  The manipulation of small objects with light has become an indispensable tool
in many areas of research ranging from physics to biology and medicine. Here we
demonstrate how to implement micro-manipulation at the optimal level of
efficiency for targets of arbitrary shape and inside complex environments such
as disordered media. Our approach is to design wave-fronts in the far-field
that have optimal properties in the near-field of the target such as to apply
to it the strongest possible force, pressure or torque as well as to achieve
the most efficient focus at the target position. Free of any iterative
optimization, our approach only relies on a simple eigenvalue problem
established from the scattering matrix of the system and its dependence on the
target parameters. To illustrate this theoretical concept, we perform a
proof-of-principle experiment in the microwave regime, which fully confirms our
predictions.
