Bayreuth 1998 – scientific programme

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SYB: Symposium Polymere und kleine Moleküle an Grenzflächen

SYB 6: Polymere und kleine Moleküle an Grenzflächen

SYB 6.4: Talk

Wednesday, March 11, 1998, 11:50–12:10, H18

Direct measurement of dipole forces in monolayers at the air/water interface using optical tweezers — •Stefan Wurlitzer, Carsten Lautz, and Thomas M. Fischer — Universit"at Leipzig, Fakult"at f"ur Physik, Linnestr. 5, 04103 Leipzig

Dipole forces in Langmuir monolayers at the air-water interface are measured by analyzing the relaxation of locally disturbed patterns into their equilibrium configuration. The local perturbation is achieved by either mechanical micro manipulation of floating silica beads using optical tweezers or by local heating of the monolayer with a focused laser beam. The relaxation dynamics observed with fluorescence microscopy allow the direct model independent determination of forces in monolayers. The power of these techniques is demonstrated for attractive and repulsive dipole forces acting between different coexisting monolayer phases (gas(G), liquid expanded (LE), and liquid condensed (LC) phases) of methyl-octadecanoate.