Method for correcting contact angle

Abstract

The present invention includes: acquiring data 1 obtained by measuring a contact angle at each inclination angle while changing an inclination angle from a minimum inclination angle to a maximum inclination angle (step S2); acquiring data 2 obtained by measuring a contact angle at a target inclination angle between the minimum inclination angle to the maximum inclination angle (step S4); and obtaining the difference between the contact angle at the target inclination angle in the data 1 and the data 2 and correcting the data 2 by using the difference as an influence on the contact angle due to volatilization (step S5).

Description

Contact angle correction method

[0001] The present disclosure relates to a method for correcting a contact angle.

[0002] Contact angle is one of the evaluation indices for the surface of a water- and oil-repellent material (Non-Patent Documents 1 and 2). The contact angle is the angle between the liquid surface and the solid surface at the contact point between the liquid droplet and the solid surface when a droplet is dropped on the solid surface. A small contact angle indicates good wetting and high hydrophilicity. A large contact angle indicates poor wetting and high water repellency.

[0003] There are two types of contact angles: static contact angles, which are measured when the droplet is almost stationary, and dynamic contact angles, which are measured when the droplet slides down an inclined surface. One known method for measuring dynamic contact angles is the sliding method, in which a droplet is dropped onto a solid surface and the contact angle is measured by tilting the surface (Non-Patent Document 1).

[0004] "Types of contact angles and measurement methods," [online], Kyowa Interface Science Co., Ltd., [Retrieved April 25, 2023], Internet <URL: https: / / www.face-kyowa.co.jp / science / literature / contactangle03.html> "What is contact angle (wettability)?", [online], Kyowa Interface Science Co., Ltd., [Retrieved April 25, 2023], Internet <URL: https: / / www.face-kyowa.co.jp / science / theory / what_contact_angle / >

[0005] When measuring the contact angle at each tilt angle while changing the tilt angle, there is a problem that the droplet evaporates over time after being dropped, making it impossible to obtain a correct contact angle. This problem is particularly noticeable in the latter half of the measurement or when measuring the contact angle using a small amount of droplet.

[0006] The present disclosure has been made in view of the above, and aims to obtain a more accurate contact angle.

[0007] A contact angle correction method according to one aspect of the present disclosure obtains a first group of measurement values ​​in which the contact angle is measured at each inclination angle while changing the inclination angle from the minimum inclination angle to the maximum inclination angle, and a second group of measurement values ​​in which the contact angle is measured at any intermediate inclination angle between the minimum inclination angle and the maximum inclination angle, calculates the difference between the contact angle at the intermediate inclination angle in the first group of measurement values ​​and the second measurement value, and corrects the first group of measurement values ​​using the difference as the effect of volatilization on the contact angle.

[0008] According to the present disclosure, a more accurate contact angle can be obtained.

[0009] FIG. 1 is a flowchart showing an example of the processing flow of a contact angle correction method. FIG. 2 is a diagram showing an example of changing the tilt angle of a sample. FIG. 3 is a diagram showing an example of setting a sample to a target tilt angle. FIG. 4 is a flowchart showing an example of the correction processing flow. FIG. 5 is a diagram plotting measured contact angle values. FIG. 6 is a diagram showing an approximation curve of measured contact angle values. FIG. 7 is a diagram showing an estimated value of the amount of decrease in contact angle due to the influence of volatilization. FIG. 8 is a diagram showing the corrected value of the estimated value. FIG. 9 is a diagram showing an example of the configuration of a correction device. FIG. 10 is a diagram showing an example of the hardware configuration of a correction device.

[0010] [Contact Angle Correction Method] An example of a contact angle correction method according to this embodiment will be described with reference to the flowchart in Fig. 1. Hereinafter, when simply referring to contact angle, it may be understood to mean either the advancing contact angle, the receding contact angle, or both the advancing contact angle and the receding contact angle.

[0011] In step S1, a droplet is dropped onto a sample to be evaluated, and in step S2, the contact angle is measured at each tilt angle while changing the tilt angle of the sample.

[0012] Figure 2 shows how the tilt angle of the sample is changed. Figure 2(a) shows the state after a droplet 200 is dropped onto the sample 100, with the tilt angle α remaining unchanged from the minimum tilt angle of 0°. Figure 2(b) shows the state when the tilt angle α is set to 45°. Figure 2(c) shows the state when the tilt angle α is set to the maximum tilt angle of 90°. For example, the advancing contact angle θa and the receding contact angle θr are measured at each tilt angle α while increasing the tilt angle α by 1° from the minimum tilt angle of 0° to the maximum tilt angle of 90°. The advancing contact angle θa is the contact angle in the direction in which the droplet 200 slides down, and the receding contact angle θr is the contact angle in the opposite direction. The advancing contact angle θa and the receding contact angle θr can be measured using images of the droplet 200 using the tangent method described in Non-Patent Document 2.

