Issue 16, 2019

3D dynamics of bacteria wall entrapment at a water–air interface

Abstract

Swimming bacteria can be trapped for prolonged times at the surface of an impenetrable boundary. The subsequent surface confined motility is found to be very sensitive to the physico-chemical properties of the interfaces which determine the boundary conditions for the flow. The quantitative understanding of this complex dynamics requires detailed and systematic experimental data to validate theoretical models for both flagellar propulsion and interfacial dynamics. Using a combination of optical trapping and holographic imaging we study the 3D dynamics of wall entrapment of swimming bacteria that are sequentially released towards a surfactant-covered liquid–air interface. We find that an incompressible surfactant model for the interface quantitatively accounts for the observed normal and tangential speed of bacteria as they approach the boundary. Surprisingly we also find that, although bacteria circulate over the air phase in counterclockwise circular trajectories, typical of free-slip interfaces, the body axis is still tilted “nose down” as found for no-slip interfaces.

Graphical abstract: 3D dynamics of bacteria wall entrapment at a water–air interface

Article information

Article type
Paper
Submitted
11 Jan 2019
Accepted
15 Mar 2019
First published
20 Mar 2019

Soft Matter, 2019,15, 3397-3406

3D dynamics of bacteria wall entrapment at a water–air interface

S. Bianchi, F. Saglimbeni, G. Frangipane, D. Dell'Arciprete and R. Di Leonardo, Soft Matter, 2019, 15, 3397 DOI: 10.1039/C9SM00077A

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