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Updated: Jun 24, 2025

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Published on: February 6, 2014
Thinning by cluster breaking: Active matter and shear flows share thinning mechanisms
Ruoyang Mo1,2,3, Ding Xu1,2,3, Ning Xu1,2,3
1Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, People's Republic of China.
Abstract:
Among many unexpected phenomena of active matter is the recently observed superfluid-like thinning (viscosity drop) behavior of bacteria suspensions. Understanding this peculiar self-propelled thinning by active matter is of theoretical and practical importance. Here, we find that, although distinct in driving mechanisms, active matter and shear flows exhibit similar thinning behaviors upon the increase of self-propulsion and shear forces, respectively. Our structural characterizations reveal that they actually share the same cluster-breaking mechanism of thinning. How fast and how shattered the cluster is broken determines the (dis)continuity of the thinning. This explains why adding active particles to Newtonian fluids can cause thinning, in which rotation of active particles play a key role in breaking clusters. Our work proposes a mechanism of self-propelled thinning and further establishes the underlying connections between active matter and shear flows.
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