Showing papers on "Nanofluidics published in 2017"
TL;DR: This work reports ion transport through ultimately narrow slits that are fabricated by effectively removing a single atomic plane from a bulk crystal, and finds that ions with hydrated diameters larger than the slit size can still permeate through, albeit with reduced mobility.
Abstract: In the field of nanofluidics, it has been an ultimate but seemingly distant goal to controllably fabricate capillaries with dimensions approaching the size of small ions and water molecules. We report ion transport through ultimately narrow slits that are fabricated by effectively removing a single atomic plane from a bulk crystal. The atomically flat angstrom-scale slits exhibit little surface charge, allowing elucidation of the role of steric effects. We find that ions with hydrated diameters larger than the slit size can still permeate through, albeit with reduced mobility. The confinement also leads to a notable asymmetry between anions and cations of the same diameter. Our results provide a platform for studying the effects of angstrom-scale confinement, which is important for the development of nanofluidics, molecular separation, and other nanoscale technologies.
372 citations
TL;DR: Permeation experiments and molecular dynamics simulations indicate that a novel nanofluidics phenomenon takes place, whereby water transport through the g-C3 N4 nanosheet membrane occurs with ultralow friction.
Abstract: Two-dimensional (2D) graphitic carbon nitride (g-C3 N4 ) nanosheets show brilliant application potential in numerous fields. Herein, a membrane with artificial nanopores and self-supporting spacers was fabricated by assembly of 2D g-C3 N4 nanosheets in a stack with elaborate structures. In water purification the g-C3 N4 membrane shows a better separation performance than commercial membranes. The g-C3 N4 membrane has a water permeance of 29 L m-2 h-1 bar-1 and a rejection rate of 87 % for 3 nm molecules with a membrane thickness of 160 nm. The artificial nanopores in the g-C3 N4 nanosheets and the spacers between the partially exfoliated g-C3 N4 nanosheets provide nanochannels for water transport while bigger molecules are retained. The self-supported nanochannels in the g-C3 N4 membrane are very stable and rigid enough to resist environmental challenges, such as changes to pH and pressure conditions. Permeation experiments and molecular dynamics simulations indicate that a novel nanofluidics phenomenon takes place, whereby water transport through the g-C3 N4 nanosheet membrane occurs with ultralow friction. The findings provide new understanding of fluidics in nanochannels and illuminate a fabrication method by which rigid nanochannels may be obtained for applications in complex or harsh environments.
247 citations
TL;DR: This review highlights the recent progress, current challenges, and future perspectives in this emerging research field of "2D nanofluidics", with emphasis on the thought of bio-inspiration.
Abstract: With the advance of chemistry, materials science, and nanotechnology, significant progress has been achieved in the design and application of synthetic nanofluidic devices and materials, mimicking the gating, rectifying, and adaptive functions of biological ion channels. Fundamental physics and chemistry behind these novel transport phenomena on the nanoscale have been explored in depth on single-pore platforms. However, toward real-world applications, one major challenge is to extrapolate these single-pore devices into macroscopic materials. Recently, inspired partially by the layered microstructure of nacre, the material design and large-scale integration of artificial nanofluidic devices have stepped into a completely new stage, termed 2D nanofluidics. Unique advantages of the 2D layered materials have been found, such as facile and scalable fabrication, high flux, efficient chemical modification, tunable channel size, etc. These features enable wide applications in, for example, biomimetic ion transport manipulation, molecular sieving, water treatment, and nanofluidic energy conversion and storage. This review highlights the recent progress, current challenges, and future perspectives in this emerging research field of “2D nanofluidics”, with emphasis on the thought of bio-inspiration.
198 citations
TL;DR: The relatively simple SPC/E water model yields results in close agreement with those obtained from polarizable water models, and the structure and thermodynamics of water confined in the slit pore between two GO sheets with both oxidized and reduced parts are provided.
