Effect of channel-width and chirality on graphene field-effect transistor based real-time biomolecule sensing

Abstract

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Graphene field-effect transistors: the road to bioelectronics

“…In real-time biosensing, the sensitivity can be quantified by the percent age change of FET current, dI DS /I DS [37]. To maximize dI DS /I DS we need to co-optimize the FET transconductance (g m ) and the total gate capacitance C G [25]. A highly sensitive GFET typically features a low limit of detection (LOD), defined as the lowest amount of targeted bio-molecules or cell-released chemicals, named as bio-target here, with a statistically significant FET readout (see the definition of signal to background ratio below).…”

“…For instance, in real-time biosensing SBR can be defined as the percentage of the FET current change, ΔI DS /I DS , between the current values before and after adding the bio-targets to GFETs (e.g. molecule absorption or cell signaling) [25,37]. The background signal (i.e.…”

“…Such strong binding assures that the target molecules will not be released from the receptors during the assay [38,45,46]. A typical biosensing assay starts with the immersion of a back-or liquid-gated GFET in the base analyte with no target molecules; the FET channel is surface functionalized and exposed to the analyte [25]. Once the threshold voltage or the current of the GFET is settled to a steady state, a second analyte containing target molecules is added to the GFET channel, where the receptor-target binding takes seconds to minutes to form.…”

“…In contrast to a GS that has a zero bandgap, GNRs and GNMs have effective energy bandgaps that depend on the ribbon width, chirality or neck-width [14,24]. These FETs transduce biomolecule charges or extracellular voltage signals at the affinity of the FET gate or the FET channel into a change of the device I-V characteristics [20,25]. The resulting GFETs can be configured for label-free biosensing or cell recording in a miniaturized platform, serving as a viable alternative to the established electrochemical [26] and optical approaches [27].…”

“…Moreover, inherent to the high carrier mobility of graphene [31], GFETs offer a high transistor gain and thus a large current change by the biomolecule charges/ cellular voltage signals in the current traces. This configuration can apply to monitoring the molecular dynamics or cell activities in a biological environment, and may help develop biotechnologies in molecule detection [25] and cell recording [22]. To date, GFET based biosensors and cell interfaces are largely demonstrated at single-device levels.…”