How to measure the contact angle? Understanding this is enough!

Why measure contact angle?

The contact angle (θ) directly reflects the wettability of the solid surface:

θ<90 °: hydrophilic surface (liquid easily spreads, such as water droplets on glass)

θ> 90 °: Hydrophobic surface (liquid forms beads, such as water droplets on lotus leaves)

——The smaller the contact angle, the better the wettability and the faster the diffusion. ——

By knowing the surface tension of a liquid, the surface tension of a solid can be inferred to optimize material design (such as waterproof coatings, pharmaceutical carriers, and oil extraction efficiency).

This parameter is extremely critical in oil recovery, material coating, biomaterials, and fine chemicals.

Measurement Tools and Procedures (Taking HARKE-SPCAX2 as an Example)

1. Sample preparation

Solid surface needs to be flat and clean - (roughness<1 μ m, avoid pollution interference)

Liquid selection: Depending on the requirements (such as water, glycerol, organic solvents), it is necessary to know their surface tension and density.

2. Dynamic contact angle measurement

Forward angle: the angle at which the liquid droplet front moves when the micro pump slowly increases its liquid volume (reflecting the low-energy region of the solid)

Backward angle: the angle at which the liquid droplet retracts after pumping (reflecting the high-energy region)

Lag phenomenon: The difference between the two reveals surface roughness or chemical inhomogeneity

3. Automated analysis

Fitting: Calculated through differential equation of droplet profile, accuracy ± 0.1 ° - Multi point testing: avoids local errors, takes the mean

Instrument advantages

High precision: ± 0.1 ° error, supporting nanoscale rough surfaces

Fully automatic: One click completion of dripping, shooting, and fitting (no longer manual strokes)

Multi method compatibility: supports extended applications such as droplet suspension method and bubble capture method