Jeudi 5 Juin 2008
Similar to electromagnetic vacuum fluctuations which can induce
long-ranged interactions between uncharged, conducting surfaces, a
rather similar effect was predicted almost 30 years ago to occur in
confined binary mixtures close to their critical point. This
so-called critical Casimir effect has attracted considerable
attention because it can strongly modify the interaction potential of
colloidal particles immersed in a binary fluid.
We present the first direct measurement of such critical Casimir
forces between a colloidal particle and a flat surface in a water -
2,6-lutidine mixture. With total internal reflection microscopy
(TIRM) which is capable to resolve forces down to 5fN, we obtain
distance resolved particle-wall interaction profiles. Upon
approaching the critical point we observe long-ranged interactions
which are attractive or repulsive depending on the specific boundary
conditions of the walls. This behavior is in good agreement with
recent theoretical predictions.
C. Hertlein, L. Helden, A. Gambassi, S. Dietrich, and C. Bechinger,
Direct measurement of critical Casimir forces, Nature 451, 172
(2008).
RECRUTEMENT ACCES DIRECT
Le département de physique
Fête de la Science 2018 