EIS Biosensor for Detection of Low Concentration DNA Molecules

The results of the theoretical simulation of an electrolyte-insulator-semiconductor (EIS) biosensor made on a silicon nanowire for the detection of low concentration DNA molecules are presented. The equivalent electrical scheme for the EIS structure is constructed. The phenomenon of charge distribution in a depletion layer of semiconductor is taken into account in computations. The behavior and dependence of the total capacitance for the EIS sensor and its capacitive sensitivity on the DNA concentration in aqueous solution are investigated and analyzed. It is shown that the capacitance of the EIS sensor is very sensitive to the presence of the DNA molecules and the sensitivity has comparatively high value at the low concentration of the DNA molecules. The increase of the DNA concentration results in the decrease of the EIS total capacity. It is shown that one can register and determine the number of charged DNA molecules in aqueous solution by measuring the changes in the EIS capacity. The sensitivity increases with the growth of the gate voltage. It is shown that the threshold of sensitivity can be very low and the signal-to-noise ratio can reach high values for the EIS biosensor.