JP2003065938A - Method of deciding interacting force between fine particle and wall surface utilizing electromagnetic migration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decide the interacting force between fine particles and a wall surface by observing the adsorption and desorption of the particles to and from the wall surface by performing electromagnetic migration using a magnetic field as a driving force by utilizing a uniform ferromagnetic field. SOLUTION: In a method of deciding interacting force between fine particles and wall surface by utilizing electromagnetic migration, a pre-prepared electrolytic solution containing the fine particles is set up in a uniform high magnetic field and a wall body is set up in the solution. Then the particles are made to be repetitively adsorbed to and desorbed from the surface of the wall body by causing electromagnetic buoyancy to act on the particles by alternately making controlled currents to flow to the solution in directions crossing the magnetic field and the interacting force between the fine particles and surface of the wall body is decided by observing the adsorbed and desorbed behaviors of the fine particles to and from the surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention repeats adsorption / desorption behavior of fine particles on a wall surface by electromagnetic buoyancy acting on the fine particles, and observes the adsorption / desorption behavior to determine the interaction force between the fine particles and the wall surface. Regarding how to decide.

[0002]

2. Description of the Related Art In the fields of environmental chemistry and biochemistry, the separation and characterization of fine particles in liquid has become a very important theme. At present, the electrophoresis method and the centrifugal separation method are already used in a wide range, but it cannot be said that the separation method is a reliable separation method in all ranges. Therefore, it is expected that the electrophoresis method using a driving force different from the electrophoresis method and the centrifugation method will facilitate the separation of fine particles, which have been difficult to separate up to now, and obtain new information on those particles. There is.

Conventionally, it has been considered to use an atomic force microscope to measure an interaction force such as adhesion and desorption between fine particles and a predetermined wall surface, but a method established yet has not been found. In particular, a method for measuring the adsorption force of fine particles floating in a solution has not been known so far.

As a new electrophoretic method, an electrophoretic method utilizing a magnetic field as a driving force is currently being studied. The electrophoretic method so far has been only a preliminary experimental method for observing the electrophoretic behavior of a micrometer-order fine particle in a cell sealed with a permanent magnet. One of the reasons for this is that the migration force acting on the fine particles is small. But,
Now, using a superconducting magnet makes it possible to use a uniform strong magnetic field, and it has become possible to easily generate a larger electrophoretic force than before. Under such circumstances, the present inventor thought that it becomes possible to separate fine particles using a magnetic field as a driving force, by making it possible to carry out an electrophoretic experiment under various conditions.

[0005]

DISCLOSURE OF THE INVENTION The present invention uses a uniform strong magnetic field to carry out electrophoretic migration using a magnetic field as a driving force, and observes adsorption / desorption between fine particles and a predetermined wall surface. It is an object to provide a method for determining the interaction force with a wall.

[0006]

A method for determining an interaction force between a fine particle and a wall surface according to the present invention is to prepare an aqueous electrolyte solution containing the fine particle and install the aqueous electrolyte solution in a uniform high magnetic field. Adsorption / desorption behavior of the fine particles on the wall surface of the wall by arranging a wall body in the electrolyte aqueous solution, applying a controlled current to the electrolyte aqueous solution alternately in a direction intersecting the magnetic field, and by electromagnetic buoyancy acting on the fine particles. By repeating the above, and observing the adsorption / desorption behavior, the interaction force between the fine particles and the wall surface is determined.

It is preferable that an electrolytic aqueous solution containing the fine particles is contained in a container. Further, it is preferable that the wall body is an inner wall of the container. Further, it is preferable to flow a current that is alternately controlled to the aqueous electrolyte solution in a direction orthogonal to the magnetic field.

The interaction force determining method of the present invention was invented based on the following consideration. For magnetophoresis,
When a current flows through a certain element: volume V (m ³ ), the electromagnetic force F (N) received by this element by this current and the magnetic field orthogonal thereto is expressed as follows. F = μ ₀ μHjV (1) where μ ₀ is the magnetic permeability of vacuum (N _s ² C ⁻² ), μ is the magnetic permeability of the object (−), H is the external magnetic field (A _m ⁻¹ ), and j is It is a current density (A _m ^-2 ) in the object. The direction of the electromagnetic force F is perpendicular to the current and the magnetic field and is the same as the Lorentz force received by the positive charges.

