Showing papers on "Nanofluidics published in 2007"

Sub-10 nm Device Fabrication in a Transmission Electron Microscope

Abstract: We show that a high-resolution transmission electron microscope can be used to fabricate metal nanostructures and devices on insulating membranes by nanosculpting metal films. Fabricated devices include nanogaps, nanodiscs, nanorings, nanochannels, and nanowires with tailored curvatures and multi-terminal nanogap devices with nanoislands or nanoholes between the terminals. The high resolution, geometrical flexibility, and yield make this fabrication method attractive for many applications including nanoelectronics and nanofluidics.

Ionic conductance of nanopores in microscale analysis systems: Where microfluidics meets nanofluidics

Abstract: In this tutorial review we illustrate the origin and dependence on various system parameters of the ionic conductance that exists in discrete nanochannels as well as in nanoporous separation and preconcentration units contained as hybrid configurations, membranes, packed beds, or monoliths in microscale liquid phase analysis systems. A particular complexity arises as external electrical fields are superimposed on internal chemical and electrical potential gradients for tailoring molecular transport. It is demonstrated that the variety of geometries in which the microfluidic/nanofluidic interfaces are realized share common, fundamental features of coupled mass and charge transport, but that phenomena behind the key steps in a particular application can be significantly tuned, depending on the morphology of a material. Thus, the understanding of morphology-related transport in internal and external electrical potential gradients is critical to the performance of a device. This addresses a variety of geometries (slits, channels, filters, membranes, random or regular networks of pores, etc.) and applications, e. g., the gating, sensing, preconcentration, and separation in multifunctional miniaturized devices. Inherently coupled mass and charge transport through ion-permselective (charge-selective) microfluidic/nanofluidic interfaces is analyzed with a stepwise-added complexity and discussed with respect to the morphology of the charge-selective spatial domains. Within this scenario, the electrostatics and electrokinetics in microfluidic and nanofluidic channels, as well as the electrohydrodynamics evolving at microfluidic/nanofluidic interfaces, where microfluidics meets nanofluidics, define the platform of central phenomena.

Reactive nanojets: Nanostructure-enhanced chemical reactions in a defected energetic crystal

Abstract: Nanofluidics of chemically reactive species has enormous technological potential and computational challenge arising from coupling quantum-mechanical accuracy with largescale fluid phenomena. Here, we report a million-atom reactive force field molecular dynamics simulation of shock initiation of an energetic crystal with a nanometer-scale void. The simulation reveals the formation of a nanojet which focuses into a narrow beam at the void. This, combined with the excitation of vibrational modes through enhanced intermolecular collisions by the free volume of the void, catalyzes chemical reactions that do not occur otherwise. We also observe a pinning-depinning transition of the shock wave front at the void at increased particle velocity and the resulting localization-delocalization transition of the vibrational energy.

Nanofluidics : Silicon for the perfect membrane

Abstract: Newly developed ultrathin silicon membranes can filter and separate molecules much more effectively than conventional polymer membranes. Many applications, of economic and medical significance, stand to benefit.

Micro/nanofluidic computing

Abstract: Fluid-based computing may smooth the transition to microscale systems.

Microfabricated devices with coated or modified surface and method of making same

Abstract: A microfabricated device or component thereof, such as microfluidics or nanofluidics device having a uniform non-wetting or non-absorbing polymeric coating or surface modification formed on a surface thereof by ionisation or activation technology such as plasma processing, to produce a surface energy of less than 15 mNm −1 . The treatment enhances the free-flowing properties of a liquid through the device during use.

Forming tiny 3D structures for micro- and nanofluidics

Abstract: Three-dimensional structures with predesigned optical functions such as waveguides, photonic crystals, and micromechanical parts can be combined into single microdevices with a number of functions. Researchers have made microfluidic devices and sensors that combine optical and microfluidic functions. For practical implementation of these devices, however, the current efficiency of production needs to be increased for 3D laser microfabrication and nanofabrication methods. We expect that a two-step approach—similar to the photographic process of exposure and development—will offer the most effective solution: first, subjecting the sample to a maskless exposure by interference and/or direct laser writing to record the structure, then wet processing to retrieve the written 3D structure. This fabrication route is compliant with batch processing, which is usually required for any practical implementation. To localize a light-matter interaction with high sub-wavelength spatial resolution for 3D structuring of materials, we need a laser source that provides a high irradiance per pulse. It became obvious long ago that femtosecond laser pulses are indispensable for this task, due to their ability to create a huge irradiance(of about a terawatt per square centimeter) with a small pulse energy, while limiting the thermally affected region around the irradiation spot. Fluidic microdevices and micro total analysis systems (μTAS) are expected to find an increasing number of applications in biomedical research and diagnostics. 3D architectures allow more integration and compactness, as well as increased sensitivity due to the small amount of analyte necessary to reliably recognize specific compounds and molecules. The function and versatility of μTAS devices can be augmented by combining optical, electrical, and fluidic systems. Thus, high optical transmissivity—especially to UV light, which can excite fluorescence of an analyte—is required. For electrophoretic applications, the host medium must have high electrical resistivity Figure 1. A confocal 3D image of photoluminescence from a rhodamine solution within a spiral structure.3 The spiral was written in the synthetic quartz Viosil by 3D direct laser writing at tight focusing conditions, using an objective lens of a numerical aperture of 1.35. Using 800nm irradiation with 180fs pulses, the volume was scanned with a separation of 200nm between pulse locations, at pulse energy equal to the two thresholds of an observable photomodification. Then the modified areas were etched with an aqueous solution of HNO3 and HF.4 The spiral depth spans 0− 62μm.