Abstract: ConspectusUnderstanding the properties of strongly confined water is important for a variety of applications such as fast flow and desalination devices, voltage generation, flow sensing, and nanofluidics. Confined water also plays an important role in many biological processes such as flow through ion channels. Water in the bulk exhibits many unusual properties that arise primarily from the presence of a network of hydrogen bonds. Strong confinement in structures such as carbon nanotubes (CNTs) substantially modifies the structural, thermodynamic, and dynamic (both translational and orientational) properties of water by changing the structure of the hydrogen bond network. In this Account, we provide an overview of the behavior of water molecules confined inside CNTs and slit pores between graphene and graphene oxide (GO) sheets.Water molecules confined in narrow CNTs are arranged in a single file and exhibit solidlike ordering at room temperature due to strong hydrogen bonding between nearest-neighbor mol...
157 citations
Book•
01 Mar 2017TL;DR: In this article, the authors present a wide range of topics within the growing field of nonequilibrium molecular dynamics (NEMD) and provide state-of-the-art algorithms and advice for designing reliable NEMD code, as well as examining applications for both atomic and molecular fluids.
Abstract: Written by two specialists with over twenty-five years of experience in the field, this valuable text presents a wide range of topics within the growing field of nonequilibrium molecular dynamics (NEMD). It introduces theories which are fundamental to the field - namely, nonequilibrium statistical mechanics and nonequilibrium thermodynamics - and provides state-of-the-art algorithms and advice for designing reliable NEMD code, as well as examining applications for both atomic and molecular fluids. It discusses homogenous and inhomogenous flows and pays considerable attention to highly confined fluids, such as nanofluidics. In addition to statistical mechanics and thermodynamics, the book covers the themes of temperature and thermodynamic fluxes and their computation, the theory and algorithms for homogenous shear and elongational flows, response theory and its applications, heat and mass transport algorithms, applications in molecular rheology, highly confined fluids (nanofluidics), the phenomenon of slip and how to compute it from basic microscopic principles, and generalized hydrodynamics.
76 citations
TL;DR: In this paper, the authors developed an analytical model taking into account many practical effects, such as the Stern layer, buffer anions (e.g., HEPES, ACES, and lactic acid), electric double layers overlap, and surface equilibrium reactions, to investigate the buffer effect on the electrokinetic energy conversion in a long, pH-regulated nanochannel.
59 citations
TL;DR: In this paper, the hydrodynamics of shale gas in nanometre-sized slit pores were investigated using nonequilibrium molecular dynamics (NEMD) and the results showed that velocity profiles manifest an obvious dependence on the pore width and they translate from parabolic flow to plug flow when the width is decreased.
Abstract: Understanding the flow characteristics of shale gas especially in nanopores is extremely important for the exploitation. Here, we perform molecular dynamics (MD) simulations to investigate the hydrodynamics of methane in nanometre-sized slit pores. Using equilibrium molecular dynamics (EMD), the static properties including density distribution and self-diffusion coefficient of the confined methane are firstly analyzed. For a 6 nm slit pore, it is found that methane molecules in the adsorbed layer diffuse more slowly than those in the bulk. Using nonequilibrium molecular dynamics (NEMD), the pressure-driven flow behavior of methane in nanopores is investigated. The results show that velocity profiles manifest an obvious dependence on the pore width and they translate from parabolic flow to plug flow when the width is decreased. In relatively large pores (6 – 10 nm), the parabolic flow can be described by the Navier-Stokes (NS) equation with appropriate boundary conditions because of its slip flow character...
35 citations
TL;DR: In this article, a biomimetic nanofluidic diode whose ionic transport characteristics can be completely modulated with the proton concentration in solution is demonstrated, where the fabrication procedure involves the electrostatic assembly of poly(allylamine hydrochloride) (PAH) into a track-etched conical nanochannel.
