CN114917754A - Microfluidic colloidal particle separation device and separation method - Google Patents
Microfluidic colloidal particle separation device and separation method Download PDFInfo
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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 first-stage separation channel and a second-stage separation channel; the primary separation channel and the secondary separation channel are arranged in front and back 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 an 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
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
The separation of the colloidal particles has good application prospect in the fields of drug screening, food safety, aerospace, environmental monitoring, military equipment and the like. At present, there are many separation techniques for colloidal particles: such as microporous membrane separation, inertial separation, magnetophoretic separation, electrophoresis/dielectrophoretic separation, thermophoretic separation, and the like.
The microporous membrane separation technology appears earlier, and the technology adopts a filtration method, but has the defects of high membrane manufacturing cost, poor universality, easy blockage of membrane pores and the like.
Inertial separation techniques utilize the geometry of microchannels to achieve separation of particles of different sizes. The inertia separator has the advantages of high flux, low cost, no damage to active particles, continuous flow and the like. For particles with sizes from a few microns to tens of microns, inertial separation is very effective; however, when the target particles are separated at high throughput, the inertial separator has relatively low separation purity, and it is difficult to effectively separate particles having similar diameters.
The magnetophoretic separation technology refers to that magnetic particles move directionally under the drive of magnetic field force so as to realize the separation of the particles. However, most of the particles are non-magnetic particles, and the non-magnetic particles cannot be separated directly by using magnetic field force, so that a method of separating the particles by combining the particles with magnetic beads and then by using magnetic field force is mostly adopted, and thus the separated particles must be labeled by magnetic beads in advance.
Electrophoretic separation techniques are the movement of charged particles under an electric field (i.e., "electrophoresis"). The dielectrophoretic separation technique is the effect of an electric field on the dipole moment of a neutral particle (i.e. "dielectrophoresis"). The throughput of the electrophoretic/dielectrophoretic separation technique is relatively high and the separation effect of the particles depends on the charge/dielectric constant, size and structure, etc. of the particles, as well as on the electrical properties of the electrolyte fluid, etc. However, some active particles are likely to be polarized in an alternating current field, creating a polarizing charge that leads to death.
The thermophoresis separation technology realizes the separation of particles by utilizing different thermophoresis forces of cold and hot areas in a temperature gradient field to the particles. But the thermophoresis separation technology has the defects of slow heating, difficult accurate control of a temperature field and the like.
Disclosure of Invention
The invention provides a device and a method for separating colloid particles, aiming at the defects of the prior art, the device has the characteristics of simple structure, simple and convenient operation, low cost and good separation effect, and can design the size of a corresponding separation channel and the separation stage number according to the different sizes of the particles to be separated so as to achieve good separation effect.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a microfluidic colloidal particle separation device, comprising: comprises a microfluid 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 primary separation channel and the secondary separation channel are respectively provided with one side channel; introducing an 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 micro-fluid main channel into the side channel of the outlet of the primary separation channel and the side channel of the outlet of the secondary separation channel, so that solution concentration gradients are generated in the primary separation channel and the secondary separation channel.
The invention relates to a microfluidic colloidal particle separation device and a separation method, and the basic principle is that through the design of the device and the control of microfluid introduced into a channel, solution concentration difference is formed inside the separation channel, and self-generated electric fields are generated due to different diffusion speeds of anions and cations with different charges under the solution concentration gradient, so that colloidal particles are driven to move.
The colloid particles to be separated are suspended in a certain electrolyte solution, the fine colloid particles present a charged characteristic in the electrolyte solution, and due to the concentration gradient of the solution existing in the separation channel of the device, ions freely moving in the electrolyte solution generate a local electric field under the action of the ion concentration gradient due to different diffusivities, and the charged particles undergo electrophoretic migration under the electric field to generate directional motion. For colloidal particles that need to be separated, they can also be suspended in a solution of certain ionic surfactants. Ions generated after ionization in water in the surfactant can be strongly adsorbed on the surfaces of the colloidal particles, so that surface charges are highly charged, and electrophoretic migration is generated in a local electric field under the action of ion concentration gradient. The surfactant may 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 colloid particles of the device, the diffusion speed of the particles should be large enough, and the expression of the diffusion speed of the particles according to the theory of diffusion electrophoresis in the electrolyte solution gradient is as follows:
wherein e is the dielectric constant, k, of the fluid B Is boltzmann's law constant, T is absolute temperature, η is fluid viscosity, z is electrolyte ionic valence, e is elemental charge, ζ is zeta potential of the particles, and C is electrolyte solution concentration.