Such an electromagnetic force works similarly even if the object is a liquid. When a current flows through a conductive liquid sealed in a cell and the entire cell is in a uniform magnetic field, a uniform magnetic force acts on the entire liquid, but the liquid is confined in the cell. It doesn't move. Therefore, a pressure gradient similar to the hydrostatic pressure in the gravitational field occurs in the liquid there. The presence of particles in a liquid under these circumstances will undergo some sort of buoyancy due to this pressure gradient. This is a very important concept in electrophoretic migration.

FIG. 1 shows the force exerted by particles in a liquid during electrophoretic migration. Here, it is assumed that the densities of particles and liquid are the same, and gravity and buoyancy are ignored. As shown in FIG. 1, when a current i is applied and a uniform magnetic field B perpendicular to the current is applied to the cell containing the sample solution, the particles migrate in the vertical direction. At this time, whether the particles migrate upward or downward depends on the magnitude relationship between the electrical conductivity αp of the particles and the electrical conductivity αf of the medium. This is because the difference in electric conductivity causes a difference in the current densities flowing through the particles and the medium, and eventually the difference between the force received by the particles and the force received by the medium. The change in the current density distribution due to the magnitude of the electrical conductivity is shown in FIG.

As shown in FIG. 1, two forces act on particles.
Ku. These two forces are compared to those in the gravitational field,
Electromagnetic Weight, F_EMW), Electric
Electromagnetic Buoyancy, F_EMB) Called
There is. Electromagnetic force FEMW is the force exerted on the particles themselves
But electromagnetic buoyancy F_EMBIs received by the medium as mentioned earlier
It is a force caused by electromagnetic force. Therefore, its size is
Equal to the force exerted on a medium of the same volume as the particle, and the direction is electromagnetic force
F_EMWAnd the opposite direction. These two forces, F _EMW,
F_EMBIs defined as follows.     F_EMW= Μ₀μ_pHj_pV (2)     F_EMB= -Μ₀μ_fHj_fV (3) Where μ_p, Μ_pIs the permeability of each of the particles and the medium, j
_p, J_fIs the current density of each of the particles and the medium.

The relational expression between the current density of the particles and the medium is such that the particles are spherical and the size thereof is sufficiently smaller than that of the cell filled with the medium, and the particles and the medium maintain a constant electric conductivity. In that case, it can be derived as follows. First,
The electric fields E _p and E _f (V _m ⁻¹ ) inside the particles and the medium have the relationship of the following expression (4). Here, ρ _p and ρ _f are electric conductivities (S _m ⁻¹ ) of the particles and the medium, respectively.

When both sides are multiplied by σ _p , equation (4) is transformed as follows, Since j = Eσ, the relational expression (6) of the current density can be obtained. Further by using the equation (6), it is as (2) the following equation (7) Clearing the j _p of, The total force on a particle can be expressed as

In the migration of particles, since the force expressed by the equation (8) and the fluid resistance force FV expressed by the following equation (9) are balanced, the migration velocity v finally becomes (10). It becomes like a formula. Here, B is the magnetic flux density (T), η is the viscosity of the medium (Pa
s) and r are particle radii (m). Also, μ _p and μ _f are 1
Was assumed to be. From this equation (10), it can be expected that the electrophoretic velocity of particles is proportional to the strengths of two external fields, current and magnetic field, and proportional to the square of the radius of the particle.

[0015]

The present invention will be described in more detail below. Using the measurement method of the present invention, (1) in the fields of environment and health, for example, the interaction between environmental fine particles and alveoli can be measured. For example, in the case of environmental fine particles and alveoli, the walls are coated with alveolar cell components,
The adsorption / desorption force between the coated alveolar cell components and environmental fine particles is measured, and their interaction is measured. (2) In the fields of molecular biology and clinical examination, for example, the adsorbability of blood cells can be measured. For example, attach the antigen to the wall,
By repeating the adsorption / desorption step of the antigen and the antibody, the interaction between the antigen and the antibody can be measured.
This makes it possible to obtain a pure sample by removing the antibody by an antigen-antibody reaction using the present adsorption method when a small amount of antibody is contained in the biological sample.
(3) In the fields of agricultural chemistry and breed improvement, the adhesive force of seeds can be measured. By this, the interaction force between the organic fine particles and the biological fine particles and the wall surface of various properties can be measured.

