Dynamic Wetting

Definition

Dynamic wetting refers to the process where a liquid droplet spreads or moves across a solid surface, influenced by the balance of adhesive and cohesive forces at the contact line. This phenomenon is key in understanding how liquids interact with surfaces and is closely related to the changes in contact angle as the droplet advances or recedes on the surface. The dynamics of this process depend on factors such as surface roughness, liquid viscosity, and the nature of the solid material.

5 Must Know Facts For Your Next Test

1. Dynamic wetting is affected by surface properties such as roughness and chemical composition, which can significantly alter how a liquid spreads on a surface.
2. The contact angle during dynamic wetting changes over time, demonstrating how quickly a droplet can wet a surface compared to its static contact angle.
3. Viscosity of the liquid plays an important role in dynamic wetting; higher viscosity can slow down the spreading process.
4. Dynamic wetting is important in applications like inkjet printing, coating processes, and biological interactions where effective spreading of liquids is crucial.
5. Understanding dynamic wetting helps in designing surfaces with tailored wettability for specific applications, such as self-cleaning surfaces or anti-fogging coatings.

Review Questions

• How do surface properties influence dynamic wetting and what role do they play in determining the contact angle?
  • Surface properties like roughness and chemical composition greatly influence dynamic wetting. A rough surface can trap air pockets, affecting how well a liquid spreads and potentially increasing contact angle hysteresis. Additionally, surfaces with different chemical functionalities can either promote or hinder adhesion with the liquid, altering the advancing and receding contact angles during wetting. Thus, optimizing these properties is key for desired wettability outcomes.
• Discuss the significance of hysteresis in dynamic wetting and its impact on real-world applications.
  • Hysteresis in dynamic wetting signifies the difference between advancing and receding contact angles during droplet movement. This difference can reflect the energy barriers present at the solid-liquid interface and is crucial for applications like coatings or adhesives. In practical scenarios, high hysteresis may lead to incomplete spreading or poor adhesion, while low hysteresis typically results in smoother flow and better performance in applications requiring efficient liquid distribution.
• Evaluate how understanding dynamic wetting can lead to advancements in technology or materials science.
  • Understanding dynamic wetting opens up possibilities for significant advancements in various technologies. For instance, engineers can design better coatings that enhance self-cleaning surfaces or improve fluid transport in microfluidic devices. By controlling factors such as surface texture and chemical treatments, researchers can tailor wettability to meet specific needs in industries like biomedical engineering or electronics. Such innovations have the potential to revolutionize product design and functionality across multiple fields.

Related terms

Contact Angle:

The angle formed at the interface between a liquid droplet and a solid surface, representing the degree of wetting; a smaller angle indicates better wetting.

Hysteresis: The difference in contact angles during the advancing and receding motion of a droplet on a surface, indicating the energy barriers faced by the liquid.

Young's Equation:

A fundamental equation that relates the contact angle to the interfacial tensions at the solid-liquid, solid-gas, and liquid-gas interfaces.