CN114917754B - Microfluidic colloidal particle separation device and separation method - Google Patents

Abstract

The invention discloses a microfluidic colloidal particle separation device and a separation method, wherein the microfluidic colloidal particle separation device comprises a microfluidic main channel, a separation channel and a side channel; the separation channel comprises a primary separation channel and a secondary separation channel; the primary separation channel and the secondary separation channel are arranged in the front and back direction along the flow direction of the microfluid main channel; the outlets of the first-stage separation channel and the second-stage separation channel are respectively provided with a side channel; introducing electrolyte solution containing colloid particles to be separated into the microfluid main channel; and introducing solutions with different concentrations and the same electrolyte as the electrolyte solution in the microfluidic main channel into the side channel at the outlet of the primary separation channel and the side channel at the outlet of the secondary separation channel. The invention separates the fine colloidal particles based on diffusion electrophoresis, and compared with the prior separation technology, the invention has the characteristics of simple device structure, low separation cost, no need of pretreatment on the colloidal particles, no other influence on the colloidal particles and the like.

Description

A microfluidic colloidal particle separation device and separation method

technical field

The invention relates to a colloid particle separation device and a separation method, in particular to a colloid particle separation device and a separation method in the field of microfluidics.

Background technique

The separation of colloidal particles has good application prospects in the fields of drug screening, food safety, aerospace, environmental monitoring and military equipment. At present, there are many separation techniques for colloidal particles: such as microporous membrane separation, inertial separation, magnetophoretic separation, electrophoretic/dielectrophoretic separation, and thermophoretic separation.

Microporous membrane separation technology appeared earlier. This technology adopts filtration method, but there are disadvantages such as high cost of membrane production, poor versatility and easy clogging of membrane pores.

Inertial separation technology utilizes the geometry of microchannels to achieve separation of particles of different sizes. Inertial separators have the advantages of high throughput, low cost, no harm to active particles, and continuous flow. For particles ranging in size from several microns to tens of microns, inertial separation is very effective; however, when high-throughput separation of target particles occurs, the separation purity of inertial separators is relatively low, and it is difficult to effectively separate particles with similar diameters .

Magnetophoretic separation technology refers to the directional movement of magnetic particles driven by magnetic field force to achieve particle separation. However, most of the particles are non-magnetic particles, and non-magnetic particles cannot be separated directly by magnetic field force. Therefore, most of the particles are combined with magnetic beads and then separated by magnetic force. In this way, the separated particles must be magnetically separated in advance. Bead tag.

Electrophoretic separation technology is the movement of charged particles under an electric field (ie "electrophoresis"). Dielectrophoretic separation technology is the effect of an electric field on the dipole moment of neutral particles (that is, "dielectrophoresis"). The flux of electrophoretic/dielectrophoretic separation technology is relatively high, and the separation effect of particles depends on the charge/dielectric constant, size and structure of the particles, as well as the electrical characteristics of the electrolyte fluid. However, some active particles are likely to be polarized in the AC electric field, resulting in polarized charges and death.

Thermophoretic separation technology uses the different thermophoretic forces of particles in the cold and hot areas in the temperature gradient field to achieve particle separation. But at the same time, the thermophoretic separation technology has the disadvantages of slow heating and difficult precise control of the temperature field.

Contents of the invention

The technical problem to be solved by the present invention is to provide a device and method for the separation of colloidal particles in view of the deficiencies of the above-mentioned prior art. The device has the characteristics of simple structure, easy operation, low cost and good separation effect, and The size and number of separation stages of the corresponding separation channel can be designed according to the different particle sizes required for separation, so as to achieve a good separation effect.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A microfluidic colloidal particle separation device, characterized in that: it includes a microfluidic main channel, a separation channel and a side channel; the separation channel includes a primary separation channel and a secondary separation channel; the primary separation channel and the secondary The separation channel is arranged forward and backward along the flow direction of the microfluidic main channel; one side channel is respectively provided at the outlet of the primary separation channel and the secondary separation channel; Electrolyte solution for separating colloidal particles; the side channel at the outlet of the primary separation channel and the side channel at the outlet of the secondary separation channel are passed into different concentrations of solutions with the same electrolyte as the electrolyte solution in the microfluidic main channel, so that a The solution concentration gradient is generated in the primary separation channel and the secondary separation channel.

