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. 2023 Aug 10;23(16):7076.
doi: 10.3390/s23167076.

Development and Characterization of Hybrid, Temperature Sensing and Heating Yarns with Color Change

Theresa Junge  1 , Rike Brendgen  1 , Carsten Grassmann  1 , Thomas Weide  1   2 , Anne Schwarz-Pfeiffer  1   2
Affiliations

Development and Characterization of Hybrid, Temperature Sensing and Heating Yarns with Color Change

Theresa Junge et al. Sensors (Basel). .

Abstract

A person's body temperature is an important indicator of their health status. A deviation of that temperature by just 2 °C already has or can lead to serious consequences, such as fever or hypothermia. Hence, the development of a temperature-sensing and heatable yarn is an important step toward enabling and improving the monitoring and regulation of a person's body temperature. This technology offers benefits to several industries, such as health care and sports. This paper focuses on the characterization and development of a hybrid yarn, which can measure and visualize temperature changes through a thermoresistive and thermochromic effect. Moreover, the yarn is able to serve as a flexible heating element by connecting to a power source. The structure of the yarn is designed in three layers. Each layer and component ensures the functionality and flexibility of the yarn and additional compatibility with further processing steps. A flexible stainless steel core was used as the heat-sensitive and heat-conducting material. The layer of polyester wrapped around the stainless steel yarn improves the wearing comfort and serves as substrate material for the thermochromic coating. The resulting hybrid yarn has a reproducible sensory function and changes its resistance by 0.15 Ω between 20 and 60 °C for a length of 30 cm. In addition, the yarn has a uniform and reproducible heating power, so that temperature steps can be achieved at a defined length by selecting certain voltages. The thermochromic color change is clearly visible between 28 and 29 °C. Due to its textile structure, the hybrid sensory and actuating yarn can easily be incorporated into a woven fabric or into a textile by means of joining technology sewing.

Keywords: coating; flexible sensor; heating; smart textiles; temperature; thermochromic; winding.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic structure of the temperature-sensing heating yarn with color change.
Figure 2
Figure 2
Schematic representation of the thread guide on the rewinding machine.
Figure 3
Figure 3
Schematic illustration of the coating process.
Figure 4
Figure 4
Illustration of the coated polyester yarn; top: uncoated textured polyester; bottom: coated textured polyester.
Figure 5
Figure 5
Microscopic picture of the temperature-sensing heating yarn with color change; top: produced with the first production route (WC); bottom: produced with the second production route (CW).
Figure 6
Figure 6
Optical characterization of the temperature sensing heating yarn; top: wrapped and coated yarn; bottom: wrapped yarn.
Figure 7
Figure 7
Optical characterization of the temperature sensing heating yarn with color change; top: normal condition, bottom: heated condition.
Figure 8
Figure 8
SEM examination of the temperature sensing heating yarn; (left) longitudinal view, (right) cross-sectional view.
Figure 9
Figure 9
Laser microscopic examination of the temperature sensing heating yarn; (left) laser and light microscopic image; (right) 3D image of the surface morphology of the coated yarn.
Figure 10
Figure 10
Temperature sensing measurement.
Figure 11
Figure 11
Color measurements of thermochromic pigments.
Figure 12
Figure 12
The color difference of thermochromic pigments is dependent on temperature.
Figure 13
Figure 13
Heated yarn with different voltage levels; (left) yarn heated with 1.01 V, (middle) yarn heated with 1.67 V, (right) yarn heated with 3.01 V.
Figure 14
Figure 14
Tensile testing with untreated steel fiber (left) and hybrid wrapped and coated yarn (right).
Figure 15
Figure 15
Light microscopic images before (top) and after (bottom) 3 consecutive washing cycles; (Left) 50× magnification, (right) 100× magnification.
See this image and copyright information in PMC

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