Soft Matter Seminar: Emile Kraus – “Rheology of Marine Sponge Tissue Shows Anisotropic Mechanics and Tuned Dynamics”

Join us for the Soft Matter Seminar on Friday April 29, 11am EST:

Dr. Emile Kraus, Department of Physics, University of Pennsylvania

Rheology of Marine Sponge Tissue Shows Anisotropic Mechanics and Tuned Dynamics

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.

Please contact contact Minh-Tri Ho Thanh at mhothanh@syr.edu for the zoom link.