SURFACE ENERGY AND CAPILLARY PRESSURE

Abstract

The energies associated with surfaces — surface energy, interfacial energy, surface tension, and work of adhesion — drive many surface phenomena including tribological ones such as adhesion and friction. This chapter discusses the physical origins of surface energies for liquids and solids, and how the concepts of capillary pressure, capillary condensation, wetting, and work of adhesion are derived from surface energy. Further, this chapter covers the different methods for measuring surface energies, including a thorough discussion of the most common method to measure the surface energy of solids: contact angle measurements of liquid droplets on surfaces. The chapter also introduces how surface energies and surface tensions lead to adhesion and adhesion hysteresis between contacting surfaces, which is followed up in the subsequent chapters on surface forces.