Roll-to-roll electrochemical fabrication of non-polarizable silver/silver chloride-coated nylon yarn for biological signal monitoring

Abstract

The main goal of this work is to develop a fabrication process and system for silver/silver chloride (Ag/AgCl)-coated yarn, as Ag/AgCl is the preferred non-polarizing material for interfacing with the body in a clinical setting when monitoring biological signals. A roll-to-roll electrochemical system was designed and built to deposit AgCl on Ag-coated nylon 6,6 yarn in a controllable process. In particular, the movement of the yarn, voltage limit and mixing of 0.9% sodium chloride solution were held constant while the applied current was varied. The Ag-coated nylon acted as the working electrode with two counter electrodes made of platinum. The optimal Ag/AgCl yarns were then further characterized. The roll-to-roll parameters identified include the applied current of approximately 1.82 mA/cm2 for the Ag-coated nylon yarn with a voltage limit of 2.00 V while in the electrochemical chamber. In addition, the yarn had a uniform movement of 0.08 cm/s, which meant that 7 cm of yarn was in the chamber for approximately 89.17 s. The fabrication process was relatively repeatable, yielding the average resistance of 11.0 ± 1.8 Ω/cm for the optimal Ag/AgCl-coated yarn with a low standard deviation between different fabrication processes. A proof-of-concept system was developed and parameters important for the fabrication of functional Ag/AgCl electronic textiles (e-textiles) were detailed. An effective roll-to-roll fabrication method for Ag/AgCl-coated yarns has the potential to significantly contribute to the design and development of wearable e-textile biological monitoring systems that require Ag/AgCl sensor materials.