A low-hysteresis and high-sensitivity extended gate FET-based chloride ion-selective sensor

This study presents an extended gate field-effect transistor (EGFET) chloride ion-selective sensor with very low hysteresis and high sensitivity for the point-of-care testing (POCT) blood analysis. All of the manufacturing processes adopted in this work are compatible with standard planar technology; hence, they are very suitable for mass production. This work firstly investigates the influence of channel width/length ratio on the gate leakage current of the EGFET. Under the optimized channel width/length ratio (1000/10 μm/μm), a very low gate leakage current (±2.3 nA) and high drain current (380 μA) of the implemented EGFET are achieved. Additionally, with the large and uniform sensing area (1 mm × 1mm) of the EGFET, the hysteresis voltage of the presented chloride ion sensor can be effectively reduced to 6 mV at pCl 3 concentration. As the testing concentration ranging from pCl 1 to pCl 5, the EGFET chloride ion sensor demonstrates a relatively high sensitivity (42 mV/pCl) if the proper PVC polymer-based chloride ion sensing membrane is deposited.