This paper reports on a low-cost, borosilicate glass-based spectroscopic sensor for the detection of water contaminants.
10 μL water samples are inserted into a sandblasted sample reservoir in a borosilicate glass substrate and are partially
evaporated with a 200 nm thin-film Cr microheater/cathode patterned to the bottom of the reservoir. The relative
contaminant concentration within the partially evaporated sample is greater, providing a means of measuring lower
concentrations of impurities. An on-chip plasma discharge is stuck to the sample, sputtering the water contaminants into
the discharge, doping its spectral emissions. Cu and Fe impurities are detected at 10 ppm in a 2.5% HNO3 solution and
Ca and Mg contaminants are detected at 100 ppm. The on-chip microheater yields temperature changes as high as 96 °C
when supplied with 100 mA. Multiple single-use sensors can be fabricated inexpensively on the borosilicate glass
substrate using simple, standard photolithography techniques.
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