affects the analysis and detection results, thereby determining the overall performance of the lab-on-a-chip system. Compared with macroscopic flow, the factors influencing the microfluidic flow are mainly surface tension and viscosity, and the corresponding operation technology is more complicated. The automatic liquid-transfering platform on the market at present is usually large in size, is difficult to integrate with a lab-on-a-chip system, and has a large sampling error when the sampling quantity is small. The traditional mechanical pumps such as injection pumps, peristaltic pumps and the like can also control the sample injection amount to a certain extent, but because a connecting device between the pump and the microfluidic chip has certain elasticity, large sample injection errors are easily generated under the influence of water capacity effect, and the traditional mechanical pumps are not suitable for controlling the sample amount below the micro-scale. Another commonly used quantitative sampling method in microfluidic systems is to control the sampling volume by using the size of the chamber, but since the volume of the chamber cannot be changed at will after the device is processed, the sampling volume is fixed and lacks flexibility in control.

Disclosure of Invention

The invention provides an automatic quantitative sampling method and system for microfluid, aiming at the defects of the quantitative sampling technology in the current microfluidic field.

The technical solution for realizing the purpose of the invention is as follows:

a microfluid automatic sampling method, inject different setting amount of reagent liquid into the capacitive metering chip many times, and gather the electric capacity signal, fit out the calibration curve according to the relation of the volume of the reagent and magnitude of the corresponding electric capacity;

during sampling, the reagent passes through the capacitive metering chip, the corresponding reagent volume is obtained according to the calibration curve, and the reagent in the capacitive metering chip is pushed out through hydraulic pressure or air pressure to obtain the measured reagent.

A microfluidic autosampler system, comprising:

the capacitance type metering chip is provided with a liquid inlet, a throttling port, a sampling cavity and a liquid outlet, wherein the liquid inlet is used as a flow inlet of a reagent and flows out of the liquid outlet after passing through the sampling cavity; a capacitor plate is arranged in the sampling cavity; the throttling port is used for introducing gas or liquid to push out the reagent in the metering chip;

the capacitance signal acquisition module is used for acquiring capacitance signals of the metering chip and transmitting the capacitance signals to the driving and control module;

the driving and controlling module is provided with a corresponding relation between the volume of the reagent and the corresponding capacitance, and is used for obtaining the reagent with a set volume according to the capacitance of the capacitance metering chip and controlling the on-off of the liquid supply and driving unit so as to control the volume of the reagent entering the capacitance metering chip and push out the reagent to obtain the measured reagent;

and the liquid supply and drive unit is used for supplying the reagent into the capacitive metering chip and pushing the measured reagent out of the sampling chamber.

Compared with the prior art, the invention has the following remarkable advantages:

1. the invention reduces the lower limit of the sampling amount and improves the precision of sampling trace liquid by the design of a miniaturized liquid volume sensor;

2. according to the invention, the capacitance signal is converted into the frequency signal, so that the drift of the capacitance signal is reduced, and the stability and the sampling precision of the system are improved;

3. according to the invention, through programmed design, automatic calibration and automatic quantitative sampling of different reagents are realized, and errors caused by manual operation are avoided;

4. the invention has expansibility, and can realize sampling of a plurality of ranges and different media through parallel design;

5. the invention has programmable function, and can set sampling quantity and sampling sequence of each medium according to specific application, thereby having good universality.

Drawings

FIG. 1 is a schematic diagram of the system components and operation of the present invention;

FIG. 2 is a system composition and structure diagram of example 1;

FIG. 3 is a cross-sectional view of the capacitive metrology chip of example 1;

FIG. 4 is a diagram of a multi-channel parallel sampling system in example 2;

FIG. 5 is a system constitution and a structural diagram in example 3;

FIG. 6 is a schematic diagram showing the structure of a capacitive metrology chip and the sampling process in example 3;

FIG. 7 is a graph showing the frequency change in the calibration of different reagents in examples 1 to 3;

FIG. 8 is a graph showing the sampling accuracy of various media in examples 1-3 in a range of 12. mu.l;

FIG. 9 is a graph showing the sampling accuracy of the reagent of examples 1 to 3 in a range of 20. mu.l.

Detailed Description

The invention is further described with reference to the following figures and embodiments.

Example 1

Referring to fig. 1, the automatic quantitative microfluidic sampling system of this embodiment comprises a capacitive metering chip 1, a capacitance-frequency converter 2, a driving and controlling module (in this embodiment, a single chip microcomputer is used), and a liquid supply and driving unit;

