Quantitative morphological characterization of bicontinuous Pickering emulsions via interfacial curvatures

Abstract

Bicontinuous Pickering emulsions (bijels) are a physically interesting class of soft materials with many potential applications including catalysis, microfluidics and tissue engineering. They are created by arresting the spinodal decomposition of a partially-miscible liquid with a (jammed) layer of interfacial colloids. Porosity L (average interfacial separation) of the bijel is controlled by varying the radius (r) and volume fraction (ϕ) of the colloids (L∝r/ϕ). However, to optimize the bijel structure with respect to other parameters, e.g. quench rate, characterizing by L alone is insufficient. Hence, we have used confocal microscopy and X-ray CT to characterize a range of bijels in terms of local and area-averaged interfacial curvatures; we further demonstrate that bijels are bicontinuous using an image-analysis technique known as 'region growing'. In addition, the curvatures of bijels have been monitored as a function of time, which has revealed an intriguing evolution up to 60 minutes after bijel formation, contrary to previous understanding.

Aerobijels: Ultralight Carbon Monoliths from Cocontinuous Emulsions

“…3D imaging of aerobijel specimens using microcomputed tomography reveals a sponge‐like structure consisting of interconnected solid and void space, while measurements of the Gaussian and mean curvatures ( Κ and H , respectively) of the reconstructed aerogel surfaces confirm the morphological signatures associated with spinodal decomposition. Distributions of the dimensionless quantities K Σ −2 and H Σ −1 (where Σ is the surface‐to‐volume ratio of the reconstructed surface derived from segmented tomography images) indicate an aerogel structure that is mostly hyperbolic with K Σ −2 < 0 and H Σ −1 ≈ 0, which is in good agreement with several recent studies on the morphology of bijels and novel classes of porous materials based on them (Figure g) …”

Hybrid electrolytes with 3D bicontinuous ordered ceramic and polymer microchannels for all-solid-state batteries

“…As detailed in Sup2, bijels are prepared by spinodal liquid-liquid demixing in the presence of neutrally wetting colloidal particles, which sequester at the liquid-liquid interface and halt further phase separation upon interfacial jamming. 30 After monomer infusion and polymerization of one of the liquid channels, followed by draining off both liquids 31 , they can, in principle, be used directly as 3D templates. However, in order to remain consistent, all templates used in this study were created by stereolithography.…”

Nanoparticle Assembly at Liquid–Liquid Interfaces: From the Nanoscale to Mesoscale

“…Two features are essential for the formation and stabilization of bijels: first, the particles must be neutrally wetting with the two liquid phases (contact angle ≈ 90°), so as to avoid the particles imposing a preferred curvature on the liquid–liquid interface during phase separation; second, fluid demixing by spinodal decomposition rather than nucleation is needed to drive a bicontinuous arrangement of the liquid domains, which always requires the fulfilment of several stringent criteria for successful preparation. These difficulties in fabrication are more severe for bijels stabilized by NPs (especially diameter < 50 nm), owing to their comparatively low binding energies to the water/oil interface, especially at the low surface tensions present in bijels, which in turn restricts the smallest accessible domain sizes in these materials …”