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Open AccessArticle

Glucose Oxidase Micropumps: Multi-Faceted Effects of Chemical Activity on Tracer Particles Near the Solid–Liquid Interface

1
Electrochemistry Laboratory, International Centre of Biodynamics, 1B Intrarea Portocalelor, 060101 Bucharest, Romania
2
Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, D-70569 Stuttgart, Germany
*
Authors to whom correspondence should be addressed.
Condens. Matter 2019, 4(3), 73; https://doi.org/10.3390/condmat4030073
Received: 27 June 2019 / Revised: 17 July 2019 / Accepted: 24 July 2019 / Published: 25 July 2019
(This article belongs to the Special Issue Dynamics of Active Matter)
We report the development of glucose oxidase pumps characterized by small lateral dimensions (≈200 μ m). We studied the effects of the activity of the enzyme pump on silica particles (“tracers”) sedimented around the enzyme pump/patch. Once the activity of the pump was turned on (i.e., the glucose substrate was added to the solution), in-plane motion of the tracers away from the enzyme patch, as well as the emergence of an in-plane region around the patch which was depleted by tracers, was observed. The lateral extent of this depletion zone increased in time at a rate dependent both on the glucose concentration and on the areal density of the enzyme in the patch. We argue that, when the tracers were very near the wall, their motion and the emergence of the depletion zone were most likely the result of diffusiophoresis and drag by osmotic flows induced at the wall, rather than that of drag by a solutal buoyancy driven convective flow. We infer that, for the glucose oxidase enzymatic pumps, bulk (solutal buoyancy), as previously reported, as well as surface (osmotic) driven flows coexist and have to be explicitly accounted for. It seems plausible to assume that this is the case in general for enzyme pumps, and these complementary effects should be considered in the design of applications, e.g., stirring or sensing inside microfluidic systems, based on such pumps. View Full-Text
Keywords: enzyme micropumps; glucose oxidase; diffusiophoresis; osmotic flow enzyme micropumps; glucose oxidase; diffusiophoresis; osmotic flow
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Munteanu, R.-E.; Popescu, M.N.; Gáspár, S. Glucose Oxidase Micropumps: Multi-Faceted Effects of Chemical Activity on Tracer Particles Near the Solid–Liquid Interface. Condens. Matter 2019, 4, 73.

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