High-strength microneedle sensor for sensitive lactic acid and pH detection

Background: In the new intelligent medical system, miniaturized wearable biological detection sensors are crucial for real-time monitoring of human health, especially when combined with flexible microneedle arrays that can penetrate skin without causing injury. In real life, moderate exercise is highly beneficial to human health, whereas excessive physical activity can cause irreversible harm to the body. Therefore, there is a need for a portable sensor capable of monitoring human movement in real time, so as to enable rational planning of exercise routines. Results: In this context, the CeO₂-PANI sensor was constructed through the photocatalytic polymerization of the flexible microneedle array (MNs array) and the detection electrode (CeO₂-PANI electrode). It features the excellent mechanical property and highly sensitive detection. MN array can withstand a stress of 116.24 N. The superior lactic acid detection performance of the sensor, including a wide linear range (0.01-50 mM), high sensitivity (0.179 mA mM⁻¹ cm⁻²) and a low detection limit (0.75 μM). Meanwhile, the sensor can measure the environmental pH value within a wide range of 2 to 10. The sensor also exhibits excellent selectivity, allowing for accurate detection even in complex simulated body fluid environment. Significance: This study proposes a strategy for an applicable biological sensor with miniature wearables, which provides the development of the health monitoring system that is non-invasive and integrated. It can also provide a novel strategy for the development of new wearable real-time sports monitoring devices, enabling rational planning of exercise status and the proportion of exercise duration.