Contact angle meterIt is a precision optical instrument that measures the contact angle formed by a liquid on a solid surface, analyzes the wetting properties, surface energy, and interfacial interactions of the solid surface. It is widely used in materials science, chemical engineering, biomedicine, electronic manufacturing, and other fields, and is one of the core tools for evaluating material surface properties.

Its working principle is based on the "wetting phenomenon": when a droplet of liquid (such as distilled water or ethanol) falls onto a solid surface, the interface between the liquid and the solid, or between the liquid and the gas, forms a specific angle, known as the "contact angle". The size of the contact angle directly reflects the wetting ability of the solid surface - usually when the contact angle is less than 90 °, the liquid can spread on the solid surface, indicating that the solid surface is hydrophilic (such as hydrophilic glass surfaces); When the contact angle is greater than 90 °, the liquid aggregates in a spherical shape, indicating that the solid surface is hydrophobic (such as hydrophobic lotus leaf surfaces or waterproof coating surfaces).

　　Contact angle meterDetailed operation steps:

1、 Equipment preparation and calibration

environmental control

Place the instrument in a dry, windless experimental environment to avoid airflow interference with droplet morphology.

Maintain a stable room temperature (such as 23 ± 2 ℃) and control the humidity at 50 ± 5% RH to reduce the impact of environmental fluctuations on measurement results.

Device initialization

Connect the power and start the dedicated analysis software, adjust the lighting intensity through the light source knob until the field of view is clear and glare free.

Use a level to calibrate the stage and ensure that droplet formation is not affected by tilting interference.

Calibration instrument

Use standard surfaces (such as polytetrafluoroethylene with known contact angles) or standard samples for calibration, adjust the light source, camera position, and focal length to ensure clear images and accurate angle measurements.

Zero point calibration: Adjust the software to display a contact angle of 0 ° in the absence of a sample.

2、 Sample and liquid preparation

Sample processing

Solid block: Cut into a 2cm x 2cm flat surface, clean it with a dust-free cloth dipped in isopropanol, and let it dry naturally.

Film material: Cut into 5cm x 5cm size and fix it in the center of the glass slide with double-sided tape.

Powder sample: A special tablet press is used to maintain a pressure of 10MPa for 30 seconds to produce a dense circular disc with a diameter of 13mm.

Moisture absorbing samples: Conduct testing in a drying oven with humidity<40% to avoid surface state changes.

Liquid preparation

Choose a suitable liquid for testing (such as deionized water, diiodomethane), ensuring that its properties and temperature are suitable for the required measurement.

Use a microsyringe or droplet dispenser to extract liquid and remove air from the needle (such as squeezing the piston upwards with the needle) to prevent inaccurate droplet volume.

3、 Install samples and adjust parameters

Sample placement

Fix the sample on the table of the tester and adjust its position using the three-point positioning method to ensure that the droplet point is located at the center of the field of view and maintains a safe distance of at least 5mm from the edge of the sample to avoid edge effects.

Parameter Settings

Set test parameters such as droplet volume (usually 0.6-1.0 μ L), measurement time, environmental temperature and humidity through the instrument panel or software interface.

Select measurement methods (such as seat drop method, trap bubble method), and adjust the camera focal length and aperture brightness to ensure clear droplet contours without jagged distortions.

4、 Generating droplets and capturing images

Droplet generation

Use a microsyringe or droplet dispenser to form droplets on the surface of the sample.

Rotate the micrometer head clockwise to advance the piston, pause when the droplet volume reaches the set value, and the droplet should present a regular spherical crown with a clear liquid gas interface and no satellite droplets.

Droplet transfer

Slowly lift the stage (speed controlled at 0.5mm/s) to bring the droplet into contact with the sample surface, and immediately lower the stage until the droplet is completely detached from the needle. This process should be completed within 8 seconds to prevent droplet evaporation.

Image capture

Complete the image freezing operation within 10 seconds after the droplet contacts the sample to ensure clear and high-resolution images for subsequent analysis.

5、 Measurement of Contact Angle and Data Analysis

angle measurement

Fully automatic mode: The software automatically identifies the three-phase contact points and generates a fitting curve, calculates the contact angle value, and is suitable for samples with surface uniformity>95%.

Manual mode: Use the crosshair to sequentially mark the left, right, and vertex coordinates of the droplet, and the system automatically calculates the tangent angle. It is suitable for heterogeneous materials with surface roughness Ra>0.8 μ m.

Dynamic contact angle test (optional)

Enable the automatic tilt table function, rotate the stage at a speed of 0.5 °/s, and synchronously record the change curves of the forward and backward angles. The rolling angle judgment standard is the critical angle at which the droplet begins to slide.

result record

Record measurement results, including contact angle values, testing conditions (such as temperature, humidity), sample information, etc.

Generate reports or save data as needed for future reference, with data traceability covering environmental temperature and humidity records as well as sample batch information.

6、 Cleaning and maintenance

Instrument cleaning

After the test is completed, clean the surface of the instrument with a clean cotton cloth or tissue to ensure that there are no residues.

For instruments that have tested organic reagents, isopropanol ultrasonic cleaning should be used for 5 minutes, followed by blowing the inside of the needle with nitrogen gas.

instrument maintenance

Regularly maintain the instrument according to the manufacturer's recommendations, including checking the working status of components such as light sources and cameras, as well as performing necessary calibration and adjustments.

Before shutting down the device, run a self-test program to confirm that the attenuation rate of the light source intensity is less than 0.5% per month, the horizontal deviation of the stage is less than 0.02 °, and the CCD pixel defect rate is less than 0.001%.