Evaporation-induced ion enrichment for high-performance glucose detection in a microfluidic thread/paper-based analytical system

A microfluidic thread/paper-based analytical device (mu TPAD) is of great significance in biomedical analysis and point-of-care diagnostics. Nevertheless, the research has not been done on the ion distribution on the thread and how it affects sensing so far. Inspired by the sweat stains on the clothes, a high-performance mu TPAD based on the evaporation-induced ion enrichment is presented for glucose monitoring in salty solutions. In comparison to the multi-ply cotton thread, the single-ply cotton thread exhibits the most significant ion-enrichment capability at the rear segment, which could be attributed to the balance between the water evaporation and the solution replenishment in the thread. The salts accumulated at the rear segment could increase the ionic strength of the solution passed through the thread, promoting the colorimetric reaction on the paper-based sensing unit. The single-ply thread with strong ion-enrichment capability was integrated with a paper-based glucose sensor to prepare a mu TPAD for highly sensitive glucose detection in both PBS and artificial sweat (-0.673 mu M-1 in PBS and - 0.253 mu M-1 in artificial sweat). Moreover, the system could detect glucose in human sweat samples with high accuracy and precision. This work may provide a strategy to prepare a highly sensitive mu TPAD for precise analysis of substances in bio-fluids, particularly human sweat.