Dual-Mode Paper-Based Epidermal Microfluidics for Sweat Rate Normalized Chloride Sensing Publisher



Keyvanara M ; Parvaneh S ; Dehghani P ; Bahramian A ; Golparvar A
Source: Sensors and Actuators B: Chemical Published:2026

Abstract

In resource-limited clinical settings, sweat chloride testing frequently departs from standardized protocols, leading to unreliable measurements and elevated false-negative rates. A central contributor to this problem is the absence of a unified, passive device for efficient sweat collection and sweat-rate–normalized quantitative chloride sensing. Here we report a dual-mode cellulose-based epidermal microfluidic sensory system that enables sweat-rate–normalized chloride analysis by integrating real-time sweat-volume quantification with distance-based and colorimetric chloride sensing in a fully passive skin-conformal patch. The laser-engraved paper microfluidic channel quantifies sweat volume with a sensitivity of 6.5 mm.µl⁻1 and a detection limit of 1.0 µl for localized sweat-rate estimation. Simultaneously, distance-based chloride sensing based on reverse Mohr chemistry provides a linear response across 0–100 mmol.l⁻1 with a sensitivity of 24.8 mm.mM⁻1 and a limit of detection of 0.1 mmol.l⁻1, while companion colorimetric zones enable rapid visual classification under low-sweat conditions. The device shows high repeatability (CV = 0.31%), selectivity against common sweat interferents, and storage stability for more than 70 days (CV = 9.25%), a 136% increase from conventional distance-based devices. Pilot on-body measurements capture dynamic sweat chloride changes during exercise and electrolyte modulation, highlighting the value of sweat-rate normalization for physiologically meaningful interpretation. With an estimated material cost of less than USD 0.02 per device, 80% less than the reported cost of distance-based devices, this platform provides a scalable approach to sweat chloride testing in resource-limited clinical settings. © 2026 Elsevier B.V.