Biomedical subjects

Matthias Brunner

Publications and source records attributed to Matthias Brunner.

4 recordsLinked to original sources

PubMed2004

Locked-floating-solid to locked-smectic transition in colloidal systems.

We investigate two-dimensional melting of a colloidal system in the presence of a one-dimensional periodic substrate potential created by two interfering laser beams. We study the commensurability ratio p=sqrt[3]a/2d=2 with a the mean particle distance and d the period of the periodic potential. In contrast with the previously investigated case p=1, here we observe that melting of the locked-floating solid occurs via a novel locked-smectic phase, predicted by recent theoretical studies.

Journal Article↗

PubMed2004

Three-body interactions in colloidal systems.

We present a direct measurement of three-body interactions in a colloidal system comprised of three charged colloidal particles. Two of the particles have been confined by means of a scanned laser tweezers to a line-shaped optical trap where they diffused due to thermal fluctuations. Upon the approach of a third particle, attractive three-body interactions have been observed. The results are in qualitative agreement with additionally performed nonlinear Poisson-Boltzmann calculations, which also allow us to investigate the microionic density distributions in the neighborhood of the interacting colloidal particles.

Journal Article↗

PubMed2004

Direct measurement of three-body interactions amongst charged colloids.

Three-body interactions amongst three charged colloidal particles are measured in a deionized aqueous solution. Two of the particles are confined to an optical line trap while the third one is approached by means of a focused laser beam. From the observed particle configurations we extract the three-body potential which is found to be attractive and roughly of the same magnitude and range as the pair interactions. In addition, numerical calculations are performed which show qualitative agreement with the experimental results.

Journal Article↗

PubMed2002

Phase behavior of colloidal molecular crystals on triangular light lattices.

We investigate the melting process of a two-dimensional charge-stabilized colloidal system in the presence of a triangular substrate potential. This potential is formed by an optical interference pattern that allows the substrate strength to be varied continuously. By means of an additional scanned optical tweezer the particle density can be adjusted to different numbers m of colloidal particles per substrate minima; here we concentrate on the case of trimers, i.e., m = 3. Because trimers exhibit additional internal degrees of rotational freedom, the phase behavior of such a system is very different from homogeneous or one-dimensional periodic substrate potentials.

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