A plasma spectroscopic microdevice for on-site water monitoring

Plasma spectroscopic techniques can provide a quick, on-site solution for monitoring the potability of water sources. This paper reports on a new, essentially disposable ceramic microdevice that utilizes on-chip doped DC plasmas to spectroscopically analyze the atomic and molecular composition of water samples on-site. The device is fabricated on an alumina ceramic substrate, which is ideal due to its low-cost, ability to be cast into micro-structures, mechanical robustness, and insulation of high-voltage. Water sample analysis is performed in air at atmospheric pressure, greatly reducing the cost and complexity of water quality monitoring on-site. Samples are partially evaporated with on-chip thin-film Cr microheater integrated into the cathode lead. Temperature changes as large as 47°C can be realized with 60 mA. With the device reported here, copper and aluminum impurities are detected at 100 ppm and ammonia contaminants are observed in concentrations as low as 1%.