Underwater micro gas detector

This article presents a novel underwater micro gas detector (UMGD), which can directly detect components and concentrations of volatile gases dissolved in water. A Pt/SnO2 alcohol gas-sensing chip fabricated by means of a silicon micromachining technique is encapsulated in a perforated superhydrophobic waterproof case. Strong surface tension in the microperforations prevents water from intruding into the case. However, volatile gas molecules that are emanated from the surface of the water become diffused inside the case. The UMGD had a sensitivity level of 14.3 mV/ppm and a nonlinearity level of less than 8.5% in the ethanol concentration range of 2.25 ppm to 22.50 ppm. The five successive measurements taken in water-based solutions with three different concentrations (0.1, 0.5, 1.0 vol%) of ethanol demonstrate that the UMGD can directly detect certain gases in water and enable real-time water monitoring.