Abstract: In this paper, the fabrication of a biomimetic nanofluidic diode whose ionic transport characteristics can be completely modulated with the proton concentration in solution is demonstrated. The fabrication procedure involves the electrostatic assembly of poly(allylamine hydrochloride) (PAH) into a track-etched conical nanochannel. A fully reversible, zwitterionic-like behavior with important implications for the supramolecular interactions of the PAH within confined spaces was observed. The experimental design constitutes a facile venue for the fabrication of functional nanofluidic devices and paves the way for a number of applications in nanofluidics and biosensing. Furthermore, in order to explain the experimental results and to obtain physicochemical information about the system, theoretical modeling using a continuous model based on Poisson–Nernst–Planck equations and a stochastic model using Monte Carlo simulations were performed. Good agreement between experiments and theory was found.
32 citations
01 Jan 2017
TL;DR: A review of the history, physics, fabrication methods and applications of microfluidics and nanofluidics can be found in this article, where a wide range of application areas including environmental sensing, medical diagnostics, drug discovery, drug delivery, micro-scale chemical production, combinatorial synthesis and assays, artificial organs, and micropropulsion, microscale energy systems.
Abstract: Microfluidics and nanofluidics is a field of science that operates in the micrometer and nanometer scale. A microfluidic–nanofluidic device consists of components such as valves, pumps and mixers for manipulating and transporting the fluid at this scale. In this chapter we review the history, physics, fabrication methods and applications of microfluidics and nanofluidics. This interdisciplinary field has a wide range of application areas including environmental sensing, medical diagnostics, drug discovery, drug delivery, microscale chemical production, combinatorial synthesis and assays, artificial organs, and micropropulsion, microscale energy systems. The global market for microfluidic devices was estimated at around $3.1 billion dollars in 2015 and is expected to rise to $7.5 billion dollars by 2020. In the future, microfluidics and nanofluidics will see miniaturization and development of novel microfabrication techniques along with more sensitive detection methods and diagnosis of diseases in a point-of-care platform. Developments in the fundamental physics of fluid flow and its control, microfabrication methods, microfluidic components, and applications in new and emerging areas are all anticipated.
29 citations
TL;DR: In this paper, the authors used the measurable size membrane of vertically aligned double-walled carbon nanotube array, which is borne with durability and flexibility, and a conventional measurement method is applied to the membranes.
26 citations
TL;DR: In this article, a non-equilibrium multiscale molecular dynamics simulation is applied to investigate the transport properties (shear viscosity, diffusion coefficient and thermal conductivity) and structural properties of dense methane for Poiseuille flow within rough silicon nano-channel.
TL;DR: In this paper, the authors present a theoretical investigation of the electroviscous effects on heat transfer in nanofluidics based on continuum fluid mechanics while boundary slip is assumed on the walls.
TL;DR: A complete patterning and pattern-transfer solution based on thermal scanning probe lithography (t-SPL) and dry etching is presented and the fabrication of 3D profiles in silicon and silicon oxide with nanometer scale accuracy of absolute depth levels is demonstrated.
Abstract: Applications for high resolution 3D profiles, so-called grayscale lithography, exist in diverse fields such as optics, nanofluidics and tribology. All of them require the fabrication of patterns with reliable absolute patterning depth independent of the substrate location and target materials. Here we present a complete patterning and pattern-transfer solution based on thermal scanning probe lithography (t-SPL) and dry etching. We demonstrate the fabrication of 3D profiles in silicon and silicon oxide with nanometer scale accuracy of absolute depth levels. An accuracy of less than 1nm standard deviation in t-SPL is achieved by providing an accurate physical model of the writing process to a model-based implementation of a closed-loop lithography process. For transfering the pattern to a target substrate we optimized the etch process and demonstrate linear amplification of grayscale patterns into silicon and silicon oxide with amplification ratios of ∼6 and ∼1, respectively. The performance of the entire process is demonstrated by manufacturing photonic molecules of desired interaction strength. Excellent agreement of fabricated and simulated structures has been achieved.
