JPH0774777B2 - Dynamic contact angle measuring device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dynamic contact angle measuring device.

[Prior Art] On the surface of a polymer material, a polar group portion of the surface is oriented so as to minimize the interfacial free energy with the surrounding environment during molding or film formation. Such a selective orientation is not constant, and the orientation can be changed depending on the external environment only when the micro Brownian motion of the surface segment is allowed. Further, the surface chemical composition of the multiphase polymer material is
It is known that, when the microphase separation is very different from the interior, the hydrophobic groups are rapidly oriented in the air and the hydrophilic groups are oriented in the water in the water, and the response to the environment is extremely short.

Therefore, evaluation of surface characteristics according to the purpose of use of the material,
For example, in the case of segmented polyurethane (SPUU) used in artificial hearts and the like, it is important to evaluate the surface properties of the part in contact with water, which is the main component of the living body.

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

Conventionally, the contact angle is measured by dropping a droplet of water or the like on a flat plate (cover glass) coated with a polymer material, etc. The angle formed is measured as the contact angle.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional contact angle measuring method,
There are the following problems.

Since it is a visual detection using a microscope, it is not possible to detect the dynamic contact angle which changes moment by moment on the sample surface quickly, easily and with high accuracy.

When a droplet is dropped on a sample surface having a complicated surface shape other than a flat plate, the droplet drops without resting on the sample surface, and the contact angle cannot be measured.

It is an object of the present invention to measure a dynamic contact angle on the surface of a sample, which changes moment by moment, quickly and with high accuracy regardless of the surface shape.

[Means for Solving Problems] The present invention provides a method for immersing a sample in a liquid or pulling it up.
A dynamic contact angle measuring device for measuring a contact angle between a liquid surface and a sample at a position where the liquid surface is in contact with the sample surface, including a pedestal, a load cell mounted on the pedestal to suspend and support the sample, and a pedestal. A container pedestal that is vertically movable to support the liquid storage container, and an elevating / lowering drive unit that elevates and lowers the container pedestal with respect to the load cell. Buoyancy slope lines (S ₁ , S ₂ ) in the load F-displacement d curve and immersion start point (d
= 0) The tension (FA, FR) obtained as the intersection point
The dynamic contact angle (θA, θR) is calculated.

[Operation] The present invention, when the container pedestal is moved up and down with respect to the load cell and the sample suspended and supported by the load cell is immersed or pulled up in the liquid in the liquid storage container supported by the container pedestal, the load cell The tensions FA and FR are determined from the buoyancy slope line in the load (F) -displacement (d) curve based on the change in the load signal of ## EQU1 ## and the contact angle is obtained using this value.

Therefore, according to the present invention, it is possible to automatically measure the dynamic contact angle which changes momentarily on the sample surface, and the contact angle can be detected quickly, easily and with high accuracy.

Further, according to the present invention, when the sample is immersed in the liquid or pulled up, based on the load signal of the load cell,
Since the tensions FA and FR exerted by the surface tension are determined and the contact angle is measured, the contact angle can be measured regardless of the surface shape of the sample.

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

The dynamic contact angle measuring device 10 is configured as shown in FIGS. 1 and 2, and is a position where the liquid surface comes into contact with the sample surface when the sample 11 is immersed in or pulled up from the liquid inside the liquid container 12 Makes it possible to measure the contact angle θ between the liquid surface and the sample surface.
The dynamic contact angle measuring device 10 is configured to include a gantry 13, a load cell 14, a container pedestal 15, an elevation drive unit 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 the fixed crosshead 19 fixed to the upper part of the guide rod 13A, and the fixed crosshead 19 is provided with the load cell 14. In the load cell 14, a chuck 22 is hung from a hook 20 connected to a sensing section of the load cell 14 via a flexible connecting tool 21 made of a thread, a thin metal wire, a chain or the like, and the sample 22 is held by the chuck 22. The load cell 14 measures a load (tension) with a highly sensitive strain gauge. The sample 11 is, for example, a polymer material,
It is thinly coated on a flat cover glass.

