JP2011106915A - Zeta potential measuring instrument and zeta potential measuring method - Google Patents

Abstract

Provided are a zeta potential measuring device and a zeta potential measuring method which are small and inexpensive and can measure the zeta potential of each measurement object.
A sample solution in which an object to be measured is dispersed is accommodated and moved between a first reservoir, a second reservoir, and between the first reservoir and the second reservoir. A microchannel 10 having an aperture 13 smaller than the first reservoir 11 and the second reservoir 12 in a cross-sectional area perpendicular to the direction in which the measurement object passes and the measurement object moves; The current measurement device 20 that measures the current value of the current flowing between the second reservoirs 12 and the measurement target by dividing the path length of the aperture 13 through which the measurement object passes by the current decrease time during which the current value temporarily decreases. And a calculation device 30 that calculates the electrophoresis speed of the object and calculates the zeta potential of the measurement object using the electrophoresis speed.
[Selection] Figure 1

Description

  The present invention relates to a zeta potential measuring device and a zeta potential measuring method for measuring a zeta potential of a measurement object dispersed in a solution.

  When the surface of a minute object such as fine particles or cells dispersed in a solution is charged, the zeta potential indicates the degree of charging of these minute objects. In order to measure the zeta potential of a minute object, various measuring methods such as a method using an ultrasonic wave or a high frequency voltage have been used. As a typical method, there is a laser Doppler method using a laser (for example, see Patent Document 1).

  The laser Doppler method is a method of measuring the zeta potential by frequency analysis of scattered light. A solution in which a measurement object is dispersed is placed in a measurement cell, a voltage is applied to the inside of the measurement cell, and a micro object is electrophoresed. Then, a zeta potential is calculated by irradiating a laser from the side of the measurement cell, detecting light scattered by the minute object being electrophoresed, and analyzing the frequency.

Japanese Patent No. 2924815

  However, many conventional zeta potential measuring devices are large and expensive. For example, the zeta potential measurement by the laser Doppler method requires optical devices such as a laser light source and a photomultiplier tube, which makes it difficult to reduce the size and cost of the zeta potential measuring device. In the above method, the zeta potential is calculated by irradiating the measurement cell with the laser and detecting and analyzing the scattered light of the measurement object existing in the irradiated range. For this reason, there has been a problem that the zeta potential of individual fine particles and cells cannot be measured.

  In view of the above problems, an object of the present invention is to provide a zeta potential measuring apparatus and a zeta potential measuring method that are small and inexpensive and can measure the zeta potential of each measurement object.

  According to one aspect of the present invention, (a) a sample solution in which an object to be measured is dispersed is accommodated and moved between a first reservoir, a second reservoir, and between the first reservoir and the second reservoir. A microchannel having an aperture smaller than the first and second reservoirs in cross-sectional area perpendicular to the direction in which the measurement object in the sample solution passes and moves, and (b) the first and second reservoirs A current measuring device that measures a current value of a current flowing between the first and second reservoirs by applying a voltage between them and (c) a current decrease in which the current value temporarily decreases within a certain time A zeta potential comprising a calculation device that calculates the electrophoresis speed of the measurement object by dividing the path length of the aperture through which the measurement object passes by time, and calculates the zeta potential of the measurement object using the electrophoresis speed Measuring device It is subjected.

  According to another aspect of the present invention, (a) a sample solution in which an object to be measured is dispersed is accommodated and moved between the first reservoir, the second reservoir, and the first reservoir and the second reservoir. Providing a microchannel having an aperture smaller than the first and second reservoirs in cross-sectional area perpendicular to the direction in which the measurement object in the sample solution passes and the measurement object moves; Applying a voltage between the first and second reservoirs to measure a current value of a current flowing between the first and second reservoirs for a certain period of time; Calculate the electrophoresis speed of the measurement object by dividing the path length of the aperture through which the measurement object passes by the decreasing current reduction time, and (d) calculate the zeta potential of the measurement object using the electrophoresis speed. Step to do The zeta potential measuring method comprising is provided.

  According to the present invention, it is possible to provide a zeta potential measuring device and a zeta potential measuring method which are small and inexpensive and can measure the zeta potential of each measurement object.

