The Center for Complex Fluids Engineering is an interdisciplinary research and education effort involving two different colleges of Carnegie Mellon University. Faculty and graduate students from the College of Engineering and the College of Science perform research to solve problems in the formulation and processing of materials based on complex fluids.
Complex Fluids are Practically Everywhere.
What do paint, pediatric liquid medicines, laundry detergent, cell membranes and mayonnaise have in common? They are all complex fluids. Complex fluids include solutions of polymers or surfactants, emulsions, foams and liquid suspensions of solid nanoparticles or micrometer sized colloidal particles. What makes a fluid a complex fluid is an exquisite sensitivity of its macroscopic properties (viscosity, for example) to strong, often long-range interactions among colloidal constituents dissolved or suspended in the fluid. In a water-borne paint, solid pigment and polymer “latex” particles are suspended in water. The active ingredients in children’s medicines are often microscopic solid particles suspended in water. Sometimes colloids form spontaneously when amphiphilic “surfactant” molecules (part water-soluble, part water-insoluble) self-assemble into ordered structures called micelles. Surfactant micelles help laundry detergents do their job. Surfactants also adsorb to soil particles and suspend them in the water. Cell membranes are made mainly of amphiphilic lipid molecules that closely resemble surfactants and self-assemble to form fluid, bilayer sheets. Lipids and other surfactants are also used to disperse oil droplets into water, making an “emulsion.” When that emulsion is made from oil, vinegar and egg yolks we call it mayonnaise.
Complex Fluids Engineering Relies on Nanoscale Phenomena to Design Materials and to Understand the Design of Living Systems.
Typically multicomponent systems, complex fluids are highly nonlinear with respect to composition changes, and often the fluid states that provide the desired mechanical or chemical properties are metastable and accessible only through precisely controlled processing and formulation steps. Committing to the challenge of developing complex fluid-based products is amply rewarded by the attainment of materials with precisely tunable rheological properties, unique phase behaviors, large solubilizing powers or unique nano- and microstructures.
Complex fluids engineering principles are used to design new materials and processes based on the control of supramolecular self-assembly and colloidal forces. Complex fluids are ubiquitous in industry and nature, making complex fluids engineering central to product design and processing in the pharmaceutical, food, personal care product, biomaterials, agrochemical, printing, coating, ceramic, mining and petrochemical industries, among many others. It is central to the design and processing of nanomaterials and plays a critical role in the development of more environmentally benign technologies that replace organic solvents with aqueous fluids.
The Center takes an open-minded approach to what constitutes complex fluids engineering. For example, similar types of self-assembly processes and colloidal forces that control the performance of an advanced coating material are also recognized to be at work in cells and physiological fluids. Accordingly, the Center provides an opportunity for biophysics research to be conducted side by side with industrially oriented research, with insights flowing both ways.