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Fernandez-Nieves, Alberto

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    Defect Unbinding in Active Nematic Tori
    (Georgia Institute of Technology, 2018-05-15) Fernandez-Nieves, Alberto
    We will discuss our recent results with active nematics on toroidal surfaces and show how, despite the intrinsic activity and out-of-equilibrium character of our system, we still observe remnants of the expected curvature-induced defect unbinding predicted for nematics in their ground state. In our experiments, however, the number of defects is far larger than what one would expect for conventional nematics. In addition, these defects move throughout the toroidal surface and explore "phase space", bringing about interesting analogies with what we could call the high-temperature limit of a nematic liquid crystal. We unravel the role of activity by comparing our results to numerical simulations. Overall, our results illustrate the interplay between order, topological constraints, local geometry and activity.
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    Mechanics of Active Networks – Lessons from Fire Ant Aggregations
    (Georgia Institute of Technology, 2018-04-19) Sridhar, Shankar Lalitha ; Vernerey, Franck ; Fernandez-Nieves, Alberto ; Shen, Tong
    Biological assemblies in nature are seen as active matter due to their ability to perform intelligent collective motion based on neighbor interactions and sometimes without any centralized control or leadership. Fire ants are a great example in this context and display a rich class of material behaviors, including elasticity, viscous flow, and self-healing. Although classical theories in mechanics have enabled us to mechanically characterize this system, there is still a gap in our understanding on how individual ant behavior affects the emerging response of the aggregation. I will discuss an alternative approach from a statistical perspective where the population distribution of ants evolves due to mechanical deformation, and individual ant’s leg detachment and attachment events. Numerical simulations of the aggregation’s response in diverse situations, such as jamming (density) and shear thinning (reduced viscosity) will be presented and compared to experimental measurements.
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    Symposium on Soft Matter Forefronts - Welcome
    (Georgia Institute of Technology, 2018-04-18) Alexeev, Alexander ; Brettmann, Blair ; Fernandez-Nieves, Alberto ; Matsumoto, Elisabetta A. ; Rocklin, D. Zeb ; Yunker, Peter J.
    The symposium aims to familiarize attendees with the soft-matter research and expertise at Georgia Tech and to demonstrate the role Georgia Tech plays in influencing and advancing the field.
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    Toroidal Fun
    (Georgia Institute of Technology, 2016-01-12) Fernandez-Nieves, Alberto
    We study the physics of soft materials and also do physics with soft materials. In this talk, I will present an overview of some of our recent work involving, in one or another way, the use of tori. We will cover how we make toroidal and how we stabilize them against surface tension instabilities; this altogether provides an interesting way to 3D print materials. We will then discuss what we use toroidal droplets and hydrogels for. This includes the study of conventional and active liquid crystals confined to toroidal spaces, and addressing whether geometry affects cell behavior. I will then leave the torus and briefly discuss our work with colloidal hydrogels and fire ant aggregations.