JP3933823B2 - Surface force measuring apparatus and method - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a surface force measuring apparatus and method for directly measuring an interaction force (repulsive force, attractive force, adhesive force, etc.) acting between the surfaces of various samples.
[0002]
[Problems to be solved by the invention]
By measuring the distance dependence of the interaction between surfaces in substances, intermolecular forces, surface forces, substance structures near the surface, etc. can be elucidated. When applied to biological substances (DNA) and biological substances, molecules in cell membranes It provides important information to know the unique molecular interactions of ecosystems such as recognition and cell-cell interactions.
[0003]
As a conventional surface force measuring device, for example, a device disclosed in Japanese Patent Laid-Open No. 9-257810 has been proposed. The surface force measuring device described in the publication includes a sample having a surface to be measured facing, a cantilever having a sample portion on which one sample is placed at the tip, and a microstep for minutely moving the cantilever or the other sample. It has a fine movement mechanism with a driver-driven stepping motor and an interference optical system for measuring the distance between the sample surfaces. The amount of force acting between the surfaces is determined by the amount of movement of the fine movement mechanism, the change in distance due to optical measurement, and the spring constant of the cantilever. The surface force of the sample is measured for distance dependency.
[0004]
Among these, in a surface force measurement device that measures the change in distance between samples by the color matching order interference method, the light emitted from the light source is transmitted through the sample film modified to the cylindrical surface of the pair of sample holders. The surface force is measured by measuring the interference fringes of the interference light by receiving the light into the spectroscopic device. However, in this device, the measurable sample is limited to the one that can transmit light, However, the surface force could not be measured for the sample that was unable to penetrate.
[0005]
In addition, the above-described uniform color order interferometry has a problem in that the measurement operation cannot be automated because the distance between the sample surfaces is measured by visually confirming the interval between the interference fringes due to the interference light.
[0006]
Furthermore, in a device that measures the surface force by detecting the amount of deflection of the cantilever to which one of the sample holders is attached using an electrical signal such as a bimorph or strain gauge, the bimorph or strain gauge itself has hysteresis, so measurement is required. The reliability of the results was low, and the surface force could not be measured with high accuracy and reliability.
[0007]
The present invention has been invented to solve the above-described drawbacks, and the problem is that the surface force between samples can be measured with high accuracy even if the sample cannot transmit light. An object of the present invention is to provide a surface force measuring apparatus and method.
[0008]
Another object of the present invention is to provide a surface force measuring apparatus and method that can automate the measurement of the surface force acting between sample surfaces.
[0009]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a first sample holder provided in the chamber, an elastic member having a predetermined spring constant whose tip is deformable relative to the first sample holder, and the elastic member. A second sample holder having a surface facing the surface of the first sample holder and having a reflecting surface on the opposite side of the surface, and a sample holder to which one is fixed A fine moving means for finely moving the other sample holder close to the other, and a diffracted light that is arranged outside the chamber and irradiates the diffracted light so as to converge on the reflective surface of the second sample holder. And an interference light detecting device that measures the amount of deflection of the elastic member based on the light intensity of the interference light coupled to each other. The amount of deflection of the elastic member detected by the interference light detecting device and its spring constant act between the sample surfaces. It is characterized in that the surface force to be measured is measured.
According to a fourth aspect of the present invention, there is provided a second sample holder provided at the tip of an elastic member having a predetermined spring constant provided in the chamber, and a first sample having a surface opposite to the surface of the second sample holder. In a surface force measurement method for measuring a surface force acting between adjacent sample surfaces by minutely moving either one of the holders in a direction close to each other by a minute moving means, the diffracted light is separated from the surface of the second sample holder. Irradiating so as to converge at the reflecting surface provided on the opposite side, and detecting the amount of bending of the elastic member based on the light intensity of the interference light combined with the reflected diffracted light from the reflecting surface. The surface force acting between the sample surfaces can be measured by the spring constant of the member.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram showing an outline of an example of a surface force measuring device, FIG. 2 is an explanatory diagram showing an enlarged sample holder, and FIG. 3 is a schematic configuration diagram of an interference light detecting device.
[0011]
A slide shaft 5 having an axial line in the vertical direction is supported in the chamber 3 of the surface force measuring device 1 so as to be slidable in the vertical direction, and the shaft end of the slide shaft 5 protruding outward from the upper surface of the chamber 3 has a minute amount. A moving device 7 is connected. The micro-moving device 7 is attached to the lower part of the slide shaft 5 so as to be replaceable. The surface is made of any one of a spherical surface, a cylindrical surface, and a flat surface, and the first sample holder 9 made of glass or metal is brought into the measurement range. A coarse movement mechanism 7a to be moved and a fine movement mechanism 7b to finely move the first sample holder 9 in units of μm and nm within the measurement range.
[0012]
As an example of the fine movement mechanism 7b, for example, a pulse motor of 500 puls / r with a five-phase excitation structure, a divided drive circuit that divides a drive pulse into a predetermined number and generates a divided drive pulse, and a pulse motor are connected. It consists of a feed screw mechanism consisting of a feed amount and a differential spring mechanism (both not shown).
