Diaper-based wearable SERS sensing system with a silver nano dual-structure composite hydrogel for the detection of biomarkers and pH in urine

Wearable sensors are essential for continuous monitoring of an individual’s health status to enable personalized health management. Urine as a typical non-invasive biological fluid is rich in biological information. Although diaper-based biosensors have been developed, the development of wearable sensors for multiple biomarkers in urine remains a major challenge to be explored. In this paper, a hydrogel SERS sensor consisting of two metal nanostructures of silver nanowires (Ag NWs) and silver nanocubes (Ag NCs) was developed and adhered to nappies to form a wearable nappy-based SERS sensor for the rapid and sensitive detection of bio markers (creatinine, uric acid and bilirubin) and pH in urine. The hydrogel’s excellent adsorption and water-locking properties greatly simplify the collection of urine samples. At the same time, its encapsulation effect can effectively maintain the freshness of the urine sample and ensure the accuracy of the test. The introduction of silver nano dual-structure improves the antimicrobial properties of the hydrogel and reduces the risk of infection when the sensor comes into contact with the skin. Moreover, the silver nano dual-structure triggers abundant electromagnetic “hot spots” around intersecting nanojunctions and gaps, which greatly improves SERS sensitivity. For the detection of creatinine, uric acid and bilirubin, the LODs were as low as 0.59 μM, 69 nM, 89 nM. Finally, the urine pH was accurately detected using a functionalized Ag NWs-Ag NCs/CCNF/Gel/PVA hydrogel. This wearable diaper sensor is expected to be used for personal health condition monitoring and holds great promise for effective care of infants, the elderly, and those with limited mobility.