The present invention greatly contributes to the fact that a high magnetic field can be obtained by using a superconducting magnet. According to the present invention, it is possible to measure the adsorbing power of fine particles on the order of micrometer, from 1 hemto N to 1000 pN. There is no particular upper limit for the particle size, but it is preferably 10 mm or less in view of the problem of gravity, and the lower limit is preferably 0.1 μm or more in view of observability.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION (1) Electrolyte Solution Although an electrolyte is added to a solvent to pass an electric current, metal and non-metal salts containing electrode constituent ions, for example, chlorine ions, can be used. For example, potassium chloride can be mentioned. Further, as the solvent, those capable of ionizing the salt can be used, and examples thereof include water.

Of these, the concentration of the aqueous solution of a metal compound such as manganese chloride is preferably in the range of 1 wt% to 10 wt%. If the concentration is too low, the desired current value cannot be secured, and if the concentration is too high, the density of the supporting liquid becomes too high,
There is a possibility that the fine particles may float.

(2) Fine Particles The fine particles to which the present invention can be applied are not particularly limited as long as their shapes and sizes can be determined, and they are solids or gels such as polymers, ceramics, semiconductors, blood cells, cells, DNA and biological particles. Particles can be mentioned. As fulfilled, as the particle size of the fine particles, those having a particle size of 0.1 μm to 10 mm can be particularly suitably applied in the present invention.

(3) There are no particular upper or lower limits on the magnetic field and the uniform high magnetic field, but in reality it is preferable to use a magnetic field in the range of 0.1 terraces to 10 terraces. It is preferable to be orthogonal to the magnetic field, but it is not necessarily required to be orthogonal. It is not limited to orthogonal as long as there is an orthogonal component and the method of the present invention can be effectively implemented.
That is, it is considered that the effective amount of the electric current or the magnetic field acting on the electric current decreases when the electric currents intersect.

The electric current was applied by, for example, immersing the electrode in an electrolytic solution and applying a voltage therebetween. The current is controlled so that the direction is alternately changed at a frequency of 0.01 Hz to 10 Hz, for example. The upper limit of the electric current strength is determined from the viewpoint of preventing the generation of Joule heat, and is, for example, 1 mA.
And the lower limit has only to be strong enough to move the fine particles. Further, the shape of the electric current is appropriately selected and used such as a sine wave or a sawtooth wave.

(4) It is preferable that the container and the wall container are made of a material inert to the electrolyte solution containing fine particles and are transparent from the viewpoint of external observation. As the container, for example, a cell can be used, and as the cell, a capillary tube, a glass cell, or a plastic cell can be used. Although the dimensions of the capillary tube and the like are not particularly limited, for example, a cross-sectional area of 100 μm
It may be mx100 μm.

The wall surface of the container may be the wall surface of the container itself, may be integrally provided on the inner surface of the container, or may be provided inside the container separately from the inner surface of the container. As the material of the wall surface, glass, plastic (for example, polyethylene, polypropylene) or the like can be used. The fine particles pass an electric current through the electrolytic solution,
On the other hand, if a magnetic field is applied to intersect, for example, in the direction orthogonal to the direction, the force moves in the direction orthogonal to the direction of the electric current and the direction of the magnetic field and moves in that direction, but the wall surface adsorbs / desorbs moving particles. Placed where possible. Further, the wall surface is preferably a flat surface, but a curved surface, an irregular surface or the like can also be used. Even a flat surface includes microscopically zigzag shapes. The wall surface is formed of a material intended to measure an interaction force with respect to the fine particles. For example, when measuring the interaction force between environmental fine particles and alveoli, the surface coated with alveolar cell components is used as the wall surface. When measuring the interaction force between the antibody microparticles and the antigen, the surface coated with the antigen is used as the wall surface.