Nonequilibrium Molecular Dynamics Approach for Nanoelectromechanical Systems: Nanofluidics and Its Applications

Abstract: Molecular dynamics (MD) simulations have been performed to provide the basic knowledge of nanofluidics and its applications at the molecular level. A nonequilibrium molecular dynamics (NEMD) code was developed and verified by comparing a micro Poiseuille flow with the classical Navier-Stokes solution with nonslip wall boundary conditions. Liquid argon fluids in a platinum nanotube were simulated to characterize the homogeneous fluid system. Also, positively charged particles were mixed with solvent particles to study the non-Newtonian behavior of the heterogeneous fluid. At equilibration state, the macroscopic parameters were calculated using the statistical calculation. As an application of MD simulation, the nanojetting mechanism was identified by simulating the full process of droplet ejection, breakup, wetting on the surface, and natural drying. For an electrowetting phenomenon, a fluid droplet with positive charges moving on the ultrathinfilm with negative charges was simulated and then compared to the macroscopic experiments. A conceptual nanopumping system using the electrowetting phenomenon was also simulated to prove its feasibility. The molecular dynamics code developed here showed its potential applicability to the novel concept design of nano- and microelectro-mechanical systems.

Drying nano particles solution on an oscillating tip at an air liquid interface: what we can learn, what we can do

Abstract: Evaporation of fluid at micro and nanometer scale may be used to self-assemble nanometre-sized particles in suspension. Evaporating process can be used to gently control flow in micro and nanofluidics, thus providing a potential mean to design a fine pattern onto a surface or to functionalize a nanoprobe tip. In this paper, we present an original experimental approach to explore this open and rather virgin domain. We use an oscillating tip at an air liquid interface with a controlled dipping depth of the tip within the range of the micrometer. Also, very small dipping depths of a few ten nanometers were achieved with multi walls carbon nanotubes glued at the tip apex. The liquid is an aqueous solution of functionalized nanoparticles diluted in water. Evaporation of water is the driving force determining the arrangement of nanoparticles on the tip. The results show various nanoparticles deposition patterns, from which the deposits can be classified in two categories. The type of deposit is shown to be strongly dependent on whether or not the triple line is pinned and of the peptide coating of the gold nanoparticle. In order to assess the classification, companion dynamical studies of nanomeniscus and related dissipation processes involved with thinning effects are presented.

Templated growth and characterization of carbon nanotubes for nanofluidic applications

Abstract: Nanofluidics deals with the static and dynamic behavior of fluids at the nanoscale. Fundamental nanofluidic studies are focused on understanding whether continuum fluid mechanics equations hold at the nanoscale and whether there is a threshold dimension below which they no longer apply. Device fabrication focuses on developing integrated systems capable of handling attoliter (10-18 liter) or less of fluid for applications ranging from single molecule detection in biology to microchip cooling.Interest in nanofluidic increased with more widespread availability of carbon nanotubes (CNT), which appeared to have the ideal characteristics for this kind of studies. Prior to the development and commercial application of nanotube-based devices, the mechanisms of nanofluidic phenomena, liquid interaction and transport within the internal cavity of carbon nanotubes has to be better understood.The proposed PhD research is dedicated to the development of carbon nanotubes with geometry, wall structure and chemistry, and properties optimized for fluidic applications, as wells as understanding the liquid-carbon interactions. The results obtained will be applied to control the flow of fluids through nanotubes. These nanotubes will be used as building blocks of nanofluidic devices.%%%%Ph.D., Materials Science and Engineering – Drexel University, 2007

Electron-beam lithography: Body sculpting

Abstract: With a transmission electron microscope, researchers are able to carve out complex metal devices that could be useful in applications as diverse as quantum electronics and nanofluidics

Fabrication of Nano Channels Using IBE for Nanofluidics Study

Abstract: This paper presents a novel approach based on the angle selectivity of ion-beam etching to fabricate nano channel. The relation between the incident angle of ion beam etching and obtained profile has been carefully investigated. Starting from micro scale features, the authors formed desired self-aligned nano scale etching windows by using specially processes. Along with other MEMS processes, nano channel arrays with double-etched triangular side-regions have been successfully developed, and a width as small as 200nm was achieved. This novel approach demonstrates its potential application in nano fluidic field.

Transport Control of Eyring-Fluids along a Transversely-Corrugated Nanoannulus

Abstract: The volume flow rates of Eyring-fluids inside the wavy-rough nanoannulus were obtained analytically (up to the second order) by using the verified model and boundary perturbation method. Our results show that the wavy-roughness could enhance the flow rate especially for smaller forcing due to the larger surface-to-volume ratio and slip-velocity effect. Meanwhile, the phase shift between the outer and inner walls of nanoannuli could tune the transport of Eyring-fluids either forward or backward when the wavy-roughness of a nanoannulus is larger enough. Our results could be applied to the flow control in nanofluidics as well as biofluidics.

Nanofluidics: Gas guzzler

Abstract: Molecular dynamics simulations reveal that the presence of gas clusters can dramatically affect fluid uptake in nanopores

Sliding and translational diffusion of molecular phases confined into nanotubes

Abstract: The remaining dynamical degrees of freedom of molecular fluids confined into capillaries of nano to sub-nanometer diameter are of fundamental relevance for future developments in the field of nanofluidics. These properties cannot be simply deduced from the bulk one since the derivation of macroscopic hydrodynamics most usually breaks down in nanoporous channels and additional effects have to be considered. In the present contribution, we review some general phenomena, which are expected to occur when manipulating fluids under confinement and ultraconfinement conditions.