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Eletrochemically Actuated Stop–Go Valves for Capillary Force-Operated Diagnostic Microsystems

Authors

  • Alemayehu P. Washe,

    1. Bioengineering and Bioelectrochemistry Group, Department of Chemical Engineering, Universitat Rovira i Virgili, Avinguda Països Catalans, 26, 43007, Tarragona (Spain)
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  • Dr. Pablo Lozano,

    1. Integrated Microsystems for the Quality of Life S.L. C/del Ferro 6, Nave 7, 43006 Tarragona (Spain)
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  • Diego Bejarano,

    1. Bioengineering and Bioelectrochemistry Group, Department of Chemical Engineering, Universitat Rovira i Virgili, Avinguda Països Catalans, 26, 43007, Tarragona (Spain)
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  • Dr. Ioanis Katakis

    Corresponding author
    1. Bioengineering and Bioelectrochemistry Group, Department of Chemical Engineering, Universitat Rovira i Virgili, Avinguda Països Catalans, 26, 43007, Tarragona (Spain)
    • Bioengineering and Bioelectrochemistry Group, Department of Chemical Engineering, Universitat Rovira i Virgili, Avinguda Països Catalans, 26, 43007, Tarragona (Spain)

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Abstract

Lateral-flow immunosensing devices continue to be the most successful commercial realization of analytical microdevices. They owe their success to their simplicity, which significantly depends on the capillary-driven flow and versatile technological platform that lends itself to fast and low-cost product development. To compete with such a convenient product, microsystems can benefit from simple-to-operate fluid manipulation. We show that the capillary-driven flow in microchannels can be manipulated with electrochemically activated valves with no moving parts. These valves consist of screen-printed electrode pairs that are transversal to the flow. One of the electrodes is solvent-etched to produce a superhydrophobic surface that provides passive stopping and facilitates low-voltage (∼1 V) actuation of the flow via electrowetting. The operation of such valves in the stop–go mode, with a response time between 2 and 45 sec depending on the type and concentration of salt, is demonstrated. Mechanistic investigations indicated that the response depends on at least three phenomena that contribute to electrocapillarity: the electrochemical double-layer capacitance, specific counterion adsorption, and possible electrohydrodynamic effects.

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