Defect engineering of 2D material for biosensing applications

2D materials offer huge potential as substrates to build devices for biosensing applications but are plagued by unwanted interactions such as binding/sticking. Controlling such interactions will be critical for the continued exploration of 2D materials in biosensing. In this work, we engineer and tune the surface interactions of hexagonal boron nitride (hBN) to direct the motion and diffusion of DNA. Using ISCAT and fluorescence microscopy techniques, we explore the nanoscopic interactions of DNA with different 2D materials. We show that pristine hBN flakes exhibit the lowest surface interactions and DNA bind preferentially to the edges and regions of high defect density of the hBN flake. We tap into a recently reported Xenon Focused Ion Beam (FIB) technique to engineer edges and defects on hBN flakes. Our technique harnesses a Xenon-FIB to lightly irradiate the desired regions of the hBN flake followed by subsequent etching in water which allows for a much cleaner hBN surface. We are able to enhance DNA binding and affinity at defined locations by inducing defects using FIB. By creating long tracks of defects, we induce diffusion along our created tracks, thereby allowing us to direct motion of the DNA molecules. We envision future devices where such engineered interactions are able to direct biomolecules to sensing regions (such as a nanopore) on 2D material based devices thereby increasing the rate of analyte capture and sensitivity of single molecule sensing devices.