It is a mimetic diagram showing the composition of the zeta potential measuring device concerning the embodiment of the present invention. It is sectional drawing along the II-II direction of FIG. It is a schematic diagram which shows the structure of the aperture of the zeta potential measuring device which concerns on embodiment of this invention. It is a schematic diagram for demonstrating zeta potential. It is a schematic diagram explaining that microparticles | fine-particles move along an electric field. It is a schematic diagram which shows the electric current which flows through the microchannel of the zeta potential measuring device which concerns on embodiment of this invention. It is a schematic diagram which shows the example which microparticles | fine-particles pass through the aperture of the zeta potential measuring device which concerns on embodiment of this invention. It is a schematic diagram which shows the example of the electric current value measured by the zeta potential measuring device which concerns on embodiment of this invention. It is a flowchart for demonstrating the zeta potential measurement method which concerns on embodiment of this invention. It is a graph which shows the relationship between the electric current value measured by the zeta potential measuring method which concerns on embodiment of this invention, and time. It is the graph which expanded a part of graph shown in FIG. It is a schematic diagram which shows the state which divided the microchannel of the zeta potential measuring device which concerns on embodiment of this invention. It is a graph which shows the relationship between the diameter of a measuring object obtained by the zeta potential measuring device concerning the embodiment of the present invention, and a current decrease value.

  Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, the embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the embodiments of the present invention include the material, shape, structure, arrangement, etc. of the component parts. Is not specified as follows. The embodiment of the present invention can be variously modified within the scope of the claims.

(Embodiment)
As shown in FIG. 1, a zeta potential measurement device 1 according to an embodiment of the present invention contains a sample solution 200 in which measurement objects such as fine particles and cells are dispersed, and includes a first reservoir 11 and a second reservoir. The cross-sectional area perpendicular to the direction in which the measurement object passes through the reservoir 12 and the sample solution 200 moving between the first reservoir 11 and the second reservoir 12 passes through the first reservoir 11 and A current flowing between the first reservoir 11 and the second reservoir 12 by applying a voltage between the first reservoir 11 and the second reservoir 12 and the microchannel 10 having an aperture 13 smaller than the second reservoir 12. The current measurement device 20 for measuring the current value of the aperture 13 and the path length of the aperture 13 through which the measurement object passes during the current decrease time during which the current value temporarily decreases within a certain time. And calculate the electrophoretic velocity of the measurement object, and a calculating device 30 for calculating the zeta potential of the measurement object by using the electrophoretic velocity. FIG. 1 shows a plan view of the microchannel 10.

  The microchannel 10 includes a first reservoir 11 in which a negative electrode 201 is disposed, a second reservoir 12 in which a positive electrode 202 is disposed, and an aperture 13 disposed between the first reservoir 11 and the second reservoir 12. It consists of the narrow part which constitutes. As will be described later, a voltage is applied between the negative electrode 201 and the positive electrode 202 by the current measuring device 20, and the current measuring device 20 passes through the current flowing between the negative electrode 201 and the positive electrode 202, that is, the first through the aperture 13. The current value of the current flowing between the reservoir 11 and the second reservoir 12 is measured.

  For example, as shown in FIG. 2, the microchannel 10 has a structure in which a silicon rubber 101 having a micropattern formed on its surface is attached to a glass substrate 102. The silicon rubber 101 can be manufactured using a photolithography technique or the like used for manufacturing a semiconductor device. The negative electrode 201 is in contact with the sample solution 200 in the first reservoir 11 in the opening 111 provided in the first reservoir 11, and the positive electrode 202 is in the second opening 121 in the second reservoir 12. Contact the sample solution 200 in the reservoir 12.

  The microchannel 10 can be formed by the following method, for example. That is, first, a photoresist film is applied on a silicon substrate. This photoresist film is formed into a pattern corresponding to the cavity shape of the microchannel 10 having the first reservoir 11, the second reservoir 12, and the aperture 13 by photolithography. Then, silicon rubber is poured using this photoresist film as a mold, and then the cured silicon rubber is peeled off from the silicon substrate. As a result, a pattern in which the first reservoir 11 and the second reservoir 12 are connected via the aperture 13 is formed on the surface of the silicon rubber 101. In the first reservoir 11 and the second reservoir 12, openings 111 and 121 for disposing the negative electrode 201 and the positive electrode 202 are formed, respectively. The silicon rubber 101 is attached to the glass substrate 102 to form the microchannel 10 shown in FIG.

