Cellulose- and paper-based substrates as sustainable carrier platforms for advanced sensing technologies

The rapid expansion of sensing technologies across healthcare, environmental monitoring, food safety, and smart packaging has intensified interest in substrates that are not only functional but also sustainable. Cellulose- and paper-based materials have emerged as compelling carrier platforms because they combine renewability, low cost, intrinsic porosity, mechanical compliance, and compatibility with scalable low-temperature processing. Far from being passive supports, these substrates actively influence sensing performance through capillary transport, surface chemistry, wetting behavior, and hierarchical architecture. Their fibrous networks enable rapid fluid wicking, gas diffusion, reagent immobilization, and mechanical transduction, making them attractive for electrochemical, optical, colorimetric, gas, and wearable sensing systems. This review critically examines the structural basis, fabrication routes, sensing modalities, nanomaterial integration, performance drivers, and translational barriers associated with cellulose- and paper-based sensing platforms. Conventional paper, coated paper, cellulose acetate, nanocellulose films, bacterial cellulose, and paper-polymer composites are compared with respect to morphology, transport, printability, and device robustness. Recent advances in printed electronics, hybrid nanocomposites, and bio functional layers are discussed, including systems incorporating metal oxides, graphene, carbon nanotubes and conductive polymers. Key limitations such as humidity sensitivity, batch variability, signal drift, pattern resolution, and durability are analysed, and practical mitigation strategies are outlined. Finally, perspectives are offered on biodegradable, distributed, and IoT-connected sensor systems designed for the next generation of sustainable sensing.