Dissolution and dissociation of CO2in 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 CO2diffusivity. The motion of colloidal particles driven by a CO2gradient is characterized by measuring the average velocities of particles as a function of distance from the CO2sources. In the same geometrical configurations, we demonstrate that the directional migration of wild-typeV. choleraeand a mutant lacking flagella, as well asS. aureusandP. aeruginosa, near a dissolving CO2source 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 CO2sources.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics