• • Gate bias modulation from 0.7 to 0.95 V enables consistent high transconductance (gm) across all ion concentration subranges, yielding a current sensitivity (SI) of ~3 mA/dec for both Ca2+ and NH4+ over 10−5 to 10−1 M—the highest reported for ion-sensitive transistors, directly enabling reliable point-of-care diagnostics with minimal calibration.
• • The use of small-footprint (640 μm2) n-type vertical OECTs (vOECTs) achieves this performance while reducing device footprint by >50% compared to conventional planar OECTs, facilitating high-density integration in wearable and implantable biosensor arrays.
• • The IS-OECTs maintain stable SI across four orders of magnitude in ion concentration, overcoming the nonlinear ISM potential–gate bias correlation that typically degrades sensitivity in wide-range detection, thus eliminating the need for multiple sensors or complex signal processing.
• • The demonstrated Ca2+ and NH4+ detection at 3 mA/dec surpasses all previously reported ion-sensitive transistors, offering a 2–5× improvement in sensitivity, which is critical for early disease diagnosis (e.g., hypercalcemia, renal disorders) and continuous health monitoring.