Fig. 2: Fabrication process of the microneedle array sensor and its performance for detecting H₂O₂.

a Schematic illustration of the preparation process for the biosensor. b Cyclic voltammograms of the sensor after the deposition of 1 and 8 cycles of Prussian blue. Solution: PBS containing 5 mM H₂O₂. Scanning rate: 100 mV/s. c Cyclic voltammograms of the sensor after the deposition of 8 cycles of Prussian blue. Solution: PBS containing 5 mM H₂O₂. Scanning rates: 30, 50, 70, and 100 mV/s. d Current versus time response curve upon the addition of H₂O₂ in PBS to the sensor. C1: 0.8 mM, C2: 2.2 mM, C3: 3.0 mM, C4: 6.0 mM, C5: 12 mM, and C6: 12 mM. e Calibration curve of the sensor for the detection of H₂O₂. Each error bar was from three sensors