As shown in FIG. 3, the aperture 13 has a width w _a , a height h, and a path length l _a . As shown in FIGS. 1 and 3, the connection portion of the first reservoir 11 and the second reservoir 12 with the aperture 13 is gradually narrowed toward the aperture 13, and the cross-sectional area gradually increases. It is formed to be smaller. Thereby, it is prevented that the measurement object 100 and the bubbles are clogged in the connection portion between the first reservoir 11 and the aperture 13 of the second reservoir 12, and the measurement accuracy can be improved.

  The zeta potential indicates the degree of charging of the surface of fine particles or the like in the solution. Usually, the surface of fine particles or the like dispersed in a solution is charged to a positive potential or a negative potential. For example, FIG. 4 shows a case where the surface of the measuring object 100 in the sample solution 200 is charged to a negative potential. For this reason, cations gather around the measurement object 100. Since the measurement object 100 is charged, as shown in FIG. 5, when a voltage is applied between the positive electrode 202 and the negative electrode 201, the measurement object 100 moves in the sample solution 200 along the electric field. The moving speed at this time depends on the degree of charging, that is, the zeta potential. Therefore, the zeta potential can be measured by measuring the moving speed of the measuring object 100.

  An electrolyte solution is used as the sample solution 200 in which the measurement object 100 is dispersed. For this reason, when the sample solution 200 is accommodated in the microchannel 10 and a DC voltage is applied between the first reservoir 11 and the second reservoir 12, current flows from the positive electrode 202 to the aperture as shown by arrows in FIG. 13, reaches the negative electrode 201, and shows a constant current value. FIG. 6 shows a case where the measurement object 100 is not dispersed in the sample solution 200.

On the other hand, when the measurement object 100 is dispersed in the sample solution 200, as described above, when a voltage is applied between the first reservoir 11 and the second reservoir 12, the measurement object 100 follows the electric field. Move. FIG. 7 shows a case where the surface of the measurement object 100 in the sample solution 200 is charged to a negative potential. When the measurement object 100 does not exist in the aperture 13, the current flows in the same manner as in the case shown in FIG. 6. However, when the measurement object 100 passes through the aperture 13, the flow of current flowing through the aperture 13 is hindered. For this reason, as shown in FIG. 8, the current value decreases for the time during which the measurement object 100 exists in the aperture 13. Hereinafter, the decrease value of the current value resulting from the measurement object 100 passing through the aperture 13 is referred to as “current decrease value ΔI”, and the time during which the current value is decreasing is referred to as “current decrease time Δt”. By dividing the path length l _a of the aperture 13 by the current decrease time Δt, the electrophoresis speed of the measurement object 100 can be calculated.

  Hereinafter, an example of a method for measuring the zeta potential of the measuring object 100 dispersed in the sample solution 200 by the zeta potential measuring device 1 shown in FIG. 1 will be described with reference to FIG. In the following, it is assumed that the measurement object 100 is a fine particle having a diameter of 3 μm, and the surface of the measurement object 100 in the sample solution 200 is charged to a negative potential.

(A) In step S1, the microchannel 10 is prepared. Here, the width w _a , height h, and path length l _a of the aperture 13 are 5 μm, 10 μm, and 40 μm, respectively.

  (B) In step S2, for example, 2-methacryloyloxyethyl phosphorylcholine is injected into the microchannel 10 as a coating solution, and a polymer coating is applied to the surface of the microchannel 10 that contacts the sample solution 200. As a result, the measurement object 100 can be prevented from adhering to the glass substrate 102, and the zeta potential due to the sample solution 200 on the surface of the microchannel 10 can be suppressed to prevent measurement of the zeta potential of the measurement object 100. Can be minimized. In order to apply the polymer coating, the coating liquid is accommodated in the microchannel 10 for about 24 hours, for example.

  (C) The coating solution in the microchannel 10 is replaced with a buffer solution such as a phosphate buffer, and the coating solution is discharged from the inside of the microchannel 10. After discharging the buffer solution from the inside of the microchannel 10, the sample solution 200 in which the measurement object 100 is dispersed is accommodated in the microchannel 10 in step S3.