referring to fig. 3, the capacitive metering chip 1 includes a liquid inlet 4, a choke 5, a sampling chamber 6, a liquid outlet 7, an insulating layer 8, and a capacitor plate 9. The liquid inlet 4 and the throttle orifice 5 are positioned at the front end of a sampling cavity 6, the sampling cavity is of a planar cavity structure, and the capacitor plates 9 are respectively positioned at two opposite sides of the cavity. The insulating layer 8 is arranged in the sampling chamber 6 and used for isolating a reagent in the sampling chamber 6 from the capacitor plate 9, the chip substrate can be selected from but not limited to high molecular polymers (such as FR-4), glass, ceramic and the like, the insulating layer 8 can be PMMA (polymethyl methacrylate), PC (polycarbonate) thin films, insulating spraying materials and the like, the main structure of the capacitor plate 9 corresponds to the shape and size of the chamber, and the materials include but not limited to gold, silver, ITO and the like. A one-way valve 10 is arranged at the position where the metering chip inlet gas 5 is connected with the sampling chamber 6, and a hydrophobic capillary valve can be adopted. The liquid to be sampled flows into the sampling chamber through the liquid inlet 4, in the process, the one-way valve 10 prevents the liquid from flowing out through the throttling port 5. When the measured amount of liquid reaches the set value, the flow is terminated and a pneumatic driving pressure is applied to the liquid sample via the throttle 5 to take it out.

In this embodiment, the capacitance-frequency conversion module 2 uses an ICL8038 precision oscillation circuit as a capacitance signal acquisition module, and is connected to the two capacitance plates 9 of the capacitance metering chip 1 through a wire, so that a capacitance signal can be converted into a frequency signal. When the sampled liquid enters the capacitive metering chip sampling chamber 6, the capacitance and frequency magnitudes change with the volume of the influent liquid. The capacitance-to-frequency conversion module may also employ other circuits capable of converting a capacitance signal to a frequency signal.

The driving and controlling module 3 is composed of a single chip microcomputer, a fluid driving device and a flow control device, wherein the fluid driving device can be an air pump, an injection pump and the like, and the fluid control device can be a one-way valve, a drain valve and the like. The frequency signal generated by the capacitance-frequency conversion module 2 can be identified, and automatic calibration of different media can be realized by utilizing the signal. During calibration, the sampling medium gradually flows into and fills the sampling chamber 6, and in the process, the drive and control module 3 continuously records the change of the frequency signal, so as to obtain a frequency-sampling amount curve (i.e. a calibration curve corresponding to the capacitance and the reagent volume) according to the measuring range of the sampling chamber 6. During sampling, the driving and control module 3 can continuously monitor the volume of the inflowing liquid according to a frequency-sampling quantity curve obtained by calibration when the liquid medium flows into the sampling chamber 6, and control the liquid supply and driving unit to immediately stop the flow of the liquid medium when the sampling quantity reaches a set value, thereby realizing the function of automatic quantitative sampling.

The liquid supply and driving unit comprises a liquid supply driving unit, a liquid pushing driving unit and a reagent storage tank (used for storing reagents), the liquid supply driving unit and the liquid pushing driving unit can adopt the same power source as a driving device, or can adopt different power sources as the driving device, and the power sources can adopt an injection pump, a peristaltic pump, a pneumatic pump and the like. The liquid medium and the driving gas can adopt independent driving devices, and can also adopt the same device to realize the conversion between a liquid channel and a pneumatic control channel by using a steering pump. When a certain amount of liquid medium needs to be taken out, the liquid medium can be taken out by adopting air pressure driving, and other liquids such as buffer solution and the like can also be used as driving media.

Referring to fig. 2, in this embodiment, the liquid supply driving unit and the liquid pushing driving unit both use an air pump, one path of the air pump is connected to the reagent storage tank through a three-way valve, and the other path is connected to a one-way valve at the throttling port of the metering chip through a two-way valve. When a sample is measured, the two-way valve is closed to control the opening of the three-way valve, and the singlechip controls the on-off of the three-way valve by utilizing a Pulse Width Modulation (PWM) technology to drive the reagent to flow into a sampling chamber in the metering chip in a balanced manner. When reagent enters the sampling chamber 6, i.e. between the two capacitor plates 9, the capacitance varies with the volume of reagent flowing in. The calibration curve is derived from the change in frequency from empty to reagent filling the sampling chamber, see figure 7. The sampling chamber 6 is then emptied ready for sampling. When the reagent is measured, a frequency value corresponding to the sampling amount is calculated according to the standard curve. The reagent is then driven to flow gradually into the sampling chamber 6 while the frequency signal is detected, and when it reaches a target value, the three-way valve is closed, the pressure built up in the gas passage flows out through the three-way valve vent, and the flow of reagent is terminated. When sampling, the two-way valve is controlled to be opened, and the reagent which is measured in the sampling chamber 6 is conveyed to the downstream channel.

In this embodiment, the one-way valve arranged in the liquid pushing driving mode is a capillary trap and is arranged at the throttling port 5 of the metering chip, and the capillary pressure of the capillary trap at the throttling port 5 is higher than the liquid supply driving pressure of the air supply pump, so that the reagent is prevented from leaking from the air inlet 5. When sampling, the driving gas flows in through the capillary trap, and the measured reagent is taken out. In the process, the one-way valve is closed to avoid reagent backflow, so that the next sampling operation is facilitated.

FIG. 8 is a result of sampling accuracy test of two different reagents by using a capacitive metering chip with a full scale of 12 μ L, and data fitting is performed on sampling points of the two reagents, and a fitting straight line is close to a diagonal line, which shows that the sampling effect is good and the error is low; FIG. 9 shows the results of the sample accuracy test using a 20 μ L full scale capacitive metrology chip, with the fitted line also close to the diagonal.

