Issue 46, 2021

Microbial Brazil nut effect


The Brazil nut effect (BNE) is a counter-intuitive process of segregation of a large object inside a vibrated granular medium (GM), which has been studied widely by subjecting GMs to various kinds of shears and vibrations. In this article, we report a new kind of BNE which occurs as a consequence of granular fluctuations induced by microbe-generated gas bubbles. We call it the ‘microbial Brazil nut effect’. The paper demonstrates microbial BNE for a bidisperse granular mixture as well as for intruder segregation. Furthermore, using X-ray μCT and a simple scaling argument for segregation velocity, the paper clarifies the transport mechanics of an intruder inside a bubbly granular bed. We think the reported phenomenon should be ubiquitous in the microbe-populated wet sandy floors of waterbodies and may have some implication on the distribution of material near the floors.

Graphical abstract: Microbial Brazil nut effect

Supplementary files

Article information

Article type
14 Sep 2021
06 Oct 2021
First published
06 Oct 2021
This article is Open Access
Creative Commons BY license

Soft Matter, 2021,17, 10428-10436

Microbial Brazil nut effect

A. Srivastava, K. Kikuchi and T. Ishikawa, Soft Matter, 2021, 17, 10428 DOI: 10.1039/D1SM01327K

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