Micro-and Nanofluidics describe fluidic regimes defined by the length scale of the flow channels, the techniques for making the devices, and the dominant physics. Microfluidics typically implies flow through channels between 100 nm-100 microns in microfabricated silicon, glass, or polymer systems.

The physics of microfluidic systems are well-described by continuum theory, but the changes in length scale make surface tension and electrokinetic effects important and inertial forces unimportant. Because microfabricated devices can be made with a variety of complex geometries, a number of novel fluidic phenomena can be explored.

Nanofluidic systems span the overlap from regions best described by continuum theory (10-100 nm) to regions best described by individual molecular dynamics (1-10 nm). In these systems, molecular confinement must be accounted for, the the no-slip condition at times does not hold fully, and fluid constitutive relations are strongly affected by the existence of the boundary.

Micro- and nanofluidic systems are invariably affected by surface phenomena, thus surface chemistry strongly affects these systems. Research often involves detailed surface measurements using macroscopic electrokinetic effects, contact angle measurements, ellipsometry, profilometry, atomic force microscopy, and electron microscopy. Surface modifications including self-assembled monolayers, covalent attachement of sol-gels and polymers, and chemical etches are also common.

Many traditional techniques for fluidic transport do not scale well for nanotechnology applications. For example, decreasing the channel size by half in a pressure driven flow system requires that the applied pressure be quadrupled to maintain a constant flow velocity. More favorable scaling laws apply to electrokinetic systems, in which an externally applied electric field is used to generate flow. Electrokinetic systems are typically better candidates for controlled fluidic transport on the nanoscale.