[0013] Both the minimum and maximum tilt angles may be set to any value. For example, if the sample has a drop that slides off at an angle of 30°, the maximum tilt angle may be set to 30°.

[0014] In step S3, a droplet is dropped onto the sample to be evaluated, and after the droplet is dropped, in step S4, the sample is quickly set to a desired tilt angle and the contact angle is measured.

[0015] Figure 3 shows the sample set at the desired tilt angle. In the example shown in Figure 3, the desired tilt angle is set to 45°, an intermediate angle between the minimum tilt angle of 0° and the maximum tilt angle of 90°. After the droplet is dropped, the tilt angle α of the sample 100 is quickly tilted to 45° to measure the advancing contact angle θa and the receding contact angle θr. If the minimum tilt angle is 0° and the maximum tilt angle is 30°, the desired tilt angle is set to 15°. Note that the desired tilt angle does not have to be an angle intermediate between the minimum and maximum tilt angles, as long as it is an angle between the minimum and maximum tilt angles. For example, if the minimum tilt angle is 0° and the maximum tilt angle is 90°, the desired tilt angle may be 30° or 60°.

[0016] The measurement results of steps S1 and S2 are referred to as Data 1, and the measurement results of steps S3 and S4 are referred to as Data 2. In other words, Data 1 is the measured value of the contact angle at each tilt angle from the minimum tilt angle to the maximum tilt angle, and Data 2 is the measured value of the contact angle at the target tilt angle. For example, Data 1 is the measured value of the advancing contact angle at 1° increments from the minimum tilt angle of 0° to the maximum tilt angle of 90°, and Data 2 is the measured value of the advancing contact angle at a tilt angle of 45°.

[0017] In step S5, the effect of volatilization on the contact angle is determined from Data 1 and Data 2, and a correction value for the contact angle is calculated. Data 1, which is obtained by measuring the contact angle while changing the tilt angle from the minimum tilt angle to the maximum tilt angle, deviates from the original value due to the influence of volatilization because the larger the tilt angle, the greater the time elapsed. Therefore, in this embodiment, Data 2, which is obtained by measuring the contact angle at the target tilt angle immediately after dropping the droplet, is obtained to determine the effect of volatilization, and a correction value for the contact angle that cancels the effect of volatilization is calculated from Data 1. For Data 2, the contact angle is measured by setting the sample at the target tilt angle immediately after dropping the droplet, so the effect of volatilization can be ignored. The effect of volatilization can be calculated by comparing the contact angle of Data 2 with the contact angle of Data 1 at the target tilt angle at which Data 2 was measured.

[0018] [Correction Process] An example of the correction process performed by the apparatus in step S5 of FIG. 1 will be described with reference to the flowchart of FIG. 4. Here, as an example, Data 1 was obtained by dropping a 2 μL droplet of water onto a sample and measuring the advancing contact angle at 1° intervals from the minimum tilt angle of 0° to the maximum tilt angle of 90°, and Data 2 was obtained by measuring the advancing contact angle with the target tilt angle set to 45°. When measuring Data 1, the waiting time after increasing the tilt angle by 1° was 1000 ms. The advancing contact angle was determined by the tangent method described in Non-Patent Document 2 using an image taken 1000 ms after changing the tilt angle.

[0019] In step S51, the device calculates an approximation curve for Data 1. Figure 5 shows the measured values ​​of Data 1 and Data 2, with the horizontal axis representing the tilt angle and the vertical axis representing the advancing contact angle. Black circles represent plots of Data 1, and white circles represent plots of Data 2. Figure 6 shows the approximation curve for Data 1. The approximation curve for Data 1 is y=0.0031x 2 The answer was -0.4678x+89.831.

[0020] In step S52, the device calculates the difference between Data 1 and Data 2. Specifically, the device calculates the advancing contact angle at the target tilt angle of Data 1 by substituting the target tilt angle at which Data 2 was measured into the approximation curve calculated in step S51, and then calculates the difference between the calculated advancing contact angle and Data 2.

[0021] In the example, Data 2 was measured at a target inclination angle of 45° and was 91°. The advancing contact angle when the inclination angle of the approximation curve for Data 1 was 45° was 75°, so the difference between Data 1 and Data 2 was calculated to be 16°.

[0022] The difference between Data 1 and Data 2 may be calculated as the difference between the measurement value of Data 1 at the target tilt angle and Data 2, without using an approximation curve.

[0023] In step S53, the device calculates an estimate of the amount of decrease in the advancing contact angle due to volatilization between the minimum and maximum tilt angles based on the difference calculated in step S52. The measured value of the minimum tilt angle in Data 1 is not affected by volatilization, and it is considered that there is almost no change in the advancing contact angle due to volatilization. The amount of decrease in the advancing contact angle due to volatilization increases by a constant amount over time, and the difference is divided by the value obtained by subtracting the minimum tilt angle from the target tilt angle to calculate an estimate of the amount of decrease in the advancing contact angle due to volatilization for each 1° increase in tilt angle.

