Technical constraints in translating paper-based CRISPR/Cas assays to wearable formats

Paper-based CRISPR diagnostics and wearable platforms represent significant advances in point-of-care molecular sensing. Each system offers distinct capabilities including sequence-guided detection from CRISPR enzymes, fluid handling and low-cost fabrication from paper substrates, and continuous sample access from skin-mounted devices. Despite individual advances, practical systems that operate under physiological conditions without external intervention remain unavailable. This review evaluates the biochemical, mechanical, and operational constraints that emerge when these technologies are brought into direct physical contact with the human body. Key barriers include enzyme degradation in ambient conditions, fluid control instability across paper layers, and variability in signal output linked to hydration, motion, and temperature. Most existing strategies address these limitations in isolation and fail to account for their compounded effects under wearable conditions. This review reframes these challenges as interrelated design problems and outlines the essential system conditions required for performance outside laboratory settings. The discussion defines new priorities for biosensor development by focusing on the physical and chemical constraints that govern on-body function across materials science, synthetic biology, and device engineering. • Systemic design conflicts across CRISPR assays, paper substrates, and wearables. • Enzyme destabilization from ambient air, motion strain, and hydration variability. • Unstable fluid control in paper microchannels under on-body deformation. • Signal drift from mechanical noise, thermal fluctuation, and skin-derived artifacts. • Fallback strategies and patch architectures for autonomous molecular diagnostics.