4–6 Oct 2023
Biozentrum, University of Würzburg
Europe/Berlin timezone

Colloidal transport by light-induced gradients of active pressure

Not scheduled
20m
Room A101 (Biozentrum, University of Würzburg)

Room A101

Biozentrum, University of Würzburg

Am Hubland
Poster

Speaker

Nicola Pellicciotta (Sapienza University of Rome)

Description

Active fluids, like all other fluids, exert mechanical pressure on confining walls. Unlike equilibrium, this pressure is generally not a function of the fluid state in the bulk and displays some peculiar properties. For example, when activity is not uniform, fluid regions with different activity may exert different pressures on the container walls but they can coexist side by side in mechanical equilibrium.
Here we show that by spatially modulating bacterial motility with light, we can generate active pressure gradients capable of transporting passive probe particles in controlled directions. Although bacteria swim faster in the brighter side, we find that bacteria in the dark side apply a stronger pressure resulting in a net drift motion that points away from the low activity region.
Using a combination of experiments and numerical simulations, we show that this drift originates mainly from an interaction pressure term that builds up due to the compression exerted by a layer of polarized cells surrounding the slow region.
In addition to providing new insights into the generalization of pressure for interacting systems with non-uniform activity, our results demonstrate the possibility of exploiting active pressure for the controlled transport of microscopic objects.

Primary author

Nicola Pellicciotta (Sapienza University of Rome)

Co-authors

Mr Dario Buonomo (La Sapienza University of Rome) Dr Giacomo Frangipane (Sapienza University of Rome) Dr Luca Angelani (ISC-CNR) Dr Matteo Pauluzzi (Departament de Física de la Matèria Condensada) Prof. Roberto Di Leonardo (Sapienza University of Rome)

Presentation materials

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