  Liquid crystal elastomers (LCEs) are a stimuli-responsive material which has
been intensively studied for applications including artificial muscles, shape
morphing structures, and soft robotics, due to its capability of large,
programmable, and fully reversible strains. To fully take advantage of LCEs,
rapid, untethered, and programmable actuation methods are highly desirable.
Here, we report a liquid crystal elastomer-liquid metal (LCE-LM) composite,
which enables ultrafast actuations and high heating programmability by eddy
current induction heating. The composite consists of LM sandwiched between two
3D-printed LCE layers via direct ink writing (DIW). When subject to a
high-frequency alternating magnetic field, the composite can be actuated in
milli-seconds. By moving the magnetic field, the eddy current can be spatially
controlled for selective actuation. Additionally, sequential heating is
achievable by programming the LM thickness distribution in a specimen. With
these capabilities, the LCE-LM composite is further exploited for multimodal
deformation of a pop-up structure, on ground omnidirectional robotic motion, in
water targeted object manipulation, and crawling.
