PHYSISORPTION INSTABILITIES DURING DYNAMIC LANGMUIR WETTING

Continuous dynamic Langmuir wetting of lipid monolayers can create regular stripe patterns on the solid substrate surface. Monolayers doped with minor amounts of fluorescence dye may be deposited in stripes of alternating high and low dye concentration. In case of pure monolayers stripes are observed with AFM. The striations run normal to the dipping direction and have widths of typically several micrometres and distances varying from 1 to almost-equal-to 100 mum. The stripe widths, distances, and fluorescence contrast depend on deposition speed, surface pressure, substrate surface preparation, and dye concentration. The patterns probably result from physisorption (meniscus) instabilities caused by a feedback between the meniscus height (contact angle) and changes of the work of adhesion at the substrate/monolayer/air interface due to variations of the monolayer molecular packing density.