Reusable 3D-printed microfluidic-on-fabric with modular electrodes for point-of-care Na⁺ and K⁺ detection in various...

In this study, we present a new 3D-printed microfluidic-on-fabric sensor platform that allows for point-of-care (POC) detection in various biofluids. Using the low-cost FDM 3D-printing, we developed a method to form well-defined microfluidic features on fabric substrates (3D-printed microfluidic-on-fabric), which could modularly house an electrode pad with desired electrodes targeting different analytes. The 3D-printed microfluidic-on-fabric integrates the comfort, robustness, and reusability (after washing) of fabric substrates with the precision, modularity, and scalability offered by 3D-printed structures. We showcased the application of the sensor platform for Na⁺ and K⁺ detections with lab-made ion-selective electrode pads. The electrodes showed high reusability, in addition to the robust Nernst sensitivity, accuracy, selectivity, and reproducibility (linear range = 5-500 mM; LOD(Na⁺) = 1.5 mM and LOD(K⁺) = 1.6 mM). The sensor platform was successfully implemented to detect Na⁺ and K⁺ in a range of biofluids, including urine, saliva, and sweat, with results validated by ion chromatographic methods. An Arduino board (~ $20) was programmed to couple to the sensor for data collection, transducing, processing, and transferring to a computer. Overall, this is a new sensor platform that is low-cost, reusable, modular, and customizable, representing an advancement in POC sensor development.