Abstract
An ion-exchange-resin-based microfluidic pump is introduced that utilizes trace amounts of ions to generate fluid flows. We show experimentally that our pump operates in almost deionized water for periods exceeding 24 h and induces fluid flows of μm s-1 over hundreds of μm. This flow displays a far-field, power-law decay which is characteristic of two-dimensional (2D) flow when the system is strongly confined and of three-dimensional (3D) flow when it is not. Using theory and numerical calculations we demonstrate that our observations are consistent with electroosmotic pumping driven by μmol L-1 ion concentrations in the sample cell that serve as 'fuel' to the pump. Our study thus reveals that trace amounts of charge carriers can produce surprisingly strong fluid flows; an insight that should benefit the design of a new class of microfluidic pumps that operate at very low fuel concentrations.
Highlights
An ion-exchange-resin-based microfluidic pump is introduced that utilizes trace amounts of ions to generate fluid flows
Our results indicate that ion-exchange-resin-based microfluidic pumps have a surprisingly small lower bound to the ion concentration under which they can operate, which we chart in this paper
The striking feature of this pump is that it operates in mmol LÀ1 ionic concentrations for periods exceeding 24 h and yet manages to produce fluid flows with speeds of several mm sÀ1 over hundreds of mm, without strongly modifying its environment
Summary
We describe the experimental setup for a single ion-exchange-resin pump and characterization of the tracer properties used in our velocimetry measurements. We provide quantification of a wide range of resin pumps and tracers to show the generality of our findings. We study the impact of added salt on the pumping
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