Enhancing Potentiometric Response of Electrochemical Sensor Using Modified Ion-Sensitive Transistor V. Abhinav a , R. Patkar a , M. Vinchurkar a , T.R.Naik a , and M. S. Baghini a a Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India In this work, we present a novel combination of solid-state ion selective electrode and field effect transistor (FET) integrated on same platform. Thus, creating an extended gate field effect transistor (EGFET). We have built an electrochemical sensing unit comprised of all solid-state electrodes, an Ag/AgCl reference electrode and ionophore coated gold electrode. Unlike any of the earlier reports, all the electrodes are integrated with a FET in a single plane of printed circuit board (PCB), hence mitigating the issues of separate wire bonding or external connection between the sensing element and the transducer by using PCB traces. In this work, we demonstrate for the first time, the use of ion sensitive electrode (ISE) in EGFET configuration without degrading the linearity and sensitivity due to the external voltage bias. Potentiometric measurement on our K + ISE shows near Nernstian limit sensitivity (49 mV/decade), low concentration for the limit of detection (10 −6 M), and linearity over a large range of detection (10 −4 M to 1 M). Introduction High sensitivity, high selectivity, reproducibility and quick response are of prime importance for ion detection in various applications. In this respect, electrochemical detection is one of the best technique as compared to the traditional flame photometry, ion chromatography and surface plasmon resonance [1,2]. In an ion sensitive FET (ISFET), directly exposing the gate oxide of FET to an ionic solution causes the problem of ion penetration into the oxide layer. This issue is reflected in I-V characteristics that show voltage-dependent hysteresis due to ion penetration [3,4]. EGFET shows great potential over traditional ISFETs or ISE. EGFET effectively improves the reliability by separating the sensor and the transducer, associating the two by interconnect. It also provides a wide range of measurement with scope for device miniaturization and ease fabrication [5]. Commercial printed circuit board (PCB) based technology is presented for the low-cost production of electrodes and the same is used for circuit board. PCB technology has been explored by Prodromakis et al. 2011 for pH monitoring with the sensitivity of ~22 mV/pH [6]. They have sputtered H + ion sensitive TiO 2 of thickness 150nm on top of gold plated copper electrodes. Trantidou et al. 2013 have used plasma treatment for deposition of Parylene-C helped it to reduce the drift parameter (2.5-10 mV/hour) but at the cost of sensitivity (~16 mV/pH) [7]. Further Moschou et al. 2015 have presented high H+ ion sensitive indium tin oxide (ITO) layer with the improved sensitivity (45 mV/pH).