Abstract:   Human lung airways are lined with a thin layer of mucus which acts as a protective barrier against foreign particles which enter the lungs. Cilia lining the lung pathways beat in a synchronized fashion to create a metachronal wave which drives the mucus layer toward the larynx. Understanding mucociliary clearance is critical for the advancement of therapies and drugs for those who suffer from cystic fibrosis, genetic disease, and environmental diseases such as chronic obstructive pulmonary disease (COPD) and asthma. This project explores stress communication throughout a mucus layer from a frequency-dependent flat source, and the potential tuning of mucus viscoelasticity and layer height to the source frequency and amplitude to enhance stress transmission across the layer. A computational model of the mucus layer using the fluid flow equations corresponding to balance of momentum simulates the experimental conditions: the mucus layer is trapped between two parallel plates, and the bottom plate is driven at a specific frequency. The model allows one to explore stress communication versus mucus material properties, thickness, and plate controls. We found that boundary normal stresses are strongly peaked at specific frequencies and minimized at others; the peak and valley frequencies appear to be higher harmonics of a fundamental resonant frequency. These results reveal a striking frequency-selection mechanism for optimal and minimal stress communication within a driven viscoelastic layer. This suggests that cilia beat frequency and relaxation times of mucus can be tuned to either amplify or attenuate the generation of normal stresses in a mucus layer. Further studies are needed to gain a better understanding of the relationships between mucus properties and stress transmission, and whether these stress levels are indeed capable of regulating cell biochemical feedback loops. Furthermore, future enhanced models will allow simulations of the effects of drugs and therapies for transport of the mucus layer and for stress communication across the mucus layer.