01.10.2024 Research team develops innovative method for measuring the conductivity of smart textiles

In the laboratory, doctoral student Alexander Jäckel uses terahertz waves to investigate the structure and electrical properties of thin conductive layers on textiles.

A research team from the Leibniz Institute of Photonic Technology (Leibniz IPHT) in Jena, the Philipps-Universität of Marburg and Brown University in the United States has developed a new method for precisely measuring the electrical conductivity of thin layers on smart textiles. The method uses terahertz radiation to analyze coatings without contact and quickly identify material defects. The research results were published in the journal Scientific Reports.

In an increasingly networked world, intelligent textiles, which can be integrated into medical technology or clothing as sensors or energy sources, for example, are becoming more and more important. Researchers at Leibniz IPHT are developing such innovative textiles, including energy-converting solar fabrics, thermoelectric generators, optical and thermal sensors, and cooling materials.  For these textiles to function reliably, they must be coated with conductive materials. A particular challenge is to apply these wafer-thin coatings evenly to the flexible and uneven textile fabric – at just a few dozen nanometers thick, they are about one thousandth the thickness of a human hair. Only in this way can the innovative functionalities be guaranteed.

In order to optimize the coating process, Leibniz IPHT is cooperating with researchers from the Philipps University of Marburg. They are using a new terahertz-based method to measure the conductivity of these ultra-thin layers precisely, contact-free and in a spatially resolved manner. This makes it possible to analyze sensitive materials, such as those used in textile technology, without damaging them. “In the electromagnetic spectrum, terahertz radiation lies between infrared and microwave radiation,” explains Alexander Jäckel, a doctoral student at the University of Marburg who carried out the measurements. Its interaction with materials provides valuable information about their structure and electrical properties.

New insights into the material quality of smart textiles 

Dr. Jonathan Plentz presents a solar fabric – a textile solar cell that was provided with two conductive layers at Leibniz IPHT, as investigated in the current study.

“The method gives us a detailed insight into the quality of the coatings on textiles that can be used as smart clothing in areas such as health monitoring, energy conversion or safety equipment. This helps to optimize the production of such textiles,” explains Dr. Jonathan Plentz from Leibniz IPHT. With the help of terahertz measurements, defects in the conductive layers can be detected at an early stage before they impair the function of the textiles.

 The research teams tested the method on two materials: silver and indium tin oxide (ITO). Both are frequently used as conductive and transparent coatings on textiles. With the help of terahertz technology, they were able to precisely map the conductivity of the layers and identify defective spots that are difficult to detect using conventional methods.

Innovative approach for new applications

The findings could advance the development of more durable and reliable smart textiles. Major advances could be made in medical technology and protective clothing in particular. Other industries, such as the automotive industry or the wearables sector, could also benefit from this technology. The method enables fast and reliable quality control in the development of sensors and flexible circuits on textiles. 

The researchers plan to further develop the technology for use in real-time industrial quality control of smart textiles.

Original publication: Jäckel, A., Hupfer, M.L., Castro-Camus, E. et al. Terahertz conductivity mapping of thin films on smart textiles. Sci Rep 14, 22029 (2024).  https://doi.org/10.1038/s41598-024-73113-4