Patrick Spicer is an Associate Professor in UNSW’s School of Chemical Engineering. He is leader of the Complex Fluids group, a team that works with industry and academic partners to design smart fluids with unique response and flow behaviour linked directly to product and material performance. His lab at UNSW combines broad microscopy, microfluidic, and rheology capability that can be used to understand the behaviour of fluid coatings, films, and other complex products. Before UNSW, Pat ran a central engineering research department for the Procter & Gamble Company in the US for 15 years. His group developed new product and process technology there for all of P&G’s billion-dollar brands. He is co-inventor of P&G’s $30 million cubosome patent portfolio that Children’s Hospital Cincinnati used to develop the first product to prevent life-threatening infections in premature infants. He is also the inventor of P&G's recently-patented responsive droplet technology.
Research Interests: Design and development of microstructured fluid materials by understanding their kinetic behavior. Most of our work deals with complex fluids, fluids containing small amounts of colloids, polymers, and surfactants that exhibit highly non-ideal behaviour with fascinating dynamics. Complex fluids are a key part of most major products and manufacturing processes. Our group uses advanced imaging and rheology techniques to understand fundamental complex fluid properties, specifically:
Shape - Particle shape affects advanced material strength, reactivity, and biological uptake.
Structure - Self-assembly creates soft structures with biological, chemical, and physical applications.
Flow - Microstructured fluids are a part of most commercial products, and processes, and their flow affects stability.
Shape-Changing Droplets: We study flow of anisotropic colloids like rods and fibers in fluids but are also exploiting the shaped droplets we developed to understand stability of emulsions in complex flows and the new types of structures that can now be formed from droplets rather than solid particles. A particular area of interest is the types of shapes, and shape-change mechanisms, that we can develop using these unique droplet building blocks.
Self-Assembly: We also have a long history of working with surfactant self-assembly and have developed new ways of making soft colloidal polyhedra with complex shapes that we are templating via polymerization and gelation. We’d also like to explore applications for such regular, but soft, shapes.
Microrheology: We have a new active technique we’ve developed that allows detection of very low yield stresses in biological fluids but also allows in situ determination of the properties of complex foods like doughs and batters as their development of gas cells during preparation and cooking is not well understood. We also perform passive microrheology of biofilms and other biological fluids as they are degraded by enzymes and antibiotics.
Bubble dynamics: Deceptively simple, bubbles can drive complex fluid flows in unique ways and can be a reservoir for enormous energy. We have open projects to study a model soft matrix containing highly pressurized micro bubbles to simulate and visualize explosions. We are also studying the ability of fluid rheology to interfere with bubble expansion and shrinkage in complex fluids.
Food and consumer product microstructure: We have mapped the formation of complex structures in foods, and other formulated materials based on emulsions, and developed physical models of their stability, rheology, and performance. Our open projects in this area are aimed at designing more sophisticated functions and performance for formulated materials, enabling new forms that increase accessibility to safe products in remote regions. We also would like to develop a new structural description of thixotropy in structured fluids: when a fluid behaves differently depending on whether it flows from low to high or high to low shear rates.
Advanced Microfluidics: Many of our microscale projects need "scaling up” to produce larger volumes of particles or droplets. Examples include new projects on the charging behavior of flow electrodes that contain nanostructured carbon particles with non-spherical shapes, allowing the exploitation of phenomena like segregation to improve charging performance. New chips are also planned to attack biofilms with rapid gradient manipulation, model complex biofluid transport through cartilage and tissue, test deposition of shaped particles onto biological surfaces, and assemble multiple shaped droplets into hierarchical structures.
Complex Surface Coatings: We have found new ways to coat tissue and skin using very weakly-structured fluids, improving efficiency by a factor of six or more over conventional delivery techniques, but need to map the mechanism of performance improvement as it is still not well understood. We are also interested in the phenomenon of detergency when it is comparable in magnitude to the rheology of the fluid being removed. The development of increasingly complex surface treatments and morphologies means a need to better understand how such surfaces can be cleaned.
Biofluids: Joint projects with Medicine and Biomedical Engineering will look at mapping the rheology and flow of biological complex fluids like synovial fluid, mucus, and blood to fingerprint their key mechnical properties, develop mimics, and understand their interactions with artificial joints and bone implants. Molding flow channels and surfaces to real biological surfaces with small-scale features will enable us to test the structural adjustments that drive extremely complex flow interactions in the mouth, blood vessels, cartilage, and on other body tissues like skin.