What is the accuracy of contact angle tester related to?

The accuracy of the contact angle tester is closely related to many ways.

The following is a description from the aspects of the instrument itself, test samples, test environment and operators:

Performance and design of the instrument itself

-Optical system

-Resolution and clarity: High-quality optical lens and high-resolution camera are the basis of accurate measurement. If the resolution of the optical system is insufficient, the captured droplet image will be blurred, resulting in the inability to accurately determine the droplet profile and contact angle. For example, when a low-resolution camera is used, the details of small droplets on the solid surface may not be clearly captured, resulting in a large error in the measurement of contact angle.

-Calibration accuracy: The optical system needs to be calibrated accurately to ensure the accuracy of shooting angle and image size. If the camera is not parallel to the horizontal plane or there are other calibration problems, the shape of the photographed droplets will be distorted, which will affect the calculation result of contact angle.

-Injection system

-Droplet size and volume control: An accurate injection system can accurately control the droplet size and volume, which is very important for repeatability and accuracy. If the droplet size is inconsistent or the volume control is inaccurate, the wetting behavior of different droplets on the solid surface will be different, which will affect the measurement result of contact angle. For example, if there is a big difference in the volume of droplets injected each time, the contact angle data obtained will be unstable.

-Stability of liquid injection: The injection system should be able to drop liquid onto the solid surface stably, so as to avoid liquid splashing or irregular droplet shape. The unstable injection process may cause the droplets to spread unevenly on the solid surface, thus affecting the accuracy of contact angle.

Test the characteristics of the sample

-Surface flatness: the flatness of the sample surface has a great influence on the measurement of the docking antenna. If the surface is uneven, droplets will form irregular shapes on the surface, and it is difficult to accurately determine the contact angle. Therefore, before the measurement, it is necessary to ensure that the surface of the sample is flat and smooth. For rough surfaces, special treatment methods can be adopted, such as coating a smooth film to reduce the influence of surface roughness on the measurement results.

-Surface cleanliness: The cleanliness of the sample surface will also affect the measurement result of contact angle. If there is oil, dust or other impurities on the surface, the wettability of liquid on the surface will change, resulting in inaccurate contact angle measurement. Before measurement, the surface of the sample needs to be cleaned to remove possible pollutants.

Test environmental factors

-Temperature and humidity: Environmental temperature and humidity will affect the surface tension and wettability of liquid, thus affecting the measurement result of contact angle. The contact angle of the same liquid on the same solid surface may be different under different temperature and humidity conditions. Therefore, when measuring, it is necessary to keep the ambient temperature and humidity stable and record the relevant data so as to correct the measurement results.

-External interference: External interference, such as airflow and vibration, should be avoided during measurement. The air flow will make the droplets shake and affect the shape and position of the droplets; Vibration may cause droplets to slide off the solid surface or form irregular shapes. In order to reduce external interference, measurements can be made in a closed environment, or appropriate wind and shock absorption measures can be taken.

Operator's factor

-Normality of operation: the operator should strictly follow the operating rules of the instrument, including sample placement, liquid injection, image shooting and data processing. Incorrect operation may lead to deviation of measurement results. For example, when injecting liquid, if the speed is too fast or the droplets are too large, the droplets may form irregular shapes on the solid surface; When shooting an image, if the focal length or shooting angle is not adjusted properly, the measurement result of contact angle will also be affected.

-Experience and skill level: The experience and technical proficiency of operators will also affect the accuracy of measurement. Experienced operators can better grasp the performance and characteristics of the instrument and correctly deal with various possible problems, thus improving the accuracy and reliability of the measurement results.