[1][2] If oil and water are mixed and small oil droplets are formed and dispersed throughout the water (oil-in-water emulsion), eventually the droplets will coalesce to decrease the amount of energy in the system.
However, if solid particles are added to the mixture, they will bind to the surface of the interface and prevent the droplets from coalescing, making the emulsion more stable.
When the contact angle is approximately 90°, the energy required to stabilize the system is at its minimum.
Ramsden emulsions have gained increased attention and research interest during the last 20 years when the use of traditional surfactants was questioned due to environmental, health and cost issues.
[4] Pickering emulsions find applications for enhanced oil recovery[5] or water remediation.
[11] Moreover, Ramsden emulsion droplets are also suitable templates for micro-encapsulation and the formation of closed, non-permeable capsules.
[12] This form of encapsulation can also be applied to water-in-water emulsions (dispersions of phase-separated aqueous polymer solutions), and can also be reversible.