UNC PHYSICS AND ASTRONOMY COLLOQUIUM
Rich Superfine, UNC-CH
“The Physics that Keeps Your Lungs Clean”
The lung maintains an air/blood interface with a surface area the size of half a tennis court. This huge surface area presents a challenge to physiology to maintain a sterile environment in the presence of continual assaults from inhaled environmental pathogens. The body is successful by secreting a layer of mucus, a viscoelastic polymeric fluid, onto the epithelial surface to trap dust and unwanted visitors. This mucus filter is then changed through the continual upward flow due to beating cilia and cough. We are attempting to understand each aspect of this process through biophysical measurements and through the development of engineered biomimetic systems. Using a magnetic microbead assay, we have measured the force developed by individual lung cilia. To understand the response of the mucus, we measure the fluid rheology using driven microbead rheology that reveals the strain thickening behavior due to high shear rates at the surface of micro and nano sized structures. To understand the flows generated by carpets of cilia, we have engineered artificial cilia at the size scale of their biological counterparts and have observed directed flow and enhanced mixing in actuated arrays. Finally, we are challenging our understanding of cilia-generated flows by performing microscopy on the flow of mucus on cell cultures that are tilted so that they need to push mucus upwards – against gravity. This is leading us to consider new boundary conditions that explain the flows in tilted channels. Altogether, our efforts at quantifying the forces that successfully generate flow, from quantitative study of biology to engineered systems that mimic biological pumping, is moving towards a full model of cilia driven flows.