(5) Observation of adsorption / desorption behavior For the adsorption / desorption behavior observation, a conventional apparatus for observing fine particles, for example, an optical microscope, ultrasonic detecting means, etc. can be used. This method uses a single particle as an interaction force between bioparticles such as blood cells, cells (immune cells-T cells, B cells, NK cells, etc.) and DNA, and chemically modified wall surfaces or affinity controlled wall surfaces. It is possible to measure at the level. As a chemically modified wall surface or a wall surface with controlled affinity, various synthetic sugar chain-containing polymer materials are commercially available. Further, the repetition frequency of adsorption / desorption is sufficient as long as the interaction force to be determined becomes clear, and is determined for each case. Those skilled in the art can easily make such a determination.

[0025]

EXAMPLES The present invention will be described in detail below based on specific examples. In this experiment, the electrophoretic behavior of polystyrene particles was applied to the flow system, and the electrophoretic behavior and migration velocity in the flow were observed. Moreover, the desorption experiment of the particles adsorbed on the wall of the cavity was conducted by the electromagnetic buoyancy.

(1) Sample solution, etc. An aqueous solution of potassium chloride is used as the sample solution, and
A dispersion of m-order polystyrene latex particles was used. The concentration of the potassium chloride aqueous solution was 1.0M. The viscosity of aqueous potassium chloride solution at this concentration is 0.8
It was 8 × 10 −3 Pas (reference value). Since the density is approximately equal to 1.05 gcm −3 of polystyrene latex particles, the effect of the difference in density between the medium and the particles did not appear in the experiment. Particle size 10 μm (3.001 ± 0.044 μm), 15 μm in this 1.0 M potassium chloride aqueous solution
(14.571 ± 1.657 μm), 22 μm (22.
001 ± 2.712 μm) of three types of polysterene latex particles (POLYBEAD-POLYTYR SmENE, manufactured by Funakoshi Co., Ltd.) were dispersed to an extent that they were individually observable to obtain a sample solution.
When the sample solution was not used, it was kept refrigerated, adjusted to room temperature (25 ° C.) during the experiment, and the polystyrene latex particles were dispersed by ultrasonic waves.

(2) Measuring Device FIG. 3 is a schematic enlarged view of the measuring device used in the experiment. In the figure, the container cell 1 has a square cavity shape with a cross section of 100 μm × 100 μm and a length of 2 cm, and both ends of the cell 1 are put in Teflon (R) tubes 5 and 6 together with Ag | AgCl electrodes 3 and 4. , And the heat-shrinkable tubes 7 and 8 were connected so as not to leak. The wall surface is the inner wall of the Teflon (R) tube and is made of Teflon (R). In the experiment, the central part of the capillary was used as the observation area for migration, and the observation was performed with an optical microscope. The Ag | AgCl electrode was produced by electrolyzing a silver wire in an aqueous potassium chloride solution. The procedure is to connect a silver wire (diameter 0.2 mm) to the positive pole of a power source, connect a platinum wire to the negative pole, and cover the two metal wires with a 1.0 M potassium chloride aqueous solution. Then, when a current is applied at 5 V for 5 minutes, silver chloride is generated at the tip of the silver wire, and thus the Ag | AgCl electrode is completed. 9 in the figure
Indicates an objective lens of an optical microscope.

The experimental apparatus is shown in FIG. Superconducting magnet 11
(JMT, JMTD-10T100HH1) The above-mentioned container cell 1 was fixed to the cell holder 12 installed in the uniform magnetic field in the bore, and the electrodes 3 and 4 were a constant current power source (Fuso Manufacturing Co., Ltd., HECS).
317B) or constant voltage power supply 13 (Metronix, HSV
1K-60). The direction of current flow was set to be orthogonal to the magnetic field. The voltage applied to the solution in the cell and the current flowing when a current is applied are measured by the voltmeter 14 (AD
VANTEST, digital multimeter R6551), ammeter 15 (Takeda RIKEN, digital multimeter TR6843)
It was made possible to measure by. In addition, a syringe pump 16 (Harvard Appara) is attached to one end of the Teflon (R) tube 1.
tus, New Harvard Syringe Pump 11), and the discharge line was connected to the other end. Syringe pump (HAMILTON, GA
STIGHT # 1701) used had an internal volume of 100 μm.

