Microfluidic Pumping by Micromolar Salt Concentrations

摘要

An ion-exchange-resin-based microfluidic pump is introduced that utilizestrace amounts of ions to generate fluid flows. We show experimentally that ourpump operates in almost deionized water for periods exceeding 24h and inducesfluid flows of um/s over hundreds of um. This flow displays a far-field,power-law decay which is characteristic of two-dimensional (2D) flow when thesystem is strongly confined and of three-dimensional (3D) flow when it is not.Using theory and numerical calculations we demonstrate that our observationsare consistent with electroosmotic pumping driven by umol/L ion concentrationsin the sample cell that serve as 'fuel' to the pump. Our study thus revealsthat trace amounts of charge carriers can produce surprisingly strong fluidflows; an insight that should benefit the design of a new class of microfluidicpumps that operate at very low fuel concentrations.