  We study the dynamics of an oscillating, free-floating robot that generates
radially expanding gravity capillary waves at a fluid surface. In open water,
the device does not self-propel; near a rigid boundary, it can be attracted or
repelled. Visualization of the wave field dynamics reveals that when near a
boundary, a complex interference of generated and reflected waves induces a
wave amplitude fluctuation asymmetry. Attraction increases as wave frequency
increases or robot-boundary separation decreases. Theory on confined
gravity-capillary wave radiation dynamics developed by Hocking in the 1980s
captures the observed parameter dependence due to these "Hocking fields." The
flexibility of the robophysical system allows detailed characterization and
analysis of locally generated nonequilibrium fluctuation-induced forces [M.
Kardar and R. Golestanian, Rev. Mod. Phys. 71, 1233 (1999)].