Under the electrolyte concentration gradient, the electric field intensity generated by diffusion of ions with different mobilities is expressed as:
wherein beta is cation (D) in the solution + ) And an anion (D) - ) The diffusion coefficient of (a) is expressed as:
as can be seen from the expression of β, -1. ltoreq. β.ltoreq.1, the value of which depends on the diffusion coefficients of the cations and anions.
To achieve a better separation effect, the diffusion speed of the particles should be increased, on one hand, the larger the difference between the diffusion coefficients of the cations and the anions in the solution is, the larger the value of | β | is, the larger the generated electric field intensity is, and the diffusion speed of the particles is also increased. On the other hand, as is clear from expression (1), the larger the zeta potential ζ of the particle, the larger the diffusion rate. The effect of the separation of colloidal particles is therefore different for different solutions.
The microfluidic technology is a technology for controlling microfluid with laminar flow or low Reynolds number as main characteristics under micron scale. The size of the colloidal particles is in the micrometer scale, and the control range of the microfluidic separation technology is just in the micrometer scale. The micro-fluidic technology has very wide application prospect in the field of colloid particle separation.
The ionic surfactant solution can be strongly adsorbed on the surfaces of colloidal particles, and the ionic surfactant solution has larger diffusion coefficient difference between cations and anions, has larger beta value and enhances the diffusion electrophoresis effect, so that the separation effect is better than that of the common electrolyte solution.
In the solution concentration gradient establishment method related by the invention, as the beta value of different solutions can be positive or negative, the direction of the self electric field generated by the solution is not unique, and different microfluids need to be controlled differently:
in the case of sodium chloride solution, since the negatively charged polystyrene colloidal particles (. zeta. < 0) move to the region of higher solute concentration due to β < 0, the higher concentration of sodium chloride solution should be introduced into the side channel compared to the main channel when the microfluidics to be introduced are controlled. Similarly, for solutions with β > 0, the negatively charged polystyrene colloid particles (ζ < 0) move to regions with lower solute concentrations, and a lower concentration of solution should be passed through the side channels as compared to the main channel.
Taking the anionic surfactant Sodium Dodecyl Sulfate (SDS) solution as an example, the beta is more than 0, and the negatively charged polystyrene colloid particles (. zeta. < 0) move to the region with lower solute concentration, so that when the microfluidics of the flowing in is controlled, the solution of Sodium Dodecyl Sulfate (SDS) with lower concentration is flowed in the side channel compared with that in the main channel.
Taking the cationic surfactant Dodecyl Trimethyl Ammonium Bromide (DTAB) solution as an example, the beta is less than 0, and the surfactant ion (DTA) with positive charge + ) Adsorbing to the surface of polystyrene colloid particles, thereby changing the charge and making it positively charged (zeta > 0). Therefore, in the microfluidic control of the flow, a lower concentration of dodecyltrimethylammonium bromide (DTAB) solution should be fed into the side channel than into the main channel.
The size and the separation stage number of the colloid particle separation channel can be designed according to the characteristics of colloid particles to be separated, so that the optimal separation effect is achieved, and the separation stage number is not limited to one stage or two stages.
Has the advantages that:
the invention relates to a microfluidic colloidal particle separation device, wherein the driving force for separating colloidal particles is generated by solution concentration gradient, so that only solution concentration difference needs to be established, no external condition is needed, and no external field force is needed. Compared with the conventional colloid particle separation device, the device structure is greatly simplified, the cost is reduced, and the method related to the device has no other physical property requirements on colloid particles and does not need to pretreat the colloid particles, so that the device has a wider application range and a very high application value.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a microfluidic colloidal particle separation device;
FIG. 2 is a schematic diagram of a microfluidic colloidal particle separation device;
FIG. 1. microfluidic Main channel; 2. a separation channel; 3. a side channel.
Detailed Description
For the understanding of the present invention, the following detailed description will be given with reference to the accompanying drawings, which are provided for the purpose of illustration only and are not intended to limit the scope of the present invention.
Fig. 1 shows a schematic diagram of the basic structure of a microfluidic colloidal particle separation device according to the present invention.
Fig. 2 shows a schematic diagram of a microfluidic colloidal particle separation device according to the present invention.
The invention relates to a microfluidic colloidal particle separation device which comprises a microfluidic main channel 1, a separation channel 2 and a side channel 3. The separation channel 2 comprises a primary separation channel and a secondary separation channel; the primary separation channel and the secondary separation channel are arranged in front and back along the flow direction of the microfluid main channel 1; and the outlets of the primary separation channel and the secondary separation channel are respectively provided with a side channel 3.
An electrolyte solution containing colloid particles to be separated is introduced into the microfluid main channel 1; and introducing solutions with different concentrations and the same electrolyte as the electrolyte solution in the microfluid 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, so that solution concentration gradients are generated in the primary separation channel and the secondary separation channel.
