Critical Casimir forces in soft matter

Gambassi, A.; Dietrich, S.

doi:10.1039/d3sm01408h

Cited by 6 publications

(2 citation statements)

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“…We stress here that

can be both positive and negative , i.e.,

can be both attractive and repulsive . Recently, a review of the exact results available for the CCE has been published [ 57 ]; overviews of different aspects of this effect can be found in [ 57 , 58 , 59 , 60 , 61 ].…”

Section: Introductionmentioning

confidence: 99%

“…We stress here that ∆ (τ) (d) can be both positive and negative, i.e., F ∥(τ) Cas (T, L) can be both attractive and repulsive. Recently, a review of the exact results available for the CCE has been published [57]; overviews of different aspects of this effect can be found in [57][58][59][60][61]. The above arguments for two semi-spaces A and B separated by a fluid C can be easily extended for bodies A and B of general shape immersed in a fluid, say, two spheres, a sphere and a semi-space (plane surface), etc.…”

Section: Introductionmentioning

confidence: 99%

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On Casimir and Helmholtz Fluctuation-Induced Forces in Micro- and Nano-Systems: Survey of Some Basic Results

Dantchev

2024

Entropy

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Fluctuations are omnipresent; they exist in any matter, due either to its quantum nature or to its nonzero temperature. In the current review, we briefly cover the quantum electrodynamic Casimir (QED) force as well as the critical Casimir (CC) and Helmholtz (HF) forces. In the QED case, the medium is usually a vacuum and the massless excitations are photons, while in the CC and HF cases the medium is usually a critical or correlated fluid and the fluctuations of the order parameter are the cause of the force between the macroscopic or mesoscopic bodies immersed in it. We discuss the importance of the presented results for nanotechnology, especially for devising and assembling micro- or nano-scale systems. Several important problems for nanotechnology following from the currently available experimental findings are spelled out, and possible strategies for overcoming them are sketched. Regarding the example of HF, we explicitly demonstrate that when a given integral quantity characterizing the fluid is conserved, it has an essential influence on the behavior of the corresponding fluctuation-induced force.

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“…We stress here that

can be both positive and negative , i.e.,

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On Casimir and Helmholtz Fluctuation-Induced Forces in Micro- and Nano-Systems: Survey of Some Basic Results

Dantchev

2024

Entropy

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Force density induced by preferential adsorption in a near-critical binary fluid mixture subject to the Soret effect

Fujitani

2024

The Journal of Chemical Physics

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We assume that two parallel plates are immersed in a binary fluid mixture lying in the one-phase region near the demixing critical point and that the surface of each plate attracts the mixture components differently via short-range interactions. It is known that the composition inhomogeneity caused by the difference can induce a force exerted on the plate at equilibrium. In the present study, we investigate how a temperature gradient imposed vertically on the plates changes the induced force by calculating the composition profile subject to the Soret effect. Numerically solving the derived differential equation, we show that a temperature gradient within the critical regime can change the force distinctly from its equilibrium value and can make the force direction opposite to the one at equilibrium.

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Critical Casimir levitation of colloids above a bull’s-eye pattern

Nowakowski,

Farahmad Bafi,

Volpe

et al. 2024

The Journal of Chemical Physics

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Critical Casimir forces emerge among particles or surfaces immersed in a near-critical fluid, with the sign of the force determined by surface properties and with its strength tunable by minute temperature changes. Here, we show how such forces can be used to trap a colloidal particle and levitate it above a substrate with a bull’s-eye pattern consisting of a ring with surface properties opposite to the rest of the substrate. Using the Derjaguin approximation and mean-field calculations, we find a rich behavior of spherical colloids at such a patterned surface, including sedimentation toward the ring and levitation above the ring (ring levitation) or above the bull’s-eye’s center (point levitation). Within the Derjaguin approximation, we calculate a levitation diagram for point levitation showing the depth of the trapping potential and the height at which the colloid levitates, both depending on the pattern properties, the colloid size, and the solution temperature. Our calculations reveal that the parameter space associated with point levitation shrinks if the system is driven away from a critical point, while, surprisingly, the trapping force becomes stronger. We discuss the application of critical Casimir levitation for sorting colloids by size and for determining the thermodynamic distance to criticality. Our results show that critical Casimir forces provide rich opportunities for controlling the behavior of colloidal particles at patterned surfaces.

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Critical Casimir forces in soft matter

Abstract: We review recent advances in the theoretical, numerical, and experimental studies of critical Casimir forces in soft matter, with particular emphasis on their relevance for the structures of colloidal suspensions and on their dynamics.

Cited by 6 publications

References 232 publications

On Casimir and Helmholtz Fluctuation-Induced Forces in Micro- and Nano-Systems: Survey of Some Basic Results

On Casimir and Helmholtz Fluctuation-Induced Forces in Micro- and Nano-Systems: Survey of Some Basic Results

Force density induced by preferential adsorption in a near-critical binary fluid mixture subject to the Soret effect

Critical Casimir levitation of colloids above a bull’s-eye pattern

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