Surface Functionalization of Ion-Sensitive Floating-Gate Field-Effect Transistors With Organic Electronics

Electrically conducting polymers are advantageous hybrid materials for microelectronic biosensors due to their high bandgap sensitivity, possibilities for nanoscale surface area formation, and well-developed surface bioconjugation strategies. In this paper, we investigated whether those organic conductors can also be used to functionalize ion-sensitive floating-gate field-effect transistors (ISFGFETs) designed to measure biological binding events. We first subjected our device to 100% relative humidity (RH) and proved its viability in such a humid environment. Subsequently, we drop-casted viscoelastic polyaniline emeraldine salt on pristine transistors to construct organo-functionalized devices. The modified ISFGFETs were stable in aqueous environments and sensitive to cationic polyethyleneimine. The directions of the ISFGFET threshold voltage (VT) shifts agree with the corresponding open-circuit potential variations for the same reaction and pH-sensitive behaviors of Al₂O₃ sensing layer on the transistor. Such organo-modified ISFGFET sensor arrays are promising alternatives to traditional conductive polymer-based potentiometric biosensors due to their signal amplification, high throughput, and scalability advantages.