TL;DR: In this article, the structure and flow of fluids in functionalized nanopores are modeled as cylindrical structures with solvophilic and solvophobic sites, and two fluids are modeled.
Abstract: We investigate through non-equilibrium molecular dynamics simulations the structure and flow of fluids in functionalized nanopores. The nanopores are modeled as cylindrical structures with solvophilic and solvophobic sites. Two fluids are modeled. The first is a standard Lennard Jones fluid. The second one is modeled with an isotropic two-length scale potential, which exhibits in bulk water-like anomalies. Our results indicate distinct dependence of the overall mass flux for each species of fluid with the number of solvophilic sites for different nanotubes’ radii. Also, the density and fluid structure are dependent on the nanotube radius and the solvophilic properties of the nanotube. This indicates that the presence of a second length scale in the fluid–fluid interaction will lead to distinct behavior. Also, our results show that chemically functionalized nanotubes with different radii will have distinct nanofluidic features. Our results are explained on the basis of the characteristic scale fluid properties and the effects of nanoconfinement.
TL;DR: In this article, the link between electronic states and hydrodynamics and accurate model predictions of transport, remain unanswered, however, the ability to produce membranes and devices from fluid phases of graphene oxide, which retain these special properties in molecular-scale flow channels, promises realization of applications in the near term.
Abstract: Carbon materials exist in a large number of allotropic forms and exhibit a wide range of physical and chemical properties. From the perspective of fluidics, particularly within the confines of the nanoscale afforded by one-dimensional carbon nanotubes (CNTs) and two-dimensional graphene structures, many unique properties have been discovered. However, other questions, such as the link between electronic states and hydrodynamics and accurate model predictions of transport, remain unanswered. Theoretical studies, experiments in large-scale ensembles of CNTs and stacked graphene sheets, and precise measurements at the single-pore and single-molecule level have helped in our understanding. These activities have led to explosive growth in the field, now known as carbon nanofluidics. The ability to produce membranes and devices from fluid phases of graphene oxide, which retain these special properties in molecular-scale flow channels, promises realization of applications in the near term.
TL;DR: It is demonstrated that spontaneous infiltration into supramolecularly templated mesoporous oxide films at the edge of a sessile drop in open air can be used to connect pairs of landmarks and contribute to unveiling subtle phenomena during spontaneous infiltration of fluids in bodies with nanoscale dimensions.
Abstract: Nanofluidics based on nanoscopic porous structures has emerged as the next evolutionary milestone in the construction of versatile nanodevices with unprecedented applications. However, the straightforward development of nanofluidically interconnected systems is crucial for the production of practical devices. Here, we demonstrate that spontaneous infiltration into supramolecularly templated mesoporous oxide films at the edge of a sessile drop in open air can be used to connect pairs of landmarks. The liquids from the drops can then join through the nanoporous network to guide a localized chemical reaction at the nanofluid–front interface. This method, here named “open-pit” nanofluidics, allows mixing reagents from nanofluidically connected droplet reservoirs that can be used as reactors to conduct reactions and precipitation processes. From the fundamental point of view, the work contributes to unveiling subtle phenomena during spontaneous infiltration of fluids in bodies with nanoscale dimensions such as...
TL;DR: This review introduces the key concepts and models in nanofluidic crystals, summarize the fabrication methods, and discusses the various applications of nanof LU crystals in depth, highlighting their advantages in terms of simple fabrication, low cost, flexibility, and high throughput.
