FIGURE 1.

Transformation of POPC monolayers by rapid compression. Films spread to initial surface pressures <42 mN/m were compressed at 26°C and 0.005 min⁻¹ to 46 mN/m, just below π_e. The bubble was then manipulated by infusion of buffer at a constant rate of either 1.4% initial volume/min (gray lines; initial area compression of 0.01 min⁻¹) for 17 min, or 109% initial volume/s (black lines; area compression of 23.1 min⁻¹) until surface pressure reached 68 mN/m. Surface pressure of the rapidly compressed film was held constant for 15 min (red lines), after which it was expanded to lower surface pressure at 2.5% initial volume/min (blue lines), and then recompressed at the same rate (green lines). (A) Variation of surface pressure (solid lines, right axis) and area (dashed lines, left axis) with time. Surface area is expressed relative to the initial area at 46 mN/m (A_o). Split timescale shows that the more rapid compression lasted ∼0.4 seconds. (B) The same measurements plotted as surface pressure versus surface area.