  Waves impart momentum and exert force on obstacles in their path. The
transfer of wave momentum is a fundamental mechanism for contactless
manipulation, yet the rules of conventional scattering intrinsically limit the
radiation force based on the shape and the size of the manipulated object.
Here, we show that this intrinsic limit can be overcome for acoustic waves with
subwavelength-structured metasurfaces, where the force becomes controllable by
the arrangement of surface features, independent of the object's overall shape
and size. Harnessing such anomalous metasurface scattering, we demonstrate
complex actuation phenomena: self-guidance, where a metasurface object is
autonomously guided by an acoustic wave, and contactless pulling, where a
metasurface object is pulled by the wave. Our results show that bringing
metasurface physics, and its full arsenal of tools, to the domain of mechanical
manipulation opens the door to diverse actuation mechanisms that are beyond the
limits of traditional wave-matter interactions.