Abstract: With various promising applications demonstrated, nanofluidics has been of broad research interest in the past decade. As nanofluidics matures from a proof of concept towards practical applications, it faces two major barriers: expensive nanofabrication and ultra-low throughput. To date, the only material that enables nanofabrication-free, high-throughput, yet precisely controllable nanofluidic systems is the close-packed nanoparticle array, i.e. nanofluidic crystals. Recently, significant progress in nanofluidics has been made using nanofluidic crystals, including high-current ionic diodes, high-power energy harvesters, efficient biomolecular separation, and facile biosensors. Nanofluidic crystals are seen as a key to applying nanofluidic concepts to real-world applications. In this review, we introduce the key concepts and models in nanofluidic crystals, summarize the fabrication methods, and discuss the various applications of nanofluidic crystals in depth, highlighting their advantages in terms of simple fabrication, low cost, flexibility, and high throughput. Finally, we provide our perspectives on the future of nanofluidic crystals and their potential impacts.
TL;DR: A novel approach is presented that is based on the combination of atomic force microscopy (AFM) and nanofluidics, also referred to as FluidFM technology, that can be applied to structure hydrogels from the large class of reversibly formed gels with superior resolution but would also allow for the selective loading of the hydrogelators with active substances or nanoparticles.
Abstract: Hydrogels have many applications in biomedical surface modification and tissue engineering. However, the structuring of hydrogels after their formation represents still a major challenge, in particular due to their softness. Here, a novel approach is presented that is based on the combination of atomic force microscopy (AFM) and nanofluidics, also referred to as FluidFM technology. Its applicability is demonstrated for supramolecular hydrogel films that are prepared from low-molecular weight hydrogelators, such as derivates of 1,3,5-benzene tricarboxamides (BTAs). BTA films can be dissolved selectively by ejecting alkaline solution through the aperture of a hollow AFM-cantilever connected to a nanofluidic controller. The AFM-based force control is essential in preventing mechanical destruction of the hydrogels. The resulting “chemical writing” process is studied in detail and the influence of various parameters, such as applied pressure and time, is validated. It is demonstrated that the achievable structuring precision is primarily limited by diffusion and the aperture dimensions. Recently, various additive techniques have been presented to pattern hydrogels. The here-presented subtractive approach can not only be applied to structure hydrogels from the large class of reversibly formed gels with superior resolution but would also allow for the selective loading of the hydrogels with active substances or nanoparticles.
TL;DR: Through the introduction of single colloidal particles, the fabrication capability of Lloyd's mirror interference can now be extended to fabrication of 3D nanostructure with complex shell geometry, which could find potential applications in the area of photonics, drug delivery, and nanofluidics.
Abstract: Light interactions with colloidal particles can generate a variety of complex three-dimensional (3D) intensity patterns, which can be utilized for nanolithography. The study of particle-light interactions can add more types of intensity patterns by manipulating key factors. Here we investigate a novel 3D nanolithography technique using colloidal particles under two-beam coherent illuminations. The fabricated 3D nanostructures are hollow, nested within periodic structures, and possess multiple chamber geometry. The effects of incident angles and particle size on the fabricated nanostructures were examined. The relative phase shift between particle position and interference pattern is identified as another significant parameter influencing the resultant nanostructures. A numerical model has been developed to show the evolution of nanostructure geometry with phase shifts, and experimental studies confirm the simulation results. Through the introduction of single colloidal particles, the fabrication capability of Lloyd's mirror interference can now be extended to fabrication of 3D nanostructure with complex shell geometry. The fabricated hollow nanostructures with grating background could find potential applications in the area of photonics, drug delivery, and nanofluidics.
01 Jan 2017
TL;DR: In this article, small volumes of liquids (microfluidics/nanofluidics) can be inserted into micro and nanoelectromechanical systems (MEMS/NEMS) to enhance systems' performances up to 2.75.
Abstract: We report a considerable improvement in the electrostatic actuation of silicon-based nano electrostatic drive (NED) structures [1] via the insertion of a liquid into the nanosystem. The dielectric liquid provides an insulating, high dielectric constant deformable medium in the electrode gaps that enhances the generated force per unit-applied volt performance. The study demonstrates that small volumes of liquids (microfluidics/nanofluidics) can be inserted into micro and nanoelectromechanical systems (MEMS/NEMS) to enhance systems' performances up to 2.75.
