Planar Nanochannels Research Articles

Capillary flow in sacrificially etched nanochannels

Planar nanochannels are fabricated using sacrificial etching technology with sacrificial cores consisting of aluminum, chromium, and germanium, with heights ranging from 18 to 98 nm. Transient filling via capillary action is compared against the Washburn equation [E. W. Washburn, Phys. Rev. 17, 273 (1921)], showing experimental filling speeds significantly lower than classical continuum theory predicts. Departure from theory is expressed in terms of a varying dynamic contact angle, reaching values as high as 83° in channels with heights of 18 nm. The dynamic contact angle varies significantly from the macroscopic contact angle and increases with decreasing channel dimensions.

A dissipative particle dynamics study of flow in periodically grooved nanochannels

SUMMARY The effect of periodic rectangular wall roughness on planar nanochannel flow is investigated by dissipative particle dynamics simulation. The wall protrusion length is varied, and its effect on the flow is examined. Analysis of particle trajectories and average residence time reveals temporary trapping of fluid particles inside the rectangular cavities for a considerable amount of time. This trapping affects the density, velocity, pressure, and temperature distribution inside and close to the cavities. Inside the cavities, low-velocity regions and regions of high density related to high pressure and high temperature are observed. When compared with that of the channel with flat walls case, lower flow velocities, temperatures, and pressures are observed for grooved channels. The reduction of the above quantities is more pronounced as the protrusion length, that is, the roughness characteristic length, decreases. Finally, the relation of friction factor, f, with the flow Reynolds number is discussed. The model predicts = constant in the range . The results of this work are of direct relevance to the design of nanofluidic devices. Copyright © 2011 John Wiley & Sons, Ltd.

Bottom-up Approach toward Titanosilicate Mesoporous Pillared Planar Nanochannels for Nanofluidic Applications

Nanofluidic transport in lab-on-chip devices requires nanochannels that are difficult to fabricate since they require challenging top-down technological approaches. We present a bottom-up, scalable...

Heat transfer and fluid flow in microchannels and nanochannels at high Knudsen number using thermal lattice-Boltzmann method

The present paper deals with the two-dimensional numerical simulation of gaseous flow and heat transfer in planar microchannel and nanochannel with different wall temperatures in transitional regime 0.1≤Kn≤1 . An atomistic molecular simulation method is used known as thermal lattice-Boltzmann method. The results of simulation are presented in four cases corresponding to the Fourier flow, shear-driven flow (Couette flow), pressure-driven flow (Poiseuille flow), and mixed shear-pressure-driven flow in the developing and fully developed regions. The mixed shear-pressure-driven flow is divided into two subcases with shear stress and pressure gradient acting in the same and the opposite directions. Normalized temperature and velocity profiles across the channel, distribution of local wall Nusselt number, and friction coefficient are illustrated. Using this method, nonlinear pressure distribution in the streamwise direction, reduction in mass flow rate, C(f) Re, and Nu by increasing the Knudsen number are studied. It is seen that for Couette flow, Nu over the hotter plate is greater than the cooler plate, but for the pressure-driven flow with stationary wall temperature dependency of viscosity and thermal conductivity causes this trend to be reversed. The reversed flow appearance in the velocity profile is captured in the case of opposite shear-pressure-driven flow.

Fabrication of Sub-10 nm Planar Nanofluidic Channels Through Native Oxide Etch and Anodic Wafer Bonding

A simple, multiple-hydrofluoric (HF)-dip process is developed and characterized to etch native silicon-dioxide (SiO2) to obtain shallow silicon trenches. The room-temperature SiO2 grow-etch-grow process yields an etch rate of ~ 1 nm/HF-dip with atomically smooth trench surface. Low-temperature, low-voltage anodic bonding yields sub-10 nm deep planar nanochannels with aspect ratios as small as 0.002.

Selective trapping and concentration of nanoparticles and viruses in dual-height nanofluidic channels

Nanofluidic systems offer advantages for chemical analysis, including small sample volumes, size-selective particle trapping, sample concentration and the ability to separate and detect single molecules. Such systems can be fabricated using planar nanochannels, which rely on standard photolithographic techniques. Nanochannel fluid flow can be driven by capillary action, which benefits from simple injection and reasonably high flow rates. We demonstrate an analysis chip fabricated with planar nanochannels that consist of two adjoining segments of different heights. When nano-analytes elute through the channel, they become physically trapped when the channel dimensions shrink below the size of the particles. We demonstrate the capability of these devices to trap and concentrate by using the following: 120-nm polymer beads, 30-nm polymer beads, Herpes simplex virus 1 capsids, and hepatitis B virus capsids. Each species was fluorescently labeled and its resulting fluorescent signal was detected using a cooled CCD camera. We show how the signal-to-noise ratio of trapped analyte intensity varies linearly with analyte concentration. The goal of this work is to eventually perform size-based fractionation of a variety of nanoparticles, including biomolecules such as proteins.

A facile route for the preparation of azide-terminated polymers. “Clicking” polyelectrolyte brushes on planar surfaces and nanochannels

In this work we describe the facile preparation of azide-terminated polymers by conventional radical polymerization (cRP) using azo initiators bearing azide groups. We show that cRP provides a convenient avenue for the preparation of azide end-functional polymers in a one-step process. The versatility of this chemical methodology was demonstrated by the synthesis of unprecedented azide end group-functionalized sodium polystyrene sulfonate (PSSNa) and poly(2-methacryloyloxyethyl-trimethylammonium chloride) (PMETAC) which were then “clicked” onto alkyne-terminated silicon surfaces and polyethylene terephthalate nanochannels to form polyelectrolyte brush layers. The facile synthesis of the end-functionalized macromolecular building blocks will enable the creation of a wide variety of “clickable” architectures using very simple synthetic tools. We are confident that these results will constitute a key element in the “click” chemistry toolbox and, as such, will have strong implications for the molecular design of interfaces using macromolecular architectures.

Fabrication of planar nanofluidic channels in a thermoplastic by hot-embossing and thermal bonding

Planar nanochannels are of particular significance in nanofluidics: keeping the width on the micrometre scale prevents the use of nanolithography while the depth stays in the nanometric range, i.e. below 100 nm. Fabrication of wide and shallow nanochannels in a plastic is known to be challenging due to the collapse of the structure during the sealing step. In this Technical Note, we demonstrate the simple and low-cost fabrication without nanolithography of monolithic and planar nanochannels by hot-embossing and bonding below the glass transition temperature.