  (D) In step S <b> 4, the current measuring device 20 applies a DC voltage of, for example, 30 V between the first reservoir 11 and the second reservoir 12. The current measuring device 20 measures the current value I of the current flowing between the negative electrode 201 and the positive electrode 202 in the sample solution 200 over a certain period of time. Since the surface of the measurement object 100 dispersed in the sample solution 200 is charged to a negative potential, the measurement object 100 passes through the aperture 13 by electrophoresis and is transferred from the first reservoir 11 to the second reservoir. Move to reservoir 12. An example of the measured current value I is shown in FIG. As already described, since the flow of the current flowing through the aperture 13 is hindered by the measurement object 100 existing in the aperture 13, as the measurement object 100 passes through the aperture 13, as indicated by D in FIG. 10. In addition, the measured current value I decreases. FIG. 11 shows the current decrease value ΔI at around time 8.18 seconds in FIG. As already described, the current decrease time Δt of the current value I is the time during which the measurement object 100 stays in the aperture 13. The observed current decrease value ΔI is transmitted to the calculation device 30.

(E) In step S5, calculation device 30, by dividing the path length l _a of the aperture 13 in the current decreasing time Delta] t, to calculate the electrophoretic velocity S of the measuring object 100. That is, S = l _a / Δt.

  (F) In step S6, the calculation device 30 calculates the electrophoretic mobility and the zeta potential of the measurement object 100 using the electrophoresis speed S.

The electrophoretic mobility U is calculated by dividing the electrophoretic velocity S by the strength of the electric field in the aperture 13. The zeta potential ζ is calculated by a known relational expression using, for example, the Smolkovsky equation shown in the following equation (1):

U = (ε / η) ζ (1)

In Equation (1), U is the electrophoretic mobility of the measurement object 100, and ε and η are the dielectric constant and viscosity coefficient of the sample solution 200, respectively.

  While the zeta potential measured by the experiment using the zeta potential measuring apparatus 1 described above was −31.09 (± 3.12) mV, the zeta potential measured by the known laser Doppler method is It was −33.35 (± 2.42) mV. Thus, it was confirmed that the zeta potential obtained by the zeta potential measuring device 1 according to the embodiment of the present invention is in good agreement with the measurement result obtained by a known measurement method.

Of course, the cross-sectional area of the aperture 13 perpendicular to the direction in which the measuring object 100 moves must be larger than the particle size M of the measuring object 100. In order to accurately measure the zeta potential, One measurement object 100 needs to pass through the aperture 13 at a time. Thus, for example, the width w _a of the aperture 13, M <w _a <is preferably about 2 × M. That is, the cross-sectional area of the aperture 13 is larger than the diameter of the measurement object 100, but it is preferable that the two measurement objects 100 cannot pass side by side.

In addition, if the path length l _a of the aperture 13 is too long, the probability that a plurality of measurement objects 100 stay in the aperture 13 at the same time increases. On the other hand, when the path length l _a is too short, the time that the measuring object 100 to the aperture 13 to stay is too short, the accuracy of the measurement is reduced. If for example a diameter of several μm of the measuring object 100, have been obtained experimentally that it is preferable path length l _a of about 20Myuemu～40myuemu.

Therefore, the width w _a , height h, and path length l _{a of the} aperture 13 are taken into consideration in consideration of the particle size of the measurement object 100, the electrical conductivity of the sample solution 200, the concentration of the measurement object 100 in the sample solution 200, and the like. May be set as appropriate.

  Further, as described below, the particle size of the measurement object 100 can be measured by the zeta potential measurement device 1 shown in FIG.

The microchannel 10 is divided into parts as shown in FIG. 12, and electrical resistance in each part of the microchannel 10 in which the sample solution 200 is accommodated is considered. Here, the electrical resistance in the aperture portion P ₁₃ and the resistor Ra. The electrical resistance at the rectangular parallelepiped portions P ₁₁₁ and P ₁₂₁ of the first reservoir 11 and the second reservoir 12 is defined as resistance Rc, and the electrical resistance at the connection portions P ₁₁₂ and P ₁₂₂ connected to the aperture 13 is defined as resistance Rb.

