Three-Dimensional Simulation of DNA Sensing by Ion-Sensitive Field-Effect Transistor: Optimization of DNA Position and Orientation

Full three-dimensional simulation of DNA detection by ion-sensitive field-effect transistor technology is presented. DNA conditions for improving the sensing characteristics, namely, increased hybridization signal, are clarified. Poisson's equation is solved using a full three-dimensional finite element method for the model, where the model space consists of an electrolyte, DNAs, a self-assembled monolayer, and an insulator. The flatband voltage shift due to the hybridization of randomly positioned and oriented DNA is similar to experimental data, and indicates the possibility of experimental prediction. We examine the effects of DNA position and orientation on flatband voltage shift, and it is noted that the hybridization signal becomes largest when the DNAs are tilted 90° and distributed at equal intervals. It is also noted that a large hybridization signal can be obtained when upright DNAs are tightly immobilized even if it is difficult to tilt the DNAs.