[0013]
In this configuration, when the number of drive pulse divisions is 250 and the feed amount of the feed screw is 1 mm / r, the feed amount of the feed screw per split drive pulse can be 0.008 μm. For example, by adopting a differential spring mechanism of a micro-movement device shown in Japanese Patent Application No. 10-17914 (Japanese Patent Laid-Open No. 11-202214) filed earlier by the present applicant, the amount of movement of the slide shaft 5 can be reduced to the unit of nm. can do. For the detailed structure of the differential spring mechanism, the matters described in the detailed description of the invention of the above application are incorporated.
[0014]
In the chamber 3 corresponding to the side of the slide shaft 5, a base end portion is fixed to the lower portion of the attachment member 11, and a cantilever 13 as an elastic member whose front end portion extends toward the lower portion of the slide shaft 5 is attached. ing. The cantilever 13 is made of a leaf spring having a predetermined spring constant, and a holder 15 having a light transmission hole 15a at the center is attached to the tip. A second sample holder 17 made of glass or metal having a surface made of any one of a spherical surface, a cylindrical surface, and a flat surface and facing upward is attached to the holder 15 in a replaceable manner. Various samples 9c and 17c such as biological substances or biological substances are formed on the surfaces of the first and second sample holders 9 and 17 by an adsorption method or an LB film method.
[0015]
Note that a configuration in which the cantilever 13 is slightly moved by the minute moving device 7 and the second sample holder 17 is brought close to the first sample holder 9 may be adopted. In addition, mica (thickness: 2 μm) excellent in smoothness is adhered to each surface of the first sample holder 9 and the second sample holder 17 to ensure smoothness of various modified samples 9c and 17c. May be. Further, although a leaf spring-shaped cantilever is used as the elastic member, any other elastic body such as a compression spring that can be bent and deformed in the moving direction of the first sample holder 9 can be used. Further, the surfaces of the first and second sample holders 9 and 17 are modified with the samples 9c and 17c for measuring the surface force. For example, if the sample to be measured is a synthetic resin or ceramics, Measurement may be performed by directly forming the first and second sample holders 9 and 17 with these materials without modifying the sample.
[0016]
As the first sample holder 9 and the second sample holder 17, samples in which the samples 9 c and 17 c are formed in advance are prepared and exchanged according to the samples 9 c and 17 c to be measured for surface force. . Further, as described above, the first sample holder 9 and the second sample holder 17 may have either a spherical surface, a cylindrical surface, or a flat surface as described above. Can be made equivalent to an arrangement in which the sphere and the plane or the sphere are close to each other.
[0017]
Of the first sample holder 9 and the second sample holder 17, a metal reflective film 17d made of a silver film or a gold film is formed on the lower surface of the second sample holder 17 attached to the cantilever 13, and diffraction is described later. Reflect light. The metal reflecting film 17d has a structure in which a reflecting plate is directly attached to the bottom surface of the holder 15 to which the second sample holder 17 is attached, or a structure in which the holder 15 itself is mirror-finished so that diffracted light described later can be reflected. May be.
[0018]
An interference light detection device 19 is disposed outside the chamber 3 located below the second sample holder 17 through a transmission window 21 provided on the bottom surface of the chamber 3. The interference light detection device 19 separates the laser light from the laser light source 19a for irradiating the parallel laser beam and the laser light from the laser light source 19a into the diffracted light of each order and reflects the diffracted light reflected from the metal reflecting film 17d as described later. The diffraction grating 19b is combined with interference light, and the diffraction lens 19b is combined with the optical lens 19c that converges the diffracted light from the diffraction grating 19b on the metal reflection film 17d of the second sample holder 17 with a predetermined spot diameter. A light receiving element 19d that receives the interference light of the diffracted light and outputs an electric signal corresponding to the light intensity, and is disposed at a position equal to the optical path length of the diffracted light from the diffraction grating 19b to the metal reflecting film 17d, It comprises a reference mirror 19e that reflects light back to the diffraction grating 19b. Note that the reference mirror 19e may be attached to an unbent portion such as a mounting base provided in the chamber 3 or a base end portion of the cantilever 13.
[0019]
As the light receiving element 19d, for example, a surface force measurement is made highly accurate by receiving interference light through a plurality of channels and outputting an electrical signal corresponding to the light intensity through each channel, such as a quadrant photodiode. At the same time, the bending direction of the cantilever 13 may be measured.
[0020]
Next, the surface force measuring action by the surface force measuring device 1 will be described.
4-5 is explanatory drawing which shows the bending state of a cantilever.
[0021]
First, the chamber 3 is filled with a liquid, an inert gas, or the like, or the chamber 3 is evacuated to drive the coarse movement mechanism 7 a of the micro-movement device 7 to the first sample holder 17 with respect to the first sample holder 17. The sample holder 9 is moved from a position where there is no influence of the surface force into a measurement range where the influence of the surface force appears.
