Protocol to assess the quality of transmission lines within smart textile structures

The washability issue is always a challenge for electronic textiles in terms of application. It reduces their reliability, makes them not robust enough, and therefore not ready for the market. In this study, a novel protocol was designed to test the performance of conductive threads under wet situation in order to simulate the washing cycle. In this content, two commercially available silver-plated polyamide threads having the same thread count were used and washing results of each thread were discussed. Transmission lines with silver-plated polyamide threads onto cotton woven fabric were produced via sewing (single-line stitch) and embroidery techniques (three-line stitch) to improve the conductivity and robustness. For the simulation of the wash process, Martindale abrasion tester was used under wet and dry conditions. Moreover, felts of abrasion tester and transmission lines were put into different solutions, i.e., water, water with standardized detergent and water with commercially available detergent. After wetting specimens, abrasion tests were performed on transmission lines, and linear electrical resistance measurements were recorded with the multi meter before abrasion and every 1500 cycles up to 4500 cycles in wet conditions and also after drying the transmission lines. Finally, abrasion impact on silver-plated polyamide threads was investigated by optical microscope. It has been found that silver coating on the conductive thread was damaged when subjected to abrasion cycles, especially in wet states. Water itself has stress impact on samples provoking the electrical resistance increase rapidly. Commercial detergent with water was found to have the most damaging effect on the conductive threads because of extra particles presence to enhance the washing performance. In terms of integration methods, better electrical conductivity values were achieved in three-line embroidery transmission lines due to multiple interconnection points in the embroidery network.