Thermophoretic Motion of Water Nanodroplets Confined inside Carbon Nanotubes

Zambrano, Harvey; Walther, Jens Honoré; Koumoutsakos, Petros; Sbalzarini, Ivo F.

doi:10.1021/nl802429s

Cited by 136 publications

(176 citation statements)

References 42 publications

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“…Alternatively, once both the heat flow and the adsorbate drift reach the steady-state regime, the mean velocity v (t → ∞) = F th /γ can be extracted (2,3,7,9,33). Neither method is very precise, however.…”

Section: System and Methodsmentioning

confidence: 99%

Ballistic thermophoresis of adsorbates on free-standing graphene

Panizon

Guerra

Tosatti

2017

Proc. Natl. Acad. Sci. U.S.A.

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The textbook thermophoretic force which acts on a body in a fluid is proportional to the local temperature gradient. The same is expected to hold for the macroscopic drift behavior of a diffusive cluster or molecule physisorbed on a solid surface. The question we explore here is whether that is still valid on a 2D membrane such as graphene at short sheet length. By means of a nonequilibrium molecular dynamics study of a test system-a gold nanocluster adsorbed on free-standing graphene clamped between two temperatures ∆T apart-we find a phoretic force which for submicron sheet lengths is parallel to, but basically independent of, the local gradient magnitude. This identifies a thermophoretic regime that is ballistic rather than diffusive, persisting up to and beyond a 100-nanometer sheet length. Analysis shows that the phoretic force is due to the flexural phonons, whose flow is known to be ballistic and distance-independent up to relatively long mean-free paths. However, ordinary harmonic phonons should only carry crystal momentum and, while impinging on the cluster, should not be able to impress real momentum. We show that graphene and other membrane-like monolayers support a specific anharmonic connection between the flexural corrugation and longitudinal phonons whose fast escape leaves behind a 2D-projected mass density increase endowing the flexural phonons, as they move with their group velocity, with real momentum, part of which is transmitted to the adsorbate through scattering. The resulting distance-independent ballistic thermophoretic force is not unlikely to possess practical applications.thermophoresis | graphene | ballistic | flexural phonons | heat transport T hermophoresis is the phenomenon by which a body immersed in a fluid endowed with a temperature gradient experiences a force and, independent of convection, drifts from hot to cold (1). We address here the less common case of thermophoresis of a physisorbed nanoobject caused by an in-plane temperature imbalance in the underlying solid substrate surface. Recent years have seen a surge of interest for methods to control nanoscale transport and manipulation, also in view of potential applications in nanodevices. The possibility to drive directional motion of adsorbates by means of thermal gradients is interesting and has been explored both theoretically (2) and experimentally (3). By a similar principle, the controlled directional motion on graphene was also explored by means of strain or wettability gradients (4-6). Carbon systems such as graphene and carbon nanotubes (CNTs) are prime candidate substrates (2, 3, 7-11) for these phoretic phenomena, owing to their remarkable mechanical strength and thermal conductivity. Computational studies have highlighted the possibility to drive thermally gold nanoparticles, water clusters, graphene nanoflakes, C60 clusters, and small CNTs over graphene layers or inside CNTs. Despite that, there appears to be so far insufficient intimate understanding of that phenomenon, besides the obvious consensus that the ...

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Section: System and Methodsmentioning

confidence: 99%

Ballistic thermophoresis of adsorbates on free-standing graphene

Panizon

Guerra

Tosatti

2017

Proc. Natl. Acad. Sci. U.S.A.

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“…Nanometer-diameter water droplets, because of their high surface-to-volume ratio and small number of molecules, present an ideal system for theoretical explorations of interfacial water dynamics induced by external forces. Such studies describe how external driving forces imposed by thermal (11), chemical (12), and topographic gradients (13) can lead to motion of nanometer-diameter droplets, and local fluctuations may result in the breakup of liquid nanojets (14). These theories imply that perturbations, either from external physical forces or chemical nonuniformities are coupled to dynamics of a nanodroplet through changes in shape and thus causing translocation of nanometer size droplets.…”

mentioning

confidence: 99%

Direct observation of stick-slip movements of water nanodroplets induced by an electron beam

