Wearable molecularly imprinted electrochemical sensor with integrated nanofiber-based microfluidic chip for in situ monitoring of cortisol in sweat

Wearable sweat sensors are highly desirable for noninvasive monitoring of personal health. Herein, we developed a flexible electrochemical sensor based on nanofiber-involved microfluidic technique and molecularly imprinted polymer (MIP) for in situ and real-time sweat analysis. The sensor with polyethylene terephthalate (PET) as the substrate consisted of two layers, a bottom MIP-modified electrode layer for sensing and an upper nanofiber-based microfluidic layer for spontaneous sweat pumping. To enhance stability and sensitivity of the sensor, porous and interconnected 3D carbon nanofiber membrane decorated with gold nanoparticles ([email protected]) served as a matrix for MIP deposition. Prussian blue nanoparticles (PBnPs) as a “built-in” redox probe were embedded into MIP skeleton, enabling in situ monitoring of sweat substance. On the microfluidic layer, the super-hydrophilic and porous nanofibers allowed sweat to be automatically and rapidly pumped to the bottom sensing chamber. On the basis of the above, the sensor demonstrated a wide detection range of 1 nM∼1 μM as well as excellent selectivity and stability with cortisol as the model analyte. On-body applicability of the sensor was also validated by real-time monitoring of cortisol in healthy volunteers’ sweat.