A fluorescent wearable platform for sweat Cl- analysis and logic smart-device fabrication based on color adjustable lanthanide MOFs

Sweat components provide plentiful potential biomarkers that can indicate the health state of a subject. The use of electrochemical methods to analyze these biomarkers has significant applications for noninvasive monitoring without the requirement of painful blood collection. However, current electrochemical analyses have the disadvantage of requiring complex and time-consuming sensor fabrication. Here, we demonstrate a novel, wearable device that uses fluorescence detection technology to noninvasively monitor Cl- in sweat. The wearable Cl- monitoring platform integrates a flexible host material (cotton piece) and two fluorescent materials (lanthanide metal-organic frameworks (MOFs): DUT-101 and Ag+/Eu3+@UiO-67) by simple ultrasonic loading. Instead of using a large circuit board, this device is comfortable for human body contact and can be routinely worn. The two lanthanide-based fluorescent materials provide high color purity and accurate measurements, where Ag+/Eu3+@UiO-67 is the working fluorescence center and DUT-101 is the reference fluorescence center. After characterizing the performance, flexibility and stability of the sensing device, quantitative Cl- measurements were successfully performed with high selectivity and sensitivity. The real-time, on-body tests with healthy human subjects demonstrate the straightforward feedback provided by the fluorescence method. By designing Cl- and fluorescence signals for a logic circuit, a codec device was constructed, which can be set as a mimetic "red-green indicator light'' for applications in healthcare and sports. This system is a simple and effective solution for wearable sweat-based monitoring.