This grant addresses the locomotion of swimming microorganisms near deformable and rigid interfaces. Most microorganisms spend much of their lives near interfaces such as soft biological surfaces (e.g. blood vessels, muscle tissue and the epithelium), rigid boundaries, and air-water interfaces. These surfaces may be characterized by complex topography, malleability and complex physicochemical characteristics. In addition to impacting the hydrodynamic stresses encountered by a swimming cell, these boundaries may affect the local concentration of chemical species including nutrients, oxygen levels and pH, consequently modifying the behavior of neighboring organisms. The research addresses a number of unsolved scientific problems through a combination of asymptotic analysis, numerical computations and experiments. Despite its prevalence and importance in a variety of ecosystems and medical applications, the dynamics of self-propelled microorganisms near boundaries remains largely unexplored. The investigators address a number of fundamental questions regarding the physical interactions between swimming cells and their environment. The required interdisciplinary work lies at the frontier of Engineering, Mathematical Sciences and Biology and combines theory, experiment and computation: this is a realm where the fundamental problems addressed herein are closely related to many natural phenomena and technological applications. Small scale locomotion at interfaces has important implications in microbiological applications including control and understanding of surface-associated infections (e.g. the most common hospital-acquired infection, catheter-associated bacteriuria), biofilm formation, and biodegradation (e.g. using bacteria at polluted sites to metabolize undesirable compounds). Knowledge gained through this research has the potential to impact biomedical applications and environmental technologies. For example, bacteria in biofims are more difficult to treat with antibiotics costing the U.S. billions of dollars every year in equipment damage, product contamination and medical infections. The societal benefits associated with the ability to understand and eventually suppress this type of film formation are significant. Educational impact includes the development of a new graduate-level course on biolocomotion, jointly taught by all three investigators, and the interdisciplinary training of graduate students jointly supervised by faculty in the Departments of Mathematics and Mechanical Engineering.
