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As the single molecules detection tool, nanopore is applied in more and more fields, such as medicine controlled delivery, ion conductance microscopes, nanosensors and DNA sequencing. When molecules pass through a nanopore, they will physically block the pore and produce measurable changes in ionic currents under an external electrical potential. Based on analyzing the resultant electrical signals, it is possible to detect various bio-molecules.Generally, the capturing ratio of nanopre for molecules is dependent on the intensity of electrical potential, to which the duration time of event is inversely proportional. It is difficult to analyze the too short duration time. Therefore, we investigate the study on concentration gradient of ionic solution effect on the capturing ratio of nanopore for DNA, which is in order to get the higher capturing ratio with the invariant duration time.In the experiments, we add different concentration solution in trans and cis parts of naopore separately to form the concentration gradient. We use three different types nanopore (α-hemolysin nanopore, Si3N4 membrane nanopore, glass capillary nanopore) to compare and get the similar results. The events of DNA translocating through nanopore are observed more compressed during the fixed time under the higher concentration gradient and there is no change to the duration time of DNA passing through the nanopore. It is demonstrated that concentration gradient could increase the capturing ratio of nanopore for DNA.

The dynamic properties of liquids in confined geometries or porous media are of both fundamental and practical importance in many physical situations, such as lubrication of micro/nanoelectromechanical systems, the flow of liquids in rocks and nanopores, and transport through porous media in filtration processes. The investigation of liquids confined at the nanoscale has been an active field for many years, but their properties remain controversial. In this work, a surface force apparatus (SFA) has been used to investigate the dynamic properties of nanoconfined octamethylcyclotetrasiloxane (OMCTS) between two mica surfaces. The dependences of normal and adhesion forces on different confinement or retraction rates were studied. The hydrodynamic effects and liquid drainage were also determined. The contribution of hydrodynamic effects to liquid drainage is limited. Our experimental results showed that normal forces are strongly changed at high loading rates, whereas adhesion forces vary slightly. The rapidly confined film behaves as a jamming liquid of enhanced viscosity for a film thickness below to a few nanometers, while the viscosity change little at slow confinement rate. These results indicate that confining rate effects play a great role in the properties of nanoconfined liquid.

Nanopore based sensors have been widely spread utilized for detection and analysis of various single charged molecules. However, collision and trap events also block the ionic current that interferes recording the actually translocation events. In order to resolve the problem, we propose inducing a salt gradient to turn the pulse form negative to positive. And the salt gradients dependence of pulse signals ranging from 1 M (cis & trans) to 1 M (cis) - 4 M (trans) is mapped. Experiment results demonstrate that applying a high salt gradient prolong translocation time 1.5 times and increase molecule capture rate by a fact of 3. It is benefit for nanopore further application.

With the miniaturization of the NEMS/MEMS, the size effect becomes significant in the nanochannels/nanopores through which fluid flows as well as the interface effect. By all-atom molecular dynamics (MD) simulations, the ion transportation is investigated in nanopores as well as the physical properties at solid-liquid interface. To describe the anion and cation distributions of NaCl solution in vicinity of graphene nanopores, a new MD model was developed, taking thermal vibration of wall atoms, the structure of solvent molecules and ion sizes into consideration. The main peak locations of ion distributions stayed unchanged by changing the nanopore size, the solution concentration and the electric field strength. The ionic currents increased linearly with the diameter and the electric field strength, while it increased non-linearly with the solution concentration.

The out-of-plane thermal conductivity of silicon thin film doped with germanium is calculated by non-equilibrium molecular dynamics simulation using the Stillinger-Weber potential model. The silicon thin film is doped with germanium atoms in a random doping pattern with a doping density of 5% and 50% respectively. The effect of silicon thin film thickness on its thermal conductivity is investigated. The simulated thicknesses of silicon thin film doped with germanium range from 2.2 to 10.9 nm at an average temperature 300K. The simulation results indicate that the out-of-plane thermal conductivity of the silicon thin film doped with germanium decreases linearly with the decreasing film thickness. As for the film thickness of 9.8nm and the average temperature ranging from 250 to 1000 K, the investigation shows that the temperature dependence of the film thermal conductivity is not sensitive.