[0024] In this example, the minimum tilt angle is 0°, the target tilt angle is 45°, and the difference is 16°. Therefore, the estimated decrease in advancing contact angle due to volatilization for each 1° increase in tilt angle is calculated as 16° / (45°-0°) = 0.4°. The estimated decrease at a given tilt angle is calculated by multiplying the estimated decrease in advancing contact angle due to volatilization for each 1° increase in tilt angle by the value obtained by subtracting the minimum tilt angle from the tilt angle. Figure 7 shows the estimated decrease in advancing contact angle due to volatilization from the minimum tilt angle to the maximum tilt angle, with the tilt angle on the horizontal axis and the estimated decrease in advancing contact angle on the vertical axis.

[0025] In step S54, the device calculates a correction value for the advancing contact angle. Specifically, the device calculates the correction value for the advancing contact angle by adding the estimated value of the decrease in the advancing contact angle between the minimum tilt angle and the maximum tilt angle calculated in step S53 to the approximation curve for Data 1. Figure 8 shows the correction value for the advancing contact angle obtained by adding the estimated value of the decrease to the approximation curve for Data 1. The solid line represents the correction value for the advancing contact angle, and the dotted line represents the approximation curve for Data 1. The correction value for the contact angle may be calculated by adding the estimated value of the decrease to the measured value for Data 1.

[0026] Although the correction of the advancing contact angle has been described above, the receding contact angle can also be corrected in the same manner.

[0027] [Configuration of Apparatus] An example of the configuration of a correction apparatus for correcting a contact angle will be described with reference to Fig. 9. A correction apparatus 10 shown in the figure includes an input unit 11, an analysis unit 12, and a calculation unit 13.

[0028] The input unit 11 inputs still images or videos of droplets for measuring Data 1 and Data 2. When a video for measuring Data 1 is input, the input unit 11 extracts frames for each tilt angle from the video and transmits them to the analysis unit 12. The input unit 11 may also input still images for each tilt angle for measuring Data 1. The input unit 11 may also be equipped with a camera to capture images of the droplets.

[0029] The input unit 11 may input data 1 and data 2. When data 1 and data 2 are input, the analysis unit 12 does not need to measure the contact angle.

[0030] The analysis unit 12 analyzes the captured image of the droplet to determine the contact angle (data 1 and data 2). The analysis unit 12 may display the image and receive input of a line segment indicating the contact angle from the operator.

[0031] The calculation unit 13 calculates the effect of volatilization on the contact angle from the data 1 and data 2 according to the flowchart of FIG.

[0032] As described above, the contact angle correction method of this embodiment acquires data 1 by measuring the contact angle at each tilt angle while changing the tilt angle from the minimum tilt angle to the maximum tilt angle, acquires data 2 by measuring the contact angle at a target tilt angle between the minimum tilt angle and the maximum tilt angle, calculates the difference between the contact angle at the target tilt angle in data 1 and data 2, and corrects data 2 by using the difference as the effect of volatilization on the contact angle. This allows a more accurate contact angle to be acquired by taking the effect of volatilization into account.

[0033] The correction device 10 described above can be, for example, a general-purpose computer system including a central processing unit (CPU) 901, a memory 902, a storage 903, a communication device 904, an input device 905, and an output device 906, as shown in Fig. 10. In this computer system, the correction device 10 is realized by the CPU 901 executing a predetermined program loaded onto the memory 902. This program can be recorded on a computer-readable non-transitory recording medium such as a magnetic disk, an optical disk, or a semiconductor memory, or can be distributed via a network.

[0034] 10 Correction device 11 Input unit 12 Analysis unit 13 Calculation unit

Claims

1. A method for correcting a contact angle, comprising: obtaining a first group of measurement values ​​in which the contact angle is measured at each inclination angle while changing the inclination angle from the minimum inclination angle to the maximum inclination angle; and obtaining a second group of measurement values ​​in which the contact angle is measured at any intermediate inclination angle between the minimum inclination angle and the maximum inclination angle; determining the difference between the contact angle at the intermediate inclination angle in the first group of measurement values ​​and the second measurement value; and correcting the first group of measurement values ​​using the difference as the effect on the contact angle due to volatilization.

2. A contact angle correction method as described in claim 1, comprising: determining an amount of change in contact angle due to volatilization per unit inclination angle in the first measurement value group from the minimum inclination angle, the intermediate inclination angle, and the difference; and correcting each of the contact angles in the first measurement value group by the amount of change in contact angle corresponding to each inclination angle.

3. A contact angle correction method according to claim 1 or 2, comprising the steps of: determining an approximation curve from the first group of measurement values; and determining a difference between the value of the approximation curve at the intermediate inclination angle and the second measurement value.