Modeling of Viscoelasticity and the Dynamics of Swimming Microorganisms

Suspensions of swimming microorganisms represent an important class of active matter. This talk will discuss two aspects of this system which incorporate viscoelasticity. The first is in concentrated groups of organisms in which hydrodynamic interactions can lead to coordinated behaviors of the group. A viscoelastic suspending fluid (such as saliva or mucus) will alter these interactions and therefore the collective behavior. We will discuss computer simulations of a mean-field description of this system, in which we show how viscoelasticity interrupts the collective behavior. Even at low concentrations of organisms and in a Newtonian suspending fluid, the suspension as a whole exhibit viscoelasticity because of the presence of the swimming organisms. Using a kinetic theory model, we have quantified this viscoelasticity and have compared it to suspensions of passive particles.