PHYSISORPTION INSTABILITIES DURING DYNAMIC LANGMUIR WETTING

Continuous dynamic Langmuir wetting of lipid monolayers can create reg ular 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 dippi ng direction and have widths of typically several micrometres and dist ances varying from 1 to almost-equal-to 100 mum. The stripe widths, di stances, and fluorescence contrast depend on deposition speed, surface pressure, substrate surface preparation, and dye concentration. The p atterns probably result from physisorption (meniscus) instabilities ca used by a feedback between the meniscus height (contact angle) and cha nges of the work of adhesion at the substrate/monolayer/air interface due to variations of the monolayer molecular packing density.