[0022]
On the other hand, among the diffracted lights obtained by operating the interference light detection device 19 and separating the laser light emitted from the laser light source 19a into ± n-order light (n is an arbitrary integer) by the diffraction grating 19b, for example, a predetermined positive order Are diffracted on the metal reflection film 17d and diffracted light of a predetermined negative order so as to converge on the reference mirror 19e, and the diffracted light reflected from the metal reflection film 17d and the reference mirror 19e is irradiated. After being combined by the diffraction grating 19b to be interference light, it is received by the light receiving element 19d. At this time, when the cantilever 13 is not bent, the optical path length for measurement reaching the metal reflecting film 17d and the optical path length for reference reaching the reference mirror 19e coincide with each other.
[0023]
When the fine movement mechanism 7b of the fine moving device 7 is driven in the above-described state to bring the first sample holding body 9 into the fine movement in the unit of nm with respect to the surface of the second sample holding body 17, the cantilever 13 first After the first sample holder 9 approaches the second sample holder 17, it is bent upward by an attractive force acting between the surfaces of the samples 9c and 17c modified to the respective cylindrical surfaces (shown in FIG. 4). When the spring force of the cantilever 13 finally becomes a force greater than the repulsive force, the two come into contact with each other.
[0024]
At this time, when the cantilever 13 is bent upward or downward by an attractive force or a repulsive force acting between both surfaces of the sample 9c and the sample 17c, the measurement optical path length from the diffraction grating 19b to the metal reflection film 17d is a reference value. Since it becomes longer or shorter than the optical path length in accordance with the deflection (displacement) of the cantilever 13, interference light is generated when diffracted light is coupled by the diffraction grating 19b, and the light intensity of the interference light is determined by the light receiving element. It is detected by 19d.
[0025]
The light intensity of the interference light received by the light receiving element 19d changes with a period of λ / 2 with respect to the bending amount of the cantilever 13. As a result, the change in the light intensity draws a sine wave with respect to the bending of the cantilever 13, so that the change in the light intensity can be converted into the amount of bending of the cantilever 13 in nm units. From the measured amount of bending of the cantilever 13 and the spring constant of the cantilever 13, the surface force such as attractive force or repulsive force acting between the sample 9c and the sample 17c can be measured.
[0026]
In the present embodiment, the surface acting between both surfaces of the samples 9c and 17c based on the light intensity of the interference light obtained by combining the diffracted light reflected by the metal reflecting film 17d and the diffracted light reflected by the reference mirror 19e. The force can be measured, and even if the samples 9c and 17c do not transmit light, the surface force acting between them can be measured with high accuracy. Further, since the amount of bending of the cantilever 13 can be measured based on the change in the light intensity of the interference light caused by the diffracted light, the surface force measurement can be automated.
[0027]
【The invention's effect】
The present invention can measure the surface force between samples with high accuracy even if the sample cannot transmit light. Further, the present invention can automate the measurement of the surface force acting between the sample surfaces.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an outline of an example of a surface force measuring device.
FIG. 2 is an explanatory view showing an enlarged sample holder.
FIG. 3 is a schematic configuration diagram of an interference light detection device.
FIG. 4 is an explanatory view showing a state where the cantilever is bent upward.
FIG. 5 is an explanatory view showing a state where the cantilever is bent downward.
[Explanation of symbols]
1-surface force measuring device, 3-chamber, 9-first sample holder, 13-cantilever as elastic member, 17-second sample holder, 19-interference light detector

Claims (6)

A first sample holder provided in the chamber, the tip portion is a resiliently deformable in phase against the first sample holder, and an elastic member having a predetermined spring constant, provided at the distal end portion of the elastic member, the A second sample holder having a surface opposite to the surface of one sample holder and having a reflecting surface on the opposite side of the surface, and the other sample holder being moved slightly relative to the sample holder to which one is fixed And a micro-moving means to be brought close to each other , and the light intensity of the interference light which is arranged outside the chamber and irradiates the diffracted light so as to converge on the reflecting surface of the second sample holder, and the diffracted light from the reflecting surface is combined. And an interference light detecting device that measures the amount of deflection of the elastic member based on the surface force, and the surface force that measures the surface force acting between the sample surfaces by the amount of deflection of the elastic member detected by the interference light detecting device and its spring constant measuring device. 2. The surface force measuring device according to claim 1, wherein the first and second sample holders are made of a substance whose surface force is measured. 2. The surface force measuring device according to claim 1, wherein the surface of the first and second sample holders is modified with a substance to be measured. The first sample holder having opposing surfaces on the surface of the second sample holder and the second sample holder was kicked set on the tip portion of the elastic member having a predetermined spring constant provided et the inside chamber In a surface force measurement method in which either one is moved minutely in a direction close to each other by a minute moving means and a surface force acting between adjacent sample surfaces is measured, the diffracted light is moved to the opposite side of the surface of the second sample holder. Irradiating so as to converge on the provided reflecting surface, detecting the amount of bending of the elastic member based on the light intensity of the interference light combined with the reflected diffracted light from the reflecting surface, the amount of bending and the spring of the elastic member A surface force measurement method that makes it possible to measure the surface force acting between sample surfaces by a constant. 5. The surface force measurement method according to claim 4, wherein the first and second sample holders are made of a substance whose surface force is measured. 5. The surface force measurement method according to claim 4, wherein the surface of the first and second sample holders is modified with a substance to be measured.

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