Spontaneous stretching of single-stranded DNA on wrinkled graphene

In solution, single-stranded DNA (ssDNA) molecules are highly flexible and tend to form self-annealed structures. Therefore, stretching ssDNA near its contour length is crucial for nanotechnology-based detection and sequence analysis. Advances in nanofabrication have enabled nanopore-based sequencing to stretch double-stranded DNA (dsDNA) and proteins effectively. However, nanopore-based ssDNA stretching remains challenging due to nonspecific interactions between ssDNA and nanostructure surfaces, which hinder both transport and interrogation. Herein, we demonstrate that the quasi-one-dimensional wrinkles in graphene provide an effective platform for ssDNA stretching. This is attributed to the stronger binding affinity of ssDNA bases to wrinkled regions compared to planar regions, leading to the preferential adsorption of ssDNA along the one-dimensional "nanochannel" formed at the wrinkle edges. Interaction energy optimization and thermal fluctuations further drive ssDNA into a fully stretched conformation. Furthermore, we show that the stretched ssDNA can be electrophoretically transported along the "nanochannel" under an applied bias voltage. The transport velocity of ssDNA can be precisely controlled by adjusting the bias voltage, thereby improving the signal-to-noise ratio. Integrated with high-resolution atomic force microscopy (AFM) or scanning tunneling microscopy (STM), this graphene wrinkle-based "nanochannel" shows great potential as a novel platform for ssDNA sequencing.