CN106323727B - Particle separation device and method based on liquid pulling effect in microchannel - Google Patents

Abstract

The invention discloses a particle separation device and method based on the liquid pulling force effect in a microchannel. The device includes a microfluidic chip, a control module and a micro injection pump. The microfluidic chip is provided with a microfluidic chip main body and a substrate sequentially from top to bottom. The microfluidic chip main body is concavely engraved with N separation channels connected end to end in sequence. Both ends are provided with liquid storage holes; the control module is connected with the electromagnetic microvalve placed at a certain position behind the junction hole in the separation channel, and the opening and disconnection of the separation channel are realized by adjusting the action of the electromagnetic microvalve; the micro injection The pump communicates with the liquid inlet hole of the first separation channel, and adjusts the speed of injecting air to promote the flow rate of the liquid. The device has the advantages of low cost, simple structure and rapid on-line separation.

Description

A particle separation device and method based on liquid pulling effect in microchannel

technical field

The invention relates to the technical field of separation of solid particles of different sizes in liquid, in particular to a particle separation device and method based on the liquid pulling force effect in a microchannel.

Background technique

It is of great significance to realize the separation of particles of different sizes in liquid. Taking lubricating oil as an example, lubricating liquid is widely used in power machinery equipment as industrial "blood". In fact, lubricating liquid contains a large number of pollutants, among which solid pollutants are the most harmful. The hardness of solid particles is high, which is easy to cause wear and tear on the moving parts of mechanical equipment; at the same time, these solid particles carry rich information about the working state of the friction pair of power mechanical equipment. It provides a powerful reference for predicting the fault state of the mechanical equipment. In order to ensure the safe operation of mechanical equipment and reduce maintenance costs, real-time detection of the operating status has become an indispensable part of mechanical equipment status detection, and the detection of lubricating oil is a very important part of it.

At present, the commonly used particle separation technologies of different sizes can be divided into the following categories according to different working principles:

1) Centrifugal method: For the centrifugal separation method, in order to achieve the required separation effect, all fluid systems must be in a state of motion. This requirement cannot be met in some cases, and it will also bring additional difficulties to the operation of the detection and analysis system.

2) Dynamic method: For the dynamic separation method, the geometry of the fixed obstacle will determine the separation efficiency of the system. And for those situations that require changing the separation parameters, this will greatly limit the use of this method.

3) Dielectrophoresis method: For the dielectrophoresis separation method, the system needs to construct a very complex chip, and it is difficult to collect the separated particles.

4) Magnetic separation method: For the magnetic separation method, the particles must be ferromagnetic particles, which will greatly limit the range of separated particles.

5) Acoustic method: For the acoustic separation method, considering that the sound force is proportional to the cube of the particle radius, this method is generally not suitable for small particles.

The above-mentioned methods all have disadvantages such as large energy supply demand, large amount of reagents, long separation time, high separation cost, etc., have relatively large limitations, and cannot fully meet the current low-cost, fast and simple detection requirements in the field of particle separation.

Contents of the invention

In view of the defects in the prior art, the object of the present invention is to provide a separation device for particles of different sizes in liquids with low cost, simple structure, fast on-line separation, and strong promotion in the field. The analysis provides a reference to realize the liquid on-line detection.

To achieve the above object, the technical scheme of the present invention is as follows:

A particle separation device based on the pulling effect of liquid in a microchannel, which includes a microfluidic chip, a control module and an air injection element, characterized in that:

The microfluidic chip includes a microfluidic chip body on which N separation channels connected end-to-end in sequence are engraved on it, and a substrate that cooperates with the microfluidic chip body to form a liquid flow channel, where N≧2 ;

And the beginning end of the first separation channel is provided with a liquid inlet hole, and the end of the Nth separation channel is provided with a waste liquid hole, so that the two separation channels connected end to end are connected through the junction hole and after the corresponding junction hole A channel control element is arranged on a separation channel to control the on-off of the separation channel;

The control module is respectively connected to each channel control element provided on each separation channel, so as to control the corresponding channel control element according to the need to realize the control process of each separation channel on and off;

The air injection element communicates with the liquid inlet hole to push air into the liquid inlet hole at a set speed.

Further, as preferred of the present invention:

The air injection unit adopts a micro syringe pump.

Further, as preferred of the present invention:

The channel control element adopts an electromagnetic microvalve.

Further, as preferred of the present invention:

The separation channels are all rectangular channels.

