ENG: Researchers at the University of Colorado Boulder are developing a new approach to aerodynamic flow control that uses engineered microscopic vibrations beneath an aircraft’s surface. Led by Mahmoud I. Hussein, the work focuses on phononic subsurfaces (PSubs), specially designed materials that interact passively with airflow without changing the external shape of a wing or fuselage. By controlling tiny internal vibrations known as phonons, these subsurfaces could delay the transition from laminar to turbulent flow, potentially reducing aerodynamic drag and improving fuel efficiency in commercial and high-speed aircraft.