ABSTRACT
In this paper, we report the fabrication and characterization of a portable transdermal alcohol sensing device via a human finger, using tin dioxide (SnO2) chemoresistive gas sensors. Compared to conventional detectors, this non-invasive technique allowed us the continuous monitoring of alcohol with low cost and simple fabrication process. The sensing layers used in this work were fabricated by using the reactive radio frequency (RF) magnetron sputtering technique. Their structure and morphology were investigated by means of X-ray spectroscopy (XRD) and scanning electron microscopy (SEM), respectively. The results indicated that the annealing time has an important impact on the sensor sensitivity. Before performing the transdermal measurements, the sensors were exposed to a wide range of ethanol concentrations and the results displayed good responses with high sensitivity, stability, and a rapid detection time. Moreover, against high relative humidity (50% and 70%), the sensors remained resistant by showing a slight change in their gas sensing performances. A volunteer (an adult researcher from our volunteer group) drank 50 mL of tequila in order to realize the transdermal alcohol monitoring. Fifteen minutes later, the volunteer's skin started to evacuate alcohol and the sensor resistance began to decline. Simultaneously, breath alcohol measurements were attained using a DRAGER 6820 certified breathalyzer. The results demonstrated a clear correlation between the alcohol concentration in the blood, breath, and via perspiration, which validated the embedded transdermal alcohol device reported in this work.
Subject(s)
Breath Tests , Ethanol , Adult , Humans , Humidity , Microscopy, Electron, Scanning , SweatABSTRACT
Membrane processes are promising methods to separate gases from feed streams without phase changing. A hybrid process, the combination of ionic liquids with a ceramic membrane (ILM), has been developed for humidity removal in a green continuous process. This new concept provides a more efficient and available ionic liquid (IL)-based membrane regeneration process, which just switches the moist feed stream to dry air. Furthermore, the ILM presents high stability and mechanical resistance during long-time operation. In addition, the influences of several operating parameters, including flow rate, temperature, absolute pressure, and feed concentration on process efficiency were investigated. The lower inlet flow rate was found to be favorable for drying humid air. Moreover, when the pressure increased, the mass of absorbed water was increased, while the feed concentration had no significant effects on the membrane separation performance. However, the operating temperature had a great effect on humidity removal. It is necessary to note that the processes at room temperature can limit the energy consumption. The absorbing process of ILM remained efficient after several absorption desorption cycles. Therefore, the new ILM hybrid process that has been developed has great potential for consecutive humidity removal processes.
ABSTRACT
A simple double thin-film coating-based device is proposed to quantify the ethanol content in humid air featuring a 10 ppm resolution and spanning a dynamic range from 0 to 1000 ppm. The transduction involves the measurement of the direct optical reflection intensity, changing upon refractive index variations induced by water and ethanol adsorption within the coatings. The first thin-film coating is a microporous methyl-functionalized, silica xerogel material more sensitive to alcohol, and the second one is a microporous pure silica xerogel material more sensitive to water. The precision of the sensor is achieved through a mathematical treatment applied on the time resolved adsorption period. Reflection signals of both the ethanol- and water-sensitive coatings are taken into account in the treatment to correct for differences in ambient conditions (temperature, relative humidity, presence of volatile organic compounds) within the same chamber previous to data analysis, which corresponds to realistic operating conditions. As the adsorption mechanism is governed by molecular dynamic equilibrium, these sensors are fast and instantaneously regenerated in ambient air. The sensor is easy to assemble and was reusable for a period exceeding 1 year (maximal tested time).
