Reconfigurable Three‐Dimensional Mesotructures of Spatially Programmed Liquid Crystal Elastomers and Their Ferromagnetic Composites

Abstract

Reversible programming of 3D soft mesostructures is desired for many applications including soft robotics and biomedical devices. The large, reversible shape changes of liquid crystal elastomers (LCEs), which result from the coupling between the alignment of liquid crystal (LC) molecules and the macroscopic deformation of polymer networks, have attracted much attention for such applications. Here, a facile and versatile strategy is introduced to create reconfigurable, freestanding 3D mesostructures of LCEs and magnetic LCE composites that are inaccessible with existing techniques via spatially programming LC molecules through mechanical buckling. Demonstrations include experimental and theoretical results of more than 20 reconfigurable 3D LCE mesostructures of diverse configurations, from coils and spirals to structures that resemble fences and frameworks, with characteristic feature sizes and thicknesses ranging from micro to macro. The large, reversible shape‐switching behaviors of these structures over multiple cycles are also demonstrated. An LCE gripper is shown to grab/release objects of both regular and irregular geometries. Furthermore, a robot of ferromagnetic LCE composites that simultaneously responds to magnetic and thermal stimuli for diverse biomimetic behaviors, especially crawling underneath a narrow crack, illustrates the integration of other functional materials to LCEs for multifunctional systems.

Three-dimensional thermochromic liquid crystal elastomer structures with reversible shape-morphing and color-changing capabilities for soft robotics

“…1B and C, the flower-like structure changes its color from red to colorless when being heated above 52 °C due to the thermochromic properties, and morphs from its 3D to 2D configuration when the temperature further increases because of the nematic-to-isotropic state transition. 56 Conversely, cooling the structure below the isotropic clearance temperature of LCEs and the melting point of the solvent preset in the thermochromic dye, the structure reverts to the original red color and recovers from the 2D state to its 3D shape. Please note that both the color-changing and shape-morphing behaviors are reversible.…”

“…In addition, a remotely controlled bioinspired underwater robot reported by Shahsavan H. et al 55 demonstrates the potential application of LCEs in biomimetic robotics. More recently, we developed a ferromagnetic soft robot with multiple biomimetic motion modes, 56 especially passing through a narrow crack under magnetic and thermal stimuli, which highlights the integration of multi-stimuli in the 3D LCE structure for applications in multifunctional soft robotics.…”

Shape-programmable, deformation-locking, and self-sensing artificial muscle based on liquid crystal elastomer and low–melting point alloy

“…For the concentric structure of artificial muscle, the outer LCE with stress-strain behavior comparable to natural muscle is used for reversible contraction/recovery and the inner solid LMPA with high stiffness is adopted for shape locking; the resistance change of LMPA squeezed by LCE is used for monitoring angle variation, and the melted section of LMPA that lowers material stiffness under light stimuli provides more deformation space for LCE, corresponding to the function of muscles, bones, nerves, and joint, respectively. As a result, the proposed multifunctional artificial muscle simultaneously exhibits excellent shapeprogrammable, deformation-locking, and self-sensing properties, which is not only superior in low-power consumption, high loadbearing capacity, and deformation locking with respect to LCE-based artificial muscle (31,39,(47)(48)(49)(50) but also excellent in response time, sensing function, flexible shape programmability, and reconfigurability compared with LMPA-based artificial muscle (28,30). To the best of our knowledge, an artificial muscle with these features has seldom been reported to date.…”

Locally controllable magnetic soft actuators with reprogrammable contraction-derived motions

“…What is more, in addition to LC alignment by mechanical forces and molding that we used in this work, is that other excellent methods and techniques such as surface alignment, compressive buckling, 3D printing, etc. can be used to create more complicated structures and micro-sized robots, the further application of which will surely open more opportunities (33)(34)(35). The great potential behind magnetic actuation and CAN-based LCE is waiting to be tapped further.…”

“…They can convert external stimuli into various substantial reversible actuation after installing suitable alignment of mesogens (by mechanical alignment, surface alignment, 3D printing, compressive buckling, etc.) (31)(32)(33)(34)(35). Although there were sporadic cases regarding magnetic LCE actuators reported, none of them can be reprogrammed, and the motions were very simple (36)(37)(38)(39).…”