Measuring multiple ions in biofluids with high sensitivity and repeatability is crucial for human healthcare monitoring. Ion-sensitive field-effect transistors have gained widespread interest for their advantages of being label-free, low cost, fast response, and CMOS-compatible fabrication processes. However, they suffer from limited voltage sensitivity, known as the Nernst limit. Current strategies for breaking the Nernst limit face problems of low integration level or unstable responses. Herein, we propose an inverter-based near-sensor amplifier to address these restrictions and realize a multi-ion super-Nernstian sensing platform with an extended-gate configuration by coupling a molybdenum disulfide (MoS2) inverter array with a multi-ion sensor chip. The high gain and stability of the MoS2 inverter array are attributed to the excellent electrical properties of MoS2, the low contact barrier between graphene and MoS2, and the defect-free surface of h-BN. The platform demonstrates super-Nernstian detection of pH (469.1 mV/pH), Na+ (472.7 mV/dec), K+ (269.4 mV/dec), and Ca2+ (221.2 mV/dec) levels within the biofluid range and exhibits stable long-term responses. Its practicality is further confirmed by selectivity investigations and artificial sweat analysis. The proposed platform is anticipated to play an important role in future point-of-care diagnostics, while this in situ amplification configuration is also expected to stimulate further near-sensor computing applications.
Zhao et al. (Mon,) studied this question.