Flexible Electrochemical Urea Sensor Based on Surface Molecularly Imprinted Nanotubes for Detection of Human Sweat

Flexible electrochemical (EC) sensors have shown great prospect in epidermal detection for personal healthcare and disease diagnosis. However, no reports have been seen in flexible device for urea analysis in body fluids. Herein, we developed a flexible wearable EC sensor based on surface molecularly imprinted nanotubes for noninvasive urea monitoring with high selectivity in human sweat. The flexible EC sensor was prepared by electropolymerization of 3,4-ethylenedioxythiophene (EDOT) monomer on the hierarchical network of carbon nanotubes (CNTs) and gold nanotubes (Au NTs) to imprint template molecule urea. This sensor exhibited a good linear response toward physiologically relevant urea levels with negligible interferences from common coexisting species. Bending test revealed that this sensor possessed excellent mechanical tolerance and its EC performance was almost not affected by bending deformation. On-body results of human subjects showed that the flexible platform could distinctly respond to the urea levels in volunteer's sweat after aerobic exercise. The new flexible epidermal EC sensor can provide useful insights into noninvasive monitoring of urea levels in various biofluids, which is promising in the clinical diagnosis of diverse biomedical applications.