Self-Assembled hBN Wrinkles as Planar Optofluidic Channels

Optically accessible, scalable and planar nanofluidic channels are attractive for studying transport and localization under confinement. Two-dimensional (2D) materials provide large area, atomically flat interfaces, 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 channel-like networks through a lithography-free process. By varying flake thickness and substrate, we quantify trends in wrinkle density and morphology, establishing a practical fabrication design space. Atomic force microscopy and electron microscopy reveal vertical confinements ranging from <2 nm to >100 nm, depending on flake thickness and substrate. Time-resolved optical imaging after droplet contact is used to visualize liquid infiltration into the wrinkle network. Complementary Raman mapping of the water OH-stretch band and capacitance-gradient mapping (dC/dz) using KPFM-based scanning dielectric microscopy confirm liquid retention within the wrinkles for more than 10 h. Finally, we demonstrate proof-of-concept biomolecule confinement by integrating a graphene overlayer to suppress fluorescence background, enabling wide-field localization of ATTO647N-labeled DNA along hBN nanochannels. Overall, self-assembled hBN wrinkles provide a scalable, optically addressable planar nanofluidic platform for confining fluids and biomolecules.