The invention relates to a microfluidic colloid particle separation device and a separation method. The basic principle is to form a solution concentration difference inside the separation channel through the design of the device and the control of the microfluid introduced in the channel. The different diffusion speeds of anions and cations with different charges will generate a self-generated electric field, thereby driving the movement of colloidal particles.

For the colloidal particles that need to be separated, suspend them in a certain electrolyte solution. The fine colloidal particles exhibit charging characteristics in the electrolyte solution. Due to the concentration gradient of the solution in the separation channel of the device, the freely moving ions in the electrolyte solution have different diffusion characteristics. Under the action of the ion concentration gradient, a local electric field is generated, and the charged particles undergo electrophoretic migration under the electric field, resulting in directional motion. For the colloidal particles that need to be separated, they can also be suspended in a certain ionic surfactant solution. The ions generated after ionization in water in the surfactant will be strongly adsorbed on the surface of the colloidal particles, making the surface charge highly charged, and electrophoretic migration occurs in the local electric field generated by the ion concentration gradient. Surfactants can induce diffusion electrophoresis of colloidal particles that are not sensitive to colloidal particle size or surface charge.

In order to optimize the separation effect of colloidal particles in the device, the diffusion velocity of the particles should be large enough. According to the theory of diffusion electrophoresis in the electrolyte solution gradient, the expression of the diffusion velocity of the particles is:

Among them, ∈ is the dielectric constant of the fluid, k _B is the Boltzmann's law constant, T is the absolute temperature, η is the fluid viscosity, z is the electrolyte ion valence, e is the element charge, ζ is the zeta potential of the particle, and C is electrolyte solution concentration.

Under the electrolyte concentration gradient, the expression of the electric field strength generated by the diffusion of ions with different mobility is:

Among them, β is the relative ratio of the diffusion coefficients of cations (D ₊ ) and anions (D _- ) in solution, and the expression is:

It can be seen from the expression of β that -1≤β≤1, its value depends on the diffusion coefficient of cations and anions.

In order to achieve a better separation effect, the diffusion velocity of the particles should be increased. On the one hand, the greater the difference in the diffusion coefficients of cations and anions in the solution, the greater the value of |β|, the greater the electric field intensity generated, and the greater the particle diffusion velocity. increase. On the other hand, it can be known from the expression (1) that the greater the zeta potential ζ of the particle, the greater the diffusion rate. Therefore, for different solutions, the effect of colloidal particle separation is also different.

The microfluidic technology involved in the present invention is a technology for manipulating microfluids whose main characteristics are laminar flow or low Reynolds number at the micron scale. The size of colloidal particles is on the micrometer scale, and the control range of microfluidic separation technology is exactly on the micrometer scale. Microfluidic technology has a very broad application prospect in the field of colloidal particle separation.

The establishment of the concentration gradient of the solution involved in the present invention, for the ionic surfactant solution, because the ionized ions can be strongly adsorbed on the surface of the colloidal particles, and the difference in the diffusion coefficients of the cations and anions is large, it has a large β Value, enhanced diffusion electrophoresis, so the separation effect is better than the general electrolyte solution.

The establishment of the concentration gradient of the solution involved in the present invention, because the β value can be positive or negative for different solutions, so the direction of its own electric field generated by it is not unique, and it needs to be controlled differently for different microfluids:

Taking sodium chloride solution as an example, because of its β<0, the negatively charged polystyrene colloidal particles (ζ<0) move to areas with higher solute concentrations, so when controlling the incoming microfluidics, it should be A higher concentration of sodium chloride solution is passed through the side channel than in the main channel. Similarly, for a solution with β>0, the negatively charged polystyrene colloidal particles (ζ<0) move to the region with a lower solute concentration, and the side channel should be filled with a lower concentration than that in the main channel. The solution.

