Scientists from the Scientific and Industrial Research Institute (SANKEN) of Osaka University, in collaboration with Chuo University, Eindhoven University of Technology and the National Institute of Advanced Industrial Science and Technology , have developed a non-intrusive sheet sensor for liquid quality monitoring. Using voltages generated in a layer of carbon nanotubes, the method does not require sampling, chemical markers or an external light source. Application of this research can enable on-site quality control of chemical plants or environmentally sensitive water sites.
Monitoring the chemical content of water flowing through pipes is essential for industrial applications, such as food or beverage production, as well as for identifying environmental contamination in effluent that reaches the environment. However, current methods require the periodic collection of samples for testing, as well as the use of chemical reagents or tags. A new approach is needed for non-disruptive continuous monitoring.
Now, a team of researchers has invented a flexible sheet that uses an embedded carbon nanotube film as a photodetector layer. When exposed to light radiation, the carbon nanotubes can produce an electrical voltage, which can be detected by attached electrodes. “Our stretch-sheet device is equipped with a high-sensitivity broadband optical sensor, which allows it to be attached to a wide variety of pipe shapes,” explain authors Li Kou and Teppei Araki.
Water temperature changes could also be passively monitored based on black body radiation. For dirt detection or beverage inspection, an external terahertz or infrared light source can be used. This allows spectroscopy methods to be applied continuously to flowing liquids. “The optical sensor sheet can easily visualize the concentration, temperature, viscosity, and location of cracks and liquids in pipes, helping to realize future environmental measurement systems,” say lead authors Yukio Kawano and Tsuyoshi Sekitani. The researchers tested the system and found a linear response between glucose concentration and passively generated voltage.
The team hopes this research can lead to the modernization of industrial quality control methods, in which contaminant concentrations can be monitored continuously, rather than during scheduled collections.