ISS: Wicking in gel-coated tubes

Surfactant replacement therapies rely on plugs of liquid to carry drugs into the lungs and treat respiratory distress syndrome. The administered liquid plugs travel through airways lined with mucus, a gel that traps inhaled contaminants. The deposition of liquid in the airways is often held responsible for therapeutic failures, yet the influence of the mucus lining on drug delivery remains to be understood.

This NSF-CASIS project will conduct experiments onboard the International Space Station (ISS) and on Earth to establish the role of a gel lining in the transport of a liquid plug. The team will examine and explain how the gel's mechanical properties affect the liquid delivery in gravity and microgravity conditions to study the different plug dynamics at high resolution.

This project will provide a unique opportunity to train and encourage students and community members to think about biological systems as a source of inspiration for engineering design, in part through ongoing collaborations with the Santa Barbara Zoo and the City of Riverside's Ameal Moore Nature Center.

This project aims to develop a comprehensive understanding of free and forced liquid imbibition through gel-coated tubes. The project will investigate how dissipation in the viscoelastic gel at the moving contact lines influences (i) the macroscopic rate of transport of the plug and (ii) the fluid deposition at its trailing edge. The project accomplishes these goals with a combination of extensive experimental and theoretical investigations.

The research team will use a model system consisting of a transparent tube lined with a clear gel to image the motion of the liquid and the deformation of the gel. Onboard the ISS, the liquid will spontaneously imbibe the gel-coated tube due to capillarity, while in Earth experiments, gravity will drive its motion in addition to capillary wicking. The team will then develop predictive models for the transport of liquid plugs in small and large ducts, accounting for both the local viscoelastic dissipation in the gel at the moving contact lines and the global viscous dissipation in the viscous fluid plug.

This work will provide new insights into the delivery of drugs in the lungs to support improved treatment strategies; the results may also lead to engineering solutions for intermittent flows in pipes.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.