Taking the anionic surfactant sodium dodecyl sulfate (SDS) solution as an example, its β>0, and the negatively charged polystyrene colloidal particles (ζ<0) move to the area with a lower solute concentration, so in the opposite When the microfluidic control is passed through, the side channel should be passed through a sodium dodecyl sulfate (SDS) solution with a lower concentration than that in the main channel.

Taking cationic surfactant dodecyltrimethylammonium bromide (DTAB) solution as an example, its β<0, the positively charged surfactant ion (DTA ⁺ ) is adsorbed on the surface of polystyrene colloidal particles, thereby changing Its charge makes it positively charged (ζ>0). Therefore, when controlling the incoming microfluid, the side channel should be fed with a lower concentration of dodecyltrimethylammonium bromide (DTAB) solution than that in the main channel.

The size and number of separation stages of the colloidal particle separation channel involved in the present invention can be designed according to the characteristics of the colloidal particles to be separated to achieve the optimal separation effect, and the number of separation stages is not limited to one or two stages.

Beneficial effect:

The invention relates to a microfluidic colloidal particle separation device. Since the driving force for the colloidal particle separation is generated by the concentration gradient of the solution, it only needs to establish the concentration difference of the solution without external conditions or external field force. Compared with the previous colloidal particle separation device, the structure of the device is greatly simplified and the cost is reduced, and the method involved in the device has no other requirements on the physical properties of the colloidal particles and does not require pretreatment of the colloidal particles, so its application range is wider and it has high Value.

Description of drawings

1 is a schematic diagram of the overall structure of a microfluidic colloidal particle separation device;

2 is a schematic diagram of the principle of a microfluidic colloidal particle separation device;

In the figure 1. microfluidic main channel; 2. separation channel; 3. side channel.

Detailed ways

In order to deepen the understanding of the present invention, the present invention will be further described below in conjunction with the accompanying drawings. This embodiment is only used to explain the present invention, and does not constitute a limitation to the protection scope of the present invention.

Fig. 1 shows a schematic diagram of the basic structure of a microfluidic colloidal particle separation device of the present invention.

Fig. 2 shows a schematic diagram of the principle of a microfluidic colloidal particle separation device of the present invention.

A microfluidic colloid particle separation device of the present invention comprises a microfluidic main channel 1 , a separation channel 2 and a side channel 3 . The separation channel 2 includes a primary separation channel and a secondary separation channel; the primary separation channel and the secondary separation channel are arranged forward and backward along the flow direction of the microfluidic main channel 1; Side channel 3.

Pass into the electrolytic solution that contains required separation colloidal particle in microfluidic main channel 1; In the side channel of one-level separation channel outlet and the side channel of secondary separation channel outlet, pass into the electrolyte solution that has the electrolyte in the microfluidic main channel of different concentrations The solution is a solution of the same electrolyte, so that a solution concentration gradient is generated in the primary separation channel and the secondary separation channel.

The primary separation channel includes at least two primary channels arranged at equal intervals; the secondary separation channel includes at least two secondary channels arranged at equal intervals; the width of the primary channel is smaller than that of the second channel.

The width of the primary channel is half the width of the second channel.

The width of the separation channel is larger than that of colloidal particles and less than 100 μm;

Colloidal particles present charged characteristics in electrolyte solution, including positively charged colloidal particles and negatively charged colloidal particles. The positively charged colloidal particles include metal oxide and metal hydroxide colloidal particles. Negatively charged colloidal particles include metal sulfides, non-metallic oxides, soil colloidal particles, silicic acid colloidal particles and silver platinum colloidal particles.