Another object of the present invention is to provide a method for particle separation based on the above-mentioned particle separation device, which is characterized in that it includes the following steps:

1) First adjust the control module to control the control elements of each channel, so that the control elements of each channel are in a closed state;

2) Add a certain amount of liquid sample dropwise into the liquid inlet hole, so that the liquid sample flows through the entire first separation channel. After the particles in the liquid settle on the bottom wall of the first separation channel, they flow into the liquid inlet at a constant speed. Push air into the hole until the liquid in the first separation channel converges into the first junction hole;

3) Adjust the control module to open the first channel control element, so that the liquid sample in the first junction hole flows to the second separation channel, and after the particles in the liquid settle on the bottom wall of the second separation channel, increase the air injection Velocity until the liquid in the second separation channel converges into the second junction hole;

4) According to step 3, turn on the remaining channel control elements in sequence until the liquid in the Nth separation channel converges into the waste liquid hole.

Compared with prior art, the beneficial effect of the present invention:

1) The invention uses a microfluidic chip as a platform for separating particles of different sizes in the liquid, and the related separation equipment is small in size and light in weight; compared with large and expensive particle separation equipment, it has the advantages of simple operation, convenient operation, and portability, etc. features.

2) The separation principle and separation technology adopted in the present invention are relatively simple, and the design of the microfluidic channel is simple, easy to implement, and has strong practical operability.

3) It is not necessary to process and mark the separation channel and the particles to be separated before separation by using the present invention, and the separation efficiency is high.

Description of drawings

Fig. 1 is the structural representation of separating device of the present invention;

Fig. 2 is a structural schematic diagram of the microfluidic chip of the present invention;

Fig. 3 and Fig. 4 are the figure of experiment result of embodiment.

In the figure: 1. Liquid inlet hole, 2. First junction hole, 3. Second junction hole, 4. Waste liquid hole, 5. First separation channel, 6. Second separation channel, 7. Third separation channel, 8. The first electromagnetic microvalve, 9. The second electromagnetic microvalve, 10. The micro injection pump, 11. The control module, 12. The main body of the microfluidic chip, 13. The substrate.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the implementation of the present invention. example, not all examples. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The so-called liquid pull effect refers to relying on the viscous effect of the liquid on the particles, so that the liquid can drive the particles to move together. The liquid moves along the flow direction under the push of the air. As the interface between the air and the liquid moves forward, a layer of liquid film will remain on the bottom wall of the channel, and particles smaller than the thickness of the liquid film will be left behind. , at this time, the frictional resistance of the particles at the bottom of the channel is greater than the pulling force of the liquid on the particles; while the remaining large particles are subjected to a greater pulling force of the liquid, and will continue to move forward with the liquid, which can separate particles of different sizes. The principle of particle sorting is realized by controlling the speed of pushing the air to control the moving speed of the interface between the air and the liquid. The faster the air pushes, the greater the thickness of the liquid film left, and the particles that can be left inside the liquid film The larger the size.

Based on the above-mentioned design background, the present invention designs a particle separation device and method based on the liquid pulling force effect in the microchannel. The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific examples:

Specific embodiment: as shown in Figure 1, a particle separation device based on the liquid pulling force effect in the microchannel includes: a microfluidic chip, and the microfluidic chip includes a microfluidic chip body 12 sequentially arranged from top to bottom and the substrate 13; the main body 12 of the microfluidic chip is concavely engraved with 3 separation channels connected end to end for separating particles of different sizes in the liquid; the 3 separation channels are all rectangular channels, and the 3 separation channels are The channels sequentially include a liquid inlet hole 1 for oil sample injection at the beginning of the first separation channel, junction holes 2 and 3 at the junction of two separation channels, and a hole at the end of the third separation channel. Waste hole 4.

The first electromagnetic microvalve 8 and the second electromagnetic microvalve 9 are respectively located at a certain distance behind the junction hole 2 between the first separation channel 5 and the second separation channel 6, the second separation channel 6 and the third separation channel 7 A certain distance behind the junction hole 3 between the first separation channel 5; when the first separation channel 5 separates the particles, the first electromagnetic microvalve 8 is closed; after the particle separation of the first separation channel 5 is completed, the first electromagnetic microvalve 8 is opened, and the second The electromagnetic microvalve 9 is closed; after the particle separation in the second separation channel 6 is completed, the second electromagnetic microvalve 9 is opened.

