Adhesion

Definition

Adhesion is the attractive force between different substances, which causes them to stick together. This phenomenon is crucial in understanding how materials interact at their interfaces, affecting processes such as coating, bonding, and the stability of emulsions and foams. Adhesion plays a significant role in various applications, including drug delivery systems, paint adhesion on surfaces, and the behavior of biological systems.

5 Must Know Facts For Your Next Test

1. Adhesion is influenced by surface roughness; rougher surfaces tend to enhance adhesion due to increased contact area.
2. Chemical interactions, such as hydrogen bonding or van der Waals forces, significantly contribute to adhesion between different materials.
3. Wetting is a key aspect of adhesion; if a liquid spreads over a solid surface, it indicates good adhesion between the two.
4. Surface treatments or coatings can be applied to enhance adhesion by altering the surface chemistry or texture.
5. In biological systems, adhesion is vital for processes like cell adhesion, which is important for tissue formation and healing.

Review Questions

• How does surface roughness affect adhesion between two materials?
  • Surface roughness increases the contact area between two materials, which can enhance adhesion. When surfaces are rough, they interlock more effectively at the microscopic level, leading to stronger adhesion forces. This physical interaction allows for a more significant number of adhesive contacts compared to smooth surfaces, ultimately improving the overall bond strength.
• Discuss how chemical interactions contribute to the adhesion process and provide examples.
  • Chemical interactions play a critical role in adhesion by providing additional attractive forces between dissimilar materials. For instance, hydrogen bonding can occur between polar molecules, while van der Waals forces can influence adhesion in nonpolar substances. An example includes how paints adhere to surfaces due to both mechanical interlocking and chemical bonding with surface contaminants or treated areas.
• Evaluate the importance of adhesion in biological systems and its implications for biomedical applications.
  • Adhesion in biological systems is crucial for processes like cell signaling and tissue formation. Understanding how cells adhere to each other and to their extracellular matrix informs biomedical applications such as drug delivery systems and tissue engineering. Innovations in these fields often rely on manipulating adhesion properties to enhance biocompatibility and ensure effective therapeutic outcomes.

Related terms

Cohesion: The attractive force between molecules of the same substance, contributing to the formation of droplets and other structures.

Surface Tension: The energy required to increase the surface area of a liquid, influenced by the cohesive forces among liquid molecules.

Interfacial Energy: The energy associated with the interface between two phases, which can affect adhesion and wetting properties.