In order to study the dynamic performance with respect to a drum type washing machine, a detailed three dimensional dynamic model considering six degrees of freedom is established in the commercial software Adams. The characteristics of model are in good consistency with the simulation results on the movement of measure point in the x-z plane and eigen modes of the rigid body system. An automatic counterbalancing model of balls with different torsion damping coefficient is designed for vibration reduction. The parameters affecting the vibration are investigated by the approach of design of experiments which can reduce design cycle significantly. Its optimization results show a good performance compared to a washing machine model without balance balls attached.

Ionic current characterization is critical for the application of nanopores with sub 5 nm as bio medical sensors and devices. Here, we demonstrate an eccentric ionic current behavior in graphene nanopore fabricated by high resolution transmission electron microscopy (HR-TEM). A spike-like current enhancement is shown in the absence of any bio molecule or nanoparticle in the LaCl3and KCl solution. By tuning the hydrophobicity of the graphene surface, the spikes diminish in the current recordings acquired in graphene nanopore after 20 seconds plasma etching. We consider that the hydrophocity-induced nanobubble is present in the nanopore area, leading to the currents change as the bubbles deformation due to the voltage driven electrostatic forces on the transported ions surrounding the bubble surface.

In order to study the characteristics of the temperature field of the heating system in a washer-dryer, a numerical model to compute airflow field and temperature field is established according to the theory of fluid-solid coupled heat transfer. Simulation is realized based on the finite element method and verified with tests. The simulation results are in good consistency with the test result on the three aspects of temperature distributions, ranges and fluctuation tendencies. The errors of the lowest, highest and average temperature are all within 5.38%. Influencing factors leading to the offset of the high-temperature region in the downstream heating channel can be found from the valid simulation and they can provide theoretical basis for further optimization. The simulation results show that the configuration of the part of channel between the volute tongue and the heater leads to the transverse offset, and the triangular hump leads to the longitudinal offset.

The CH4-CO2replacement method to recover CH4from hydrate-bearing sediments has received great attention because it enables the long term storage of CO2and is expected to maintain the stability of gas hydrate-bearing sediments. This paper extends our previous study of the stability of CH4hydrate-bearing sediments to CO2hydrate-bearing sediments to evaluate the safety of the CH4-CO2replacement method. Low temperature, high pressure triaxial compression apparatus was used to measure the mechanical properties of CO2hydrate-bearing sediments. The triaxial tests results for CH4and CO2hydrate-bearing sediments were then compared. It was found that the failure mode of both the CO2and CH4hydrate-bearing sediments was a bulging deformation at mid-height on the samples. Moreover, the stress-strain curves of both the CO2and CH4hydrate-bearing sediments appear to be hyperbolic in shape, and could be divided into three stages: the quasi-elastic stage, the hardening stage and the yield stage. However, the strength of the CO2hydrate-bearing sediments was approximately 15% larger than that of the CH4hydrate-bearing sediments under the same conditions. The results imply that the stability of gas hydrate-bearing sediments could be maintained using the CH4-CO2replacement method to recover CH4from these sediments.

Nanopore and nanopore based biosensing and DNA sequencing have attracted more and more interests in the past ten years. In this paper, a simplified model is addressed to depict biomolecules passing through ultrafiltration membrane (containing nanopores). Based on this model, the passing velocity of biomolecules will not increase continuously but first increase, then decrease and stabilize with the IgG concentration increasing. Due to the physical place-holding effects and the simulation results, it can be predicted that, with biomolecules concentration increasing, the ionic current will first decrease, then increase and finnally stabilize. These predictions based on the simulation match our experimental results well.

Nanopore and nanopore based bio-sensing technology have become into more and more interesting research area in the past ten years. In this work, micro-pore in Si-S3N4 chips was fabricated and characterized by Focused Ion Beam (dual Beam), and then the S3N4 pore was covered by Polycarbonate (PC) membrane containing 50nm nanopores and sealed by using polydimethylsiloxane (PDMS) to get hybrid micro-nanopores. The obtained chip with hybrid nanopores together with two liquid cells was integrated into an ionic current detection device for biosensing. Based on this device, λ-DNA in the electrolytic solution can be detected when it is electrophoretically driven through the hybrid nanopores, and different gestures of λ-DNA in translocation also can be discriminated.

To understand the capture of charged polymer in salt solution, we investigated the effect of the temperature, concentration of DNA molecules and electrical field to the polynucleotide capture rate by using a single graphene nanopore. From the result of the molecular dynamics simulations, it suggested that the capture rate becomes higher with increasing temperature and that it increases exponentially with the electrical field, and that low and high concentration of the polymer do not exhibit optimal capture rate. By analyzing the simulations results we predict that the capture rate is related to the aperture and the structure of the pore.

