Papers by Keyword: Nanochannel

Abstract: This study presents the possibility of control of nanofluidics in the bio-inspired nanosized ion channel using a field effect transistor (FET) structure. We analyzed effects from main dominant factors to control the ion flow in nanosized channel such as electro-osmosis, diffusion effect, Coulomb force between ions and pressure force. Additionally, we suggest a strategy to control the ion flow accurately at the specific position in the nanochannel by handling the viscosity, ion molecular density, pressure, gate and trans-cis voltages of FET structure.

Abstract: The paper provides a physical description of ionic transport through the rigid symmetrical channel. A three-dimensional mathematical model, in which the ionic transport is treated as the electrodiffusion of ions, is presented. The model bases on the solution of the 3D Nernst-Planck-Poisson system for cylindrical geometry. The total flux includes drift (convection) and diffusion terms. It allows simulating the transport characteristics at the steady-state and time evolution of the system. The numerical solutions of the coupled differential diffusion equation system are obtained by finite element method. Examples are presented in which the flow characteristics at the stationary state and during time evolution are compared. It is shown that the stationary state is achieved after about 2×10 ^-8 s since the process beginning. Various initial conditions (channel charging and dimensions) are considered as the key parameters controlling the selectivity of the channel. The model allows determining the flow characteristic, calculating the local concentration and potential across the channel. The model can be extended to simulate transport in polymer membranes and nanopores which might be useful in designing biosensors and nanodevices.

Abstract: We investigated the nanoscale thermal bubble nucleation based on the principle of Coulter counter. With micro-nanofabrication technologies, a device was designed and fabricated, and a detection platform was set up which was used to investigate the thermal bubble nucleation of aqueous solution confined in a nanochannel with a cross size of about 100 nm×100 nm. Results show that with the temperature of the solution confined in the nanochannel increasing, the current through the channel increases first and then decreases, and vanishes after a fluctuating period. It can be found that the generating thermal bubbles can hinder the current flowing through the nanochannel. In addition, the shrinking and expanding of thermal bubbles’ volume correspond to the increase and decrease of the current. Finally, the thermal bubbles block the nanochannel entirely. Through the experiment results, our device can be applied to investigate the complex behaviors of thermal bubble produced in aqueous solution confined in nanochannels, effectively.

Abstract: The paper innovatively proposes using atomic force microscopy (AFM) and the concept of specific down force energy (SDFE) to establish a method for fabricating T shape nanochannel grooves on silicon (Si) substrate. Using the single-pass multi-layer cutting method of nanochannel groove using AFM proposed by the paper, a nanochannel looked like T shape is fabricated. For fabricating T shape nanochannel, it is set that cutting is firstly carried out for one pass on each cutting layer at a fixed down force. Then the probe carries out cutting for repeated passes. Using this cutting way by AFM and SDFE theory, the cutting depth and width of each pass can be predicted. The results of simulation and experiment of fabricating method for T shape nanochannel is further compared.

Abstract: Molecular dynamics simulation method was used to study the rarefied gaseous flows in nanochannels. A pressure-driven force was introduced to drive the gas to flow between two parallel walls. The effects of driven force magnitude and channel height were investigated. The results show that a single layer of gaseous molecules is adsorbed on the wall surface. The density of adsorption layer decreases with the increase of channel height, but doesnt vary with driven force. The velocity profile across the channel has the traditional parabolic shape. The average velocity and gas slip velocity on the wall increase linearly with the increase of pressure-driven force. The gas slip velocity decreases linearly with the increase of channel height. The ratio of slip to average velocity decreases linearly with the increase of channel height.

Abstract: Molecular dynamics simulations are carried out to explore the fluid flows in parallel-plate nanochannels. A “channel moving” pressure-driven model is utilized to study the planar Poiseuille flows. Considering the slip boundary conditions, relationships among the pressure gradient, mean flow velocity and the channel width are investigated to couple the atomistic regime to continuum. The results show that the mean flow velocity almost linearly increases with the increase of the pressure gradient. The slope of the linear relationship between the pressure gradient and the mean flow velocity is nonlinearly decreased with increasing the channel width. The results indicate that the approximate accuracy is reduced with decreasing the channel width while the pressure-driven flows confined in nanochannels are approximately described by the Navier-Stokes equations.

Abstract: Electroporation through nanochannels has potential as a useful tool for cell transfection. This potential is due to: the low voltage required; the centralized distribution of the potential penetration; the fact that this method causes no harm to the cell membrane, and; the even expression pattern of the target gene after electroporation. Additionally, the stable production process and improved yield rate can reduce the cost of producing the nanochannels and thus make the commercialization of this technique more feasible. This study aims to investigate the relationship between the speed of DNA stretching and the yield rate of nanochannels. We found that when the length of nanochannels is 2 µm, the yield rate can exceed 90% at a stretching speed of 2.3 mm/s . With a similarly high yield rate, longer nanochannels (3 µm) displayed a wider range of stretching speed. We have determined that the stretching speed can influence the adhesion of DNA and the subsequent fabrication of nanochannels. Therefore, this speed must be appropriately controlled.

Abstract: Simulation of microscale thermo-fluidic transport has attracted considerable attention in recent years owing to rapid advances in nanoscience and nanotechnology. The three-dimensional molecular dynamics simulations are performed for coupling between flow and heat transfer in a nanochannel. Effects of interface wettability, shear rate and wall temperature are discussed. It is found that there exist the relatively immobile solid-like layers adjacent to each solid wall with higher number density. Both slip length and Kapitza length at the solid-liquid interface increase linearly with the increasing wall temperature. The Kapitza length decreases monotonously with the increasing shear rates. The slip length is found to be overestimated by 5.10% to 10.27%, while Kapitza length is overestimated by 8.92% to 19.09% for the solid-solid interaction modeled by the Lennard-Jones potential.

Abstract: A physical model of the bulk-nanochannel-bulk with buffer bathes has been set up in this paper using molecular dynamics (MD) simulation. The distribution of water molecules and counterions Na⁺ in the nanochannel region with different surface charge densities is studied when silicon atoms vibrate. Simulation results show that the interaction between the charged surfaces and the ions in the channel results in an enrichment of counterions. With the increase of the surface charge density, the vibration effect of silicon atoms on the distribution of water molecules and Na⁺ ions cannot be ignored, which results in the decreasing of adsorbed peak and increasing of the first hydration peak. The concentration of Na⁺ increases and it distributes farther away from the wall. In addition, the ion exchange between nanochannel region and bath boxes is considered, so it is not electrical neutrality in the nanochannel region, and its electrical property depends on the surface charges.

Abstract: Monodisperse nanowires of rare earth phosphates were synthesized by chemical precipitation method using anodic aluminum oxide (AAO) template. Scanning electron microscope (SEM) images indicated that rare earth phosphate nanowires are parallelly arranged in AAO template, all of which are in uniform diameter of about 50 nm. X-ray diffraction (XRD) patterns and high magnification transmission electron microscopy (HRTEM) images showed that the nanowires were polycrystal structure.