• Capillary elastic instabilities with applications to airway closure
  
• Thin film instabilities and pattern formation
  
• Surfactant spreading in thin liquid layers
  
• Airway reopening mechanics
  
• Evolution of gas bubbles in the circulation with applications to the bends
  
• Motion of red blood cells in the microcirculation
  
• Gas dispersion
  

Surfactant spreading on thin liquid layers

Pulmonary surfactant is a vital component of the liquid layer that lines lung airways and alveoli because, by reducing the surface tension at the air-liquid interface, it helps to maintain high lung compliance and to retard the surface-tension-driven instabilities that lead to airway closure. Since the lungs of prematurely born infants may not produce sufficient quantities of natural surfactant, a substitute may be delivered to them, either by inhalation of an aerosol or by direct intratracheal instillation. The delivered surfactant spreads throughout the lung under the action of gravity, surface-tension gradients and surface diffusion.

Halpern, D. and Grotberg, J.B. Dynamics and transport of a localized soluble surfactant on a thin film. J. Fluid Mech. 237: 1-11, 1992. 

Jensen, O.E., Halpern, D. and Grotberg, J.B. Transport of a passive solute by surfactant-driven flows. Chem. Eng. Sci. 49(8): 1107-1117, 1994. 

Grotberg, J.B., Halpern, D. and Jensen, O.E. The interaction of exogenous and endogenous surfactant: spreading-rate effects. J. Applied Physiology 78: 750-756, 1995. [Abstract] [PDF]

Halpern, D., Jensen, O.E. and Grotberg, J.B. A theoretical study of surfactant and liquid delivery into the lung. J. Applied Physiology 85: 333-352, 1998. [Abstract] [Full Text] [PDF]

Jensen, O.E. and Halpern, D. The stress singularity in surfactant-driven-film flows. Part 1. Viscous effects. J. Fluid Mech. 372: 273-300, 1998.

Halpern, D., Bull, J.L. and Grotberg The effect of Airway Wall Motion on Surfactant Delivery.   J. Biomech.l Eng. 126(4): 410-419, 2004.