Simultaneous Monitoring of Sweat and Interstitial Fluid Using a Single Wearable Biosensor Platform

TLDR

Wearable biosensors for continuous noninvasive biomarker monitoring have traditionally been limited to a single biofluid. This study demonstrates simultaneous noninvasive sampling and analysis of sweat and interstitial fluid using a single epidermal wearable platform. The platform achieves on‑demand dual‑fluid sampling by stimulating sweat with transdermal pilocarpine at an anode and extracting interstitial fluid at a cathode, integrating separate electrochemical biosensors on a flexible, screen‑printed tattoo‑like substrate with wireless readout for real‑time measurement. In human volunteers, the device accurately measured sweat‑alcohol and ISF‑glucose, showing that the distinct sweat and ISF compositions correlate well with blood levels and highlighting the platform’s potential to broaden noninvasive epidermal biosensing.

Abstract

Abstract The development of wearable biosensors for continuous noninvasive monitoring of target biomarkers is limited to assays of a single sampled biofluid. An example of simultaneous noninvasive sampling and analysis of two different biofluids using a single wearable epidermal platform is demonstrated here. The concept is successfully realized through sweat stimulation (via transdermal pilocarpine delivery) at an anode, alongside extraction of interstitial fluid (ISF) at a cathode. The system thus allows on‐demand, controlled sampling of the two epidermal biofluids at the same time, at two physically separate locations (on the same flexible platform) containing different electrochemical biosensors for monitoring the corresponding biomarkers. Such a dual biofluid sampling and analysis concept is implemented using a cost‐effective screen‐printing technique with body‐compliant temporary tattoo materials and conformal wireless readout circuits to enable real‐time measurement of biomarkers in the sampled epidermal biofluids. The performance of the developed wearable device is demonstrated by measuring sweat‐alcohol and ISF‐glucose in human subjects consuming food and alcoholic drinks. The different compositions of sweat and ISF with good correlations of their chemical constituents to their blood levels make the developed platform extremely attractive for enhancing the power and scope of next‐generation noninvasive epidermal biosensing systems.