A colloidal gel consists of a percolated network of particles in a fluid medium, providing mechanical properties in particular the rise of elastic behaviour. The particles can show attractive interactions through osmotic depletion or through polymeric links. 
Colloidal gels have three phases in their lifespan: gelation, aging and collapse. The gel is initially formed by the assembly of particles into a space-spanning network, leading to a phase arrest. In the aging phase, the particles slowly rearrange to form thicker strands, increasing the elasticity of the material. Gels can also be collapsed and separated by external fields such as gravity. Colloidal gels show linear response rheology at low amplitudes. These materials have been explored as candidates for a drug release matrix.