Inkjet-Printed Soft Intelligent Medical Bracelet for Simultaneous Real-Time Sweat Potassium (K+), Sodium (Na+), and Skin Temperature Analysis

Abstract

Truly wearable, fully flexible, multi-parametric sweat analysis with soft and socially discrete packaging offers tremendous potential to enable the next generation of non-invasive digital biomarkers analysis. Several examples of miniaturized potentiometric ion selective electrodes (ISE) have been proposed. However, several challenges remain unsolved concerning their long-term stability due to variations in physical sweat parameters. We hypothesize that the simultaneous monitoring of such parameters (e.g., skin-surface temperature, sweat rate, and pH) may pave the way for accurate and robust sweat biomarker analysis. Therefore, we propose a flexible multiparameter sensory interface fabricated on Kapton polyimide (PI) foil with high-resolution inkjet printing using silver nanoparticles (AgNPs). A facile controlled drop-casting of a custom synthesized ion-selective membrane ensures the selectivity of the biosensing. Next, we interfaced the fabricated sensory array with a custom-designed compact flexible biosignals conditioning embedded system, which enables system calibration, data processing, and wireless data transmission to a smartphone device. Later, we validate the proposed system in simultaneous sweat multi-ion (K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> and Na <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ) and skin-surface temperature recording. After that, we characterize the system by embedding the smart medical bracelet in a soft microfluidic platform to mimic <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> analysis on the body. Overall, the reported results represent the fundamental evidence proof for the development of the wearable multimodal sweat parameter analyzer.