What is Cassie-Baxter model?

The Cassie-Baxter model considers the flat surface but with chemical heterogeneity [2]. In the Wenzel model, the surface roughness r is defined as the ratio of the actual area to the projected area of the surface. The Wenzel equation can be written as: cosθ*=r cosθY E2.

What is wettability of a surface?

Wettability is the ability of a liquid to maintain contact with a solid surface, and it is controlled by the balance between the intermolecular interactions of adhesive type (liquid to surface) and cohesive type (liquid to liquid).

How does surface roughness affect contact angle?

As roughness goes hand-in-hand with an enlarged surface area, it affects the wettability of a solid, the contact angle (CA) of a liquid, and the adhesion. A solid is wettable by a given liquid when a contact angle of less than 90° is formed. The contact angle is smaller on a rough surface of the same material.

How is critical surface tension related to wettability?

Wettability is a measure of how well a liquid spreads and how complete the contact of the liquid is across the surface of a solid interface. The critical surface tension is the highest liquid surface tension that can completely wet a specific solid surface.

How do you calculate surface energy?

The most common way to calculate the surface free energy is through contact angle measurements. Pure liquids with the known surface tension are used for the measurements. Surface free energy is most typically measured through sessile drop measurements but the force tensiometer can be used as well.

What is meant by the degree of wetting?

Wetting is the ability of liquids to form interfaces with solid surfaces. To determine the degree of wetting, the contact angle (q) that is formed between the liquid and the solid surface is measured. The smaller the contact angle and the smaller the surface tension, the greater the degree of wetting.

Can the properties of a surface be changed?

In a proposed scheme for a polymer coating, the surface could change its properties in less than a second. Researchers want to develop “smart surfaces” using polymer coatings that would alter their properties in response to environmental changes, such as shifts in temperature, pH level, or light.

How is surface wettability measured?

Wettability of a solid surface is commonly measured with an optical tensiometer by utilizing the sessile drop method. A water droplet is placed on the surface and the formed contact angle is measured from the three-phase boundary where liquid, gas and solid intersect.

What is roughness of a surface?

Surface roughness is the measure of the finely spaced micro-irregularities on the surface texture which is composed of three components, namely roughness, waviness, and form.

How is surface roughness calculated?

Ra is calculated as the Roughness Average of a surfaces measured microscopic peaks and valleys. RMS is calculated as the Root Mean Square of a surfaces measured microscopic peaks and valleys. Limited runtimes result in real world surface roughness improvements from 10 to 35%.

What is the critical surface tension?

Critical surface tension is defined as the value of γLV when the contact angle approaches zero, Eq.

How does surface tension work easy?

Surface tension in water owes to the fact that water molecules attract one another, as each molecule forms a bond with the ones in its vicinity. This inward net force causes the molecules on the surface to contract and to resist being stretched or broken.