Gregory M. Kuhlman

Advanced electronic tongue concept

This effort, directed at developing a sensor for evaluating water quality, is based on electrochemical techniques that detect and identify ions in solution. This paper discusses the use of Cyclic Voltammetry (CV), corrosion measurements, and Anodic Stripping Voltammetry (ASV) to measure three marker ions Cu, Fe, and Zn using the electronic tongue concept. The use of genetic algorithms is suggested as an approach to facilitate the search for optimum measurement conditions. In addition, the possibility of changing the physical conditions of the sample chamber is discussed as a way of increasing the sensors apparent sensitivity of and confidence in the measurements.

Designing a water-quality monitor with ion selective electrodes

This effort is directed at developing a sensor for evaluating water quality. A set of nine ion selective electrodes (ISEs) are being fabricated on a 4.5-cm diameter ceramic substrate. This paper discusses the design and fabrication of the deposition chamber and the ceramic substrates that form the basis for the ISEs. The chamber, substrate and electronics design was validated to assure that the multiplexing electronics functions, the ceramic substrate mounted is stress-free, and the deposition chamber is water tight. Results from the electrolysis of a dilute nitric acid solution are presented to further validate the design concept.

Detecting heavy metals in solution using electronic-tongue 3 REDOX water quality sensors

This paper describes results obtained from the E-Tongue 3 apparatus used to characterize residual contaminates in water. This apparatus is intended for use in water quality measurements for the ISS (International Space Station). The apparatus contains nine planar electrochemical cells and a conductivity sensor. Detection of contaminate ions in solution uses ASV (anodic stripping voltammetry) with a detection limit in the 10 /spl mu/M range. A linear calibration curve was achieved using Zn, Pb, Cu, and Mn cations. A robust method for identifying electroactive species is presented and uses the Savitzky-Golay second derivative method.

Planar Array REDOX Cells and pH Sensors for ISS Water Quality and Microbe Detection

This paper describes results acquired from E-Tongue 2 and E-Tongue 3 which are arrays of planar three-element electrochemical cells and pH sensors. The approach uses ASV (Anodic Stripping Voltammery) to achieve a detection limit, which in the case of Pb, is below one μM which is needed for water quality measurements. The richness of the detectable species is illustrated with Fe where seven species are identified using the Pourbiax diagram. The detection of multiple species is illustrated using Pb and Cu. The apparatus was used to detect the electroactivity of the metabolic-surrogate, PMS (phenazine-methosulphate). Finally, four types of pH sensors were fabricated and characterized for linearity, sensitivity, and responsiveness.

Measuring water content of Martian soil simulants using planar four-probes

A miniature four-point probe instrument has been developed and applied to the characterization of the moisture content of the Martian soil simulants using fine and coarse silica sand and Moses Lake basalt. The results indicate that the soil resistivity varies over four orders of magnitude as the moisture content varied from 0.1% to over 10%. In addition it was found that forcing too much current through the sand sample resulted in a curious breakdown in the current-voltage characteristic.