The migration behavior of polystyrene particles is as follows. Light is incident from the light source 18 (OLYMPAS, light source MODEL ILV) from the bottom of the cell, and the microscope 19 (manufactured by Chuo Seiki) and CCD from the top.
Observed by the camera 20 (ELMO, L4E421R) and the monitor 21, recorded by the video recorder 22 and analyzed.

(4) Measurement of Adsorption / Desorption A current was applied to the sample solution in the cell to adsorb polystyrene particles having a particle size of 20 μm and 15 μm on the first wall of the cavity by electromagnetic buoyancy. At this time, a current of 200 μA and a current of 800 μA were applied to adsorb the polystyrene particles, respectively.
Shed for a second. Next, the polystyrene particles adsorbed on the wall were desorbed by applying an electric current in the opposite direction to that at the time of adsorption. At this time, the current was gradually increased to about 0 to 1000 μA, and the current value for desorption of particles was measured. In this experiment, the flow was stopped when particles advancing to the observation region were adsorbed by the flow, and the medium was completely stationary.

(5) Results and discussion (5-1) Electrophoretic behavior and migration velocity Even during the flow, the particle size was 10 μm while the current was flowing.
It was possible to observe that polystyrene particles of m and 22 μm both migrated. In addition, the direction was the direction of electromagnetic buoyancy, and the direction of migration was reversed when the direction of current was switched. From this, it was confirmed that electromagnetic buoyancy acts on the polystyrene particles in the flow system as in the closed system.

FIG. 5 shows the dependence of the electrophoretic velocity on the current value. Here, the positive direction of velocity is aligned with the direction of electromagnetic buoyancy. Experiments with particle sizes of 10 μm and 22 μm
Of the two types of polysterene particles. At this time, the magnetic flux density in the uniform magnetic field in the superconducting magnet is 10T. The flow rate is 5 μl / hr, and the range of current value is 5 to 5.
It was set to 100 μA. As shown in FIG. 5, the electrophoretic migration rate was proportional to the current value, as expected by the equation (10), as in the closed system, and a larger migration rate was observed for particles having a larger particle size. The migration speed of polystyrene particles having a particle size of 22 μm is 3.6 times that of polystyrene particles having a particle size of 10 μm.
It was double.

FIG. 6 shows the dependence of the electrophoretic velocity of 10 μm polystyrene particles on the magnetic flux density. The current value at this time was 50 μA, the flow rate was 5 μl / hr, and the magnetic flux density was set between 3 and 10 T. As is clear from FIG. 6, the migration velocity of particles is proportional to the magnetic flux density. This agrees with formula (10).

(5-2) Adsorption State of Polystyrene Particles FIG. 7 shows the dependence of the desorption rate of polystyrene particles having a particle size of 15 μm and 22 μm on the current value. The desorption rate is defined by the following formula. The desorption rate indicates the ratio of particles desorbed up to the current value. The total number of times of desorption was 94 for polystyrene particles having a particle size of 15 μm and 60 times for polystyrene particles having a particle size of 22 μm. It can be seen from FIG. 7 that the desorption rate is around 20% for each of the 15 μm and 22 μm polystyrene particles, and that the desorption rate is widely distributed with respect to the current value. From this, it is considered that the adsorption state of the polystyrene particles to the cavity wall has not one stage but a plurality of stages. There are multiple stages in the adsorption state,
It is considered that this is because the state of the surface of the particles and the surface of the cavity wall are not uniform, and the adsorption force varies depending on the location where the particles come into contact with the cavity wall.

Particle size 15 whose shape is clearly shown in FIG.
The force Fv required for desorption of the polysterene particles at 170 μA and 850 μA at μm and 150 μA at 22 μm in particle diameter was calculated based on the equation (8). At this time, the electric conductivity of the polystyrene particles is 0.0383 Scm.
-1 was used. From this result, it was found that the force required for desorption of polystyrene particles was on the order of 270 pN on average.

