Photo-actuated ionogel microvalves for real-time water quality analysis in a micro-fluidic device

Abstract

In the recent years, advances in micro-fluidic techniques for environmental applications have brought wide opportunities for improving of the capacity to monitor water quality. However, the development of fully integrated micro-fluidic devices capable of performing complex functions requires the integration of mico-valve with appropriate performance, since they are essential tools for the control and manipulation of flows in micro-channels.[1] The incorporation of ionic liquids within responsive gel matrices (ionogels) produces hybrid materials with many advantages over conventional materials. Depending on the ionic liquid, ionogels give the possibility of tuning several micro-valve actuation times and so independently control liquid flows within the channels under a common illumination source.[2] The undeniable advantage of these materials arise from the use of non invasive, non-contact stimuli such as light, offering improvements in versatility during manifold fabrication, and control of the actuation mechanism. Here we present an attractive approach for water quality analysis, nitrite determination, based on photo-switchable ionogel actuators wherein the micro-valve opening/closing mechanism is controlled by simply applying localised white light irradiation using optical fibres. The nitrite concentration of water samples is detected by a highly sensitive, low cost wireless paired emitter detector diode device. [1] M. Czugala et. al., “Materials Science: The Key to Revolutionary Breakthroughs in Micro-fluidic Devices”, Proceedings SPIE 8107, 81070C, (2011); doi:10.1117/12.895330. [2] F. Benito-Lopez et. al., Ionogel-based light-actuated valves for controlling liquid flow in micro-fluidic manifolds, Lab Chip 10, (2010), 195-20