{"id":7374,"date":"2023-05-10T12:02:23","date_gmt":"2023-05-10T10:02:23","guid":{"rendered":"https:\/\/www.uni.lu\/fstm-en\/events\/physics-seminar-life-in-complex-fluids\/"},"modified":"2024-04-11T15:37:18","modified_gmt":"2024-04-11T13:37:18","slug":"physics-seminar-life-in-complex-fluids","status":"publish","type":"events","link":"https:\/\/www.uni.lu\/fstm-en\/events\/physics-seminar-life-in-complex-fluids\/","title":{"rendered":"Physics Seminar: Life in Complex Fluids"},"content":{"rendered":"\n
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Speaker<\/strong>
Prof. Paulo E. Arratia
Dept. Mechanical Engineering & Applied Mechanics
University of Pennsylvania, USA
Invited by Dr. J\u00f6rg Baller and prof. Anupam Sengupta<\/em><\/p>\n\n\n\n

Life in Complex Fluids<\/strong><\/p>\n\n\n\n

While much of our understanding of microbial swimming is derived from Newtonian fluid mechanics, many microorganisms including bacteria, algae, and sperm cells move in fluids or liquids that contain (bio)-polymers and\/or solids. Examples include human cervical mucus, intestinal fluid, wet soil, and tissues. These so-called complex fluids often exhibit non-Newtonian rheological behavior due to the non-trivial interaction between the fluid microstructure and the applied stresses. In this talk, I will show how the presence of polymers<\/i> in the fluid medium can strongly affect the motility behavior of microorganisms. In particular, I will focus on the effects of fluid elasticity (and viscosity) on the swimming behavior of the bacterium E. coli <\/i>(\u201cpuller\u201d) and the green algae C. reinhardtii <\/i>(\u201cpusher\u201d). Results show that elastic and viscous stresses can significantly affect motility kinematics (speed, beating frequency and amplitude) and energetics of such microorganisms in unexpected ways. For example, the run-and-tumble mechanism characteristic of E. coli<\/i> is suppressed, and its speed is enhanced by fluid elasticity (and possibly shear-thinning). On the other hand, elastic stresses hinder the swimming speed of both sperm cells and C. reinharditti<\/i> and lead to significant hypertension in their flagellum, indicating a common trait among the \u201c9+2\u201d axoneme structures in complex fluids. Finally, I will discuss how even minute amounts of polymer can affect the collective motion of swimming E. coli<\/i>. These results demonstrate the intimate link between swimming kinematics, biology, and fluid rheology and present an exciting research direction for physicists and engineers alike.<\/p>\n\n\n\n

About the speaker<\/strong><\/p>\n\n\n\n

Paulo E. Arratia received the B.Sc. degree in chemical engineering from Hampton University, Hampton, VA, USA, in 1997, and the M.Sc. and Ph.D. degrees in chemical and biochemical engineering from Rutgers University, New Brunswick, NJ, USA, in 2001 and 2003, respectively. He was a postdoctoral fellow at Haverford College (2003\u20132005) and the University of Pennsylvania (2005\u20132007). He is currently a Full Professor in the Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA, USA. He is the Director of the Penn Complex Fluids Lab where his research interests focus on interdisciplinary soft-condensed matter and fluid dynamics, including swimming of microorganisms, blood flow in microfluidic devices, and viscoelasticity.<\/p>\n\n\n\n