A microfluidic model to study fluid dynamics of mucus plug rupture in small lung airways

TLDR: A microfluidic model to study mucus plug rupture in a collapsed airway of the 12th generation shows that a plug needs to overcome yield stress before deformation and rupture, and shows that it takes relatively long time to yield at the high Bingham number.

Abstract: Fluid dynamics of mucus plug rupture is important to understand mucus clearance in lung airways and potential effects of mucus plug rupture on epithelial cells at lung airway walls We established a microfluidic model to study mucus plug rupture in a collapsed airway of the 12th generation Mucus plugs were simulated using Carbopol 940 (C940) gels at concentrations of 015%, 02%, 025%, and 03%, which have non-Newtonian properties close to healthy and diseased lung mucus The airway was modeled with a polydimethylsiloxane microfluidic channel Plug motion was driven by pressurized air Global strain rates and shear stress were defined to quantitatively describe plug deformation and rupture Results show that a plug needs to overcome yield stress before deformation and rupture The plug takes relatively long time to yield at the high Bingham number Plug length shortening is the more significant deformation than shearing at gel concentration higher than 015% Although strain rates increase dramatically at rupture, the transient shear stress drops due to the shear-thinning effect of the C940 gels Dimensionless time-averaged shear stress, T xy , linearly increases from 37 to 56 times the Bingham number as the Bingham number varies from 0018 to 01 The dimensionless time-averaged shear rate simply equals to T xy /2 In dimension, shear stress magnitude is about one order lower than the pressure drop, and one order higher than yield stress Mucus with high yield stress leads to high shear stress, and therefore would be more likely to cause epithelial cell damage Crackling sounds produced with plug rupture might be more detectable for gels with higher concentration