Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA.
School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK.
Soft Matter. 2021 Mar 11;17(9):2568-2576. doi: 10.1039/d0sm02023k.
Dissolution and dissociation of CO2 in an aqueous phase induce diffusiophoretic motion of suspended particles with a nonzero surface charge. We report CO2-driven diffusiophoresis of colloidal particles and bacterial cells in a circular Hele-Shaw geometry. Combining experiments and model calculations, we identify the characteristic length and time scales of CO2-driven diffusiophoresis in relation to system dimensions and CO2 diffusivity. The motion of colloidal particles driven by a CO2 gradient is characterized by measuring the average velocities of particles as a function of distance from the CO2 sources. In the same geometrical configurations, we demonstrate that the directional migration of wild-type V. cholerae and a mutant lacking flagella, as well as S. aureus and P. aeruginosa, near a dissolving CO2 source is diffusiophoresis, not chemotaxis. Such a directional response of the cells to CO2 (or an ion) concentration gradient shows that diffusiophoresis of bacteria is achieved independent of cell shape, motility and the Gram stain (cell surface structure). Long-time experiments suggest potential applications for bacterial diffusiophoresis to cleaning systems or anti-biofouling surfaces, by reducing the population of the cells near CO2 sources.
二氧化碳在水相中的溶解和离解会引起带有非零表面电荷的悬浮颗粒的扩散泳动。我们报告了在圆形亥姆霍兹流（Hele-Shaw）几何形状中胶体颗粒和细菌细胞的 CO2 驱动扩散泳动。通过实验和模型计算相结合，我们确定了 CO2 驱动扩散泳动的特征长度和时间尺度与系统尺寸和 CO2 扩散系数的关系。通过测量粒子从 CO2 源的距离的平均速度，来表征 CO2 梯度驱动的胶体粒子的运动。在相同的几何配置中，我们证明了在溶解的 CO2 源附近，野生型霍乱弧菌和缺乏鞭毛的突变体以及金黄色葡萄球菌和铜绿假单胞菌的定向迁移是扩散泳动，而不是趋化性。细胞对 CO2（或离子）浓度梯度的这种定向响应表明，细菌的扩散泳动是独立于细胞形状、运动和革兰氏染色（细胞表面结构）实现的。长时间实验表明，细菌扩散泳动具有应用于清洁系统或抗生物污染表面的潜力，可减少 CO2 源附近细胞的数量。