Example 2

In this embodiment, the automatic microfluidic sampling system in the embodiment performs sampling operation on multiple reagents simultaneously in a parallel manner, and the structural composition of the system is shown in fig. 4. In this example, two different reagents were sampled simultaneously using a 12 μ L full scale capacitive metrology chip. The air pump is also used as a driving source, and the reagent channel and the sampling driving channel are controlled by a plurality of three-way valves.

Because the dielectric constants of different media are different, the capacitance-frequency conversion module comprises a plurality of capacitance-frequency conversion units, so that capacitance signals generated when different media flow into the sampling chamber can be converted into frequency signals respectively, and the frequency signals are transmitted to the driving and control module. The driving and control module respectively and automatically calibrates the media according to the frequency signals of the media, as shown in fig. 7. And samples were taken according to the respective calibration curves.

Example 3:

on the basis of embodiment 1, in this embodiment, a membrane type check valve is used to replace the drain valve 10 at the front end of the sampling chamber, two precise injection pumps are used to replace an air pump as a driving source, and a driving motor of the injection pump is controlled by a single chip microcomputer, as shown in fig. 5. When calibrating and measuring the reagent, the injection pump 1 flows the reagent into the sampling chamber; during sampling, the syringe pump 2 takes out the measured reagent with a buffer solution, as shown in FIG. 6.

Claims

1. a microfluidic automatic sampling method, it is characterized in that, the reagent liquid that repeatedly passes into different setting amounts passes into capacitive metering chip, and collects capacitance signal, according to the relationship between the volume of this reagent and the corresponding capacitance size is simulated. Combine the calibration curve;

When sampling, the reagent passes through the capacitive metering chip, and the corresponding reagent volume is obtained according to the calibration curve, and the reagent in the capacitive metering chip is pushed out by hydraulic pressure or air pressure to obtain the measured reagent.

2. a microfluidic automatic sampling system, is characterized in that, comprises:

The capacitive metering chip is provided with a liquid inlet, a throttling port, a sampling chamber and a liquid outlet. The liquid inlet serves as an inflow port for reagents, and flows out from the liquid outlet after passing through the sampling chamber; the sampling chamber The chamber is provided with a capacitor plate; the throttling port is used to introduce gas or liquid to push out the reagent in the metering chip;

Capacitance signal acquisition module, used to collect the capacitance signal of the metering chip and transmit it to the drive and control module;

The drive and control module has a corresponding relationship between the volume of the reagent and the corresponding capacitance, which is used to obtain the set volume of reagent according to the capacitance of the capacitive metering chip and control the on-off of the liquid supply and the drive unit to control the entry Capacitance measuring the volume of the reagent in the chip and pushing out the reagent to obtain the measured reagent;

The liquid supply and drive unit is used for supplying reagents into the capacitive metering chip and pushing out the measured reagents from the sampling chamber.

3 . The microfluidic automatic sampling system according to claim 2 , wherein the sampling chamber is provided with an insulating layer that isolates the reagent from contacting the capacitor. 4 .

4. The microfluidic automatic sampling system according to claim 2, wherein the capacitance signal acquisition module collects the capacitance signal of the capacitance plate, and converts the capacitance signal into a frequency signal and transmits it to the drive and control module .

5. The microfluidic automatic sampling system according to claim 2, wherein the liquid supply and driving unit comprises a liquid supply driving unit, a liquid pushing driving unit, and a reagent storage tank;

The liquid supply driving unit is communicated with the liquid inlet of the capacitive metering chip through the reagent storage tank and the one-way valve, and is used for pushing the reagent in the reagent storage tank into the capacitive metering chip;

The liquid pushing drive is communicated with the throttling port of the capacitive metering chip through a one-way valve, and the unit is used to push the measured reagent out of the sampling chamber;

The one-way valve stops the liquid flow direction of the capacitive metering chip in the reverse direction.

6 . The microfluidic automatic sampling system according to claim 5 , wherein the liquid supply driving unit and the liquid pushing driving unit can use the same power source as the driving device, or can use different power sources as the driving device. 7 .

7 . The microfluidic automatic sampling system according to claim 6 , wherein the driving source is a syringe pump, a peristaltic pump or a pneumatic pump. 8 .

8 . The microfluidic automatic sampling system according to claim 2 , wherein a plurality of capacitive signal acquisition modules and a plurality of capacitive metering chips are arranged in parallel, and the driving and control modules are provided with reagents of various media. 9 . The corresponding relationship between the volume and the corresponding capacitance is obtained according to the capacitance of the reagent in the corresponding medium to obtain the amount of the reagent in the corresponding medium.

9 . The microfluidic automatic sampling system according to claim 7 , wherein when the power source of the push liquid drive is an air pump, the one-way valve provided is a capillary trap, which is provided at the orifice of the metering chip, 10 . The capillary pressure of the trap is higher than the drive pressure of the air supply pump.