JPH01152339A - Dynamic contact angle measuring apparatus - Google Patents

Abstract

PURPOSE:To measure a dynamic contact angle at a high accuracy free from a surface shape, by determining not only a surface tension but also a contact angle with a computing section depending on a change in a load detection signal of a load cell when a sample is dipped into a liquid or pulled out therefrom. CONSTITUTION:A container receiving base 15 is lifted to or lowered from a load cell 14 and a sample 11 supported in suspension on the load cell 14 is dipped into or pulled out from a liquid in a liquid container 12 supported with the container receiving base 15. Here, a controller as computing section determines surface tensions FA and FR based on a change in a load detection signal of the load cell 14 and, furthermore, contact angles thetaA and thetaR are obtained based on the results. In addition, responsiveness to the environment of molecules of the surface of the sample can be studied by varying the speed of dipping the sample into water diversely.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a dynamic contact angle measuring device.

[Prior Art] Polar group portions on the surface of a polymeric material are oriented so as to minimize interfacial free energy with the surrounding environment during molding or film formation. This preferred orientation is not permanent and can only change orientation in response to the external environment if micro-Brownian motion of the surface segments is allowed. In addition, the surface chemical composition of multiphase polymer materials is
It is known that when microphase separation is good, which is significantly different from the inside, hydrophobic groups are quickly oriented on the surface in air and hydrophilic groups are oriented on the surface in water, and it responds to the environment in an extremely short time.

Therefore, evaluation of surface properties according to the intended use of the material 1
For example, consider segmented polyurethane (SPUU) used in artificial hearts.

It is important to evaluate the surface properties of the parts that come into contact with water, which is the main component of living organisms.

Also, when immersing or pulling up a solid sample into a liquid,
It is known that the contact angle formed between the liquid surface and the solid sample surface at a position where the liquid surface contacts the solid sample wall is used as an evaluation item for the surface characteristics of a material.

Conventionally, the contact angle measurement method described above involves dropping droplets of water or other liquid onto a flat plate (cover glass) coated with a polymeric material, etc., and visually detecting the droplet surface with respect to the flat plate surface using a microscope. The angle of contact is measured as the contact angle.

[Problems to be solved by the invention] However, in the above conventional contact angle measurement method,
There are the following problems.

■Since visual detection is performed using a microscope, dynamic contact angles that change moment by moment on the sample surface cannot be detected quickly, easily, and with high precision.

@If a droplet is dropped onto a sample surface with a complex surface shape other than a flat plate, the droplet will fall without coming to rest on the sample surface! Unable to measure antennae.

■ No consideration is given to accurately measuring the contact angle under specific environmental temperature conditions.

A first object of the present invention is to quickly and accurately measure the dynamic contact angle that changes from time to time on the surface of a sample, regardless of the surface shape.

A second object of the present invention is to quickly and accurately measure the dynamic contact angle that changes from time to time on the surface of a sample under specific environmental temperature conditions, regardless of the surface shape.

[Means for Solving the Problems] The first aspect of the present invention is to measure the contact angle between the liquid surface and the sample surface at a position where the liquid surface contacts the sample surface when the sample is immersed in or pulled up from the liquid. A dynamic contact angle measurement device that includes a pedestal, a load cell disposed on the pedestal to suspend and support a sample, a container holder disposed movably on the pedestal to support a liquid container, and a container. A lifting drive unit that raises and lowers the pedestal relative to the load cell, and a surface that receives the load detection signal of the load cell when the container pedestal is raised and lowered, and that the sample is immersed in or pulled up from the liquid based on changes in the load detection signal. The device includes a calculation section that calculates the tension and calculates the contact angle based on the surface tension.

The second aspect of the present invention is a dynamic contact angle measuring device that measures the contact angle between the liquid surface and the sample surface at a position where the liquid surface contacts the sample surface when the sample is immersed or pulled up into the liquid. , a pedestal, a load cell disposed on the pedestal to suspend and support a sample, a container pedestal disposed on the pedestal so as to be movable up and down to support seven liquid storage containers, and an elevating mechanism for raising and lowering the container pedestal relative to the load cell. a drive unit; a temperature control device capable of controlling the temperature of the liquid in the liquid storage container supported by the container pedestal;
Receive the load detection signal from the load cell when the container pedestal goes up and down, calculate the surface tension when the sample is immersed or pulled up into the liquid based on the change in the load detection signal, and calculate the surface tension under a specific temperature condition based on this surface tension. and a calculation unit that calculates the contact angle at.