Mirsaidov

Zheng

Bhattacharya

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

108

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Dynamics of the first few nanometers of water at the interface are encountered in a wide range of physical, chemical, and biological phenomena. A simple but critical question is whether interfacial forces at these nanoscale dimensions affect an externally induced movement of a water droplet on a surface. At the bulk-scale water droplets spread on a hydrophilic surface and slip on a nonwetting, hydrophobic surface. Here we report the experimental description of the electron beam-induced dynamics of nanoscale water droplets by direct imaging the translocation of 10-to 80-nm-diameter water nanodroplets by transmission electron microscopy. These nanodroplets move on a hydrophilic surface not by a smooth flow but by a series of stick-slip steps. We observe that each step is preceded by a unique characteristic deformation of the nanodroplet into a toroidal shape induced by the electron beam. We propose that this beam-induced change in shape increases the surface free energy of the nanodroplet that drives its transition from stick to slip state. Although much is known about the movement of bulk water, most of what is known about interfacial water results from modeling and computational simulations (9, 10). Nanometer-diameter water droplets, because of their high surface-to-volume ratio and small number of molecules, present an ideal system for theoretical explorations of interfacial water dynamics induced by external forces. Such studies describe how external driving forces imposed by thermal (11), chemical (12), and topographic gradients (13) can lead to motion of nanometer-diameter droplets, and local fluctuations may result in the breakup of liquid nanojets (14). These theories imply that perturbations, either from external physical forces or chemical nonuniformities are coupled to dynamics of a nanodroplet through changes in shape and thus causing translocation of nanometer size droplets. Interestingly, very recent simulations also predict that nanometer-diameter water droplets will slip on hydrophilic surfaces (15) similar to those on hydrophobic surfaces (16,17). However, studying the structural dynamics of nanodroplets is experimentally challenging because one needs to be able to externally induce the movement and be able to image the subsequent dynamic process of nanoscale droplets. Although atomic force microscope probes have measured the interfacial forces between liquids (18) and scanning transmission electron microscopy (TEM) has imaged small numbers of static water molecules confined in carbon nanotubes (19), these approaches fail to directly relate structure and dynamics of nanoscopic liquids. The ability to externally induce the movement and directly study the motion of model nanodroplets in contact with substrate interface may provide an insight to dynamic properties of interfacial water by experimentally complementing theoretical simulations. Such studies will be critical in the design of materials tailored to the adhesion and flow of liquids at the interface (20, 21).Hydrodynamic slip of water that re...

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“…Conventionally, pumping in nanofluidic systems is accomplished mainly using osmotic or hydrostatic pressure gradient, or chemical or thermal gradient. [15][16][17][18] Recently, various novel concepts and blueprints for nanoscale pump have been proposed. [19][20][21][22][23][24][25][26][27][28][29] In 1999, Král and Tománek 19 proposed a laser-driven pump.…”

Section: Introductionmentioning

confidence: 99%

Controllable transport of water through nanochannel by rachet-like mechanism

Nie

et al. 2012

The Journal of Chemical Physics

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By using molecular dynamics simulation, we have investigated systematically the feasibility of continuous unidirectional water flux across a deformed single-walled carbon nanotube (SWNT) driven by an oscillating charge outside without osmotic pressure or hydrostatic drop. Simulation results indicate that the flux is dependent sensitively on the oscillating frequency of the charge, the distance of the charge from the SWNT, and the asymmetry of the water-SWNT system. A resonance-like phenomenon is found that the water flux is enhanced significantly when the period of the oscillation is close to twice the average hopping time of water molecules inside the SWNT. These findings are helpful in developing a novel design of efficient functional nanofluidic devices.

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Thermophoretic Motion of Water Nanodroplets Confined inside Carbon Nanotubes

Cited by 136 publications

References 42 publications

Ballistic thermophoresis of adsorbates on free-standing graphene

Ballistic thermophoresis of adsorbates on free-standing graphene

Direct observation of stick-slip movements of water nanodroplets induced by an electron beam

Controllable transport of water through nanochannel by rachet-like mechanism

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