Roll-to-roll printed in-pad biosensors for colorimetric detection of key biomarkers in artificial vaginal fluid

Gynecological conditions often lack accessible, non-invasive diagnostic tools, leading to delayed detection and treatment, especially in resource-limited settings. Vaginal discharge and menstrual blood offer abundant but underutilized biomarkers for diagnosing gynecological disorders. Although sanitary pads represent an ideal platform for continuous fluid monitoring, direct high-throughput fabrication of sensors onto commercial pads remains challenging. Here, we introduce a roll-to-roll (R2R) wax-printing method optimized for large-scale production of fluidic colorimetric sensor patches designed for integration into sanitary pads. Utilizing specially formulated wax inks, this scalable approach enables consistent, cost-effective sensor fabrication. The sensor patches were functionalized with colorimetric reagents, incorporating enzymatic sensing elements for uric acid and glucose and physicochemical indicators for pH and moisture. This configuration enabled robust multi-analyte detection with clear and interpretable visual outputs, observable directly by the naked eye or via smartphone-based analysis. Validation in artificial vaginal fluid (AVF) confirmed reliable sensor performance, underscoring a practical and scalable platform with potential to advance proactive women's health monitoring in both home-based and point-of-care settings.