Soft Matter Seminar: Dr. Emile Kraus, University of Pennsylvania

Guest Speaker: Dr. Emile Kraus from Department of Physics at University of Pennsylvania

“Rheology of Marine Sponge Tissue Shows Anisotropic Mechanics and Tuned Dynamics”

Abstract: Sponges are animals that inhabit many aquatic environments while filtering small particles and ejecting metabolic wastes. They are composed of cells in a bulk extracellular matrix, often with an embedded scaffolding of stiff, siliceous spicules. We hypothesize that the mechanical response of this heterogeneous tissue to hydrodynamic flow influences cell proliferation in a manner that generates the body of a sponge. Toward a more complete picture of the emergence of sponge morphology, we dissected a set of species and subjected disks of living tissue to physiological shear and uniaxial deformations on a rheometer. In various species, sponge tissue exhibited rheological properties such as anisotropic elasticity, shear softening and compression stiffening, negative normal stress, and non-monotonic dissipation as a function of both shear strain and frequency. Erect sponges possessed aligned, spicule-reinforced fibers which endowed three times greater stiffness axially compared with orthogonally. By contrast, tissue taken from shorter sponges was more isotropic but time-dependent, suggesting greater mechanical sensitivity in these compared with erect forms. We explore ecological and physiological implications of our results and speculate about flow-induced mechanical signaling in sponge cells.

To join remotely, please email Minh Tri Ho Thanh at mhothanh@syr.edu for zoom link