Complex Fluids Engineering
Particle suspensions, nanomaterials, electrokinetics, environmental nanotechnology, interfaces and adsorption, microfluidics, polymers, rheology, self-assembly, wetting.
Liquids that contain interacting dispersed particles, dissolved polymers or surfactants are known as complex fluids. Their signature characteristic is an exquisite sensitivity of macroscopic fluid properties to strong intermolecular interactions among the dissolved or dispersed constituents in the fluid. Complex fluids are widespread and are invariably characterized by molecular and physical complexity. For example, short-range anisotropic interactions among surfactant molecules may produce dynamic self-assembled micellar structures that in turn may interact with one another via long-range colloidal forces with profound effects on the fluid’s rheological properties. Products ranging from slurries for chemical mechanical planarization to medicinal lotions are complex fluids. Many solid materials such as ceramics or polymeric membranes are processed as complex fluids, and complex fluids often provide self-assembled templates needed to produce nanoparticles or other nanostructured materials.
The design of such high performance functional materials relies on the preparation and organization of distinct chemical structures with key features engineered on nanometer to micrometer length scales. Interfacial forces typically dominate their performance characteristics and the methods by which they are processed. Hence, the principles of colloid science guide their design and manufacture. Such materials find application not only in high value added emerging technologies such as nanomedicine drug delivery vectors, nanocomposite optical coatings, and charged particle electrophoretic displays, but also in materials that are manufactured at large scale yet still meet increasingly sophisticated performance expectations. Examples of the latter include durable low volatile-organic-content coatings, agricultural emulsions, lubricants and a host of personal care products.
The Complex Fluids Engineering group has a diverse research portfolio consistent with the broad applicability of this field. One theme, however, unifies much of this work, and that is the knowledge that one must possess to understand and control physical forces on the nanometer scale. Phenomena at the nanometer scale (self-assembly of surfactants and polymers in solution or on surfaces, migration of charge in the electrical double layer) control phenomena at the micrometer scale (nucleation of multi-particle aggregates, electrophoresis of charged particles). These in turn control phenomena at the macroscopic scale (viscoelastic flows, phase separation, assembly of ordered particulate films). The goal of the Complex Fluids Engineering group is to discover and control the intertwined links between the nano-, micro-, and macro-scales that make advanced materials engineering possible. This group is uniquely positioned to address the higher level complexities that are introduced by strongly interacting solutes in multi-component mixtures.
Students in the Complex Fluids Engineering group enjoy a highly collaborative environment. Faculty members with complementary expertise often co-advise students. With collaborations promoted by the Center for Complex Fluids Engineering, students have opportunities to participate in multi-disciplinary teams of students from different departments that organize to solve especially challenging research problems, ranging from environmental engineering to drug delivery. Students benefit from the well-equipped, multi-user PPG Industries Colloids, Polymers and Surfaces Laboratory that provides instrumentation and advanced training for research and education, as well as a policy to openly share the specialized instrumentation housed in individual faculty laboratories.
The Complex Fluids Engineering group conducts scientifically challenging, fundamental research to meet future technological needs. Students are currently exploiting diverse experimental and theoretical techniques to investigate, for example, complex electrokinetic flows in microfluidic devices, the origin and exploitation of electrostatic charge in nonpolar liquids, fundamental interfacial phenomena underlying the use of surfactants as “chemical dispersants” for oil spills, and the design of composite nanoparticles as high performance surfactants.