AI 中文总结
本研究发现运动性大肠杆菌可改变静置液滴蒸发的盐结晶模式，通过多模型解释该现象，揭示微生物主动控制蒸发结晶的潜力。
AI 中文摘要
运动性大肠杆菌可改变静置液滴蒸发过程中的盐结晶模式。在去离子水的稀细菌悬浮液中，干燥后细菌细胞主要聚集在液滴边缘，符合经典的“咖啡环效应”。然而在较高细胞密度下，细菌分布变得更均匀。无细菌时，纯磷酸盐缓冲盐水也会形成咖啡环图案的盐晶体。当细菌与盐溶质共存时，液滴中心附近会出现额外的孤立晶体，其丰度随细菌浓度增加而上升，而边缘的晶体则呈现径向延伸的树枝状形态。为探究这些现象，我们使用基于斯托克斯的分析模型估算内部流场的演化，并将其与细菌运动性对比；随后实施有限体积模型描述细菌与盐的输运及吸附，还开发了盐成核的随机模型，该模型成功解释了实验中观察到的结晶模式。我们的结果表明，细菌运动性可在蒸发早期克服蒸发诱导的流场，使细菌细胞成为成核位点，从而改变最终的晶体形态。本研究凸显了运动性微生物主动控制蒸发结晶的潜力，对多孔介质流动和微流体沉积过程具有启示意义。
英文摘要
Motile Escherichia coli bacteria can alter salt crystallization patterns during the evaporation of sessile droplets. In dilute bacterial suspensions in deionized water, dried bacteria cells predominantly accumulate at the droplet periphery, consistent with the classic "coffee-ring" effect. At higher cell densities, however, the bacterial distribution becomes more uniform. In the absence of bacteria, pure Phosphate Buffered Saline also forms salt crystals in a coffee-ring pattern. When bacteria are present alongside the salt solute, additional isolated crystals appear near the droplet center, with their abundance increasing with bacterial concentration, while crystals at the periphery adopt dendritic morphologies that extend radially. To investigate these phenomena, we used a Stokes-based analytical model to estimate the evolution of internal flow fields and compare them with bacterial motility. Then a finite volume model is implemented for bacteria and salt transport and adsorption, and a stochastic model for salt nucleation was developed, which successfully explains the crystallization pattern seen in the experiments. Our results show that bacterial motility can overcome evaporation induced flow during early stage, enabling bacteria cells to serve as nucleation sites and thereby altering the final crystalline morphology. This work highlights the potential of motile microorganisms to actively control evaporative crystallization, with implications for porous media flow and microfluidic deposition processes.
Comments11 main pages, 9 appendices pages, 10 figures
