Flexible wearable hydrogel patch integrated with a “sponge-like” cellulose SERS chip for sweat analysis of urea and lactate

Recent years have witnessed remarkable progress in cellulose and hydrogels, facilitating the development of wearable green sensing technology. This study presents a novel flexible hydrogel patch designed as a skin-adhesive platform for wearable sensors, synthesized through the strategic integration of hydrogel and porous “sponge-like” technologies. Fabricated from acrylamide and sodium alginate matrices enhanced with tannic acid modification, the composite exhibits superior mechanical performance, biocompatibility (98.75 % cell viability), antimicrobial efficacy (92.03 % inhibition rate against S. aureus ), and tissue adhesion. A sulfonated cellulose nanofibril/sodium alginate/silver nanoparticle (S–CNF/SA/Ag NPs) composite membrane was engineered as a surface-enhanced Raman spectroscopy (SERS) detection module, achieving remarkable sensitivity for sweat biomarkers with detection limits of 10 −6  M for urea and 10 −5  M for lactic acid. Experimental validation confirms exceptional epidermal conformability and sustained adhesion. This technological advancement establishes a foundation for transformative applications in personalized healthcare monitoring, exercise physiology assessment, clinical diagnostics, and preventive medicine, thereby accelerating innovation in wearable biosensing platforms.