Gel

Gel is a semi-solid system that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state. A gel has been defined phenomenologically as a soft, solid or solid-like material consisting of two or more components, one of which is a liquid, present in substantial quantity.

Composition

Gels consist of a solid three-dimensional network that spans the volume of a liquid medium and ensnares it through surface tension effects. This internal network structure may result from physical bonds (physical gels) or chemical bonds (chemical gels), as well as crystallites or other junctions that remain intact within the extending fluid.

Types of Gels

There are two types of gels: hydrogels and organogels. Hydrogels are gels whose liquid component is water, while organogels have an organic liquid component.

Hydrogels

Hydrogels are highly absorbent (they can contain over 90% water) natural or synthetic polymeric networks. They also possess a degree of flexibility very similar to natural tissue, due to their significant water content.

Organogels

Organogels, on the other hand, are usually based on a nonpolar liquid organic solvent, and most commonly based on an apolar liquid. Organogels have potential for use in a number of applications, such as in pharmaceuticals, cosmetics, art conservation, and food.

Applications

Gels have diverse applications, ranging from culinary uses to medical and industrial applications. In the medical field, for instance, gels are used in drug delivery systems, tissue engineering scaffolds, and as sealants for bleeding in trauma and surgery.

See Also

• Polymer
• Sol-gel
• Aerogel
• Xerogel

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