FIG. 8 shows the number of desorbed particles at a current value between 0 to 600 μA in 10 μA intervals. By plotting the number of desorptions on the vertical axis and the current value on the horizontal axis, the illustrated histogram was obtained. In FIG. 8, it can be seen that the polysterene particles having a particle size of 22 μm are desorbed most per 100 μA, and most of them are desorbed by 200 μA. On the other hand, the particle size is 15 μm
The polystyrene particles are widely distributed up to 50 to 1000 μA, and are most desorbed per 350 μA. In the range of desorption of polystyrene particles having a particle size of 22 μm to 200 μA, about 20% of the polystyrene particles having a particle size of 15 μm are desorbed. From this result, it is considered that the distribution of the desorption number with respect to the current value can be different in the peak position of the desorption number depending on the size of the fine particles, and therefore the difference can be used to separate the fine particles by adsorption and desorption.

[0037]

INDUSTRIAL APPLICABILITY In the present invention, an electrolyte aqueous solution containing fine particles is prepared, the electrolyte aqueous solution is placed in a uniform high magnetic field, a wall is placed in the electrolyte aqueous solution, and the electrolyte aqueous solution is crossed with a magnetic field. By alternately passing a controlled electric current in the direction in which the particles are adsorbed and desorbed by the electromagnetic buoyancy acting on the particles to the wall surface of the wall, and observing the adsorption and desorption behavior, Since the acting force can be determined, it becomes possible to obtain new information on the fine particles by a simple method.

By using the method of the present invention, the interaction force between the environmental fine particles and the alveoli, the interaction force between the antibody fine particles and the antigen, and the biological fine particles such as blood cells, cells (immune cells), DNA, etc. can be given. It is possible to measure the surface affinity or the like with respect to the wall surface of the.

[Brief description of drawings]

FIG. 1 schematically shows a force that particles in a liquid receive when undergoing electrophoretic migration.

FIG. 2 shows a change in current density distribution due to the magnitude relationship of electric conductivity when particles in a liquid undergo electrophoretic migration.

FIG. 3 is a schematic enlarged view of a measuring device used for observing adsorption / desorption behavior of particles.

FIG. 4 schematically shows an experimental apparatus used for observing adsorption / desorption behavior of particles.

FIG. 5 is a diagram showing a relationship between an electrophoretic velocity and a current value when particles are suspended in a solution and electrophoresed.

FIG. 6 is a diagram showing a relationship between an electrophoretic velocity and a magnetic flux density when particles are suspended in a solution and electrophoresed.

FIG. 7 is a diagram showing the relationship between the current value and the desorption rate of particles when the particles are suspended in a solution and electrophoresed.

FIG. 8 is a diagram showing a relationship between a current value and the number of desorbed particles.

[Explanation of symbols]

1 Container Cell 19 Microscope 3,4 Electrode 20 CCD Camera 5,6 Teflon (R) Tube 21 Monitor 7,8 Heat Shrink Tube 22 Video Recorder 9 Optical Microscope Objective Lens 11 Superconducting Magnet 12 Cell Holder 13 Constant Current (Constant Voltage) Power supply 14 Voltmeter 15 Ammeter 16 Syringe pump 18 Light source

Claims (4)

[Claims] 1. An electrolyte aqueous solution containing fine particles is prepared, the electrolyte aqueous solution is placed in a uniform high magnetic field, and a wall is placed in the electrolyte aqueous solution, and the electrolyte aqueous solution is alternated in a direction intersecting the magnetic field. By applying a controlled current to the particles, the adsorption and desorption behavior of the particles is repeated on the wall surface of the wall by electromagnetic buoyancy acting on the particles, and the interaction force between the particles and the wall surface is determined by observing the adsorption and desorption behavior. how to. 2. The method according to claim 1, wherein the aqueous electrolyte solution containing the fine particles is contained in a container. 3. The method according to claim 2, wherein the wall is an inner wall of the container. 4. The method according to any one of claims 1 to 3, wherein a current that is alternately controlled is passed through the aqueous electrolyte solution in a direction orthogonal to a magnetic field.