Engineered Soft Materials and Interfaces

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Soft materials, which represent an extremely important material class and constitute a multi-billion dollar industry, are still formulated largely by combinatorial methods, due to a lack of the fundamental relationships that connect composition, processing, and structure, to properties. The CRC program will remedy this gap for two important soft materials: emulsions and yield stress suspensions.An emulsion is a mixture of two immiscible liquids in the form of drops of one liquid suspended in the other. Mayo, soft drinks, creams, vaccines, and paints are examples of emulsions. Two emulsion-related phenomena will be explored in detail in this program: wetting and coalescence. In many applications, it is critical to fine tune emulsion coalescence and wetting rates to achieve desirable properties or specific functions, but rate-focused studies are sparse in the literature. To elucidate the dynamics of these phenomena, the force between a drop and a solid-fluid or fluid-fluid interface will be measured down to a fraction of a nanoNewton, simultaneously measuring the separation between them down to a nanometer, using in-house instruments.The second soft material of focus is a particle-liquid mixture (suspension) that exhibits a yield stress, i.e. the mixture behaves like a solid below a critical stress, and like a liquid above it. Toothpaste, blood, and drilling/fracking fluids are examples of yield stress suspensions. The lack of relationships between suspension flow properties and the rate of transport of a solute present in the suspension (e.g. oxygen and proteins in blood, viscosifiers and gel breakers in petroleum/ gas extraction, etc.), particularly under flowing conditions, represents a key lacuna in this area. This research will fill the gap by performing experiments in a microfluidic setup coupled to a confocal microscope, to unearth mechanistic and quantitative details of solute mass transfer rates.The knowledge and technologies from this research will lead to a transition away from the current empirical design of soft materials to a more systematic, science-based design, resulting in emulsions tailored for specific functions, and more efficient dialyzers, oxygenators and drilling/fracking fluid additives. Emulsion-based industries, biomedical device industries and the petroleum industry are billion dollar industries in Canada. When HQP trained in the project join the workforce, they will provide Canadian industry a huge competitive edge.