A paper-based microfluidic device for real-time sweat potassium monitoring

Wearable electrochemical sensors have attracted tremendous attention in recent years. Here, a three-dimensional paper-based microfluidic electrochemical integrated device (3D-PMED) was demonstrated for real-time monitoring of sweat potassium. The 3D-PMED was fabricated by wax printing patterns on cellulose paper and then folding the pre-patterned paper four times to form five stacked layers: sweat collector, vertical channel, transverse channel, electrode layer and sweat evaporator. A sweat monitoring device was realized by integrating a screen-printed potassium ion selective sensor on PET substrate with the fabricated 3D-PMED. The sweat flow process in 3D-PMED was modelled with red ink to demonstrate the capability of collecting sweat. The detection range of potassium ion selective sensor is 1-32 mM, and the electrode response potential is 59.2 mV per decade of concentration. The electrodes have shown good selectivity for both anion and cation, and a stable performance within 2 weeks.