[Function] In the first and second aspects of the present invention, the container pedestal is raised and lowered relative to the load cell, and the sample suspended and supported by the load cell is placed inside the liquid storage container supported by the container pedestal. When immersed in liquid or pulled up, the calculation unit
The surface tension is determined based on the change in the load detection signal of the load cell, and the contact angle is determined based on this surface tension.

Therefore, according to the first and second aspects of the present invention, it is possible to automatically measure the dynamic contact angle that changes from moment to moment on the sample surface, and the contact angle can be detected quickly, easily, and with high precision.

Furthermore, according to the first and second aspects of the present invention, the contact angle is measured based on the load detection signal of the load cell when the sample is immersed in or pulled up from the liquid.
Contact angle can be measured regardless of the surface shape of the sample.

Furthermore, in the second aspect of the present invention, when measuring the contact angle,
A temperature control device can be used to control the temperature of the liquid within the liquid container. Therefore, the contact angle can be accurately measured under specific environmental temperature conditions such as biological temperature.

[Example] Figure 1 is a schematic diagram showing an example of a dynamic contact angle measuring device, and Figure 2 is a schematic diagram showing an example of a dynamic contact angle measuring device.
The figure is a block diagram showing the control system of the dynamic contact angle measuring device.
Figure 3 is a piping diagram showing the temperature control device, Figure 4 is a schematic diagram showing the load acting on the sample, Figure 5 is a diagram showing the dynamic contact angle hysteresis loop, and Figure 6 is the acceleration acting on the sample. Fig. 7 is a schematic diagram showing the displacement of the load cell, Fig. 8 is a diagram showing an example of measuring the time dependence of surface tension, and Fig. 9 is an example of measuring the dynamic contact angle hysteresis loop. FIG.

The dynamic contact angle measuring device tio is configured as shown in FIGS. 1 and 2, and when the sample 11 is immersed or pulled up into the liquid inside the liquid container 12, the position where the liquid surface contacts the sample surface is measured. The contact angle θ between the liquid surface and the sample surface can be measured. The dynamic contact angle measuring device 10 includes a pedestal 13, a load cell 14, a container pedestal 15, a lifting drive section 16, a temperature control device 17, and a control device 18.

That is, the pedestal 13 of the dynamic contact angle measuring device 10 has a rad 19 fixed to a fixed cross on the upper part of the guide rod 13A, and the fixed cross head 19 is equipped with a load cell 14. The load cell 14 has a thread attached to a hook 20 connected to its sensing part.

A chuck 22 is suspended via a flexible connector 21 made of thin metal wire, chain, etc., and the sample 11 is held by the chuck 22. The load cell 14 measures load using a highly sensitive strain gauge. The sample 11 is made of, for example, a polymer material and is thinly coated on a flat cover glass.

In addition, the dynamic contact angle measuring device 10 includes a guide rod 13A.
Container holder (movable crosshead) 15 that can be raised and lowered along the
A constant temperature bath 23 of a temperature control device 17 is installed on the top surface of the container holder 15, and the container 12 is held in the constant temperature bath 23. 24 is a container holder.

In addition, the dynamic contact angle measuring device IO is located at the bottom of the pedestal 13.
The feed screw 2 includes a pulse motor 25 and a feed screw 26 that constitute the lifting drive unit 16, and is driven by the motor 25.
6 is screwed onto the container holder 15. The motor 25 is equipped with an encoder 27.

The temperature control device 17 is configured as shown in FIG.
9 to set the temperature of the heat medium inside the constant temperature bath 23 to a desired temperature state.

In addition, in the dynamic contact angle measuring device 10, the load cell 14 and the container pedestal 15 are covered with a windshield cover 30.

