  Switchable adhesives have the potential to improve the manufacturing and
recycling of parts and to enable new modes of motility for soft robots. Here,
we demonstrate magnetically-switchable adhesion of a two-phase composite to
non-magnetic objects. The composite's continuous phase is a silicone elastomer,
and the dispersed phase is a magneto-rheological fluid. The composite is simple
to prepare, and to mould to different shapes. When a magnetic field is applied,
the magneto-rheological fluid develops a yield stress, which dramatically
enhances the composite's adhesive properties. We demonstrate up to a nine-fold
increase of the pull-off force of non-magnetic objects in the presence of a 250
mT field.
