A Fingertip-Wearable Osmotic Lateral Flow Assay Platform for Noninvasive Monitoring of Addictive Biomarkers in Sweat at Rest

Noninvasive monitoring of addictive substance biomarkers remains challenging due to the lack of autonomous sampling and portable analytical platforms suitable for resting conditions. Here, we present a fingertip-wearable sweat sensing platform that integrates osmotic sweat extraction with competitive lateral flow assay (LFA) for the simultaneous detection of cotinine and morphine in sweat. The device employs an ethylene glycol-modified poly(vinyl alcohol)-poly(acrylamide) (EG-PVA-PAAm) hydrogel to actively extract sweat from the fingertip and sustain capillary-driven transport toward a multichannel LFA detection zone. Gold nanoparticle-labeled monoclonal antibodies enable visual competitive immunochromatographic detection, where test-line intensity decreases with increasing analyte concentration. The LFA strips exhibit high specificity and wide linear detection ranges, with low limits of detection for cotinine and morphine and negligible cross-interference. Hydrogel-assisted osmotic pumping significantly enhances sweat collection compared to natural perspiration, ensuring sufficient sample delivery under resting conditions. In vitro evaluations in artificial sweat confirm concentration-dependent responses for both analytes, while on-skin studies successfully differentiate exposure levels between active smokers, passive and nonsmokers and allow dynamic monitoring of cotinine metabolism. This integrated wearable LFA system provides a portable and autonomous strategy for point-of-care testing (POCT) of addictive biomarkers in sweat.