Further, the dynamic contact measurement device 10 includes a container pedestal (movable crosshead) 15 that can be moved up and down along the guide rod 13A.
A constant temperature bath 23 of a temperature control device 17 is installed on the upper surface of the container support 15, and the constant temperature bath 23 holds the container 12. 24 is a container holder.

Further, the dynamic contact angle measuring device 10 is provided with a pulse motor 25 and a feed screw 26 that constitute the lifting drive unit 16 at the bottom of the pedestal 13, and the feed screw 26 driven by the motor 25 is screwed onto the container pedestal 15. I'm wearing it. The motor 25 includes an encoder 27.

Further, the temperature control device 17 is configured as shown in FIG.
The circulation pipe 28 connected to the constant temperature bath 23 is introduced into the heat exchanger 29 to set the heat medium temperature inside the constant temperature bath 23 to a desired temperature state.

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 includes, for example, a microcomputer,
As shown in FIG. 2, a CPU (central processing unit) 31, a ROM (read only memory) 32, a RAM (read / write memory) 33, an input / output device 34 are provided, a keyboard 35, an XY display unit ( An XY plotter, an XY recorder 36, and a printer 37 are additionally provided. The control device 18 drives and controls the motor 25 on the basis of an operation command given by the keyboard 35.

Further, the control device 18 receives the output of the load cell 14 via the amplifier 38 and also receives the output of the encoder 27 to form an arithmetic unit. That is, the control device 18 receives the load detection signal of the load cell 14 when the container pedestal 15 is moved up and down, and the sample 11 is immersed or pulled up in the liquid based on the change of the load detection signal, as described in detail below. At this time, the contact angle of the liquid under the specific temperature condition is calculated.

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

A sample 11 such as a polymer material is thinly coated on the cover glass. This sample 11 has a hook 20 and a flexible connector.
It is hung and supported by the load cell 14 via 21.

For example, a container 12 containing pure water (which has been converted into ultrapure water by a pure water manufacturing apparatus after ion exchange) is held in a constant temperature bath 23 installed on a container pedestal 15.

The motor 23 of the lifting drive unit 16 is driven, and the container 12 approaches (raises) or separates (falls) from the sample 11 suspended in the load cell 14 at a constant speed.

Output of load cell 14 and displacement of container pedestal 15 (encoder
27 outputs) are transferred to the memory of the controller 18 in synchronization with each other and stored as a load F-displacement d curve as shown in FIG.

When the container pedestal 15 rises and the lower end of the sample 11 touches the water surface of the container 12 to form a meniscus, interfacial tension is observed. At this time, the formation of the meniscus on the water surface of sample 11 and sample 11
The force acting on is shown in FIG. The forces F1, F2, F3 acting on the sample 11 in FIG.
= 2 (t + w), surface tension of water is γ, contact angle is θ, sample
When the mass of 11 is m and the buoyancy acting on the sample 11 is Fb, the following is obtained.

F1 = mg (1) F2 = mg + Pγ cosθ (2) F3 = mg + Pγ cosθ-Fb (3) In the above, the advancing contact angle θA is evaluated from the tension FA generated when the sample 11 contacts the water surface. To be done.

cos θA = FA / Pγ (4) Furthermore, when the sample 11 is immersed in water, the tension decreases as the buoyancy decreases. When the sample 11 reaches a certain depth and the container pedestal 15 begins to descend, the buoyancy decreases and the observed tension increases. At this time, sample from the water surface
The receding contact angle θR is evaluated from the tension FR when 11 is separated.

cos θR = FR / Pγ (5) Here, the tensions FA and FR are the buoyancy slope lines (s1 and s2) and the immersion start point (d = 0) from the load F-displacement d curve stored above. ) Is obtained as the intersection.

The immersion start point (d = 0) is determined from the load F-displacement d curve as shown in FIG. 5 by reading the tension change F0 when the sample 11 comes into contact with the liquid surface. The tension change F0 can be set and changed within a range that does not impair the measurement accuracy of the device 10, and the immersion start point can always be read stably with respect to disturbance such as external vibration.

