Low cost and flexible electrodes with NH3 plasma treatments in extended gate field effect transistors for urea detection

In this study, the ammoniated indium tin oxide (ITO) films prepared by different condition of NH3 plasma treatment on flexible polyethylene terephthalate substrates are proposed as sensing electrodes of extended-gate field-effect transistors (EGFETs). pH sensitivity calculated from the output voltage in buffer solution from pH 2.1 to pH 12.1 in the samples with NH3 plasma treatment for 6 min is slightly increased about 2.8 mV/pH. For urea sensing performance comparison, longer time in the plasma treatment of ITO/PET-EGFET has higher sensitivity in urea detection, which could be explained by more amine groups for more urease binding on ITO surface. Low-cost substrate and high-reproducibility surface modification of NH3 plasma treatment are suggested to investigate the lifetime and stability for future urea sensor application.