ELectrochemical principles for active control of liquids on submillimeter scales

Electrochemical methods were combined with redox-active surfactants to acti vely control the motions and positions of aqueous and organic liquids on mi llimeter and smaller scales. Surfactant species generated at one electrode and consumed at another were used to manipulate the magnitude and direction of spatial gradients in surface tension and guide droplets of organic liqu ids through simple fluidic networks. Solid microparticles could be transpor ted across unconfined surfaces. Electrochemical control of the position of surface-active species within aqueous films of liquid supported on homogene ous surfaces was used to direct these films into periodic arrays of droplet s with deterministic shapes and sizes.