TL;DR: In this paper, two e-beam lithography methods to fabricate nanofluidic channels based on hydrogen silsesquioxane, a high-resolution negative-tone inorganic resist, are presented.
Abstract: Nanofluidics show great promise for the control of small volumes and single molecules, especially for biological and energy applications. To build up more and more complex nanofluidics systems, a versatile and reproducible fabrication technique with nanometer precision alignment is desirable. In this article, two e-beam lithography methods to fabricate nanofluidic channels based on hydrogen silsesquioxane, a high-resolution negative-tone inorganic resist, are presented. The robustness and versatility of the fabrication processes are demonstrated on silicon, glass, and flexible substrates. The high precision ability is illustrated with nanometric alignment of nanofluidic channels on gold nanoparticles and nanotransistor sensors, as well as for 3D nanofluidics prototyping. Furthermore, an unexpected extremely slow water evaporation rate (≈1 week for 300 μm long nanochannels) is noticed. This feature enables a simple and reliable manipulation of nanofluidic chips for various studies.
TL;DR: In this paper, the authors describe the use of micro/nanofluidics-based lab-on-a-chip devices for the analysis of chemical and biological samples over the past two decades.
Abstract: Micro/nanofluidics-based lab-on-a-chip devices have found extensive applications in the analysis of chemical and biological samples over the past two decades. Electrokinetics is the method of choice in these micro/nano-chips for transporting, manipulating and sensing various analyte species (e.g., ions, molecules, fluids and particles, etc.) [1,2].[...]
Dissertation•
05 Jul 2017
TL;DR: In this paper, the ability of photon antibunching to probe molecular stoichiometry in solution is explored and the underlying theoretical model is elucidated and subsequently applied to samples of different labeling stochometry.
Abstract: A mechanistic understanding of biological function requires a quantitative determination of macromolecular subunit architecture and interaction. Optical microscopy and spectroscopy provide a noninvasive method to characterize the stoichiometric ratios of molecular complexes. Though target-bound fluorescence labeling techniques can help to detect single molecules, counting molecules in a molecular complex remains challenging. In solution, diffusion limits the observation times of single molecules and, thus reduces the number of detectable photons. Current methods have limited resolving power or are constrained by a complex experimental configuration. Therefore, they are not able to precisely quantify the number of labeled fluorophores. In this dissertation, I first explore the ability of photon antibunching to probe molecular stoichiometry in solution. The underlying theoretical model is elucidated and subsequently applied to samples of different labeling stoichiometry. It enables determining the average number of emitters per molecular complex. In the second part of my thesis, to obtain the full distribution of species with a particular number of fluorescent labels, another method is developed. It is based on molecular brightness analysis using imaging-based photon counting histograms. This is assisted by a nanofluidic device that enables direct imaging of diffusing molecules with extended observation time. I performed a systematic study of the experimental conditions which guarantee an optimal performance of this method. The capability of correctly determining distributions of stoichiometries of molecular mixtures is verified by both simulation and measurements of small molecules. The nanofluidics system allows both single-molecule detection and manipulation under microscopic imaging, which is simple and implementation-friendly.
TL;DR: In this paper, the authors report ion transport through ultimately narrow slits that are fabricated by effectively removing a single atomic plane from a bulk crystal, and find that ions with hydrated diameters larger than the slit size can still permeate through, albeit with reduced mobility.
Abstract: It has been an ultimate but seemingly distant goal of nanofluidics to controllably fabricate capillaries with dimensions approaching the size of small ions and water molecules. We report ion transport through ultimately narrow slits that are fabricated by effectively removing a single atomic plane from a bulk crystal. The atomically flat angstrom-scale slits exhibit little surface charge, allowing elucidation of the role of steric effects. We find that ions with hydrated diameters larger than the slit size can still permeate through, albeit with reduced mobility. The confinement also leads to a notable asymmetry between anions and cations of the same diameter. Our results provide a platform for studying effects of angstrom-scale confinement, which is important for development of nanofluidics, molecular separation and other nanoscale technologies.
