Graphene nanoelectrodes for biomolecular sensing
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Nanoscale biosensor technology has attracted considerable attention with its promise of revolutionizing techniques ranging from biological interfaces to rapid pathogen detection to enabling DNA data storage. Many approaches, such as nanopore sequencing, have been explored and are already achieving tremendous success; however, new sensing modalities and architectures are emerging that are envisioned for the next generation of ever more capable biosensors. These novel devices, combined with advances in machine learning, are moving concepts from simulation to experimentation and demonstration. In recent years, rapid advances have been made and many architectures have been put forward for novel approaches to biomolecular sensing using nanoelectronics, including the advent of tunnel junctions as a sensing platform. With high accuracy, sensitivity, and affordability, these sensors are predicted to drive a shift to personalized medicine and rapid diagnostics in real-time anywhere in the world. Here we give an overview of tunneling sequencing and its application in biomolecular sensing and provide a perspective on the use of scalable tunneling sequencing methods utilizing graphene as the active component.
I. TUNNELING-BASED SEQUENCING
The first successful demonstration of translocation and sensing of DNA and RNA strands through an alphahemolysin pore was reported by Kasianowicz et al. just over two decades ago in 1996.1 Since then, many advances have been made toward reading the sequence of bases that encode the genetic instructions for life. These approaches, collectively termed nanopore sequencing, began first with biological nanopores followed by synthetically made solid-state nanopores. Now a mature technology, biological nanopore sequencing is capable of sequencing long unlabeled DNA strands with high accuracy and with miniaturized devices that offer both portability and affordable sequencing.2 However, limitations resulting from the finite dimensions of both biological and solid-state nanopores remain.3 Even nanopores in atomically thin membranes formed from 2D materials, such as graphene and MoS2, suffer from these limitations as the effective channel length is increased by stray electric fields.4,5 Sensitivity of the nanopore is also decreased by the formation of an electrical double layer and noise caused by the mechanical vibrations of the membrane.6,7 To continue to advance the accuracy, miniaturization, and affordability of these devices a paradigm shift is envisioned from the ionic current blockade to quantum electron Contributing Editor: Venkatesan Renugopalakrishnan a) Address all correspondence to this author. e-mail: [email protected] b) These authors contributed equally to this work. DOI: 10.1557/jmr.2017.256
tunneling-based sequencing (see Fig. 1).8 In this configuration, analytes must pass between two electrodes placed just nanometers apart, known as a tunnel junction, allowing electrons to tunnel from one electrode to the other via the analyte molecule through a potential barrier that particles
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