Regensburg 2004 – wissenschaftliches Programm

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SYLS: Life Sciences on the Nanometer Scale - Physics Meets Biology

SYLS 3: Symposium "Life Sciences on the Nanometer Scale - Physics Meets Biology"

SYLS 3.6: Poster

Mittwoch, 10. März 2004, 16:00–18:30, B

Tuning of microcapsule adhesion by varying capsule stiffness — •Nils Elsner and Andreas Fery — MPI for Colloids and Interfaces 14424 Potsdam

We have been studying the adhesion polyelectrolyte (PE) capsules composed from Polyallylamine (PAH) and Polystyrenesulfonate (PSS). These PE capsule can be produced in sizes up to 20 mm, while the thickness remains tunable on the nanometer scale. This makes it possible to vary the elastic properties by changing the wall thickness, which has been shown by us recently [1].

The interaction of these capsules with a glass surface was studied by Reflective Interference Contrast Microscopy measurements. It was found, that negatively charged capsules adhere to glass, which was coated with positively charged polyelectrolyte, whereas these capsules do not adhere to bare glass. We found that the adhesion area increases with decreasing shell thickness for shells with identical surface interactions. The data for the adhesion area for different thicknesses and different radii could be fitted with a simple model based on [2], having the surface energy as the only fitting parameter.

In pH-experiments, the stiffness of the capsules is found to decrease upon increasing pH as revealed by force spectroscopy measurements. Consequently, we observe an increase of the adhesion areas although the surface interactions are not strongly changed in this pH range.

[1] F. Dubreil, N. Elsner, and A. Fery, Eur. Phys. J. E in press (2003).

[2] L. D. Landau and E. M. Lifschitz, Elastizitätstheorie (Akademie Verlag, Berlin, 1991).