## What is a sliding angle?

The sliding angle is a measure of the mobility of a drop on the surface, which is of concern to a variety of applications from textiles to microfluidics. The tilted plate method is also sometimes used to determine the advancing and receding contact angles.

### What is meant by contact angle?

Contact angle, θ (theta), is a quantitative measure of wetting of a solid by a liquid. The contact angle is geometrically defined as the angle formed by a liquid at the three-phase boundary where a liquid, gas, and solid intersect.

#### What is receding angle?

The receding angle is the contact angle between a liquid and a solid which has already been wetted with the liquid and which is in the course of being de-wetted. Like the advancing angle, the receding angle is a dynamic contact angle.

What is advancing and receding contact angle?

In effect, the advancing contact angle is the largest contact angle in the free energy range, while the receding contact angle is the lowest contact angle in the free energy range.

What is contact angle and hydrophobicity?

Contact angle hysteresis is simply the difference between θA and θR. In the scientific community, we have come to accept the definition that a surface is hydrophobic when its static water contact angle θ is >90° and is hydrophilic when θ is <90°.

## What is contact angle and wettability?

When an interface exists between a liquid and a solid, the angle between the surface of the liquid and the outline of the contact surface is described as the contact angle θ (lower case theta). The contact angle (wetting angle) is a measure of the wettability of a solid by a liquid.

### What is dynamic contact angle?

The term dynamic contact angle measurements refers to techniques that measure the contact angle during movement. This is usually accomplished by adding liquid to a static droplet on a surface and thus pushing the front of the liquid across the unwetted surface.

#### What is a contact angle goniometer?

A contact angle goniometer is an instrument that measures the contact angle of a droplet on a surface. This is a useful, indirect measurement of surface wetting. When a droplet starts to spread out over a surface, its contact angle becomes <90°.

Why do we measure contact angle?

Significance. The contact angle is important wherever the intensity of the phase contact between liquid and solid substances needs to be checked or assessed: coating, painting, cleaning, printing, hydrophobic or hydrophilic coating, bonding, dispersing etc.

What is the meaning of wettability?

Wettability is defined as the attraction of a liquid phase to solid surface, and it is typically quantified using a contact angle with the solid phase.