Flexible Sensor Prototype to Discretely Monitor the Inside of Pipes

June 03, 2022 by Kristijan Nelkovski

A new optical sensor prototype is said to provide real-time chemical composition data without directly interacting with the substance being monitored.

Various industries from food and beverage production to water treatment rely on continuous chemical monitoring in fluids to maintain health standards. 

Modern fluid monitoring techniques still face some challenges, however: they often require chemical reagents—substances added to a sample to test if some type of reaction occurs. This requires intermittent sampling, which can disrupt a process or waste valuable commodities. Other methods include biomarker and biofluid testing or even centrifugation measurements. But these methods are often considered time-consuming and require specialized equipment, making them unsuitable for onsite and real-time sensing.


Example of a water monitoring system

Example of a water monitoring system. Image used courtesy of the National Library of Medicine

These obstacles have prompted scientists and engineers to look for new approaches to continuously monitor fluids without disrupting any environmental or industrial processes. Some of these emerging methods in the field focus on photodetection.

Recently, a multinational team of engineers from the Tokyo Institute of Technology, the Institute of Scientific and Industrial Research in Osaka, the Eindhoven University of Technology, and other scientific organizations developed a novel carbon nanotube photodetector device to implement in industrial processes.


Nanotube Photosensors in Pipes

Standing out from its competition, this new optical sensor is said to provide real-time chemical composition data without directly interacting with the substance that’s being monitored. The researchers used carbon nanotubes as photodetectors and embedded them into a flexible sheet. This sheet can be attached to a variety of surfaces, such as industrial pipes.

The nanotubes provide a small amount of electrical current when exposed to light radiation. Small discrepancies in the reflected light are continuously picked up by the sensor. This allows operators to implement spectroscopy methods to monitor and analyze the chemical composition of a flowing substance in real-time, detecting impurities within a flowing liquid.


Overview of the photodetector device

Overview of the photodetector device. Image used courtesy of SANKEN

According to the senior authors of the paper, doctors Yukio Kawano and Tsuyoshi Sekitani, the system can also visualize other properties such as concentration, temperature, viscosity, and even cracks in the pipes and containers of the flowing substance. 

The researchers used different types of light radiation (like in the terahertz or infrared wavelengths, for example) depending on the liquid, impurities, and properties that are being monitored. Measuring temperature, for instance, can be achieved by passively monitoring the blackbody radiation emitted from the substance or the pipes themselves.

The goal of this project is to modernize industrial quality control without disturbing, contaminating, or stopping any part of the procedure. With these sensors, the team aims to replace periodic sample collection with continuous and real-time monitoring.


Use Cases for Carbon Nanotube Sensors

While current applications for this sensor remain mainly in the food and beverage industry, this system may also open the door for similar uses in other fields with certain modifications to the technology. This can include medical diagnostic tools such as blood work analysis without direct intervention—for example, glucose monitoring for diabetic patients. It might also be used to determine the sugar content of agricultural products in a similar manner.


The flexible broadband photo-sensor array sheet

The flexible broadband photo-sensor array sheet. Image used courtesy of Science Advances

In a post-pandemic era where cutting time and saving resources have become vital for many businesses, the engineers from this international team hope their photodetector device can protect public health and safety in the food industry and environmental sector.