Modified technique for dynamic surface pressure and relaxation measurements at the air–water interface

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Abstract
A modified Wilhelmy surface balance design is presented which permits the use of both ’’dam’’ and ’’ribbon’’ compression barriers in the measurement of surface pressure behavior. Both kinds of barrier are interchangeable in a single‐surface balance trough, and this allows utilization of the strong points of each. Both barrier designs give rise to a linear surface area change upon compression, although the recessed dam barrier results in a more regularly shaped surface. The ribbon barrier, on the other hand, gives a completely contained surface free from barrier leakage artifacts. The utility of both barrier designs is demonstrated by dynamic surface pressure–area (π‐A) and relaxation experiments on dipalmitoyl lecithin (DPL) monolayers at 23 and 37 °C. The dual barrier design is shown to optimize the potential for the unambiguous interpretation of dynamic surface pressure measurements for this highly important component of pulmonary surfactant.