Self-Assembled hBN Wrinkles as Planar Optofluidic Channels

TL;DR

This paper presents a scalable, self-assembled method using thermally induced hBN wrinkles to create optically accessible nanofluidic channels for studying fluid and biomolecule confinement, with potential applications in biosensing.

Contribution

It introduces a lithography-free, self-assembly approach to fabricate long-range, liquid-accessible nanofluidic channels using hBN wrinkles, with detailed characterization and a biomolecule confinement demonstration.

Findings

Wrinkle geometries depend on flake thickness and substrate.

Channels can confine liquids for over 10 hours.

Successful fluorescence localization of DNA in nanochannels.

Abstract

Optically accessible, scalable planar nanofluidic channels are attractive for studying transport and localization under confinement. Two dimensional (2D) materials provide large area, atomically flat interfaces for generating such platforms, yet achieving long range one-dimensional (1D) confinement with top-down nanofabrication remains challenging because it requires reproducible nanoscale feature control over extended distances, high yield, and low nonspecific adsorption of analytes under aqueous conditions. Here we demonstrate that thermally induced wrinkling of exfoliated hexagonal boron nitride (hBN) produces self-assembled, liquid-accessible, channel-like networks through a lithography-free process. By varying flake thickness and substrate choice, we quantify statistical trends in wrinkle density and morphology, thereby establishing a practical fabrication design space. Atomic force microscopy and electron microscopy reveal wrinkle-derived geometries with vertical confinement ranging from <2 nm to >100 nm depending on flake thickness and substrate. We further employ time-sequence optical imaging upon droplet-contact, which together with Raman mapping of the water OH-stretch band and capacitance-gradient mapping (dC/dz) by scanning dielectric microscopy (KPFM-based) measurements, demonstrates liquid infiltration and long-term liquid retention within the wrinkle network for more than 10 h. We finally show a proof-of-concept biomolecule confinement application in which we integrate a graphene overlayer as a background suppression interface, enabling wide-field fluorescence localization of ATTO647N labeled DNA along hBN wrinkle-induced nanochannels. Overall, this work establishes self-assembled hBN wrinkles as a scalable, and optically addressable planar nanofluidic platform for confinement of fluids and biomolecules.