Cross-linked polyaniline network on highly-ordered nanopillar arrays integrated with microfluidics for rapid detection of calcium ions in small sample volumes

Abstract Wearable sensor technology has garnered significant attention due to its considerable potential in personal healthcare and medical care. Various biomarkers present in human sweat, tears, and saliva can provide insights into an individual’s physiological state. However, the small volume of these noninvasive fluids poses challenges for the reliability and stability of sensor measurements. Efficient collection of body fluids and the use of nanostructured sensor electrodes is crucial for accurate detection. In this study, a cross-linked polyaniline network was synthesized directly onto highly ordered Au nanopillars. A potentiometric Ca 2+ sensor was then fabricated using an as-synthesized nanoscale electrode, which was integrated into a microfluidic channel. The sensor exhibited a theoretical Nernst response (∼28.32 mV log −1 [Ca 2+ ]), a rapid response time (approximately <0.1 s), excellent repeatability, and high selectivity (all K POT values < 10 −3 ). The microfluidic - integrated sensor exhibited good sensitivity for small samples of < 10 μl. Furthermore, an on-body wearable sensor test was performed to monitor real-time Ca 2+ dynamics in human sweat during physical activity.