Microfluidic optoelectronic sensor based on a composite halochromic material for dissolved carbon dioxide detection

We present a microfluidic optoelectronic cross-reactive sensor based on a novel composite material for selective detection of dissolved CO2. A microfluidic device contains an array of micro-wells filled with ion-exchange polymeric microbeads doped by halochromic dyes paired to quaternary ammonium cations. The sensor configuration allows incorporation of virtually any combination of halochromic ion-pairs, providing a route for cross reactive sensing. A versatile optical arrangement based on a white LED and a miniature portable USB spectrometer allows recording optical spectra, which are easily translated into electronic readouts. Rather than monitoring response at a particular absorption or emission wavelength of the dye, data acquisition is performed over a broad continuous spectrum. This results in a rich multidimensional readout useful for ultrasensitive detection. The sensor provides distinctive responses to different concentrations of dissolved CO2, with no cross sensitivity to other sources of acidity. Our findings could lead to the development of a cost-effective, lightweight, and low-power sensor for detection of dissolved CO2 for a variety of applications.