The Colloidal Domain
Colloids are ubiquitous: blood, milk, laundry detergent, nanomaterials, ice cream, clouds, cell membranes, and drilling fluids represent just a small selection of colloidal systems. A colloid is any material that contains a second, finely divided, material, where “finely divided” means having one dimension that is between ~ 10 and 1000 nanometers – this is the “Colloidal Domain“!
We seek to understand the fundamental relationship between particle interactions, microstructure, and bulk properties for materials in the Colloidal Domain. Given the importance of these phenomena to everyday life, we will supplement our fundamental research program by working with coatings, polymer, biomedical, and oil & gas companies.
We currently have activities spread across three independent, but related projects:
1) Measurement and control of weak ~kT scale interactions. The importance of colloidal interactions to the microstructure of materials is well established. Weak colloidal interactions operate on a ~kT energy scale over a ~1 – 1000 nm length scale. Despite the small magnitude of these forces, they are essential to a wide range of natural and synthetic systems. We study the role of weak colloidal interactions in systems of anisotropic colloids. In particular, we are concerned with systems that are technologically relevant to soft materials, namely carbon nanotubes, ellipsoids, and Janus particles.
2) Electric field assisted directed assembly of anisotropic colloidal particles. Particle anisotropy, or the directional dependence of a material property, means that a particle is locally hard or soft, displays variations in surface charge or chemistry, contain gradients in dielectric permittivity, or may be oblong or branched. Particle anisotropies will substantially impact the motion, separation, and assembly of colloidal particles, especially when responding to external fields. We study the dynamics and microstructure of colloidal dispersions comprising anisotropic particles in response to an electric field. The central hypothesis of this work is that particle anisotropy can be used as an additional facet in the design and “bottom-up” assembly of soft matter.
3) Interactions between colloidal particles pinned at fluid/fluid interfaces. Planar and curved interfaces laden with particles are found in a variety of natural and consumer products and are often more stable than interfaces containing molecular surfactants. Superior stability arises from a combination of the large energy necessary to remove particles from an interface and also the viscoelastic properties imparted by the particles. We study how the material properties of colloids with large fluid/fluid interfacial area (i.e. foams and emulsions) can be tuned by engineering the interfacial microstructure, especially with anisotropic colloidal particles.