Flexible tape fits inside the tube to detect changes in water temperature in real time, contaminants

Researchers from the Institute for Scientific and Industrial Research (SANKEN) at 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-destructive sheet sensor for fluid quality monitoring. Using voltages generated in a layer of carbon nanotubes, the method does not require sampling, chemical labels or an external light source. The application of this study can enable on-site quality control of chemical plants or environmentally sensitive water bodies.

Monitoring the chemical content of water flowing through pipes is crucial for industrial applications, such as food or beverage production, as well as for identifying environmental pollution in wastewater that reaches the environment. However, current methods require periodic collection of test samples as well as the use of chemical reagents or labels. A new approach is needed for continuous monitoring without interruption.

Now a team of researchers has invented a flexible sheet that uses a built-in film of carbon nanotubes as a photodetector layer. When exposed to light, carbon nanotubes can produce electrical voltages that can be detected by attached electrodes. “Our extensible device is equipped with a high-sensitivity, broadband optical sensor that allows it to be attached to a wide variety of tube shapes,” say authors Lee Kou and Tepei Araki.

Changes in water temperature can also be observed passively based on black body radiation. An external terahertz or infrared light source may be used to detect impurities or inspect beverages. This allows spectroscopic 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, contributing to the realization of future environmental measurement systems,” say senior authors Yukio Cavanaugh and Tsuyoshi Sekitani. The researchers tested the system and found a linear response between glucose concentration and passively generated voltage.

The team hopes that this study could lead to the modernization of industrial quality control methods, in which pollutant concentrations can be monitored continuously rather than during planned collection. The study was published in Scientific achievements.