Resistance Ra, Rb, Rc when the measuring object 100 does not exist in the aperture 13 is represented by the following formulas (2) to (4):

Ra = l _a / (σhw _a ) (2)
Rb = l _b / {σh (w _c −w _a )} × ln (w _c / w _a ) (3)
Rc = l _c / (σhw _c ) (4)

Here, σ is the electrical conductivity of the sample solution 200, l _a and w _a are the path length and width of the aperture part P ₁₃ , l _b is the path length of the connection parts P ₁₁₂ and P ₁₂₂ , and l _c and w _c are rectangular parallelepipeds. The path lengths and widths of the portions P ₁₁₁ and P ₁₂₁ , h is the height of the microchannel 10.

On the other hand, when the electrical resistance of the aperture 13 when the measurement object 100 exists in the aperture 13 is a resistance Raa, the resistance Raa is expressed by the following equation (5):

Raa = 2arctan {(φ / 2) / (hw _a / π− (φ / 2) ² ) ^1/2 } / [σ {π (hw _a −π (φ / 2) ² )} ^1/2 ] + (L _a −φ) / (σhw _a ) (5)

In Expression (5), φ is the diameter of the measurement object 100.

The resistance R1 of the entire microchannel 10 when the measurement object 100 is not present in the aperture 13 is expressed by the following equation (6). The resistance R2 of the entire microchannel 10 when the measurement object 100 is present in the aperture 13 is It is represented by the following formula (7):

R1 = Ra + 2 × (Rb + Rc) (6)
R2 = Raa + 2 × (Rb + Rc) (7)

Using the applied voltage V and the current decrease value ΔI applied between the first reservoir 11 and the second reservoir 12, the relationship of the following equation (8) is established:

V / R1−V / R2 = ΔI (8)

  The diameter φ of the measuring object 100 can be calculated using the equations (2) to (8). An example in which the diameter φ of the measurement object 100 is calculated is shown in FIG. FIG. 13 is a graph showing the relationship between the diameter φ of the measurement object 100 and the current decrease value ΔI, and the value calculated by calculation is shown by a solid line.

  Further, the values indicated by dots in FIG. 13 are measurement results obtained by measuring the current decrease value ΔI by the zeta potential measurement device 1 using fine particles having diameters of 2 μm and 3 μm as the measurement object 100. . As shown in FIG. 13, the measurement result and the calculation result are in good agreement. Therefore, it was confirmed that the particle size can be measured by the zeta potential measuring device 1 shown in FIG.

  Although the case where the measurement object 100 is a fine particle has been described above, the zeta potential measurement device 1 according to the embodiment of the present invention can also measure the zeta potential of a single cell. The zeta potential of cells is closely related to cell surface biochemical reactions. For example, sheep-derived erythrocytes were reacted with rabbit-derived anti-sheep erythrocytes IgG, and the electrophoretic mobility was measured by the zeta potential measuring device 1. As a result, it was clarified that there was a correlation between the number of antibodies attached to the cell surface measured by a flow cytometer and the electrophoretic mobility. Here, the electrophoretic mobility U is represented by the above formula (1). Therefore, it was found that a biochemical reaction such as an antigen-antibody reaction occurring on the cell surface can be evaluated by the zeta potential measurement method using the zeta potential measurement apparatus 1 shown in FIG.

  Using the sample solution 200 in which red blood cells were dispersed in a phosphate buffer as the measurement object 100, an experiment for measuring the zeta potential was performed. In the measurement using the zeta potential measuring apparatus 1 shown in FIG. 1, the zeta potential was −12.83 (± 1.01) mV, whereas the zeta potential measured by the known laser Doppler method was − It was 15.39 (± 0.45) mV. Thus, it was confirmed that the zeta potential of erythrocytes obtained by the zeta potential measuring device 1 is in good agreement with the measurement result obtained by a known measuring method.

In the measurement example using the zeta potential measurement device 1 already described, the measurement object 100 has a diameter of about 3 μm. For this reason, the width w _a and the height h of the aperture 13 are set to, for example, about w _a = 5 μm and h = 10 μm. However, by performing further fine processing by electron beam lithography or the like on a glass substrate 102, the width w _a and the height h of the aperture 13 it is possible to create nanochannels a nanometer order. For example, the width w _a and the height h of the aperture 13 can be set to 100 nm or less. A sample solution 200 in which biomolecules such as DNA and protein and nanoparticles are dispersed is accommodated in the nanochannel, and the individual quantity, size, and zeta potential of these nanomaterials are measured using the zeta potential measuring device 1. Can do.

