A team of researchers from the Leibniz Institute for Photonic Technologies (Leibniz IPHT) in Jena, the Philipps University of Marburg and Brown University in the US has developed a new method for precisely measuring the electrical conductivity of thin layers on smart textiles. The method uses terahertz radiation to analyse coatings without physical contact and quickly identify material defects. The findings have been published in the journal Scientific Reports.

 In an increasingly connected world, smart textiles – such as those used in medical technology or clothing as sensors or energy sources – are becoming increasingly important. Researchers at Leibniz IPHT are working on the development of these innovative textiles, including energy-converting solar fabrics, thermoelectric generators, optical and thermal sensors, and cooling materials. For these textiles to work reliably, they need to be coated with conductive materials. A particular challenge is to apply these ultra-thin coatings uniformly to the flexible and uneven textile surface – at just a few tens of nanometres thick, they are about one thousandth the thickness of a human hair. This level of precision is essential to maintain the advanced functionality of these textiles. 

To optimise the coating process, Leibniz IPHT is working with researchers at Philipps University in Marburg. The team is using a new terahertz-based method to precisely measure the conductivity of these ultra-thin layers in a non-contact, spatially resolved manner. This makes it possible to analyse sensitive materials, such as those used in textile technology, without causing damage. “Terahertz radiation lies in the electromagnetic spectrum between infrared and microwave radiation,” explains Alexander Jäckel, a PhD student at Philipps University in Marburg, who conducted the measurements. The interaction of terahertz radiation with materials provides valuable insights into their structure and electrical properties.

New Insights Into the Material Quality of Smart Textiles

“This method gives us a detailed understanding of the quality of coatings on textiles that could be used in smart clothing for applications such as health monitoring, energy conversion or safety equipment. It helps to optimise the production of these textiles,” says Dr Jonathan Plentz, group leader at Leibniz-IPHT. The terahertz measurements make it possible to detect defects in the conductive layers at an early stage, thus preventing these defects from impairing the function of the textiles.

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

Innovative Approach for New Applications

The findings could drive the development of more durable and reliable smart textiles. In particular, significant advances could be made in medical technology and protective clothing. Other industries, such as the automotive sector or wearable technology, 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 to enable real-time quality control of smart textiles on an industrial scale.

 

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