Vertically Aligned AZO Nanorods and Porous Membranes for Dual-Mode Glucose and pH Detection in Sweat

High Resolution Image Download MS PowerPoint Slide Noninvasive sweat glucose monitoring requires flexible sensing platforms that provide reliable interfacial transduction, enzyme retention, and stable operation in complex ionic environments. Herein, we report an extended-gate field-effect transistor (EGFET) platform for dual-mode pH and glucose detection based on vertically aligned aluminum-doped zinc oxide (AZO) nanorods integrated with a glucose oxidase (GOx)-containing porous membrane on a polyimide (PI) substrate. The device combines a 1 at. % AZO seed layer, vertically aligned 3 at. % AZO nanorods, and a porous enzymatic membrane to form a hierarchical working electrode. The AZO nanorods serve as the proton-sensitive transduction interface, while the porous membrane provides a localized microenvironment for GOx immobilization and glucose oxidation. AZO nanorods with an average height of 429.3 nm were grown by a low-temperature hydrothermal process. By tuning Al incorporation and seed-layer conditions, dense nanorod arrays with well-defined hexagonal facets and strong c -axis orientation were obtained. In contrast, excessive Al doping (18 at. %) induced structural degradation and sheet-like morphologies. X-ray diffraction and X-ray photoelectron spectroscopy confirmed that moderate Al incorporation preserved the wurtzite ZnO framework and strong (002) texture while regulating oxygen-related surface chemical states relevant to interfacial proton-sensitive transduction. The resulting sensor exhibited a pH sensitivity of 26.6 mV/pH with linearity ( R 2 = 0.995) and a glucose sensitivity of 62.4 mV mM –1 with linearity ( R 2 = 0.987) over the range of 0.08–1.00 mM. This range overlaps with reported sweat-glucose concentration windows. To bypass the complex interference of the blood matrix, analytical recovery obtained from artificial sweat was 95.1–104.0% for spiked 0.1–1.0 mM glucose. This work highlights AZO nanorod/PI EGFET architectures as a promising material–device platform for sweat-compatible pH/glucose biosensing and future pH-compensated glucose analysis.