A technique for the manipulation of Langmuir-monolayers at the air/water in
terface is presented. Optical tweezers are combined with fluorescence and B
rewster angle microscopy to produce a system capable of mechanical and ther
mal handling of monolayers on a micrometer scale. The viscoelastic, electri
cal, and thermodynamic properties of the monolayer can be determined by ana
lysis of the perturbations of its structure. A method for force and heat ca
libration of the tweezers is given. Both kinds of micromanipulations are ap
plied to the star shaped condensed domains in liquid expanded surroundings
of bis[8-(1,2-dipalmitoyl-snglycero-3 -phosphoryl)-3,6-dioxaoctyl]disulfide
("thiolipid") monolayers. The stability of the stars and the consequence o
f their interlocking on the interfacial flow are investigated.