Abstract
Impedance sensing with silicon nanowire field-effect transistors (SiNW-FETs) shows considerable potential for label-free detection of biomolecules. With this technique, it might be possible to overcome the Debye-screening limitation, a major problem of the classical potentiometric readout. We employed an electronic circuit model in Simulation Program with Integrated Circuit Emphasis (SPICE) for SiNW-FETs to perform impedimetric measurements through SPICE simulations and quantitatively evaluate influences of various device parameters to the transfer function of the devices. Furthermore, we investigated how biomolecule binding to the surface of SiNW-FETs is influencing the impedance spectra. Based on mathematical analysis and simulation results, we proposed methods that could improve the impedimetric readout of SiNW-FET biosensors and make it more explicable.
Highlights
Since the introduction of the first ion-sensitive field-effect transistor (ISFET) by PietBergveld, researchers have been striving to use ISFETs effectively as biosensors [1]
Unlike a metal-oxide semiconductor field-effect transistor (MOSFET), which employs a metal or polysilicon as gate electrode material, a SiNW-FET biosensor employs a system of a reference electrode and an electrolyte solution as a gate electrode contact
In previous studies [26], we introduced and validated a Simulation Program with Integrated Circuit Emphasis (SPICE) behavioral macro model and developed an electrically equivalent circuit for SiNW-FETs to understand the effect of device geometries such as drain and source parasitic capacitances as well as the effect of conductivity and pH of the electrolyte solution on the transfer function of the system
Summary
Since the introduction of the first ion-sensitive field-effect transistor (ISFET) by Piet. The biomolecules of interest are detected by measuring the change in the threshold voltage [17,18,19] or the change in the drain-source current (IDS ) [4,5,10] of the SiNW-FET device upon the binding to specific receptor molecules at the gate surface Their concentration can be calculated by applying the respective adsorption models [20]. Biomolecular binding events on the gate surface cause a change in the frequency response, which is mostly prevalent at the low-pass characteristics Through this impedimetric sensing technique, Schwartz et al [27] demonstrated that it was possible to detect DNA hybridization in high ionic strength buffer solutions close to physiological concentrations using SiNW-FETs at frequency of 100 kHz and above, thereby overcoming the classical Debye-screening limitation of potentiometric sensing. We proposed future directions to make the biomolecular detection with the TTF method for SiNW-FETs more explicable
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