Skin-Attachable Ink-Dispenser-Printed Paper Fluidic Sensor Patch for Colorimetric Sweat Analysis.

In situ analysis of sweat biomarkers potentially provides non-invasive lifestyle monitoring and early diagnosis. Quantitative detection of sweat rate is crucial for thermoregulation and preventing heat injuries. Here, we report a skin-attachable paper fluidic patch for in situ colorimetric sensing of multiple sweat markers (pH, glucose, lactate, uric acid) with concurrent sweat rate tracking. Two sets of fluidic patterns - multiplexed detection zones and a longitudinal sweat rate channel - are directly printed by an automated ink-dispenser from a specially-developed ceramic-based ink. The ceramic ink thermal-cures into an impervious barrier, confining sweat within the channels. The ceramic ink-printed boundary achieves higher pattern resolution, prevents fluid leakage, attains pattern thermal stability, and resistant to organic solvents. The cellulose matrix of the detection zones is modified with nanoparticles to improve the colour-homogeneity and sweat sensor sensitivity. The sweat rate channel is made moisture-sensitive by incorporating a metal-salt-based dye. The change in saturation/colour of the detection zones and/or channels upon sweat addition can be visually detected or quantified by a smartphone camera. We provide a cost-effective way to fabricate paper fluidic sensor patches, successfully demonstrated for on-body multiplexed evaluation of sweat analytes. Such skin-wearables offer on-site analysis, meaningful to an increasingly health-conscious population. This article is protected by copyright. All rights reserved.