Effect of screening on the sensitivity of field-effect devicesused to detect oligonucleotides

The effect of screening and the establishment of the Donnan potential at the floating gate of field-effect transistors (BioFETs) are calculated for a model that includes proton site binding on metal oxides used as gate insulators. Variations of response with p H , electrolyte concentration, and the fixed charge density of oligonucleotides are calculated assuming the charge is distributed homogenously in an ion-permeable membrane of finite thickness. Derived expressions describe the change in threshold voltage with electrolyte concentration and p H . These could be used to predict the sensitivity of the BioFET to hybridization, and provide a means of calibration prior to use.