Surfactant Assemblies Directing Chemical Transfer Cascades in Convective Marangoni Flow Pumps

Convective Marangoni flow pumps can drive liquid streams in microfluidic devices and allow static channel layouts to be replaced by “virtual” boundaries that emerge in the liquid phase. However, while transfer from location A → location B can be modified easily via physicochemical control over the surface tension gradients involved, it remains a challenge to establish chemical transfer cascades A → B → C, which is prerequisite to more complex reconfigurable liquid systems. Here, a bottom-up approach is presented for convective Marangoni flow pumps, combining the self-assembly of a linear amphiphile into myelin filaments with the emulsification of oil microdroplets and the occurrence of Marangoni backflows underneath the air/water interface. The system allows chemical transfer over multiple steps amongst droplets that are positioned at the air/water interface. This concept provides a toolbox for the design of controllable surface tension gradients and triggered release of emulsified microdroplets as chemical signal carriers that travel along Marangoni flow patterns emerging in reconfigurable all-in-liquid microfluidics.