  As described above, according to the zeta potential measuring device 1 according to the embodiment of the present invention, zeta potentials of individual fine particles and cells dispersed in the solution can be measured. In addition, the diameter of the fine particles to be measured can be measured simultaneously with the zeta potential measurement by using the magnitude of the decrease value of the current flowing through the aperture 13.

  Furthermore, since the microchannel 10 used in the zeta potential measuring device 1 shown in FIG. 1 has a simple structure and low material cost, a small zeta potential measuring device can be provided at low cost. Therefore, according to the zeta potential measuring device 1 according to the embodiment of the present invention, it is possible to provide a zeta potential measuring device and a zeta potential measuring method that are small and inexpensive and can measure the zeta potential of each measurement object 100. .

  As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. In other words, the present invention includes various embodiments and the like not described here. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  The zeta potential measuring device and the zeta potential measuring method of the present invention can be used for applications utilizing the electrical characteristics of the surface of a minute object such as fine particles or cells dispersed in a solution. For example, it can be applied to evaluation of dispersibility of colloidal solutions, structural analysis of cell membranes, development of wastewater treatment methods, verification of papermaking additives, and the like.

DESCRIPTION OF SYMBOLS 1 ... Zeta potential measuring device 10 ... Micro channel 11 ... 1st reservoir 12 ... 2nd reservoir 13 ... Aperture 20 ... Current measuring device 30 ... Calculation device 100 ... Measurement object 101 ... Silicon rubber 102 ... Glass substrate 111, 121 ... Opening part 200 ... Sample solution 201 ... Negative electrode 202 ... Positive electrode

Claims (7)

The measurement object in the sample solution containing the sample solution in which the measurement object is dispersed and moving between the first reservoir, the second reservoir, and the first reservoir and the second reservoir is provided. A microchannel having an aperture smaller than the first and second reservoirs in a cross-sectional area passing through and perpendicular to a direction in which the measurement object moves,
A current measuring device that applies a voltage between the first and second reservoirs and measures a current value of a current flowing between the first and second reservoirs for a certain period of time;
The electrophoresis speed of the measurement object is calculated by dividing the path length of the aperture through which the measurement object passes by the current decrease time during which the current value temporarily decreases within the fixed time, and the electrophoresis A zeta potential measurement device comprising: a calculation device that calculates a zeta potential of the measurement object using a velocity.   2. The zeta potential measuring device according to claim 1, wherein a connection portion of the first and second reservoirs with the aperture has a structure in which a cross-sectional area gradually decreases toward the aperture.   3. The zeta potential measuring device according to claim 1, wherein a polymer coating is applied to a surface of the microchannel that contacts the sample solution. 4.   The calculation device calculates a particle size of the measurement object using a decrease value of the current value during the current decrease time and an electric resistance of the sample solution in the microchannel. The zeta potential measuring device according to any one of items 1 to 3. The measurement object in the sample solution containing the sample solution in which the measurement object is dispersed and moving between the first reservoir, the second reservoir, and the first reservoir and the second reservoir is provided. Providing a microchannel having an aperture that is smaller than the first and second reservoirs and has a cross-sectional area passing through and perpendicular to a direction in which the measurement object moves;
Applying a voltage between the first and second reservoirs and measuring a current value of a current flowing between the first and second reservoirs for a predetermined time;
Dividing the path length of the aperture through which the measurement object passes by a current decrease time during which the current value temporarily decreases within the predetermined time, and calculating an electrophoresis speed of the measurement object;
Calculating the zeta potential of the measurement object using the electrophoresis speed. The zeta potential measurement method comprising:   The zeta potential measurement method according to claim 5, further comprising applying a polymer coating to a surface of the microchannel that contacts the sample solution.   6. The method according to claim 5, further comprising the step of calculating a particle size of the measurement object using a decrease value of the current value during the current decrease time and an electric resistance of the sample solution in the microchannel. 6. The zeta potential measurement method according to 6.

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