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

In the above-mentioned dynamic contact angle measuring device 10, the container 11 is moved up and down with respect to the load cell 14, and the sample 11 suspended and supported by the load cell 14 is supported by the container 15 as a liquid container. When the liquid is immersed or pulled up in the liquid inside 12, the control device 18 as a calculation unit obtains the tensions FA and FR based on the change of the load detection signal of the load cell 14, and further the contact angle θA based on this tension. , ΘR are obtained. If the surface composition changes during the first immersion process, the tension-displacement curve observed during the second immersion is 1
Different from the first time. In addition, the responsiveness of the molecules on the surface of the sample to the environment can be examined by variously changing the immersion speed of the sample in water. The difference between θA and θR is called the hysteresis of the contact angle, and the mobility of the molecular chains in the surface layer can be evaluated by this value. Moreover, the relaxation time of the molecular motion in the surface layer can be evaluated by changing the ascending or descending speed of the container variously.

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

Further, according to the above-described embodiment, the tension FA and FR exerted by the surface tension are determined based on the load detection signal of the load cell 14 when the sample is immersed in the liquid or pulled up, and the contact angle is measured. The contact angle can be measured regardless of the surface shape of the sample.

Further, in the above embodiment, the temperature of the liquid in the liquid container can be controlled by using the temperature control device 17 when measuring the contact angle. Therefore, the contact angle can be accurately measured under a specific environmental temperature condition such as the living body temperature.

In the dynamic contact angle measuring device 10, the load cell
When the load applied to the sample 11 is measured by immersing or pulling up the sample 11 suspended and supported in the liquid 14,
A method of moving the load cell 14 and a method of moving the liquid container 12 can be considered. In the method of (1), when the load cell 14 is accelerated or decelerated, for example, while the lift table supporting the load cell 14 reaches a constant speed from a stopped state (see FIG. 6A), the sample (mass: m ) Receives acceleration α (see FIG. 6 (B)). Load cell when stopped
The load T1 acting on 14 is T1 = mg, and the load T2 acting on the load cell 14 during acceleration is T2 = mg + mα. That is, the load T2 acting on the load cell 14 during acceleration increases (or decreases) by mα under the influence of the acceleration α, and the load cell 14 detects this. When the acceleration α is rapidly applied (or removed) by the method of,
Spring system consisting of load cell 14 and sample 11 (spring constant: k)
Oscillates according to the equation of motion consisting of mα = −kx (see FIG. 6 (C)). On the other hand, in the method, it is possible to eliminate the influence of the acceleration α and the vibration of the sample 11 on the detected load of the load cell 14, and only the load change caused by the surface characteristics of the sample 11 is detected. By this, stable measurement can be performed.

Further, the measurement state of the load F due to the spring strain of the load cell 14 used in the dynamic contact angle measuring device 10 is schematically shown in FIG. 7 (A). Load cell 14 and sample
When 11 and 11 are connected by a connector made of a high-rigidity body as shown in FIG. 7 (C), the deflection of the sample 11 causes the displacement (r to r ') of the sensing portion of the load cell 14. The load is greatly changed, and the measurement result by the load cell 14 is greatly changed. In contrast, as in the above embodiment, the load cell
A flexible connector 21 as shown in FIG.
If the sample 11 is swingably connected to the sensing part using a connecting tool consisting of the hook 20 and / or the hook 20,
The deflection of 11 does not significantly change the displacement (r) of the sensing portion of the load cell 14, and the load acting on the sample 11 can be measured with high accuracy.

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

The segmented polyurethane (SPUU), which is applied to artificial hearts and has excellent antithrombotic properties and mechanical properties, was evaluated for surface properties when it comes into contact with water, which is the main component of the living body.
Figure and Figure 9 were obtained.

