Wafer-Scale Fabrication of Miniaturized Graphene-Based Ion-Selective Field-Effect Transistor Chips for Clinical Plasma Test

Rapid and reliable point-of-care plasma electrolyte analysis is critical for patient management under extensive care, driving demand for miniaturized sensors capable of ultralow sample consumption and multiplexed detection. We present a wafer-scale fabricated ion-selective graphene field-effect transistor (ISGFET) array that overcomes limitations of conventional ion-selective electrodes through a 2 μm × 5 μm sensing area and monolithic integration of K⁺/Na⁺/Ca²⁺ selective membranes. The ISGFET sensor exhibited high sensitivity (52.43 mV/decade for K⁺, 53.62 mV/decade for Na⁺, and 28.72 mV/decade for Ca²⁺) and selectivity in ion detection, as well as notable stability under physiological conditions and long-term reusability for over a month. The ISGFET-based sensing platform for the first time demonstrated its 100% diagnostic accuracy for potassium measurement in human plasma with an error of 4.37% (0.17 mM), when consuming less (<30 μL) sample volume, compared to hospital-based instrumentation. This manufacturable biosensor architecture not only addresses current needs in emergency blood testing but also establishes a foundation for next-generation wearable or in vivo electrolyte monitors through scalable graphene bioelectronics fabrication.