The morphology of surfactant monolayers is typically studied on the planar surface of a Langmuir trough, even though most physiological interfaces are curved at the micrometer scale. Here, we show that, as the radius of a clinical lung surfactant monolayer-covered bubble decreases to ~100 μm, the monolayer morphology changes from dispersed circular liquid-condensed (LC) domains in a continuous liquid-expanded (LE) matrix to a continuous LC linear mesh separating discontinuous LE domains. The curvature-associated morphological transition cannot be readily explained by current liquid crystal theories based on isotropic domains. It is likely due to the anisotropic bending energy of the LC phase of the saturated phospholipids that are common to all natural and clinical lung surfactants. This continuous LC linear mesh morphology is also present on bilayer vesicles in solution. Surfactant adsorption and the dilatational modulus are also strongly influenced by the changes in morphology induced by interfacial curvature. The changes in morphology and dynamics may have physiological consequences for lung stability and function as the morphological transition occurs at alveolar dimensions.
|Original language||English (US)|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Jan 9 2017|
Bibliographical noteFunding Information:
ACKNOWLEDGMENTS. We thank Benjamin Stottrup, Todd Squires, David Morse, Ka Yee Lee, and Sarah Keller for their insights into monolayer morphology and dynamics, and Lynn Walker, Shelley Anna, and their students for their help in building the experimental apparatus and an introduction to dilatational rheology. High-speed confocal imaging was done at the University of Minnesota Imaging Center. We acknowledge support from National Institutes of Health Grants HL 51177 and HL 135065 and National Science Foundation Grant CBET 170378.
- Capillary pressure
- Palmitic acid