Towards reliable smart textiles: Investigating thermal characterisation of embedded electronics in E-Textiles using infrared thermography and mathematical modelling

Abstract

The smart textiles field, which includes e-textiles, has seen rapid development in recent years due to its wide market applications such as wearables, architecture, energy and product design. Electronic circuits of e-textiles involve devices such as LEDs, sensors and batteries that are embedded within the yarns. Since temperature is a crucial element causing profound problems to the electronic devices when it exceeds a certain threshold, extensive research efforts have to be done to reduce its negative effect and enhance the sustainability of such embedded devices. In this work, infrared thermographic imaging technology is utilised to experimentally study the thermal distribution profile of LEDs in their bare, encapsulated and embedded state in e-yarns manufacturing stages. The experimental results are compared with numerical analysis models carried out when solving the time-dependent and partial differential equations of the heat transfer process. In this work, infrared camera with 320 × 240 pixel vanadium oxide microbolometer that detects temperature differences of less than 0.1 °K is utilised with a special micro close-up lens to take close-up infrared images of the LED samples. Additionally a point-measurement technique, using a thermocouple, is utilised to ensure accurate temperature measurements are recorded for calibration. The results of this work prove that using infrared thermography with suitable lens can provide significant information about the thermal behaviour of smart textiles. It has been found that the thermal distribution of the integrated LEDs has a Gaussian-like shape. This bell-shaped distribution gets higher and wider by adding an additional LED device to the circuit within a specific distance range. It has been found that in the case of multiple LEDs, the distance between them plays a crucial role in determining the overall temperature of the system and shaping the final overall thermal distribution, and hence the reliability of the smart textile on the long term. The results also show that the cover yarn can influence the heat dissipation process. Consequently, the selection of yarn’s material and structure could be a critical factor to the thermal performance of electronic devices embedded within e-textiles.