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Materials that undergo shape morphing in response to external stimuli have numerous applications, e.g., in soft robotics and biomedical devices. Shape memory polymers utilize kinetically trapped states to, typically irreversibly, transfer between a programmed morphed shape and an equilibrium shape. Liquid crystal elastomers (LCEs), in turn, can undergo reversible actuation in response to several stimuli. This study combines the irreversible and reversible shape morphing processes to obtain LCEs that undergo shape‐programming via the shape memory effect and subsequent reversible actuation of the programmed shape. This is enabled by an LCE crosslinked via dynamic hydrogen bonds that break at high temperatures and reform upon cooling, endowing the shape memory effect, while mild thermal or photothermal stimulation yields the reversible actuation. Through this combination, proof‐of‐concept robotic application scenarios such as grippers that can adjust their shape for grabbing different‐sized objects and crawling robots that can morph their shape to adapt to constrained spaces, are demonstrated. It is anticipated that this work adds new diversity to shape‐programmable soft microrobotics. [ABSTRACT FROM AUTHOR]

Shape‐changing polymeric materials have gained significant attention in the field of bioinspired soft robotics. However, challenges remain in versatilizing the shape‐morphing process to suit different tasks and environments, and in designing systems that combine reversible actuation and self‐healing ability. Here, we report halogen‐bonded liquid crystal elastomers (LCEs) that can be arbitrarily shape‐programmed and that self‐heal under mild thermal or photothermal stimulation. We incorporate halogen‐bond‐donating diiodotetrafluorobenzene molecules as dynamic supramolecular crosslinks into the LCEs and show that these relatively weak crosslinks are pertinent for their mechanical programming and self‐healing. Utilizing the halogen‐bonded LCEs, we demonstrate proof‐of‐concept soft robotic motions such as crawling and rolling with programmed velocities. Our results showcase halogen bonding as a promising, yet unexplored tool for the preparation of smart supramolecular constructs for the development of advanced soft actuators. [ABSTRACT FROM AUTHOR]

Polymers with large and reversible light‐induced deformation offer a plethora of opportunities for the wireless control of small‐scale soft robots. However, their widespread adoption in real‐world applications is hindered, mainly due to their intrinsic softening upon illumination. Such limitation has detrimental effects on the achievable stress, durability, and precise positional control of the soft actuators after multiple cycles of use. Here, a synthetic rubber from a polybutadiene‐polyethylene copolymer is reported as a durable material for light‐controlled soft robots. The rubber can be programmed to exhibit various deformation modes controlled by visible‐to‐infrared light through a photothermal effect. Semi‐crystallinity of polyethylene within the rubbery network provides this material with a remarkable modulus at high temperatures (2.5 MPa at 100–140 °C), deformation repeatability (>90%) and shape‐recovery (>98%) after 100 actuation cycles subject to loads ranging from 10 to 10 000 times of its body weight (1.4 kPa–1.4 MPa). Soft robotic applications are demonstrated, such as thermally‐driven jumping and photo‐driven cargo transport carrying up to 1200 times its own weight. The results expand the portfolio of materials in designing remotely‐controlled, robust, and resilient soft robots working at small scales. [ABSTRACT FROM AUTHOR]

Snapping is an abrupt reaction, in which mechanical instability allows the structure to rapidly switch from one stabilized form to another. Snapping is attained through a sudden release of prestored elastic energy. It is perfected by natural species to enhance their preying, locomotion, and reproduction abilities. Recent developments in responsive materials research has allowed the realization of bioinspired snappers and rapidly moving soft robots triggered by external stimuli. However, it remains a grand challenge to reversibly and accurately control the snapping dynamics in terms of, e.g., onset timing and speed of motion. Here, a facile method to obtain light‐fueled snapping‐like launching with precise control over the elastic energy released and the onset timing is reported. The elastic energy is prestored in a light‐responsive liquid crystal elastomer actuator, and the launching event is dictated by releasing the energy through a photothermally induced crystal‐to‐liquid transition of a liquid‐crystalline adhesive latch. The method provides manual control over the amount of prestored energy, motion speed upon multiple launching events, and enables demonstrations such as jumping and catapult motions in soft robots and concerted motions of multiple launchers. The results provide a practical solution for controlled fast motions in soft small‐scale robotics. [ABSTRACT FROM AUTHOR]

Abstract: Liquid crystal elastomers are among the best candidates for artificial muscles, and the materials of choice when constructing microscale robotic systems. Recently, significant efforts are dedicated to designing stimuli‐responsive actuators that can reproduce the shape‐change of soft bodies of animals by means of proper external energy source. However, transferring material deformation efficiently into autonomous robotic locomotion remains a challenge. This paper reports on a miniature inching robot fabricated from a monolithic liquid crystal elastomer film, which upon visible‐light excitation is capable of mimicking caterpillar locomotion on different substrates like a blazed grating and a paper surface. The motion is driven by spatially uniform visible light with relatively low intensity, rendering the robot “human‐friendly,” i.e., operational also on human skin. The design paves the way toward light‐driven, soft, mobile microdevices capable of operating in various environments, including the close proximity of humans. [ABSTRACT FROM AUTHOR]