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1.
Contact angle hysteresis on nano-structured surfaces 总被引:1,自引:0,他引:1
We present results from an experimental study on the phenomenon of contact angle hysteresis on solid surfaces decorated by a random array of nanometric hollows. For weak values of the areal density of defects φd, the hysteresis H increases linearly with φd. This evolution is described by a pinning–depinning process of the contact line by individual defects. At higher values of φd, a collective pinning effect appears and H decreases with increasing φd. In the linear regime, our experimental results are compared to theoretical predictions for contact angle hysteresis induced by a single isolated defect on the solid surface. We suggest that the crossover from the individual to the collective pinning effects could be interpreted in terms of an overlapping of wetting cross sections. Finally, we analyse the influence of both the size and the morphology (hollows/hillocks) of defects on the anchorage of the contact line. 相似文献
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The hysteresis of the contact angle of a sessile drop on top of a disordered substrate is studied within a two-dimensional solid-on-solid model using Monte Carlo dynamics. Numerical and analytical evidence is given to show that there is always a hysteresis even for small densities of impurities. 相似文献
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《中国物理 B》2015,(8)
Contact angle hysteresis(CAH) is one of the significant physical phenomena in electrowetting on dielectric(EWOD).In this work, a theoretical model is proposed to characterize electrowetting evolution on substrates with CAH, and the relationship among apparent contact angle, potential, and some other parameters is quantified. And this theory is also validated experimentally. The results indicate that our theory and equation based on energy balance succeed in describing the electrowetting response of potential with significant contact angle hysteresis. The CAH in EWOD, ranging from 0° to about 20° in electrowetting cycle, increases with the increase of voltage and climbs up to about 20° when voltage is increased to about 38 V, and then decreases to zero with the further increase of voltage. 相似文献
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We report the first observation of a stick-slip transition of surfactant solution flow through nanopores. From the experimental data, we were able to determine both the slip length and the critical wall shear stress from which slip occurs. Whereas the latter is found to increase linearly with the concentration, the former remains constant and approximately equal to 20 nm over the studied range of concentrations. We model slip to occur in the surfactant bilayer adsorbed at the nanopore wall. The stick-slip transition is then related to a reorganization of the surfactant bilayer from an entangled structure into independent layers flowing past one another, as evidenced by independent surface plasmon resonance experiments. We conclude from our analysis that surfactant solutions are always slipping in larger tubes. However, the larger the tube diameter, the smaller the relative slip contribution to the total flow. 相似文献
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Célarié F Prades S Bonamy D Ferrero L Bouchaud E Guillot C Marlière C 《Physical review letters》2003,90(7):075504
We report in situ atomic force microscopy experiments which reveal the presence of nanoscale damage cavities ahead of a stress-corrosion crack tip in glass. Their presence might explain the departure from linear elasticity observed in the vicinity of a crack tip in glass. Such a ductile fracture mechanism, widely observed in the case of metallic materials at the micrometer scale, might be also at the origin of the striking similarity of the morphologies of fracture surfaces of glass and metallic alloys at different length scales. 相似文献
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Viorel P. Paun 《Central European Journal of Physics》2009,7(3):607-613
In this paper the driven transport of linear polymers through a nanopore is presented. Biopolymer physical behavior in an
external electric field is modeled and its motion is simulated using the Langevin impulse integrator method. Within fairly
large limits, the polymer translocation time is inversely proportional with the electric field intensity and directly proportional
with the polymer chain length.
相似文献
7.
Gao CL Ernst A Fischer G Hergert W Bruno P Wulfhekel W Kirschner J 《Physical review letters》2008,101(16):167201
Hot electrons injected into antiferromagnetic Mn layers from the tip of a low temperature scanning tunneling microscope have been used to determine the energies, lifetimes, and momenta of antiferromagnetic spin waves on the nanometer scale. The spin waves show a linear dispersion with a velocity of 160+/-10 meV A and lifetimes that scale linearly with energy in agreement with neutron scattering and theory. It is shown that the method is sensitive enough to detect the influence of surface anisotropies on the spin wave dispersion. 相似文献
8.
Adhesion of zein to solid substrates has been studied using surface energy profiles as indices and by adhesion mapping using
atomic force microscopy (AFM). Different plasticizers like glycerol and sorbitol have been used to form mixed films with zein
and properties of these films are studied using surface energy profiles. Comparison of the results from the different mixed
samples with those from the pure zein films showed that force mapping could identify areas rich in protein. The adhesion maps
produced were deconvoluted from sample topography and contrasted with the data obtained from contact angle measurements. A
comparison of the two methods shows that the extent of contact angle hysteresis is indicative of both hydrophobicity of the
surface as well as the force of adhesion. Mechanical properties and microstructure of zein films prepared by casting from
solutions and using Langmuir-Blodgett film technique have been investigated. Pure zein seemed brittle and exhibited an essentially
linear relationship between stress and strain. Films with plasticizer were tougher than these films. In general, mixed films
showed better mechanical properties than pure films and had higher ultimate tensile strength and increased per cent elongation.
Further, the mixed films of zein showed a higher force of adhesion compared to the pure films. 相似文献
9.
导电聚合物自20世纪70年代以来得到了广泛的研究.然而,关于聚合物纳米器件的研究则鲜有报导.从纳米尺度上研究导电聚合物,不仅有利于从更小的尺度上解析聚合物的光电性能、电荷传输机理,也可以将导电聚合物和纳米电子学有机地结合起来,发展聚合物纳米电子学的研究.文章介绍了最近由胡文平等[1,2]采用自组装的方法构筑的聚合物纳米器件和在纳米器件中观察到的一些有趣的现象. 相似文献
10.
