The vocal folds are a complex self-oscillating biological system. In the current research, an equation was developed to model viscous adhesion forces that occur when the collision of the vocal folds results in the formation of a liquid bridge. The adhesion equation was validated using experimental data, and simplified to a one-dimensional approximation with an included correction factor that adjusted the predicted pressure in situations where the one-dimensional approximation was invalid. A non-oscillating vocal fold model with a modeled liquid bridge was used to study stress resulting from viscous adhesion. The vertical normal stress magnitude ranged from about 80 to 1700 Pa. This was shown to be of the same order of magnitude as the stress due to collision of the vocal folds. Also the stress resulted in large normal strains that occurred at small distances below the surface of the vocal folds consistent with lesion development. Therefore, it was determined that the viscous adhesion may be a contributor to damage of the vocal folds that leads to the development of benign lesions, such as vocal nodules. This conclusion was further validated by adding the adhesion equation in a self-oscillating vocal fold model. The influence of adhesion on the dynamics of the model was significant. The frequency of vibration was reduced by nearly 2.5% for the case of adhesion with a mucus viscosity of 0.01 Pa-s. Also adhesion induced positive tensile stress that resulted in normal strain distributions similar to those seen in the non-oscillating cases. These results also indicated that liquid mediated viscous adhesion may be a contributor to the development of benign lesions (nodules). However, further research is needed to validate these conclusions.



College and Department

Ira A. Fulton College of Engineering and Technology; Mechanical Engineering



Date Submitted


Document Type





vocal folds, adhesion, airway surface liquid, liquid bridge, mucus, intraglottal pressure