Bijels: a new class of soft materials

Bicontinuous interfacially jammed emulsion gels ('bijels') were proposed in 2005 as a hypothetical new class of soft materials in which interpenetrating, continuous domains of two immiscible fluids are maintained in a rigid state, by a jammed layer of colloidal particles at their interface. Such gels should have unusual material properties relevant to catalysis and other applications. Although initially proposed on the basis of computer simulation, the existence of bijels has since been confirmed in the laboratory. However, a wide gap remains between the simulated and the experimental systems. This leaves room for continuing debate on the cause of stability in these materials; in particular, it is not known whether an attraction between the colloidal particles is essential for stability.