I. Principle

The droplet angle refers to the angle between the tangent line of a droplet's edge and the solid surface when it forms on a solid surface.

A large droplet angle (>90°) indicates that the droplet shrinks on the surface, indicating that the material is hydrophobic and has low surface energy.

A small droplet angle (<30°) indicates that the droplet spreads rapidly, indicating that the material is hydrophilic and has high surface energy.

By measuring the droplet angle, we can infer the wettability and surface energy level of the material surface.

II. Functions

Evaluating Surface Wettability
The droplet angle directly reflects the material surface's affinity for liquids; smaller values indicate better wettability.

Quantitative Surface Energy Analysis
By measuring the droplet angle with various test liquids (such as water and diiodomethane), we can calculate the material's surface energy and polar/dispersive components.

Verifying Surface Treatment Effectiveness
Used to detect changes in surface properties after plasma cleaning, chemical modification, and coating.

Quality Control
As a rapid test method for surface cleanliness, adhesion, and coating effectiveness during the production process.

III. Applications

Electronics and Semiconductors

Verify the cleanliness and activation of surfaces such as PCBs, semiconductor chips, and display modules;

Ensure the stability of welding, coating, and lamination processes.

Glass and Displays

Measure the surface energy of cover glass and OLED encapsulation glass to ensure lamination and coating quality;

Evaluate the performance of waterproof and anti-fingerprint coatings (AF/AR/AG).

Plastics and Packaging

Confirm whether the plastic surface energy meets the requirements for printing, spraying, and bonding;

Commonly used for quality control in industries such as medical consumables and food packaging.

New Energy (Lithium Batteries, Solar Energy)

Measure the wettability of electrode and diaphragm surfaces to electrolytes to optimize battery performance and cycle life;

Verify the waterproof/antifouling effectiveness of photovoltaic module surface coatings.

Biomaterials

Study the affinity of material surfaces for cells and proteins;

Evaluate surface modifications of artificial bones, stents, and medical implants.

Research and Teaching

As a fundamental experiment, it helps understand wetting theory, interfacial energy, and the mechanisms of material surface modification.

It is also used in the development and characterization of new materials.

Summary

Contact angle measurement is a simple, rapid, and intuitive surface characterization method. By analyzing the droplet morphology, it can assess the wettability, surface energy, and surface modification effects of materials. It is widely used in electronics, displays, plastics, new energy, biomedical materials, and research institutions, serving as a crucial testing tool connecting surface science and industrial production.