Detecting charged particles and proteins with high frequency field using silicon nanowire field effect biosensors

Silicon nanowire field effect transistors have been widely used as highly sensitive and label-free biosensors. The conventional potentiometric measurement works on the principle that the binding of charged biomarkers to the specific receptors on the sensor surface equivalently changes the gate potential, thus changing the conductance of the nanowires. Despite its success in detecting DNAs, proteins, and viruses, this method suffers greatly from the Debye screening, which arises from the Coulomb interaction of charged species, and low frequency noises, and performs poorly when the solution's ionic strength is strong. Here, we propose and validate a novel frequency domain approach to detect charged particles and proteins in high ionic solutions, where the existence of biomarkers can be read out through the sideband strength measurement on the frequency spectrum. We show that our radio frequency (RF) mixing approach shows better performance when compared to the direct current (DC) conductance measurement in detecting pH and protein solutions of various concentrations. Parametric study results on both the drain and gate signals will be discussed at the end.