Probing the shear viscosity of an active nematic

TL;DR

This paper demonstrates how to measure the shear viscosity of an active nematic film by analyzing disclination motion and hydrodynamic coupling, enabling better control of active fluid dynamics.

Contribution

It introduces a method to determine the shear viscosity of active nematic films through rheological probing using disclination dynamics and hydrodynamic modeling.

Findings

Estimated shear viscosity of the active nematic film.

Validated the use of disclination motion as flow tracers.

Provided a new approach for controlling active fluid behavior.

Abstract

In vitro reconstituted active systems, such as the ATP-driven microtubule bundle suspension developed by the Dogic group, provide a fertile testing ground for elucidating the phenomenology of active liquid crystalline states. Controlling such novel phases of matter crucially depends on our knowledge of their material and physical properties. In this letter, we show that the rheological properties of an active nematic film can be probed by varying its hydrodynamic coupling to a bounding oil layer. Using the motion of disclinations as intrinsic tracers of the flow field and a hydrodynamic model, we obtain an estimate for the as of now unknown shear viscosity of the nematic film. Knowing this now provides us with an additional handle for robust and precision tunable control of the emergent dynamics of active fluids.