Advancing Paper-Based Sensors toward Reliable Wearable and Onsite Applications

Abstract Paper-based sensors offer a low-cost, biodegradable, and easily patterned platform for decentralized monitoring in food safety, agriculture, and human health. Their porous cellulose networks enable capillary sampling and efficient immobilization of functional materials, but the same structure also makes them vulnerable to humidity, mechanical deformation, biofouling, and matrix-induced signal drift. This review examines paper-based sensors for wearable and onsite applications from the perspective of manufacturability and field reliability. We discuss how substrate selection; surface modification; antifouling interfaces; conductive and recognition materials; low-cost fabrication methods; microfluidic architectures; and electrochemical, optical, and mechanical transduction strategies shape device performance. Particular attention is given to applications in plant health monitoring, agrochemical residue detection, food freshness assessment, and non-invasive biofluid analysis. Wearable systems are distinguished from portable and onsite paper assays. These applications expose a common bottleneck: paper-based sensors must be produced reproducibly, remain stable in wet and deformable matrices, and deliver readable signals outside the laboratory. For these platforms, the decisive tests are practical: reproducible manufacture, tolerance to wet and heterogeneous matrices, and readouts that remain interpretable at the point-of-use. We also discuss selected paper-based chemical and biosensing studies when they clarify transduction chemistry, recognition behavior, enrichment effects, or paper-sample interfaces relevant to wearable or field-deployable formats. Overall, paper is currently most mature as a disposable sampling and sensing interface; sustained wearable operation remains limited by wet-state stability and system integration.