Transparent, Stretchable PVC–Liquid Metal Composite Sensor for Smart Wearable Electronics

Flexible sensors based on liquid metal (LM) fillers have attracted increasing attention due to their excellent stretchability, flexibility, and biocompatibility. However, simultaneously achieving transparency, high sensitivity, and robust mechanical performance remains a major challenge. In this study, we present a transparent and stretchable flexible composite sensor fabricated by combining poly(vinyl chloride) (PVC) with dibutyl adipate (DBA) and incorporating a low concentration (0.1 wt %) of LM as the conductive phase. The sensor exhibits a transparency of 50.12%, resulting from the optical clarity of the PVC/DBA matrix, the nanoscale dispersion of LM droplets, and the formation of Ga3+ ions upon partial surface oxidation, which collectively reduce light scattering and absorption. PVC also acts as a stabilizing matrix, forming a protective interface around LM droplets to enhance dispersion and interfacial stability. The resulting composite sensor demonstrates excellent stretchability (530%), high sensitivity (gauge factor = 4.27), and reliable performance in humid and saline environments. This work offers a practical strategy for developing transparent, durable, and high-performance composite sensors for wearable electronics and intelligent systems.