Fig. 1. Broad applications of liquid crystal elastomers. （a） Soft actuator^［12］； （b） Optical device^［13］； （c） Self-sensing system^［14］； （d） Biomedical device^［15］.

Fig. 2. Schematic diagram of macroscopic reversible deformation of liquid crystal elastomer under external stimulation

Fig. 3. Preparation strategies of liquid crystal elastomers. （a） Schematic illustration of one-step polymerization method^［24］； （b） Liquid crystal monomers are aligned through surface induction and directly photo-polymerized to fix the alignment^［13］； （c） Schematic of two-step polymerization method^［24］； （d） Thiol-acrylate Michael addition and photopolymerization reactions are used to synthesize monodomain liquid crystal elastomer^［29］； （e） Schematic diagram of dynamic covalent network method^［24］； （f） Polydomain liquid crystal elastomer is programmed into monodomain state by dynamic covalent bond exchange reaction^［6］.

Fig. 4. Manufacturing process of liquid crystal elastomers. （a） Preparation of liquid crystal elastomer using customized mold^［59］； （b） Preparation of liquid crystal elastomer with 3D structure by pre-stretching substrate^［62］； （c） Direct ink writing 3D printing technology^［73］； （d） Digital light processing 3D printing technology^［78］.

Fig. 5. Crawling motion mode. （a） Electric controlled continuous crawling of liquid crystal elastomer^［103］； （b） A liquid crystal elastomer soft robot crawls through narrow space^［104］； （c） Crawling of liquid crystal elastomer-based untethered robot^［105］； （d） Crawling of liquid crystal elastomer soft robots on a curved surface^［106］.

Fig. 6. Rolling motion mode. （a） Rolling of carbon nanotube-liquid crystal elastomer cylindrical rod on a hot surface and under illumination^［107］； （b） A rolling liquid crystal elastomer soft robot with physical intelligence escapes autonomously from complex maze^［109］； （c） Untethered self-propulsion of liquid crystal elastomer with pentagonal prism structure^［110］； （d） Multimodal self-propelled motion of hybrid tensegrity structure containing thermally responsive liquid crystal elastomer cables^［112］.

Fig. 7. Jumping motion mode. （a） Jumping motion of liquid crystal polymer network monolith under light irradiation^［113］； （b） Carbon nanotube-liquid crystal elastomer with three-leaf panel double-folded structure can achieve continuous jumping under photothermal actuation^［114］； （c） Jumping liquid crystal elastomer element with modulus gradient^［115］.

Fig. 8. Different strategies to reduce the size of liquid crystal elastomers. （a） Schematic of the electrospinning^［91］； （b） Schematic illustration of dry spinning^［123］； （c） Schematic diagram of the multi-drawdown spinning technique^［124］； （d） Preparation of ultrathin liquid crystal elastomer films using compression assisted mold-casting technology^［125］.

Fig. 9. Active heating and cooling systems in liquid crystal elastomers. （a） Introducing the microfluidic channels^［127］； （b） Integrating thermal electric devices^［128］.