Overcoming the Debye screening length with radiofrequency-operated graphene biosensors
Can a proposed new radiofrequency approach to graphene biosensors lead to groundbreaking changes in genome mapping?
Owing to its high carrier mobility, large surface-to-volume ratio, and chemical stability, graphene has drawn considerable attention as the building block for next generation label-free electrical biochemical sensors. However, under physiological conditions, graphene sensors typically can not detect a biological stimuli occurring at a distance larger than a nanometer from its surface (the so called 'Debye screening length') due to the presence of movable ions. Consequently, graphene is generally disregarded as a potent biological sensor. This project promises to shed light on this distance dependent sensing paradigm by proposing a new radiofrequency (RF) approach to deeply probe biological pathways. This is because at high frequencies the ions in the electrolyte start to lag behind the alternating current (AC) electric field due to the viscosity of the solution. As a result, the electrolyte behaves as a pure dielectric at RF/microwave frequencies.
In this project, Wangyang Fu proposes to:
i) monitor the layer-by-layer deposition of polyelectrolyte multilayers (PEMs): systematically investigate the distance dependent sensitivity of graphene RF sensors;
ii) detect the binding/unbinding events at the level of a single DNA polymerase molecule: explore the potential of RF sensing beyond the Debye screening, and
iii) resolve/discriminate the incorporation of nucleotides by the DNA polymerase (DNA sequencing) in the presence of a strong magnetic field (preferentially > 10 T), where sharp RF adsorptions due to distinct proton nuclear magnetic resonances (NMRs) are expected: reach structural information.
Fu believes that this project has the potential to lead to groundbreaking changes in complete genome mapping which will bring enormous benefits to the healthcare sector. Indeed, with the prospects of on-chip integration of sensor arrays and low-cost mass production, the expected results on graphene RF devices will also represent a novel approach for a new generation of portable, point-of-care, label-free biochemical sensors.