The impact of geometrical confinement in a slab on the behavior of tracer particles near active glucose oxidase micropum
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INVITED ARTICLE
The impact of geometrical confinement in a slab on the behavior of tracer particles near active glucose oxidase micropump Raluca-Elena Munteanu1
· Mihail N. Popescu2
´ ar ´ 1 · Szilveszter Gasp
Received: 29 April 2020 / Revised: 3 August 2020 / Accepted: 31 August 2020 © The Author(s) 2020
Abstract Patches of surface-immobilized and catalytically active enzyme, immersed into a solution with the corresponding substrate, induce flow in the solution. Such systems are currently investigated as a promising direction in the development of selfpowered micropumps that could operate autonomously within microfluidic devices. Here, we investigate the influence of confinement, within a slab of height H , on the response exhibited by silica tracer particles sedimented near a chemically active glucose oxidase patch which is immersed into a glucose solution of very low ionic strength. Irrespective of the value H , within the range explored in this study, a region depleted of tracers forms around the patch. When H is not much larger than the radius of the patch, the rate of growth of the depletion zone depends on H ; somewhat surprisingly, this dependence is influenced by the glucose concentration. The results are discussed within the context of a simple model for a chemically active patch. Keywords Chemically active systems · Enzyme micropumps · Glucose oxidase · Diffusion
Introduction Microfluidic systems are often used together with bulky, external pumps; these significantly increase the costs of the system and, moreover, compromise—to a large extent— their autonomy and portability. Consequently, there is significant interest in exploring new methods of pumping, as well as in translating them into miniaturized devices that can operate autonomously and can be integrated within microfluidic channels or chips, for achieving active fluid transport [1]. Patches of enzyme immobilized on surfaces have been shown to induce flow in the solution surrounding them, Mihail N. Popescu
[email protected] Szilveszter G´asp´ar
[email protected] Raluca-Elena Munteanu [email protected] 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
when the solution contains the corresponding substrate and the enzyme is catalytically active [2]. This finding has motivated several studies aimed at investigating their use as self-powered micropumping systems suitable to carry out various tasks within microfluidic channels. “Proof-ofprinciple” experimental studies of such micropumps have employed several types of enzymes: glucose oxidase (GOX) [2, 3], catalase [2, 3], urease [2, 4–7], lipase [2], acid phosphatase [3, 8], and DNA polymerase [9]. Although the enzyme micropumps are relatively new concepts, a number of applications based on them have been proposed, such as transport of microparticles between different points of a microchamber [6], or detection of toxic comp
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