Mesochannels

Mesochannels are fluidic channels whose characteristic dimensions place them in the mesoscopic range, bridging microfluidics and nanofluidics. Depending on the field, mesochannels typically have cross-sectional dimensions from roughly 50 nanometers to a few micrometers, though some definitions extend to tens of nanometers up to tens of micrometers. The mesoscopic scale is where surface forces and confinement strongly influence transport, and where classical hydrodynamics can interact with electrokinetic phenomena.

Fabrication and materials: Mesochannels are commonly fabricated in silica, glass, silicon, or polymers using lithography and etching (photolithography, electron-beam lithography, reactive ion etching) or replication techniques like soft lithography and nanoimprinting; three-dimensional printing and two-photon polymerization expand accessible geometries. Achieving smooth walls and precise dimensions is critical due to high surface-to-volume ratios.

Transport and physics: In mesochannels, Debye lengths, double-layer effects, and slip conditions can dominate flow behavior. Electrokinetic transport, ion selectivity, and steric effects become important, and flow profiles may deviate from classic Poiseuille predictions. Surface chemistry and charge regulation strongly affect performance.

Applications: They are explored for nanoscale separation and analysis, single-molecule detection, DNA sequencing, nanoparticle sorting, and integrated lab-on-a-chip systems where confinement enhances sensitivity or selectivity.

Limitations: Fabrication precision, channel clogging, and surface roughness pose challenges; scaling to large numbers of channels or integration with sensors requires careful design.

See also: microfluidics, nanofluidics, mesoporous materials, lab-on-a-chip.

Notes: The term is used variably; some authors reserve mesochannels for channels within mesoporous matrices, others use it to describe mesoscale fluidic channels between micro- and nano-fluids.