Performance limitations for nanowire/nanoribbon biosensors.

Field-effect transistor-based biosensors (bioFETs) have shown great promise in the field of fast, ultra-sensitive, label-free detection of biomolecules. Reliability and accuracy, when trying to measure small concentrations, is of paramount importance for the translation of these research devices into the clinical setting. Our knowledge and experience with these sensors has reached a stage where we are able to identify three main aspects of bioFET sensing that currently limit their applications. By considering the intrinsic device noise as a limitation to the smallest measurable signal, we show how various parameters, processing steps and surface modifications, affect the limit of detection. We also introduce the signal-to-noise ratio of bioFETs as a universal performance metric, which allows us to gain better insight into the design of more sensitive devices. Another aspect that places a limit on the performance of bioFETs is screening by the electrolyte environment, which reduces the signal that could be potentially measured. Alternative functionalization and detection schemes that could enable the use of these charge-based sensors in physiological conditions are highlighted. Finally, the binding kinetics of the receptor-analyte system are considered, both in the context of extracting information about molecular interactions using the bioFET sensor platform and as a fundamental limitation to the number of molecules that bind to the sensor surface at steady-state conditions and to the signal that is generated. Some strategies to overcome these limitations are also proposed. Taken together, these performance-limiting issues, if solved, would bring bioFET sensors closer to clinical applications.