Potassium ions (K + ) are essential electrolytes in the human body, crucial for maintaining cell membrane potential, neuromuscular excitability, and cardiac function, with blood potassium (BP) levels needing to stay within 3.5–5.5 mmol/L to prevent serious health issues. Current BP detection methods rely on lab testing, which is costly, slow, and unsuitable for remote areas. This study developed a handheld micro-volume BP detection device using paper-based ion-selective electrodes (ISEs). The device, built on a PET substrate with screen printing and a custom ion-sensitive membrane, features a miniaturized sensor that requires only 2 µL of fingerstick blood for rapid BP measurement, reducing costs significantly. A handheld reader with built-in electrochemical signal processing and wireless transmission allows instant results display and data upload to smartphones. The device demonstrated excellent linearity, repeatability, and stability, indicating its potential for acute care, chronic disease management, and sports medicine.
In this paper, we report a point-of-care (POCT) testing strip based on a porous membrane structure for whole blood separation and colorimetric analysis without external supporting equipment. Conventional blood tests rely on large instruments for blood pretreatment and separation to improve measurement accuracy. Cellulose acetate (CA) membranes with different pore diameters and structures were prepared via a non-solvent method for the separation of whole blood. Among them,[email protected]membranes with nano-pores on the surface and micro-pores in the interior facilitated the capture of blood cells on the surface, as well as the free diffusion of plasma through the porous interior structure. The fluid flow of blood in the asymmetric porous structure can be theoretically estimated using the Lucas-Washburn equation. Compared with the conventional paper strips and other porous membranes, the[email protected]membrane with an immobilized sensing layer exhibited efficient blood separation, a short response time (less than 2 min), an ultralow dosage volume (5 μL), and high sensitivity. The fabricated blood separation membranes can be further used for the detection of various biomarkers in whole blood, providing additional options for rapid quantitative POCT tests.Keywords:blood separation;porous membranes;colorimetric assay
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