Nano fluidics


Nano fluidics deals with the study, manipulation, and control of a few molecules or minute quantities of fluids often confined to a channel with nanoscale (1–100 nm) dimensions. Nano fluidic devices are often fabricated by etching tiny channels on silicon or a glass wafer and have potential applications in DNA sequencing, epigenetic analysis, gene therapy, drug delivery, and toxicity analysis (Ali et al., 2012). Using anisotropic wet etching of crystalline silicon and anisotropic reactive ion etching, Liang et al. (2007) fabricated a long Nano channel with a pair of perpendicular detectors separated by a 9-nm gap. A single 1.1-kb DNA molecule dissolved in TBE buffer was forced to enter the Nano channel (45 nm wide and 45 nm deep) with linear dimensions and electrical conductance was measured using the Nano gap detectors.

Nano fluidics is the study of the transport of fluids that are confined to structures of nanometre length scale. The study of transport and chemical reactions of ions and molecules in confined liquid is also included. In most Nano fluidics studies, water and aqueous solutions have been considered. Although water seems simple in structure and chemistry, water has challenged scientists with the complexity of its interaction with each other as well as other molecules. Its high dielectric constant and polarizability allows it to dissolve ionic solids to form hydrated ions. In addition, water can form hydrogen-bonding networks with unusual properties rarely found in other liquids, which is critical to the process of protein folding and DNA hybridization.

There has been a long history of the study of water in the nature of intermolecular force in water, especially in its interaction with other molecules and solid surfaces. However, Israelachvili and Pashley [2] measured the short-range force between two curved mica surfaces of radii R ≈ 1 cm in 10−3 M KCl aqueous solution and found that while the hydration force is overall repulsive when the distance between the surfaces is below about 4 nm, it is not always monotonic below about 1.5 nm, but exhibits oscillations of mean periodicity 0.25 ± 0.03 nm, roughly equal to the diameter of the water molecule.Hydration interactions rely on the bond hydrogen forms with water molecules, as well as with other molecules. In order to bring two hydrophilic surfaces closer together, it is necessary to break the hydrogen-bonding network between them. Consequently, hydration is generally a repulsive interaction, since it is associated with the increased enthalpy necessary to break the bonds.

As an emerging field, Nano fluidics offers unique phenomena compared to well-established microscale devices. Most importantly, it gives an opportunity to investigate molecules closely at the single molecule level. Distinctive capabilities include stretching DNA to identify single sequence variations, optical mapping of the whole human genome, distinctive separation and electrophoresis phenomena to separate small biopolymers, and DNA/RNA sequencing. The importance of such applications motivates the commercialization of these methods. Thermoplastic nanofluidics may increasingly be popular due to their low cost and suitability for in-vitro diagnostic applications compared to expensive glass-based and Si-based devices. Future research and development is anticipated with the goal of clinical translation of such diagnostic devices and their inclusion in commercial production pipelines with a high-scale production rate.