DNA charged negatively could be transported through a solid nanopore by the force of an electrical field. Recently, the nice properties of graphene attract a lot of researchers. In this paper, A single graphene membrane was punched to form a nanopore and a ds-DNA was driven to pass through the pore by all-atom molecular dynamics simulations. The single graphene membrane was demonstrated useful in DNA sequencing. It suggested that the velocity of DNA translocating through a single graphene pore could be controlled by adjusting the appropriate voltage and the diameter of the nanopore.

For studying DNA electrical double layer in electrolyte solution, the key process is to create the template for DNA processing. In this paper, we described a straightforward method for depositing DNA on a substrate. The mica was chosen as the substrate materials because of its atomically flat and negatively charged surface in solution, and mica was coated by the polylysine to absorb the DNA molecules. Using by AFM, the DNA molecules have been probed obtaining a high resolution in air and liquid, and the method is simple and easy operated. This method can be used for nano-manipulation and the quality of the DNA under physiological conditions.

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.

Contact thermal resistance between two individual silicon nanowires is investigated by nonequilibrium molecular dynamic simulations as a function of temperature, overlap, bonding strength and spacing between them. The results indicate that contact thermal resistance per unit area increases with temperature increasing. The increasing overlap leads to the increase of the contact areas, which enhances the per unit area contact thermal resistance. With a weakened interfacial van der Waals bonding strength, the contact thermal resistance per unit area increases significantly. Additionally, a method to verify the effect of the bonding strength is used by changing the interfacial spacing, and a reasonable result is observed.

Nonequilibrium molecular dynamics (NEMD) approach is developed to investigate the thermal transport across a solid-solid interface between two different materials with an interlayer around it. The effects of system size and the interlayer material’s properties on the interface thermal resistance are considered in our model. The NEMD simulations show that the addition of an interlayer between two highly dissimilar lattices depresses the interface thermal resistance effectively. Meanwhile, the effective thermal conductivity along the direction of heat flux is enhanced with the increasing system temperature. Moreover, the interface thermal resistance after including an interlayer does not depend strongly on the simulation system size.

A kind of Carbon nanotube-implanted mesoporous carbon sphere (CNTs-MCS) is successfully prepared by a facile polymerization-induced colloid aggregation method using gelatin as a soft template. SEM, TEM, BET measurement and BJH method reveal that the obtained CNTs-MCS possess a mesoporous character, with specific surface area (284 m2•g-1) and uniform pore size of 3.9 nm. As the electrode material for supercapacitor in 6 mol•L-1 KOH, a low equivalent series resistance of 0.9 Ω cm2 and a maximum specific capacitance of 189 F•g-1 with a measured power density of 8 kW•kg-1 at energy density of 26.3 Wh•kg-1 are obtained.

The stable and homogeneneous aqueous suspension of carbon nanotubes was prepared in this study. The stability of the nanofluids was improved greatly due to the use of a new dispersant, humic acid. The thermal conductivity of the aqueous suspension was measured with the 3ω method. The experimental results showed that the thermal conductivity of the suspensions increases with the temperature and also is nearly proportional to the loading of the nanoparticles. The thermal conductivity enhancement of single-walled carbon nanotubes (SWNTs) suspensions is better than that of the multi-walled carbon nanotubes (MWNTs) suspensions. Especially for a volume fraction of 0.3846% SWNTs, the thermal conductivity is enhanced by 40.5%. Furthermore, the results at 30°C match well with Jang and Choi’s model.

Nonequilibrium molecular dynamics simulation is used to simulate the hydrodynamics lubrication in the nanoscale bearing. A physical model of the nanascale bearing that the thin liquid water film confined between two solid walls has been set up. The simulation results indicate that the hydrodynamic pressure profiles as the macroscopic state are formed in nanoscale bearings. The hydrodynamic pressure increases with increasing shear velocity, and corresponding load capacity also increases with increasing sliding velocity of the upper driven wall. These results are in accordance with classical Reynolds’ theory about hydrodynamic lubrication. On the other hand, the shear thinning behavior of the liquid water film appears, so that effective viscosity decreases under high shear velocity. Although effective viscosity of water film decreases under high shear velocity, this phenomenon doesn’t affect the hydrodynamic lubrication of the nanoscale bearing.