Dynamic wetting

Definition

Dynamic wetting refers to the process where a liquid makes contact with a solid surface and spreads over it, influenced by both the properties of the liquid and the solid as well as the rate at which the liquid is applied. This phenomenon is crucial for understanding how liquids behave when interacting with surfaces, especially in applications like coatings and printing. Dynamic wetting can lead to changes in contact angle over time, influenced by factors like surface roughness and liquid viscosity.

5 Must Know Facts For Your Next Test

1. Dynamic wetting is influenced by both the intrinsic properties of the liquid and solid, such as surface energy and viscosity, as well as external factors like temperature and pressure.
2. In dynamic wetting, the contact angle can change over time as the liquid spreads, which is different from static wetting where the contact angle remains constant after equilibrium is reached.
3. The rate of spreading during dynamic wetting is often described using models such as the Tanner's law, which relates spreading velocity to time.
4. Surface roughness can significantly enhance or hinder dynamic wetting; textured surfaces may promote greater wettability compared to smooth surfaces.
5. Understanding dynamic wetting is essential for optimizing processes in industries like inkjet printing and paint application, where precise control over liquid behavior on surfaces is required.

Review Questions

• How does dynamic wetting differ from static wetting in terms of contact angle behavior?
  • Dynamic wetting differs from static wetting primarily in that dynamic wetting involves changes in contact angle over time as a liquid spreads on a surface, while static wetting reaches a constant contact angle once equilibrium is established. In dynamic conditions, factors such as surface roughness and liquid viscosity play key roles in determining how quickly and effectively a liquid can spread. This means that during dynamic wetting, monitoring the contact angle provides insight into the behavior and interaction between the liquid and solid.
• Discuss how surface roughness affects dynamic wetting and provide examples of applications that benefit from this understanding.
  • Surface roughness has a significant impact on dynamic wetting because it can either enhance or inhibit the spreading of liquids. Textured surfaces can create a greater area for adhesion, leading to improved wettability and faster spreading, while smooth surfaces may lead to higher contact angles and slower spreading rates. Applications like self-cleaning surfaces take advantage of enhanced wettability on rough surfaces, allowing liquids to easily remove contaminants. Similarly, in coating technologies, controlling surface texture is crucial for achieving desired wetting properties.
• Evaluate the implications of dynamic wetting in practical applications such as inkjet printing and why it matters for product performance.
  • Dynamic wetting plays a critical role in practical applications like inkjet printing because it directly affects how ink droplets interact with various substrates. A thorough understanding of this phenomenon allows manufacturers to optimize droplet formation and control spreading behavior, ensuring uniform coverage without excessive bleeding or pooling. This impacts overall product performance since effective ink application influences color accuracy, print resolution, and durability. By manipulating dynamic wetting characteristics through material selection or surface treatments, companies can enhance print quality and reduce waste during production.

Related terms

Contact angle: The angle formed between the tangent to the liquid surface and the solid surface at the three-phase contact line, indicating the wettability of the solid by the liquid.

Capillary action: The ability of a liquid to flow in narrow spaces without the assistance of external forces, driven by adhesive and cohesive forces between the liquid and surrounding materials.

Surface tension: The property of a liquid's surface that allows it to resist an external force due to the cohesive nature of its molecules, impacting how the liquid interacts with solids.