Matteo Paoluzzi — Università di Roma La Sapienza # Active Matter in confining geometries # Active Matter focuses on systems composed by self-driven units, also called active particles, that are capable of converting free energy into movement. While an unified framework to describe the phenomenology of the active matter is still missing, different approaches converge on the importance of the density fluctuations that result to be long-lived leading to non-Boltzmann stationary states with no vanishing probability currents.
In order to stabilize the spontaneous currents, environment and confinement play a crucial role: in recent years, it has been shown that the density fluctuations of active baths can produce unidirectional flux in asymmetric environments [1], sustain spontaneous flow in confined geometry [2], move micro gears [3,4], exert effective attractive forces [5], and deliver passive colloids [6].
We focus our attention on run-and-tumble particles, i. e., a model that captures the dynamics of low Reynolds number swimming organisms such as E. coli, embedded into (i) confining geometries[7] and (ii) subjected to external random fields[8]. The results obtained by mean of numerical simulations can been experimentally studied by mean of (i) microfluidic devices and (ii) speckle fields.

References

[1] P. Galajda et al., J. Bacteriol. 189, 1033 (2007).
[2] T. Sanchez, et al., Nature 491, 431 (2012).
[3] R. Di Leonardo, et al., Proc. Natl. Acad. Sci. 107, 9541 (2010).
[4] A. Sokolov, et al., Proc. Natl. Acad. Sci. U.S.A. 107, 969 (2010).
[5] L Angelani, et al., Phys. Rev. Lett. 107, 138302 (2011).
[6] N. Koumakis, et al., Nature Communications, 4, 2588 (2013).
[7] M. Paoluzzi, et al. http://arxiv.org/abs/1412.1131 (2014).
[8] M. Paoluzzi, et al. J. Phys.: Condens. Matter 26 375101 (2014).