Fig. 1. Liquid crystal polymer mechanisms for actuation and material intelligence. （a） Schematic of the conditional switching of optical properties of liquid crystals with electrical stimuli in the （i） off- and the （ii） on- state， labelled with typical potential differences used in the liquid crystal display industry^［47-48］. （b） Overview of liquid crystal polymerization with the （i） structural formulae of a typical reactive mesogen molecule， marked with its polymerizable functional group and rigid core that enables in-situ photopolymerization and alignment， respectively； （ii） a schematic of the formation of cross-links between aligned reactive mesogens during the in-situ photopolymerization process^［10］. （c） Schematic of the alignment-based deformation mechanism for liquid crystal polymers， annotated with the stimuli-responsive contraction and expansions with respect to the molecular alignment director， n^^［68］. （d） Images and schematics of liquid crystal polymer alignment techniques that include both （i） nm-resolution photomask-based lithography techniques^［53］ and （ii） mechanically-induced alignment. （e） Examples of liquid crystal polymer actuation in replication of the （i） bending and （ii） twisting actions of biological muscles， with a visualization of the corresponding liquid crystal alignment displayed next to the image. Light-responsive actuation is used to show the ability of liquid crystal polymer materials to surpass the options for stimuli that biological muscles have^［60］. （f） Schematic of the self-regulated feedback loop established by an LCP actuator component within a Joule-heating hybrid circuit^［67］.

Fig. 2. Liquid crystal polymer learning and forgetting mechanisms. （a） Schematic illustration of the associative learning of a liquid crystal polymer material， where the conditioning of the material replicates the conditioning of dogs in Pavlov’s iconic experiments^［27］. （b） Schematic of implicit memory behavior in SP-LCNs： （i） initial state； （ii） response to electric actuation stimuli with no loaded memory； （iii） implicit memory loading through the UV-gated SP-to-MC transition within the LCN material； （iv） memorized increase to responsiveness to electric actuation stimuli； （v） memory erasure to restore standard response to electric actuation stimuli via heating or green light illumination to promote the MC-to-SP transition， （vi） UV illumination to reload forgotten implicit memory to reinstate increased responsiveness to electric actuation stimuli^［41］. （c） Liquid crystal polymer feature-based switching intelligence shown in （i） scanning electron microscopy （SEM） measurements of a thermally-activated micro-gap switch of about 6 µm， with scale bars indicating 100 and 30 µm in the left and right images， respectively； （ii） the switching mechanism is further visualized in a 3D illustration^［42］. （d） Graphical and illustrative representations of memory-erasure methods in liquid crystal polymers in the form of （i） merocyanine-to-spiropyran relaxation and （ii） conditional thermal and response electrical stimuli removal^［42］. （e） Graphical representation of the control and acceleration of liquid crystal polymer memory-erasure with a green-light ‘forgetting’ agent^［42］.

Fig. 3. Prospective applications of liquid crystal polymer material intelligence. （a） Comparison of human heart functions with liquid crystal polymer self-regulated oscillation in （i） graphical representation of liquid crystal polymer self-regulated， electrically-driven oscillation^［67］ and （ii） electrocardiogram of a healthy human heart^［84］； （b） Examples of polysiloxane-based heart valve implants that have been used commercially in the medical sector^［73］； （c） Examples of capsule endoscopic systems that are not capable of self-propulsion or navigational， which can possibly be supplemented with liquid crystal polymer actuators^［75］； （d） Schematic of a conceptual navigational liquid crystal polymer wearable haptic technology guiding a user across a complicated traffic junction with a combination of nature-like squeeze， shear and friction functions； （e） Illustration of the nature-like haptics transferrable with wearable liquid crystal polymer haptic technology for virtual communication.