Abstract:
Impact of Fluid Viscoelasticity on Crystal-like Structure Formation in Microfluidic Flows: Fundamentals and Applications
Crystals are defined as homogeneous pieces of solid substance having a natural geometrical regular form with symmetrically arranged planes. The term crystal has seen a substantial evolution over time, and nowadays, it refers to systems, either liquid or solid, that display a certain degree of regularity or order. In this context, microfluidics emerged as a very suitable field to enable the formation and the study of crystal-like structures owing to the possibility of controlling fluid and solid elements at the sub-micrometre scale. Crystal-like structures in microfluidic devices, hereafter microfluidic crystals, can either be formed thanks to external fields (e.g., electric or magnetic field) or because of hydrodynamic interactions among the different objects forming the crystal. To experience hydrodynamic interactions, the objects need to ‘feel’ each other, meaning that the local concentration should be sufficiently large to enable hydrodynamic interactions to take place. In such conditions, hydrodynamic interactions can promote the self-assembly of individual objects in crystal-like structures depending on several parameters such as channel geometry, fluid properties, and flow rate. Here, we show how fluid viscoelasticity impacts two classes of microfluidic crystals, namely droplet-based and particle/cell-based crystals. For droplet crystals, we discuss how non-Newtonian fluid behaviour leads to different droplet formation dynamics depending on whether the viscoelasticity is in the continuous or the dispersed phase. For particle/cell crystals, we show how, even for bulk particle concentration well below 5% in volume (i.e., in the established "dilute regime"), hydrodynamic interactions in microfluidic flows are non-negligible, and fluid viscoelasticity mediate such interactions with resulting crystal depending upon the rheology of the suspending liquid. Finally, we show how the two forms of crystals can be combined together in the context of particle compartmentalisation to "beat" the Poisson stochastic limits in encapsulation applications. We provide future directions for use in the broad field of material science, biomedical engineering, and biology.
Brief Biography:
Dr. Francesco Del Giudice, a recognised Chartered Chemical Engineer and Scientist, leads the Rheological Microfluidic lab at Swansea University Bay Campus. His expertise in Microfluidics and Soft Matter has led to innovative solutions, such as improving the encapsulation of flowing particles using viscoelastic flows in microfluidic devices. His team has also developed microfluidic techniques to evaluate rheological parameters not measurable via conventional techniques. Francesco has a long-term vision of challenging the status quo by introducing disruptive technologies and methodologies across a broad range of fields. We are exploring new methodologies for manufacturing materials, while tackling some fundamental questions in multiphase microfluidic flows. We are also implementing machine learning within microfluidic applications. We are also interested in solving new and exciting problems across the broad spectrum of Soft Matter and polymer physics. Francesco has several roles across national and international institutions, including Functional Chartered Member of the IChemE, ICP Panel member of the IChemE, Council Member of the British Society of Rheology, and core member of the Institute of Non-Newtonian Fluid Mechanics.
