Original article Roll-to-roll electrochemical fabrication of non-polarizable silver/silver chloride-coated nylon yarn for biological signal monitoring Peter A Haddad 1 , Amir Servati 2 , Saeid Soltanian 1 , Peyman Servati 1 and Frank Ko 2 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/cm 2 for the Ag-coated nylon yarn with a voltage limit of 2.00V 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 V/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. Keywords electronic textiles, electrically conductive yarn, coating, electrochemical, electrodes A significant component in enhancing the delivery of healthcare for a variety of patients is the development and improvement of medical devices. More specifically, progress in the field of biomedical engineering and wear- able systems can aid in providing vital and timely infor- mation on patients, regardless of their geographical location. 1 There is a need to address the limitations of the current rigid and non-breathable silver/silver chlor- ide (Ag/AgCl) electrodes, the most common sensors used in the clinical setting, to enable more long-term wearable systems. 2–4 A major challenge for long-term monitoring with the current non-polarizing Ag/AgCl electrodes is the potential need to use gels and strong adhesives, which irritate the surface of the skin. 2–4 Non-polarizing electrodes allow current to cross the electrode–electrolyte interface, while polarizing electrodes have no actual charge cross the electrode– electrolyte interface when a current is applied; instead, a displacement current causes the electrodes to function 1 Electrical and Computer Engineering Department, University of British Columbia, Canada 2 Materials Engineering Department, University of British Columbia, Canada Corresponding author: Peter A Haddad, University of British Columbia, 4060 – 2332 Main Mall, Vancouver, BC, V6T 1Z4, Canada. Email: peter.haddad@alumni.ubc.ca Textile Research Journal 0(00) 1–10 ! The Author(s) 2018 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0040517518817060 journals.sagepub.com/home/trj