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Covalent adaptable networks (CANs) represent a novel covalently cross-linked polymer that is capable of being reprocessed and recycled relying on reversible covalent bond structures and present exceptional opportunities in a wide range of prospective applications. However, it is genuinely difficult to fabricate bulk CAN blocks with solid-core geometries that possess complex shapes or multiple materials, which are crucial in cutting-edge fields such as soft robotics, flexible electronic devices and biomedical engineering. