  Hydrogel-based soft actuators can operate in sensitive environments, bridging
the gap of rigid machines interacting with soft matter. However, while
stimuli-responsive hydrogels can undergo extreme reversible volume changes of
up to ~90%, water transport in hydrogel actuators is in general limited by
their poroelastic behavior. For poly(N-isopropylacrylamide) (PNIPAM) the
actuation performance is even further compromised by the formation of a dense
skin layer. Here we show, that incorporating a bioinspired microtube graphene
network into a PNIPAM matrix with a total porosity of only 5.4 % dramatically
enhances actuation dynamics by up to ~400 % and actuation stress by ~4000 %
without sacrificing the mechanical stability, overcoming the water transport
limitations. The graphene network provides both untethered light-controlled and
electrically-powered actuation. We anticipate that the concept provides a
versatile platform for enhancing the functionality of soft matter by combining
responsive and two-dimensional materials, paving the way towards designing soft
intelligent matter.
