Touch‐Based Stressless Cortisol Sensing

Abstract

Tracking fluctuations of the cortisol level is important in understanding the body's endocrine response to stress stimuli. Traditional cortisol sensing relies on centralized laboratory settings, while wearable cortisol sensors are limited to slow and complex assays. Here, a touch‐based non‐invasive molecularly imprinted polymer (MIP) electrochemical sensor for rapid, simple, and reliable stress‐free detection of sweat cortisol is described. The sensor readily measures fingertip sweat cortisol via highly selective binding to the cortisol‐imprinted electropolymerized polypyrrole coating. The MIP network is embedded with Prussian blue redox probes that offer direct electrical signaling of the binding event to realize sensitive label‐free amperometric detection. Using a highly permeable sweat‐wicking porous hydrogel, instantaneously secreted fingertip sweat can be conveniently and rapidly collected without any assistance. By eliminating time lags, such rapid (3.5 min) fingertip assay enables the capture of sharp variations in cortisol levels, compared to previous methods. Such advantages are demonstrated by tracking cortisol response in short cold‐pressor tests and throughout day‐long circadian rhythm, along with gold‐standard immunoassay validation. A stretchable epidermal MIP sensor is also described for directly tracking cortisol in exercise‐induced sweat. The rapid touch‐based cortisol sensor offers an attractive, accessible, stressless avenue for quantitative stress management.

Wearable Sweat Loss Measuring Devices: From the Role of Sweat Loss to Advanced Mechanisms and Designs

“…Fingertip touch sampling through hydrogel for wider applications will be the focus of sampling in future sweat sensing. [ 67 , 206 , 207 , 208 , 209 ]…”

Recent advances in flexible and wearable sensors for monitoring chemical molecules

“…6d). 163 Different from previous work, 161 they developed a stretchable epidermal patch based on SEBS which can adhere to skin. It can be seen from past studies that the monitoring of biomarkers often requires specific markers to match them.…”

Recent progress in the fabrication of flexible materials for wearable sensors

“…109 Tang et al also used highly permeable sweating porous hydrogels to collect sweat. 110 Their research avoids the use of irritant perspiration drugs, simplifies the process of sweat collection, and improves the efficiency of sweat collection. In the future, hydrogels will be used to design human epidermal liquid microfluidic detection equipment, and also as drug carriers to achieve drug stimulation or treatment.…”