  We study an elastic filament beating in a viscous fluid with
curvature-dependent bending stiffness. Our numerical and experimental
investigations reveal that such differential stiffness can sustain planar
bending waves far along flexible filaments. In particular, basal actuation is a
viable, parsimonious mechanism for generating high-amplitude planar bending
waves, in stark contrast to the uniform-stiffness case. Further, the resulting
beat patterns closely resemble the power-and-recovery strokes of propulsive
biological filaments, suggesting applications in robotic and engineered
systems.
