title: Colloids in active fluids: anomalous microrheology and negative drag.
abstract: We simulate an experiment in which a colloidal probe is pulled through an active nematic fluid. We find that the drag on the particle is non-stokesian (not proportional to its radius). Strikingly, a large enough particle in contractile fluid (such as an actomyosin gel) can show negative viscous drag in steady state: the particle moves in the opposite direction to the externally applied force. We explain this, and the qualitative trends seen in our simulations, in terms of the disruption of orientational order around the probe particle and the resulting modifications to the active stress.
authors.affiliation: SUPA, School of Physics and Astronomy, University of Edinburgh, Mayfield Road, Edinburgh, EH9 3JZ, United Kingdom.
authors.forename: G
authors.initials: G
authors.lastname: Foffano
authors.forename: J S
authors.initials: JS
authors.lastname: Lintuvuori
authors.forename: K
authors.initials: K
authors.lastname: Stratford
authors.forename: M E
authors.initials: ME
authors.lastname: Cates
authors.forename: D
authors.initials: D
authors.lastname: Marenduzzo