Bacher G Maksimov AA Schömig H Kulakovskii VD Welsch MK Forchel A Dorozhkin PS Chernenko AV Lee S Dobrowolska M Furdyna JK 《Physical review letters》2002,89(12):127201
Statistical fluctuations of the magnetization are measured on the nanometer scale. As the experimental monitor we use the characteristic photoluminescence signal of a single electron-hole pair confined in one magnetic semiconductor quantum dot, which sensitively depends on the alignment of the magnetic ion spins. Quantitative access to statistical magnetic fluctuations is obtained by analyzing the linewidth broadening of the single dot emission. Our all-optical technique allows us to address a magnetic moment of only approximately equal 100 micro(B) and to resolve statistical changes on the order of a few micro(B). 相似文献
11.
The formation mechanism of the contact angle and the sliding angle for a liquid drop on a solid surface plays an important role in producing hydrophobic surfaces. A new half soakage model is established in this paper as a substitute for Wenzel (complete soakage) and Cassie (no soakage) models. The model is suited to many solid surfaces, whether they are hydrophilic or hydrophobic, or even superhydrophobic. Based on the half soakage model, we analyse two surfaces resembling lotus, i.e. taper-like surface and corona-like surface. Furthermore, this new model is used to establish a quantitative relationship between the sliding angle and the parameters of surface morphology. 相似文献
12.
We probe the local mechanical properties of microtubules at the nanometer scale by radial indentation with a scanning force microscope tip. We find a linear elastic regime that can be described by both thin-shell theory and finite element methods, in which microtubules are modeled as hollow tubes. We also find a nonlinear regime and catastrophic collapse of the microtubules under large loads. The main physics of protein shells at the nanometer scale shows simultaneously aspects of continuum elasticity in their linear response, as well as molecular graininess in their nonlinear behavior. 相似文献
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" href="/content/?Author=F.+Dubourg%cORF+RID%d%A%%e">F. Dubourg " href="/content/?Author=S.+Kopp-Marsaudon%cORF+RID%d%A%%e">S. Kopp-Marsaudon " href="/content/?Author=Ph.+Lecl%c%are%cORF+RID%d%A%%e">Ph. Leclère " href="/content/?Author=R.+Lazzaroni%cORF+RID%d%A%%e">R. Lazzaroni " href="/content/?Author=J.P.+Aim%c%a%cORF+RID%d%A%%e">J.P. Aimé 《The European physical journal. E, Soft matter》2001,6(5):387-397
16.
Dubourg F. Kopp-Marsaudon S. Leclre Ph. Lazzaroni R. Aim J.P. 《The European physical journal. E, Soft matter》2001,6(1):387-397
The European Physical Journal E - This work is an attempt to investigate viscosities at the nanometer scale. To do so, the tapping mode atomic force microscopy is used on a triblock copolymer... 相似文献
17.
Zhuang
Liu Xiaotao Xiao Xueqiao Xu Nami Li Tengfei Tang Dezhen Wang 《等离子体物理论文集》2020,60(5-6):e201900136
Dust poses a serious threat to tokamak operation and safety. It is important to study the behaviour of dust grains under tokamak's discharge conditions, which depends heavily on their size and charge. Existing simulations mainly address issues on dust grains with radii larger than 1 μm, in which case, the drift effect due to electromagnetic fields can be safely ignored. For nanometer scale dust grains, however, the drift effect becomes significant and a new model based on guiding-centre system needs to be established. In this work, the NDS has been done under BOUT++ framework. The simulation contains two parts. Part one, NDS evaluates the charging and ablation processes of the dust grains. In the second part, the guiding-centre orbits of dust particles are tracked in tokamak plasmas, whose parameters are obtained from BOUT++, a highly desirable C++ code package for performing parallel plasma fluid simulations with an arbitrary number of equations in 3D curvilinear coordinates. The orbit of nanodust dynamics is described by guiding centre equations for simplicity, and these equations are numerically solved by conventional fourth-order Runge Kutta method. Simulations provide results such as trajectories and evolutions of dust particles with different sizes and velocities for different tokamak geometries. Results show tungsten dust grains with a radius of a few nanometers launched from outer midplane will oscillate before totally ablated in C-Mod. The oscillation in this case is driven by the ion drag force. Larger Nanodust with a radius of 100 nm, on the contrary, cannot be completely constrained by the electromagnetic field. The high plasma temperature and density in the seperatrix region causes severe dust ablation, resulting in total ablation within several ms. 相似文献
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The optical tweezer is a versatile set-up that can be employed in a wide variety of studies investigating the microscopic
properties of materials. In particular, this set-up has in recent times been gainfully employed in probing rheological properties
of materials that exhibit viscoelasticity. These measurements can provide data at the micro and nanometer scales, not normally
accessible by rheometers that are used for measurements on bulk samples. In this work we describe a single laser beam optical
tweezer set-up, which is built around an inverted open microscope. The trapped polystyrene particle bead’s deviation from
the trap potential minimum is monitored by laser backscattering technique and the bead position measured by a quadrant photodiode
detector. Additionally, a provision is made for video microscopic studies on dispersed beads using a CCD camera. A single
particle microrheological experiment that can be performed using the set-up is described with relevant calculations. 相似文献