Using controlled spinodal decomposition, we have created bicontinuous emulsions stabilized by interfacially jammed colloidal particles (Fig.1). The colloids, silica modified to yield partial wettability, are initially dispersed in the single-fluid phase. The sample is warmed (in the case of water-lutidine) into the two-fluid phase. The colloids become trapped on the newly created interface; as the fluid domains coarsen the amount of interface decreases and the colloids jam together arresting phase separation. The arrangement of domains reflects the demixing kinetics: warming through the critical point leads to a bicontinuous structure. (Structures can also be created via an upper critical point which we illustrate using silica colloids in alcohol-oil mixtures). We will present fluorescence confocal microscopy studies showing the arrangement of domains, the stabilization by interfacial colloids over many weeks, and the changes in structure with both sample composition and warming rate. We will give preliminary indications of the mechanical properties (Fig.2). Our results demonstrate that by varying the fluid composition systematically, and hence the demixing kinetics, an emulsion inversion occurs where the bicontinuous soft-solid is found at the inversion point.

Figure 1. A fluid-bicontinuous structure stabilized by silica colloids (white) imaged by fluorescence confocal microscopy at 40C. The two fluid domains (black) are water-rich and lutidine-rich respectively. The scale bar is 100mm.

Figure 2. An ~8mm long copper wire supported against gravity by a fluid-bicontinuous gel. The wire remained in place for the duration of the study (several days); this demonstrates that the colloid-stabilized structure has a significant shear modulus.