Nanofluidic devices for the separation of biomolecules

Over the last 30-years, microchip electrophoresis and its applications have expanded due to the benefits it offers. Nanochip electrophoresis, on the other hand, is viewed as an evolving area of electrophoresis because it offers some unique advantages not associated with microchip electrophoresis. These advantages arise from unique phenomena that occur in the nanometer domain not readily apparent in the microscale domain due to scale-dependent effects. Scale-dependent effects associated with nanochip electrophoresis includes high surface area-to-volume ratio, electrical double layer overlap generating parabolic flow even for electrokinetic pumping, concentration polarization, transverse electromigration, surface charge dominating flow, and surface roughness. Nanochip electrophoresis devices consist of channels with dimensions ranging from 1 to 1000 nm including classical (1-100 nm) and extended (100 nm - 1000 nm) nanoscale devices. In this review, we highlight scale-dependent phenomena associated with nanochip electrophoresis and the utilization of those phenomena to provide unique biomolecular separations that are not possible with microchip electrophoresis. We will also review the range of materials used for nanoscale separations and the implication of material choice for the top-down fabrication and operation of these devices. We will also provide application examples of nanochip electrophoresis for biomolecule separations with an emphasis on nano-electrophoresis (nEP) and nano-electrochromatography (nEC).