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Biomedical subjects

T Bickel

Publications and source records attributed to T Bickel.

6 recordsLinked to original sources
PubMed2006

Brownian motion near a liquid-like membrane.

The dynamics of a tracer molecule near a fluid membrane is investigated, with particular emphasis given to the interplay between the instantaneous position of the particle and membrane fluctuations. It is found that hydrodynamic interactions creates memory effects in the diffusion process. The random motion of the particle is then shown to cross over from a "bulk" to a "surface" diffusive mode, in a way that crucially depends on the elastic properties of the interface.

Colloids↗
PubMed2006

Entropic interactions in soft nanomaterials.

We review the forces that rule interactions between phospholipid membranes and other soft nanomaterials such as polymers and colloids. Contrary to traditional nanostructures, soft materials display a high susceptibility to the fluctuations of the thermal environment, leading to new forces of an essentially entropic nature.

Adsorption↗
PubMed2004

Statistical mechanics of a colloidal suspension in contact with a fluctuating membrane.

Surface effects are generally prevailing in confined colloidal systems. Here we report on dispersed nanoparticles close to a fluid membrane. Exact results regarding the static organization are derived for a dilute solution of nonadhesive colloids. It is shown that thermal fluctuations of the membrane broaden the density profile, but on average colloids are neither accumulated nor depleted near the surface. The radial correlation function is also evaluated, from which we obtain the effective pair potential between colloids. This entropically driven interaction shares many similarities with the familiar depletion interaction. It is shown to be always attractive with range controlled by the membrane correlation length. The depth of the potential well is comparable to the thermal energy, but depends only indirectly upon membrane rigidity. Consequences for the stability of the suspension are also discussed.

Colloids↗
PubMed2002

Scale-dependent rigidity of polymer-ornamented membranes.

We study the fluctuation spectrum of fluid membranes carrying grafted polymers. Contrary to usual descriptions, we find that the modifications induced by the polymers cannot be reduced to the renormalization of the membrane bending rigidity. Instead we show that the ornamented membrane exhibits a scale-dependent elastic modulus that we evaluate. In ornamented lamellar stacks, we further compute the polymer contribution to the Caillé parameter characterizing the power law singularities of the Bragg peaks.

Journal Article↗
PubMed2000

Pressure patches for membranes: the induced pinch of a grafted polymer.

Achieving control of membrane shape and topology is of crucial importance to regulate function and performance of many systems in the realms of biology, physics, and chemical sciences. The design of a kit of versatile microscopic tools for tuning the shapes of fluid membranes relies ultimately on the possibility of tailoring molecules for applying a given, well-chosen force, to the self-assembled interfaces. Here we discuss theoretically the ability of grafted polymers to perform as mesoscopic pressure patches. We compute the pressure that a grafted polymer applies to the supporting surface. We also show that this entropic pressure leads to a well-defined pinched form of the membranes. Moreover, new membrane-mediated forces result from the action of these pressure tools, enabling action upon their spatial distribution along the membrane surface.

Elasticity↗