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arXiv · 1708.02003

Large scale Micro-Photometry for high resolution pH-characterization during electro-osmotic pumping and modular micro-swimming

Ran Niu·Stanislav Khodorov·Julian Weber·Alexander Reinmüller·Thomas Palberg
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Abstract

Micro-fluidic pumps as well as artificial micro-swimmers are conveniently realized exploiting phoretic solvent flows based on local gradients of temperature, electrolyte concentration or pH. We here present a facile micro-photometric method for monitoring pH gradients and demonstrate its performance and scope on different experimental situations including an electro-osmotic pump and modular micro-swimmers assembled from ion exchange resin beads and polystyrene colloids. In combination with the present microscope and DSLR camera our method offers a 2 \mu m spatial resolution at video frame rate over a field of view of 3920x2602 \mu m^2. Under optimal conditions we achieve a pH-resolution of 0.05 with about equal contributions from statistical and systematical uncertainties. Our quantitative micro-photometric characterization of pH gradients which develop in time and reach out several mm is anticipated to provide valuable input for reliable modeling and simulations of a large variety of complex flow situations involving pH-gradients including artificial micro-swimmers, microfluidic pumping or even electro-convection.

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Ran Niu, Stanislav Khodorov, Julian Weber, Alexander Reinmüller, Thomas Palberg. 2017-08-07. Large scale Micro-Photometry for high resolution pH-characterization during electro-osmotic pumping and modular micro-swimming. https://doi.org/10.1088/1367-2630/aa9545

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