3D-assembled microneedle ion sensor-based wearable system for the transdermal monitoring of physiological ion fluctuations

Monitoring human health is of considerable significance in biomedicine. In particular, the ion concentrations in blood are important reference indicators related to many diseases. Microneedle array-based sensors have enabled promising breakthroughs in continuous health monitoring due to their minimally invasive nature. In this study, we developed a microneedle sensing-array integrated system to continuously detect subcutaneous ions to monitor human health status in real time based on a fabrication strategy for assembling planar microneedle sheets to form 3D microneedle arrays. The limitations of preparing 3D microneedle structures with multiple electrode channels were addressed by assembling planar microneedle sheets fabricated via laser micromachining; the challenges of modifying closely spaced microneedle tips into different functionalized types of electrodes were avoided. The microneedle sensing system was sufficiently sensitive for detecting real-time changes in Ca2+, K+, and Na+ concentrations, and it exhibited good detection performance. The in vivo results showed that the ion-sensing microneedle array successfully monitored the fluctuations in Ca2+, K+, and Na+ in the interstitial fluids of rats in real time. By using an integrated circuit design, we constructed the proposed microneedle sensor into a wearable integrated monitoring system. The integrated system could potentially provide information feedback for diseases related to physiological ion changes.

Automated summary

Monitoring human health is crucial in biomedicine, and blood ion concentrations serve as important reference indicators for many diseases. Microneedle array-based sensors have enabled continuous health monitoring by being minimally invasive. In this study, we developed a microneedle sensing-array integrated system that can continuously detect subcutaneous ions for real-time human health monitoring. The system overcomes limitations in preparing 3D microneedle structures with multiple electrode channels and tackles challenges in modifying closely spaced microneedle tips into different types of electrodes. The system exhibits sufficient sensitivity and good detection performance, as demonstrated by in vivo experiments on rats. By integrating the sensor into a wearable monitoring system, it can potentially provide feedback on diseases related to physiological ion changes.