Advances in Projected Capacitive Touch Panels: Innovations in Materials and Fabrication Techniques

Touch panels are one of the most commonly used technologies in a wide range of applications, including mobile phones, tablets, and displays. Among the various types of touch panel sensors, projected capacitive touch panels (PCTPs) are the most popular due to their excellent optical performance, high durability, multi-touch functionality, and precise touch-point detection. A PCTP features a multi-layer structure consisting of two layers of electrode materials and an insulating adhesive layer. The patterning of touch panel conductors significantly impacts the performance, accuracy, and sensitivity of the touch panels. Indium tin oxide (ITO) is the most commonly employed transparent conductive material in touch panel technologies. However, its drawbacks, including the scarcity of indium, elevated cost, and intrinsic mechanical fragility, have been well recognized. Among the alternative materials for replacing ITO, poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) has emerged as a strong alternative because of its outstanding properties, such as high transparency, excellent conductivity, and mechanical flexibility. The traditional electrode patterning technique for PEDOT:PSS electrodes in touch panel applications is printing, which offers several advantages over conventional methods, including low cost, high accuracy, and rapid processing. In this study, we review the recent advancements in PEDOT:PSS-based electrode patterning techniques for PCTPs, emphasizing printing technologies such as inkjet printing, screen printing, and other emerging methods. We evaluate their compatibility with PEDOT:PSS, technical challenges, performance metrics, and their role in replacing ITO. The paper also outlines future directions for the development of cost-effective, scalable, and flexible touch panel devices.