Direct Measurement of Repulsive and Attractive van der Waals Forces between Inorganic Materials

Meurk, Anders; Luckham, Paul F.; Bergström, Lennart

doi:10.1021/la9610967

Cited by 114 publications

(43 citation statements)

References 14 publications

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“…Repulsion occurs when the plates with dielectric permittivities ε 1 and ε 2 along the imaginary frequency axis are immersed inside a medium with the dielectric permittivity ε 0 such that ε 1 < ε 0 < ε 2 or ε 2 < ε 0 < ε 1 (Mahanty, Ninham, 1976). At short separations in the nonretarded van der Waals regime this effect has been discussed for a long time and measurements have been reported [see, e.g., review by Visser (1981) and one of the later experiments by Meurk et al (1997)]. At separations of about 30 nm the same effect was measured by Munday et al (2009).…”

Section: Pulsating Casimir Forcementioning

confidence: 61%

The Casimir force between real materials: Experiment and theory

2009

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Section: Pulsating Casimir Forcementioning

confidence: 61%

The Casimir force between real materials: Experiment and theory

2009

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“…In Refs. [31][32][33][34][35][36] QED Casimir repulsion has indeed been observed experimentally for the sphere-plate geometry. In order to minimize the potential negative effects of all possible circuitry at such a small distances and the complications with the isolation, as well as possible problems involving chemical reactions it seems that one promising strategy for overcoming the obstacles mentioned above is to choose such a fluid as a medium that possesses no free changes dissolved in it and that is inert and do not interact chemically with the materials.…”

Section: Introductionmentioning

confidence: 93%

Sign change in the net force in sphere-plate and sphere-sphere systems immersed in nonpolar critical fluid due to the interplay between the critical Casimir and dispersion van der Waals forces

Valchev

Dantchev

2017

Phys. Rev. E

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We study systems in which both long-ranged van der Waals and critical Casimir interactions are present. The last arise as an effective force between bodies when immersed in a near-critical medium, say a nonpolar onecomponent fluid or a binary liquid mixture. They are due to the fact that the presence of the bodies modifies the order parameter profile of the medium between them as well as the spectrum of its allowed fluctuations. We study the interplay between these forces, as well as the total force (TF) between a spherical colloid particle and a thick planar slab, and between two spherical colloid particles. We do that using general scaling arguments and mean-field type calculations utilizing the Derjaguin and the surface integration approaches. They both are based on data of the forces between two parallel slabs separated at a distance L from each other, confining the fluctuating fluid medium characterized by its temperature T and chemical potential µ. The surfaces of the colloid particles and the slab are coated by thin layers exerting strong preference to the liquid phase of the fluid, or one of the components of the mixture, modeled by strong adsorbing local surface potentials, ensuring the socalled (+, +) boundary conditions. On the other hand, the core region of the slab and the particles, influence the fluid by long-ranged competing dispersion potentials. We demonstrate that for a suitable set of colloids-fluid, slab-fluid, and fluid-fluid coupling parameters the competition between the effects due to the coatings and the core regions of the objects involved result, when one changes T , µ or L, in sign change of the Casimir force (CF) and the TF acting between the colloid and the slab, as well as between the colloids. This can be used for governing the behavior of objects, say colloidal particles, at small distances, say in colloid suspensions for preventing flocculation. It can also provide a strategy for solving problems with handling, feeding, trapping and fixing of microparts in nanotechnology. Data for specific substances in support of the experimental feasibility of the theoretically predicted behavior of the CF and TF have been also presented.

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“…Since the development of the atomic force microscope (AFM) by Binnig et al (1), it has become possible to measure forces between a sharp tip and a flat surface of a specific material, whether in air (2) or liquids (3,4). Recent advances allowed the use of metallic (5) or inorganic (6) spheres as tip.…”

Section: Introductionmentioning

confidence: 99%