Nanofluidics

Nanofluidics is the study of fluid transport and manipulation at nanometer length scales, where channel dimensions are typically less than one micrometer. It focuses on nanochannels, nanopores, and nanostructured surfaces and often intersects with microfluidics in the development of integrated lab-on-a-chip systems. At these scales, surface forces and chemical interactions dominate over bulk fluid properties, leading to transport behaviors distinct from those observed in larger vessels.

Key physical effects include electrokinetic phenomena such as electroosmosis and electrophoresis, ionic transport influenced by surface charge, and confinement effects that alter diffusion and reaction rates. The presence of the electrical double layer, Debye length considerations, and partial slip on hydrophobic or engineered surfaces contribute to unusual flow and transport characteristics. Modeling often combines continuum hydrodynamics with electrostatics or uses molecular dynamics for detailed insight.

Common materials for nanofluidic devices include silicon, silicon nitride, glass, and polymer membranes, as well as two-dimensional materials like graphene and carbon nanotubes. Fabrication methods range from lithography and focused ion beam milling to track-etch pores and chemical etching, enabling channels and pores with diameters from a few nanometers to hundreds of nanometers.

Techniques such as nanopore sensing and resistive-pulse analysis enable single-molecule detection and sequencing, while pressure-driven and electrokinetic flows enable sample transport and manipulation. Applications span biomolecule analysis and sequencing, DNA and protein sensing, desalination and energy conversion, and integrated biosensing platforms in lab-on-a-chip devices.

Challenges include precise control of surface chemistry, reproducible fabrication at scale, and accurate modeling that accounts for coupled fluid, electrical, and chemical processes at the nanoscale. Ongoing research seeks to extend understanding of slip, ion selectivity, and fluid-structure interactions, and to translate nanofluidic principles into robust, deployable technologies.