As shown in Figure 2, assuming that the colloidal particles to be separated have diameters of 0.5 μm and 1 μm polystyrene colloidal particles, the fluid passed through is sodium dodecyl sulfate (SDS) solution. The main channel is designed with a width of 5 μm, a primary channel with a width of 1 μm, a length of 5 μm, and a spacing of 2 μm, and a secondary channel with a width of 2 μm, a length of 5 μm, and a spacing of 2 μm. A sodium dodecyl sulfate (SDS) solution with a concentration of 10×10 ^-3 mol/L containing polystyrene colloidal particles is passed into the main channel, and a concentration of 0.1×10 ^-3 mol is passed into the two-stage side channels. /L of sodium dodecyl sulfate (SDS) solution. When the device is working, the anions (dodecylsulfate ion, DS ^- ) ionized from the sodium dodecyl sulfate (SDS) solution will be adsorbed on the surface of the colloidal particles, making the polystyrene colloidal particles negatively charged. And the ion concentration difference will be formed in the separation channel of the device. Under the ion concentration gradient, because the diffusion speed of cations (Na ⁺ ) is faster than the diffusion speed of anions (dodecyl sulfate ion, DS ^— ), the cations go to the When the separation channel migrates, the negatively charged polystyrene colloidal particles also migrate to the separation channel under the attraction of cations to achieve the purpose of separation. Small colloidal particles are separated in the primary channel, and large colloidal particles are separated in the secondary channel.

Claims (6)

1. A microfluidic colloidal particle separation device, characterized in that: comprise a microfluidic main channel, a separation channel and a side channel; the separation channel comprises a primary separation channel and a secondary separation channel; the primary separation channel and The secondary separation channel is arranged forward and backward along the flow direction of the microfluidic main channel; one of the side channels is respectively arranged at the outlet of the primary separation channel and the secondary separation channel; The electrolytic solution of the required separation colloidal particles; the side channel at the outlet of the primary separation channel and the side channel at the outlet of the secondary separation channel are passed into a solution with the same electrolyte as the electrolyte solution in the microfluidic main channel, and a The solution concentration of the side channel at the outlet of the primary separation channel and the side channel at the outlet of the secondary separation channel is lower than the concentration of the electrolyte solution in the microfluidic main channel, so that a solution concentration gradient is generated in the primary separation channel and the secondary separation channel; The primary separation channel includes at least two primary channels arranged at equal intervals; the secondary separation channel includes at least two secondary channels arranged at equal intervals; the width of the primary channel is smaller than the width of the second channel; The width of the separation channel is greater than that of colloidal particles and less than 100 μm; The colloidal particles exhibit charging characteristics in the electrolyte solution, including positively charged colloidal particles and negatively charged colloidal particles. 2. The microfluidic colloidal particle separation device according to claim 1, wherein the width of the primary channel is half of the width of the second channel. 3. The microfluidic colloidal particle separation device according to claim 1, wherein the positively charged colloidal particles include metal oxides and metal hydroxide colloidal particles. 4. microfluidic colloidal particle separation device according to claim 1, is characterized in that: the negatively charged colloidal particle comprises metal sulfide, soil colloidal particle, silicic acid colloidal particle, silver colloidal particle, platinum colloidal particle and gold colloidal particles. 5. The microfluidic colloidal particle separation device according to claim 1, characterized in that: the electrolyte in the electrolyte solution is sodium chloride, ammonium sulfate, ferric nitrate, dodecyltrimethylammonium bromide, Cetylpyridinium Chloride, Sodium Lauryl Sulfate, or Sodium Dodecylbenzene Sulfonate. 6. A microfluidic colloidal particle separation method based on the microfluidic colloidal particle separation device described in any one of claims 1-5, characterized in that the steps are: The electrolyte solution containing the colloidal particles to be separated is passed into the microfluidic main channel; A solution with the same electrolyte as the electrolyte solution in the microfluidic main channel is passed into the two side channels, and the concentration of the solution passed into the two side channels is lower than that of the electrolyte solution in the microfluidic main channel. The solution concentration gradient is generated in the secondary separation channel to cause diffusion electrophoresis, and the colloidal particles move directionally under the diffusion electrophoresis, the small colloidal particles enter the primary separation channel, and the large colloidal particles enter the secondary separation channel.

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