# Difference between revisions of "Surface tension"

## Definition

Surface tension is a property of liquid surfaces caused by cohesion. Cohesion is the physical property resulting from the intermolecular forces attracting like-molecules. The molecules on the surface of a liquid have a greater attraction to like-molecules around them than to unlike-molecules.

Molecules on the surface of a liquid experience an inward force balanced by the resistance to compression. Another important point in understanding surface tension is the liquid molecules seek the lowest possible surface area. This is the reason that liquids form droplets on hydrophobic surfaces. The interface of lke-molecules has a lower energy than the interface of unlike-molecules, therefore surface molecules seek to have as many like-molecule interfaces as possible resulting in the lowest surface area.

## Units

Surface tension ($\gamma$) has dimensions of force per unit length, $\frac{F} {L}$.

## Examples

### Topological Changes in Bipolar Nematic Droplets under Flow

Fernández-Nieves et. al. describe how they can change the configuration of the defects and director field in nematic liquid crystal droplets immersed in water. They use microfluidics to periodically change from bipolar and escaped concentric configurations, and when flow is stopped the droplets remain in whichever configuration they are in, even tough the bipolar state has a lower energy. The surface tension between the liquid crystal and the water stabilizes the droplets and determines their shape.

### Self-assembled Shells Composed of Colloidal Particles: Fabrication and Characterization

Hsu et. al. showed how they can influence the morphology and mechanical properties of self-assembled polystyrene colloidal monolayers around emulsified drops by tuning the surface tension, molecular interaction, and stabilization of organic/water emulsions. Various emulsions were made using different solvents and stabilization techniques to explore how self-assembly was effected by solution and post-assembly parameters. The morphology and mechanical properties of each different emulsion were documented using scanning electron microscopy and axisymmetric compression. Surface tension governed both the assembly structure and the feasibility of the colloidal monolayers to act as size sieves for controlled liquid release.