Development of a highly sensitive and ultrafast enzymatic continuous glucose monitoring system integrated with a porous microstructured microneedle-based glucose energy harvester

We report the first development of a minimally invasive continuous glucose monitoring (CGM) system integrated with a porous microstructured microneedle based glucose energy harvester. For the first time, a three electrode microneedle system is co-integrated using a porous microneedle structure that is separated into two chambers, top and back electrodes, completing the current path and effectively forming a glucose fuel cell (GFC) capable of energy harvesting. The platform comprises multiple 5 mm long microneedles with a base diameter of 0.4 mm, functioning as the working electrode (WE), counter/reference electrode (CE/RE), and integrated energy harvester. The harvester employs a porous microstructured geometry over a microneedle to enable energy harvesting within a single compact unit. The WE is functionalized with gold nanoparticles (Au NPs), an intermediate Prussian blue (PB) layer, and dendrite-incorporated glucose oxidase (GOx). CE/RE needles share the WE’s dimensions to ensure identical insertion depth and electrical characteristics. The operating mechanism was confirmed through detailed COMSOL simulations, constituting the first comprehensive simulation of microneedle-based glucose energy harvesting. The developed CGM sensor exhibited a linear current response to 1–20 mM glucose (R² = 0.9246), with a sensitivity of 1.004 μA·mM⁻¹ and a detection limit of 0.68 mM. Selectivity tests showed negligible responses to 0.1 mM ascorbic acid, 0.1 mM uric acid, and 2 mM lactate. Furthermore, the energy harvester delivered open-circuit voltages up to 210 mV at 400 mM glucose, with OCV scaling linearly with concentration (R² ≈ 0.99), demonstrating potential capability to power the CGM sensor and its interface electronics.