The control module 11 is connected to the channel control element placed in each channel, that is, the electromagnetic microvalve, and is used to control the opening and closing of the first electromagnetic microvalve 8 and the second electromagnetic microvalve 9, so as to realize the separation channel Open circuit and open circuit to prepare for the separation of particles in the remaining liquid in the next stage;

The micro-injection pump 10 communicates with the liquid inlet hole of the first separation channel, and pushes air into the liquid inlet hole at a specific speed, so that the air pushes the liquid in the channel to flow. The movement of the interface will leave a layer of liquid film in the area where the air pushes through. By controlling the speed of the air to control the movement speed of the interface between the air and the liquid, the thickness of the liquid film attached to the bottom surface of the channel is controlled, and the size is smaller than Particles with the thickness of the liquid film will be left behind, and large-sized particles will move forward with the movement of the interface, thus realizing the separation of particles of different sizes.

The following will take solid particles of different sizes in lubricating oil as an example to separate,

The device for separating particles of different sizes in lubricating oil is shown in FIG. 1 , which is mainly composed of a microfluidic chip, an electromagnetic microvalve, an additional micro injection pump 10 , and a control module 11 . As shown in Figure 2, the microfluidic chip is composed of a microfluidic chip main body 12 and a substrate 13, wherein the microfluidic chip main body 12 is made of PDMS (polydimethylsiloxane) material, and the substrate 13 is made of PMMA (polydimethylsiloxane) material. Methyl methacrylate), that is, plexiglass. There is good adhesion between PDMS material and PMMA material, and it has good chemical inertness; and it can be seen from Figure 2 that there are 3 separation channels on the main body of the microfluidic chip to complete the separation from 3 different sizes in the liquid. Particle separation process; at the same time, the microfluidic chip main body 12 is sequentially provided with a liquid sample inlet hole 1, a first separation channel 5, a first junction hole 2, a first electromagnetic microvalve 8, and a second separation hole in the order of particle separation. Channel 6, the second junction hole 3, the second electromagnetic microvalve 9, the third separation channel 7, and the waste liquid hole 4; the corresponding example diagrams of the experimental results are shown in Fig. 3 and Fig. 4 .

The method for particle separation based on the above-mentioned particle separation device comprises the following steps

1) First, adjust the control module 11 to control the opening and closing of each electromagnetic microvalve according to the particle separation steps, that is, when the first separation channel 5 is working, the first electromagnetic microvalve 8 is in the closed state and the second electromagnetic microvalve 9 is in the closed state state, when the separation of the first separation channel 5 ends, the first electromagnetic microvalve 8 is opened, and the second electromagnetic microvalve 9 is in the closed state at the same time, the liquid flows to the second separation channel 6 for separation operation, when the second separation channel 6 operates When finished, the second electromagnetic micro-valve 9 is opened, and the liquid flows to the third separation channel 7 for separation operation.

2) Use a pipette to add an appropriate amount of oil sample to the liquid inlet hole 1. At this time, the liquid sample will fill the entire first separation channel 5, and the particles in the liquid will adhere to the bottom wall of the channel. Secondly, adjust the micro-injection pump 10 so that it keeps a constant speed to push air into the liquid inlet hole 1. At this time, the air entering the first separation channel 5 will push the liquid forward. Moving forward, there will be a layer of liquid film left on the bottom wall of the channel, and particles smaller than the thickness of the liquid film will be left behind, and large particles will continue to move forward with the liquid, which can achieve different sizes of particles. Particle separation; finally, the liquid in the first separation channel 5 converges into the first interface hole 2, so that the first separation stage is over, and the separated particles

will remain in the first separation channel. And it needs to be explained that the faster the air pushes, the thicker the liquid film left

The larger the value, the larger the particle size that can be left inside the liquid film.

3) At this time, control the action of the first electromagnetic microvalve 8, so that the liquid in the first junction hole 2 flows to the second branch

from the channel 6; adjust the micro-injection pump 10 again to increase the speed of injecting air, the operating principle is the same as that of the first

The separation channels 5 are the same, so that the second separation channel 6 will get larger particles than the first separation channel 5 .

4) Similarly, the third separation channel 7 can obtain larger particles than the second separation channel 6 . certainly

It is also possible to design several more separation channels to achieve separation of more particles of different sizes.

It should be noted that when the pulling force of the liquid on the particle is greater than or equal to the friction force of the channel on the particle, the particle

It will flow forward with the liquid instead of stagnant on the wall.

Its corresponding formula is:

F _DR ≥μF _AD

F _DR is the pulling force of the liquid on the particle, μ is the coefficient of friction, and F _AD is the viscous force between the bottom surface and the particle.

in:

F _DR ＝6πηυr

η is the dynamic viscosity of the liquid, υ is the speed at which the liquid moves, and r is the radius of the particle.

