Invisible sweat sensor: ultrathin membrane mimics skin for stress monitoring

TL;DR

This paper presents an ultrathin, skin-mimicking sweat sensor with nanochannels for continuous, non-invasive stress monitoring through cortisol detection, achieving seamless integration and real-time health assessment.

Contribution

Introduction of an imperceptible, skin-integrated sweat sensor using nanomembranes and molecular imprinting for continuous cortisol monitoring.

Findings

Detects cortisol from 0.05 to 0.5 μM

Achieves seamless skin integration via van der Waals forces

Enables real-time, non-invasive stress monitoring

Abstract

Epidermal skin sensors have emerged as a promising approach for continuous and noninvasive monitoring of vital health signals, but to maximize their performance, these sensors must integrate seamlessly with the skin, minimizing impedance while maintaining the skin's natural protective and regulatory functions.In this study, we introduce an imperceptible sweat sensor that achieves this seamless skin integration through interpenetrating networks formed by a porous, ultra-thin, ultra-high molecular weight polyethylene (UHMWPE) nanomembrane. Upon attachment to the skin by van der Waals force, the amphiphilic sweat extrudates infuse into the interconnected nanopores inside the hydrophobic UHWMPE nanomembrane, forming "pseudo skin" nanochannels for continuous sweat perspiration. This integration is further enhanced by the osmotic pressure generated during water evaporation. Leveraging the efficient transport of biomarkers through the "skin" channels within the porous membrane, we developed an organic electrochemical transducer (OECT) cortisol sensor via in-situ synthesis of a molecularly imprinted polymer (MIP) and poly(3,4 ethylenedioxythiophene) (PEDOT) within the nanomembrane. This demonstrates the capability to detect cortisol concentrations from 0.05 to 0.5 {\mu}M for seamless monitoring of stress levels. This work represents a significant advancement in self-adhesive sweat sensors that offer imperceptible and real-time non-invasive health monitoring capabilities.