Measurement Example 1 That is, FIG. 8 shows the time dependence of tension when a flat plate coated with each SPUU was immersed in pure water for 10 mm. PEG (1000) EDA containing polyethylene glycol (molecular weight 1000) which is a hydrophilic soft segment and polypropylene glycol (molecular weight 30 which is a hydrophobic soft segment)
In the case of completely phase-separated PPG (3000) EDA containing 00), the surface tension changes over a long period of time, and the degree of relaxation corresponding to the rearrangement of the molecular chain aggregation state on the surface is also significantly large. It is considered that this is because a hydrophilic molecular chain is deposited on the surface layer with the immersion in water to stabilize the solid-water interface. On the other hand, soft segment molecular weight 700
In the case of PPG (700) EDA and PPG (1000) EDA containing 1000 and 1000 PPGs, the change in tension over time is small, indicating that the surface chemical structure is regulated and stabilized during film formation.

Measurement Example 2 The adsorption state of the plasma protein on the material surface was measured by immersing each sample in an aqueous solution of bovine serum albumin (BSA) in a phosphate buffer and measuring the dynamic contact angle hysteresis loop of the SPUU surface. 9 (A), (B), and (C) show the PPG (100
0) EDA, PPG (3000) EDA, and PEG (1000) EDA are soaked in water to reach equilibrium, and further soaked in BSA aqueous solution for 1 hour, until the hysteresis loop of dynamic contact angle reaches a steady state. Figure 4 shows the dynamic contact angle hysteresis loop after rinsing with PBS. In the case of PPG (1000) EDA, the advancing and receding contact angles changed remarkably after immersion in BSA, and the receding contact angle showed superhydrophilic value. This indicates that the BSA adsorption layer was formed on the surface of SPUU. However, the large advancing contact angle indicates that the BSA locally shows segment inversion or the entire BSA has inverted. On the other hand, in the case of PPG (3000) EDA, the receding contact angle value after immersion in BSA was higher than that in PPG (1000) EDA. This suggests that the adsorbed BSA showed some conformational change. PEG (1000) E
In the case of DA, no change was observed in the hysteresis loop even after immersion in the BSA aqueous solution. This is PEG (1000) EDA surface is BS
It shows that A is hardly adsorbed.

[Effects of the Invention] As described above, according to the present invention, the dynamic contact angle on the surface of a sample is changed at any time regardless of the surface shape.
It is possible to measure quickly and with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a dynamic contact angle measuring device, and FIG.
Figure is a block diagram showing the control system of the dynamic contact angle measuring device,
FIG. 3 is a piping diagram showing the temperature control device, FIG. 4 is a schematic diagram showing a load acting on the sample, FIG. 5 is a diagram showing a dynamic contact angle hysteresis loop, and FIG. 6 is an acceleration acting on the sample. Fig. 7 is a schematic diagram showing the influence of the load cell, Fig. 7 is a schematic diagram showing the displacement of the load cell, Fig. 8 is a diagram showing a measurement example of the time dependence of surface tension, and Fig. 9 is a measurement example of a dynamic contact angle hysteresis loop. FIG. 10 …… Dynamic contact angle measuring device, 11 …… Sample, 12 …… Container, 13 …… Stand, 14 …… Load cell, 15 …… Container cradle, 16 …… Lift drive unit, 17 …… Temperature control device , 18 ... Control device (arithmetic unit).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 62-46232 (JP, A) JP 47-31674 (JP, A)

Claims (1)

[Claims] 1. A dynamic contact angle measuring device for measuring a contact angle between a liquid surface and a sample at a position where the surface of the liquid is in contact with the surface of the sample when the sample is immersed in or pulled up from the liquid. A load cell disposed on the gantry to suspend and support the sample; a container pedestal erected on the gantry to support the liquid storage container; and an elevating and lowering drive unit for elevating the container pedestal with respect to the load cell. And the intersection of the buoyancy slope line (S ₁ , S ₂ ) and the immersion start point (d = 0) in the load F-displacement d curve, which is obtained from the displacement of the container pedestal when it is moved up and down and the load cell load signal. A dynamic contact angle measuring device characterized in that the dynamic contact angle (θA, θR) is calculated by the tension (FA, FR) obtained as