The control device 18 consists of a microcomputer, for example, and includes a CPU (central processing unit) 31, as shown in FIG.
ROM (read-only memory) 32, RAM (read-writable memory) 33. In addition to an input/output device 34, it is also provided with a keyboard 35, an x-y display section (x-y display, X-Y recorder), and a printer 37 at 36 degrees. The control device 18 drives and controls the motor 25 based on operation commands applied via the keyboard 35 .

Further, the W control device 18 receives the output of the load cell 14 via the amplifier 38, and also receives the output of the encoder 27, thereby forming a calculation section. That is, the control device 1
As will be described in detail below, B is the surface tension when the sample 11 is immersed or pulled up into the liquid based on the change in the load detection signal received from the load cell 14 when the container pedestal 15 is raised or lowered. The contact angle of the liquid under a specific temperature condition is calculated based on this surface tension.

Hereinafter, a procedure for measuring a dynamic contact angle using the dynamic contact angle measuring device 10 will be described.

■A sample 11 of polymeric material or the like is thinly coated on a cover glass. This sample 11 is suspended and supported by the load cell 14 via a hook 20 and a flexible connector 21.

(2) For example, a container 12 containing pure water (purified into ultrapure water after ion exchange using a water purification device) is held in a constant temperature bath 23 installed on a container pedestal 15.

(2) The motor 25 of the lift drive section 16 is driven, and the container 12 approaches (raises) or separates (descends) from the sample 11 suspended from the load cell 14 at a constant speed.

■The output of the load cell 14 and the displacement of the container pedestal 15 (output of the encoder 27) are transferred to the memory of the control device 18 in synchronization with each other, and stored as a load F-displacement convex curve as shown in FIG. be done.

(2) When the container pedestal 15 rises and the lower end of the sample 11 touches the water surface of the container 12 and a meniscus is formed, interfacial tension is observed. The formation of a meniscus on the water surface of the sample 11 at this time and the force acting on the sample 11 are shown in FIG. 4. Force F1 acting on sample 11 in FIG. F2. F3 is
The circumference of sample 11 is P = 2 (t + w), the surface tension of water is γ, the contact angle is 0, the mass of sample 411 is m, sample 11
When the buoyant force acting on is Fb, it is as follows.

F1=mg =+(1)F
2 = m g + 'P y case ・
(2) F 3 = m g + P y case-p
b・(3)(ΦIn (■), the advancing contact angle O is calculated from the interfacial tension FA that changes when sample 11 contacts the water surface.
A is evaluated.

case A = FA / P y
-(4) Furthermore, when the sample 11 is immersed in water, the tension decreases because it becomes lighter by the amount of buoyancy. When the sample 11 reaches a certain depth and the container pedestal 15 begins to descend, the buoyant force decreases and the observed tension increases. At this time,
The receding contact angle θR is evaluated from the tension FR when the sample 11 separates from the water surface.

caseR= FR/Py - (5) Here, the above tensions FA and FR are calculated from the load F-displacement convex curve stored in ① above, the buoyancy slope line (sl, s2) and the immersion start point (d= o) Obtained as 171 intersection points.

The immersion start point (d=0) is determined from the load F-displacement convex curve as shown in FIG. 5 by reading the tension change FO when the sample 11 contacts the liquid surface. This tension change F
The setting of O can be changed within a range that does not impede the measurement accuracy of this device IO, so that the immersion starting point can always be read stably against disturbances such as external vibrations.

Next, the operation of the above embodiment will be explained.

In the dynamic contact angle measurement device IO, the container pedestal 15
is raised and lowered relative to the load cell 14, and when the sample 11 suspended and supported by the load cell 14 is immersed or pulled into the liquid inside the liquid storage container 12 supported by the container holder 15, the calculation unit The control device 18 determines surface tensions FA and FR based on changes in the load detection signal of the load cell 14, and further determines contact angles θA and θR based on these surface tensions. Note that if the surface composition changes during the first immersion process, the tension-displacement curve observed during the second immersion will be different from the first one. Furthermore, by varying the rate at which the sample is immersed in water, the responsiveness of molecules on the sample surface to the environment can be investigated. θA and θR
The difference in contact angle is called contact angle hysteresis, and this value can be used to evaluate the mobility of molecular chains in the surface layer. Furthermore, by varying the rate of rise or fall of the container, it is possible to evaluate the relaxation time of molecular motion in the surface layer.

