Probing the sensitivity of nanowire-based biosensors using liquid-gating.

We have used liquid-gating to investigate the sensitivity of nanowire (NW)-based biosensors for application in the field of ultrasensitive biodetection. We developed an equivalent capacitance model of the biosensor system to explore the dependence of the sensitivity on the liquid-gate voltage (V(lg)), which was influenced by capacitive competition between the NW capacitance and the thin oxide capacitance. NW biosensors with highest sensitivity were obtained when we operated the device in the subthreshold regime while applying an appropriate value of V(lg); the influence of leakage paths through the ionic solutions led, however, to significant sensitivity degradation and narrowed the operating window in the subthreshold regime.

Poly-silicon nanowire field-effect transistor for ultrasensitive and label-free detection of pathogenic avian influenza DNA.

Enhanced surveillance of influenza requires rapid, robust, and inexpensive analytical techniques capable of providing a detailed analysis of influenza virus strains. Functionalized poly-crystalline silicon nanowire field-effect transistor (poly-SiNW FET) was demonstrated to achieve specific and ultrasensitive (at fM level) detection of high pathogenic strain virus (H5 and H7) DNA of avian influenza (AI) which is an important infectious disease and has an immediate need for surveillance. The poly-SiNW FET was prepared by a simple and low-cost method that is compatible with current commercial semiconductor process without expensive E-beam lithography tools for large-scale production. Specific electric changes were observed for AI virus DNA sensing when nanowire surface of poly-SiNW FET was modified with complementary captured DNA probe and target DNA (H5) at fM to pM range could be distinguished. With its excellent electric properties and potential for mass commercial production, poly-SiNW FET can be developed to become a portable biosensor for field use and point-of-care diagnoses.

Novel poly-silicon nanowire field effect transistor for biosensing application.

A simple and low-cost method to fabricate poly-silicon nanowire field effect transistor (poly-Si NW FET) for biosensing application was demonstrated. The poly-silicon nanowire (poly-Si NW) channel was fabricated by employing the poly-silicon (poly-Si) sidewall spacer technique, which approach was comparable with current commercial semiconductor process and forsaken expensive E-beam lithography tools. The electronic properties of the poly-Si NW FET in aqueous solution were found to be similar to those of single-crystal silicon nanowire field effect transistors reported in the literature. A model biotin and avidin/streptavidin sensing system was used to demonstrate the biosensing capacity of poly-Si NW FET. The changes of I(D)-V(G) curves were consistent with an n-type FET affected by a nearby negatively (streptavidin) and positively (avidin) charged molecules, respectively. Specific electric changes were observed for streptavidin and avidin sensing when nanowire surface of poly-Si NW FET was modified with biotin and streptavidin at sub pM to nM range could be distinguished. With its excellent electric properties and the potential for mass commercial production, poly-Si NW FET can be a very useful transducer for a variety of biosensing applications.

Ultrasensitive detection of dopamine using a polysilicon nanowire field-effect transistor.

An unprecedented high sensitive sensing of neurotransmitter dopamine at fM level was demonstrated using a poly-crystalline silicon nanowire field-effect transistor (poly-SiNW FET) fabricated by employing a simple and low-cost poly-Si sidewall spacer technique, which was compatible with current commercial semiconductor processes for large-scale standard manufacture.