The primary separation channel comprises at least two primary channels which are arranged at equal intervals; the secondary separation channel comprises at least two secondary channels which are arranged at equal intervals; the width of the primary channel is less than the width of the secondary channel.
The width of the primary channel is half the width of the secondary channel.
The width of the separation channel is larger than the colloid particles and smaller than 100 mu m;
the colloidal particles exhibit a charged characteristic in the 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 metallic sulfides, non-metallic oxides, soil colloidal particles, silicic acid colloidal particles, and silver platinum gold colloidal particles.
As shown in FIG. 2, assuming that the desired separated polystyrene colloidal particles having a diameter of 0.5 μm and 1 μm, the fluid to be introduced was a Sodium Dodecyl Sulfate (SDS) solution. The width of the main channel is 5 μm, the width of the primary channel is 1 μm, the length is 5 μm, the distance is 2 μm, the width of the secondary channel is 2 μm, the length is 5 μm, and the distance is 2 μm. And the main channel is filled with the mixture with the concentration of 10 multiplied by 10 -3 The Sodium Dodecyl Sulfate (SDS) solution containing polystyrene colloidal particles was introduced into the two side channels at a concentration of 0.1X 10 mol/L -3 mol/L ofSodium Dodecyl Sulfate (SDS) solution. When the device works, anions (dodecyl sulfate radical ions, DS) are ionized from Sodium Dodecyl Sulfate (SDS) solution — ) It adsorbs to the surface of the colloidal particles, and negatively charges the polystyrene colloidal particles. And the ion concentration difference formed in the separation channel of the device is due to cation (Na) under the ion concentration gradient + ) Diffusion rate greater than anion (dodecyl sulfate ion, DS) — ) The diffusion speed is higher, the positive ions migrate to the separation channel at a higher speed, and the polystyrene colloid particles with negative charges also migrate to the separation channel under the attraction of the positive ions, so that the purpose of separation is achieved. The small colloidal particles are separated in the primary channel and the large colloidal particles are separated in the secondary channel.
Claims (9)
1. A microfluidic colloidal particle separation device is characterized in that: comprises a microfluid 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 primary separation channel and the secondary separation channel are respectively provided with one side channel; introducing an 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 micro-fluid main channel into the side channel of the outlet of the primary separation channel and the side channel of the outlet of the secondary separation channel, so that solution concentration gradients are generated in the primary separation channel and the secondary separation channel.
2. The microfluidic colloidal particle separation device of claim 1, wherein: the primary separation channel comprises at least two primary channels arranged at equal intervals; the secondary separation channel comprises at least two secondary channels arranged at equal intervals; the width of the primary channel is less than the width of the secondary channel.
3. The microfluidic colloidal particle separation device of claim 2, wherein: the width of the primary channel is half the width of the secondary channel.
4. The microfluidic colloidal particle separation device of claim 1, wherein: the width of the separation channel is larger than the colloid particles and less than 100
。
5. The microfluidic colloidal particle separation device of any of claims 1-4, wherein: the colloidal particles exhibit a charging characteristic in the electrolyte solution, including positively charged colloidal particles and negatively charged colloidal particles.
6. The microfluidic colloidal particle separation device of claim 5, wherein: the positively charged colloidal particles include metal oxide and metal hydroxide colloidal particles.
7. The microfluidic colloidal particle separation device of claim 5, wherein: negatively charged colloidal particles include metallic sulfides, non-metallic oxides, soil colloidal particles, silicic acid colloidal particles, and silver platinum gold colloidal particles.
8. The microfluidic colloidal particle separation device of claim 1, wherein: the electrolyte in the electrolyte solution is sodium chloride (NaCl) and ammonium sulfate (NH) 4 ) 2 SO 4 Fe (NO), iron nitrate 3 ) 3 Dodecyl trimethyl ammonium bromide, cetyl pyridinium chloride, sodium dodecyl sulfate or sodium dodecyl benzene sulfonate.
9. A microfluidic colloidal particle separation method based on the microfluidic colloidal particle separation device according to any one of claims 1 to 8, comprising the steps of:
electrolyte solution containing colloid particles to be separated is introduced into the microfluid main channel;
and introducing solutions with different concentrations and the same electrolyte as the electrolyte solution in the microfluid main channel into the two side channels, generating solution concentration gradient in the primary separation channel and the secondary separation channel to generate diffusion electrophoresis, wherein 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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| CN117088336A (en) * | 2023-10-09 | 2023-11-21 | 中南大学 | Recycling recovery method and separation method of elemental sulfur in sulfur paste |
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