Therefore, according to the above embodiment, it is possible to automatically measure the dynamic contact angle that changes from moment to moment on the sample surface.
The contact angle can be detected quickly, easily, and with high precision.

Furthermore, according to the above embodiment, the contact angle is measured based on the load detection signal of the load cell 14 when the sample is immersed in or pulled up from the liquid. It is also possible to measure the contact angle.

Furthermore, in the above embodiment, the temperature of the liquid in the liquid container can be controlled using the temperature control device 17 when measuring the contact angle. Therefore, the contact angle can be accurately measured under specific environmental temperature conditions such as biological temperature.

In the dynamic contact angle measuring device 10, when the sample 11 suspended and supported by the load cell 14 is immersed or pulled up into a liquid and the load acting on the sample 11 is measured, two methods are used: (1) moving the load cell 14; (2) A method of moving the liquid container 12 is considered. In method (1), when the load cell 14 is accelerated or decelerated, for example, while the lifting platform supporting the load cell 14 reaches a constant speed from a stopped state (see FIG. 6(A)), the sample (
quality i:m) is subjected to acceleration α (see Figure 6(B)),
The load TI acting on the load cell 14 when stopped is TI=m
g, the load T2 acting on the load cell 14 during acceleration is T2
=mg+mα. In other words, load cell 1 during acceleration
The load T2 acting on the load T2 increases (or decreases) by mα under the influence of the acceleration α, and the load cell 14 detects this. Furthermore, when the above acceleration α is suddenly applied (or removed) by method (2), the spring system (spring constant ark) consisting of the load cell 14 and the sample 11 is m
It vibrates according to the equation of motion consisting of α=-kx (Fig. 6 (
In contrast, in method (2), the influence of the acceleration α and the vibration of the sample 11 on the load detected by the load cell 14 can be eliminated, and the load caused by the surface characteristics of the sample 11 can be eliminated. Only changes in can be stably measured by the load cell 14.

Further, the load cell 14 used in the dynamic contact angle measuring device 10 is schematically shown in FIG.
When the sample 11 and the sample 11 are connected by a connector made of a highly rigid body as shown in FIG. 7(C), the vibration of the sample 11 causes the displacement (r to r/ )
This causes a large change in the measurement result by the load cell 14. On the other hand, as in the above embodiment, the load cell 14 and the sample 11 are connected to the sensing part by using a connector consisting of a flexible connector 21 and/or a hook 20 as shown in FIG. 7(B). If the sample 11 is swingably connected to the load cell 14,
without significantly changing the displacement (τ) of the sensing part of
The load acting on the sample 11 can be measured with high precision.

Hereinafter, specific implementation results of the present invention will be explained.

Segmented polyurethane (SPUU), which is used in artificial hearts and other devices and exhibits excellent antithrombotic properties and mechanical properties, was evaluated for its surface properties when it comes into contact with water, which is the main component of living organisms. Figure 9 was obtained.

Measurement Example 1 That is, FIG. 8 shows the time dependence of tension when a flat plate coated with each 5 PUU was immersed in pure water for 10 layers. PE G (100
0) In the case of completely phase-separated PPG (3000)EDA containing EDA and a hydrophobic soft segment polypropylene glycol (molecular weight 3000),
The surface tension changes over a long period of time, and the degree of relaxation corresponding to the reorganization of the molecular chain aggregation state on the surface is also extremely large. This is due to the precipitation of hydrophilic molecular chains on the surface layer as it is immersed in water. This is thought to be due to stabilization of the solid-water interface. On the other hand, PPG(TOO)ED containing PPG with a soft segment molecular weight of 700 and 1000
In the case of A and PPG (1000) E D A, the change in tension over time is small, indicating that the chemical structure of the surface is regulated and stabilized during film formation.

Measurement Example 2 The adsorption state of plasma proteins on the material surface was determined by measuring the dynamic contact angle hysteresis loop of the SPUU surface after each sample was immersed in an aqueous phosphate buffer solution of bovine serum albumin (BSA).

