Paulo Arratia

Paulo Arratia is a professor in the Departments of Mechanical Engineering and Applied Mechanics and Chemical and Biomolecular Engineering at the University of Pennsylvania School of Engineering and Applied Science. He holds the position of Eduardo D. Glandt Distinguished Scholar and serves as Faculty Director of Undergraduate Research. Arratia joined the University of Pennsylvania in 2007 and has been teaching since 2005. His research centers on the rheology and flow behavior of complex fluids in physical and biological systems, including viscoelastic instabilities at low Reynolds numbers, the motility of microorganisms such as bacteria, nematodes, and algae in non-Newtonian fluids, granular creep and plasticity in jammed suspensions, physiological flows like blood plasma rheology, and sediment transport. Notable contributions include demonstrating elastic instabilities in polymer solutions, the impact of fluid elasticity on bacterial swimming speeds and kinematics, nonlinear elastic instabilities in channel flows, and the viscoelastic versus Newtonian behavior of human blood plasma under extensional flows. He has pioneered experimental studies showing how shear-thinning enhances bacterial rheotaxis and how fluid elasticity orders red blood cells in channels.

Arratia has received major honors including election as a 2022 Fellow of the American Physical Society Division of Fluid Dynamics for creative and insightful experimental discoveries in complex and biological fluid mechanics, and a 2025 Fellow of the Society of Rheology for his work on reversible plastic regimes in dense suspensions, viscoelastic flow instabilities, and biological motility. He received a 2018 University Award for Distinguished Teaching. His highly influential publications include 'Rheology of human blood plasma: Viscoelastic versus Newtonian behavior' (Physical Review Letters, 2013), 'Structure-property relationships from universal signatures of plasticity in disordered solids' (Science, 2017), 'Elastic instabilities of polymer solutions in cross-channel flow' (Physical Review Letters, 2006), 'Running and tumbling with E. coli in polymeric solutions' (Scientific Reports, 2015), and 'Undulatory swimming in viscoelastic fluids' (Physical Review Letters, 2011). Arratia has served as editor of the Rheology Bulletin and delivered invited colloquia such as at Georgia Tech on life in complex fluids. His work bridges microstructure, rheology, and transport in out-of-equilibrium systems, impacting fields from biology to geophysics.

Professional Email: parratia@seas.upenn.edu