TL;DR: In this article, the authors proposed a method to characterize the line tension by fitting measured droplet shape to a macroscopic theoretical model that incorporated the shape of droplets into the model and showed that this ratio is orders of magnitude larger in lyotropic liquid crystal systems comprising micrometer-long colloidal particles.
Abstract: Line tension, i.e., the force on a three-phase contact line, has been a subject of extensive research due to its impact on technological applications including nanolithography and nanofluidics. However, there is no consensus on the sign and magnitude of the line tension, mainly because it only affects the shape of small droplets, below the length scale dictated by the ratio of line tension to surface tension σ/τ. This ratio is related to the size of constitutive molecules in the system, which translates to a nanometer for conventional fluids. Here, we show that this ratio is orders of magnitude larger in lyotropic liquid crystal systems comprising micrometer-long colloidal particles. Such systems are known to form spindle-shaped elongated liquid crystal droplets in coexistence with the isotropic phase, with the droplets flattening when in contact with flat solid surfaces. We propose a method to characterize the line tension by fitting measured droplet shape to a macroscopic theoretical model that incorpor...
TL;DR: In this article, the direction of electrically charged microparticles is controlled by the electric forces not only on the particle but also in the liquid, where an electrohydrodynamic flow is applied by preparing electrically polarised solutions.
Abstract: Molecular transport technology is one of the hottest topics in micro- and nanofluidics. Target molecules are often transported by electric forces, e.g. capillary electrophoresis (EP), gel EP, biological and artificial nanopores. On the other hand, such methods are sometimes disturbed by surrounding environments because the surface effects tend to be prominent. The surface charges on the channel walls cause peculiar liquid flows in micro- and nanochannels. Thus, the isolation of electrophoretic transport from the fluidic effects is important to achieve the precise control of targets in confined spaces. In this study, a novel technique to control the transport of microparticles is proposed, where a liquid flow is involved by applying electric body forces. The direction of electrically charged microparticles is controlled by the electric forces not only on the particle but also in the liquid. Herein, an electrohydrodynamic flow is applied by preparing electrically polarised solutions. In this setup, the transport direction of particles can be changed depending on the electric forces by excessive ions, which is estimated by measuring electric conductivity.
TL;DR: In this article, the current response along the micro/nanocapillaries can be significantly influenced by the diameter of the capillaries and the pH value of the solutions.
Abstract: In practical applications of biochips and bio-sensors, electrokinetic mechanisms are commonly employed to manipulate single bio-molecules and analyze their characteristics. To accurately and flexibly control the movement of single-molecule within micro/nanofluidic channels which are the basic components of Lab-chips, the current signals in micro/nanocapillaries filled with solutions of DNA molecules or polystyrene (PS) nanoparticles are systematically studied. Experimental results indicate that the current response along the micro/nanocapillaries can be significantly influenced by the diameter of the capillaries and the pH value of the solutions. Specifically, when there is only a pure (TBE) solution, the electric conductance does not monotonically decrease with decreasing the diameter of the capillaries, but slightly increases with decreasing the capillary diameter. When λ-DNA molecules or PS nanoparticles are added into the TBE buffer, the size effect on the electric conductance of the solutions are quite different. Although in the former, the electric conductance behaves differently from that in the pure TBE solution and decreases with the decreasing diameter, in the latter, the change is similar to that in the pure TBE solution. Besides, an abnormal 'falling' of the electric conductance is observed in a capillary with diameter of 200 nm. The investigation will significantly enhance the understanding on the electric properties of the solutions of biomolecules and particles in micro/nanofluidics. This is especially helpful for designing functional Lab-chip devices.
03 Nov 2017