In Fig. 9 (A), (B), and (C), P P G (100
0) E D A , P P G (3000) E D
A, and PEG (1000) E D After A was immersed in water to reach equilibrium and further immersed in BSA aqueous solution for 1 h, and after rinsing with PBS until the dynamic contact angle hysteresis loop reached a steady state. P P G (1000)E, showing a dynamic contact angle hysteresis loop
In the case of DA, the receding contact angle changed significantly after immersion in BSAS liquid, and especially the receding contact angle showed a value of female hydrophilicity. This indicates that a BSA adsorption layer was formed on the 5PUU surface. However, the large value of the advancing contact angle suggests that the BSA is showing local segment inversion or that the BSA as a whole is inverted. On the other hand, in the case of P P G (3000) EDA, B
The value of receding contact angle after SA immersion is P P G (1000
) showed a higher value than ED A.

This suggests that the adsorbed BSA showed some conformational change. PEG(100G)E
In the case of DA, no change in the hysteresis loop was observed even after immersion in the BSA aqueous solution. This is P E G (
1000) indicates that the EDA surface hardly adsorbs BSA.

[Effects of the Invention] As described above, according to the first aspect of the present invention, the dynamic contact angle that changes from time to time on the sample surface can be measured quickly and with high precision regardless of the surface shape. can.

According to the second aspect of the present invention, it is possible to quickly and accurately measure the dynamic contact angle that changes momentarily on the surface of a sample under specific environmental temperature conditions, regardless of the surface shape. can.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing an example of a dynamic contact angle measurement device, Figure 2
The figure is a block diagram showing the control system of the dynamic contact angle measuring device.
Figure 3 is a piping diagram showing the temperature control device, Figure 4 is a schematic diagram showing the load acting on the sample, Figure 5 is a diagram showing the dynamic contact angle hysteresis loop, and Figure 6 is the acceleration acting on the sample. Fig. 7 is a schematic diagram showing the displacement of the load cell, Fig. 8 is a diagram 1 showing an example of measuring the time dependence of surface tension, and Fig. 9 is a measurement of dynamic contact angle hysteresis loop. FIG. 3 is a diagram illustrating an example. 10...Dynamic contact angle measuring device. 11... Sample, 12... Container, 13... Frame, 14... Load cell. 15... Container pedestal, 16... Lifting drive unit, 17... Temperature control device. 18...Control unit W (calculation unit). Agent Patent Attorney Osamu Shiokawa Figure 1 Figure 2 Figure 4 b Virtue Figure 5! 31''''Figure 6 (A) (B) (C) 7th Figure 8 Time/s

Claims (2)

[Claims] (1) A dynamic contact angle measurement device that measures the contact angle between the liquid surface and the sample surface at a position where the liquid surface touches the sample surface when the sample is immersed or pulled up into the liquid, and includes a mount;
a load cell disposed on a pedestal to suspend and support a sample; a container pedestal disposed on the pedestal so as to be movable up and down to support a liquid storage container; a lift drive unit for raising and lowering the container pedestal relative to the load cell; Receives the load detection signal from the load cell when the container pedestal goes up and down, determines the surface tension when the sample is immersed or pulled up into the liquid based on the change in the load detection signal, and calculates the contact angle based on this surface tension. A dynamic contact angle measuring device comprising: (2) A dynamic contact angle measurement device that measures the contact angle between the liquid surface and the sample surface at a position where the liquid surface contacts the sample surface when the sample is immersed or pulled up in the liquid, the device comprising a mount;
a load cell disposed on a pedestal to suspend and support a sample; a container pedestal disposed on the pedestal so as to be movable up and down to support a liquid storage container; a lift drive unit for raising and lowering the container pedestal relative to the load cell; A temperature control device that can control the temperature of the liquid in a liquid storage container supported by a container pedestal, and a temperature control device that receives a load detection signal from a load cell when the container pedestal is raised and lowered, and controls the temperature of the sample based on changes in the load detection signal. A dynamic contact angle measurement device comprising: a calculation section that determines surface tension when being immersed in or pulled up from a liquid, and calculates a contact angle under a specific temperature condition based on this surface tension.