Crack patterns of drying dense bacterial suspensions

Xiaolei Ma, Zhengyang Liu, Wei Zeng, Tianyi Lin, Xin Tian, Xiang Cheng

Research output: Contribution to journalArticlepeer-review


Drying of bacterial suspensions is frequently encountered in a plethora of natural and engineering processes. However, the evaporation-driven mechanical instabilities of dense consolidating bacterial suspensions have not been explored heretofore. Here, we report the formation of two different crack patterns of drying suspensions of Escherichia coli (E. coli) with distinct motile behaviors. Circular cracks are observed for wild-type E. coli with active swimming, whereas spiral-like cracks form for immotile bacteria. Using the elastic fracture mechanics and the poroelastic theory, we show that the formation of the circular cracks is determined by the tensile nature of the radial drying stress once the cracks are initiated by the local order structure of bacteria due to their collective swimming. Our study demonstrates the link between the microscopic swimming behaviors of individual bacteria and the mechanical instabilities and macroscopic pattern formation of drying bacterial films. The results shed light on the dynamics of active matter in a drying process and provide useful information for understanding various biological processes associated with drying bacterial suspensions.

Original languageEnglish (US)
Pages (from-to)5239-5248
Number of pages10
JournalSoft Matter
Issue number28
StatePublished - Jun 20 2022

Bibliographical note

Funding Information:
We thank Justin Burton and Xudong Liang for fruitful discussions, and Greg Haugstad, Shashank Kamdar, Samantha Porter and Yiming Qiao for the assistance in the experiment. We acknowledge the AISOS at the University of Minnesota for the access of a Nanoveal Profilometer. This work was supported by NSF CBET-2028652.

Publisher Copyright:
© 2022 The Royal Society of Chemistry.

PubMed: MeSH publication types

  • Journal Article


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