F _AD ＝-F _vdw -F _BG

F _vdw is the van der Waals force and F _BG is the combined force of gravity and buoyancy.

A is the Hamaker constant, A=0.4×10‐21J, a is the radius of the particle, d is the distance between the particle and the channel wall

Distance, λ=1×10-7, s=11.116.

_ρp is the density of the particle, _ρoil is the density of the liquid, λ is the London characteristic wavelength, and s is the correction of the formula

coefficient.

Therefore, the speed of the air push cannot be too large, otherwise when the viscous pulling force sum of the liquid to the particle is greater than the particle and the

The friction between the walls will cause the particles to flow with the liquid, so that they cannot be separated well.

The particle separation device and method provided in the embodiments of the present invention are proposed based on microfluidic technology, control technology, and the principle of tension effect between liquid and particles, and the technologies and principles used are relatively simple, so that the described The separation device has the advantages of simple equipment, portability, less reagent consumption, and high detection efficiency. Therefore it can be said that the present invention provides a new method for the separation of particles of different sizes in liquid.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any person familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Any equivalent replacement or change of the inventive concepts thereof shall fall within the protection scope of the present invention.

Claims (4)

1. The utility model provides a particle separation device based on liquid pulling force effect in microchannel, its includes micro-fluidic chip, control module and air injection component, its characterized in that:

the microfluidic chip comprises a microfluidic chip main body on which N separation channels which are connected end to end in sequence and are used for separating particles with different sizes in liquid are concavely carved, and a substrate which is matched with the microfluidic chip main body to form a liquid flow channel, wherein N is not less than 2; the starting end of the first separation channel is provided with a liquid inlet, the tail end of the nth separation channel is provided with a waste liquid hole, two separation channels connected end to end are connected through a junction hole, and a channel control element for controlling the on-off of the separation channel is arranged on the next separation channel corresponding to the junction hole; the channel control element comprises a first electromagnetic micro valve and a second electromagnetic micro valve, wherein the first electromagnetic micro valve and the second electromagnetic micro valve are respectively positioned at a certain distance behind a junction hole between the first separation channel and the second separation channel and a certain distance behind a junction hole between the second separation channel and the third separation channel; when the first separation channel performs particle separation, the first electromagnetic micro valve is closed; after the first separation channel particles are separated, the first electromagnetic micro valve is opened, and the second electromagnetic micro valve is closed; after the second separation channel particles are separated, opening a second electromagnetic micro valve;

the control module is respectively connected with each channel control element, namely a first electromagnetic micro valve and a second electromagnetic micro valve, arranged on each separation channel so as to control the corresponding channel control element according to the need to realize the control process of opening and closing each separation channel, thereby realizing the open circuit and the open circuit of the separation channel and preparing for separating particles in the residual liquid in the next stage;

the air injection element is communicated with the liquid inlet hole, so that air is pushed into the liquid inlet hole according to the set speed, liquid in the air pushing channel flows, a layer of liquid film is left in the area where the air pushes along with the movement of the air and liquid interface, the speed of the movement of the air and liquid interface is controlled by controlling the speed of the air, the thickness of the liquid film attached to the bottom surface of the channel is controlled, particles with the size smaller than the thickness of the liquid film are left, and large-size particles move forwards along with the movement of the interface, so that the separation of particles with different sizes is realized.

2. The particle separation device of claim 1, wherein:

the air injection element adopts a microinjection pump.

3. The particle separation device of claim 1, wherein:

the separation channels are rectangular channels.

4. A method of particle separation by the particle separation device of claim 1, wherein: the method comprises the following steps:

1) Firstly, the control module is regulated to control each channel control element so that each channel control element is in a closed state;

2) A certain amount of liquid sample is dripped into the liquid inlet hole, so that the liquid sample flows into the whole first separation channel, particles in the liquid are deposited on the bottom wall surface of the first separation channel, and then air is pushed into the liquid inlet hole at a constant speed until the liquid in the channel is converged into the first junction hole;

3) Starting a first channel control element to enable a liquid sample in the first interface hole to flow into the second separation channel, depositing particles in the liquid on the bottom wall surface of the second separation channel, and increasing the air injection speed until the liquid in the channel is converged into the second interface hole;

4) And (3) sequentially starting the rest channel control elements until the liquid in the Nth separation channel is converged into the waste liquid hole.

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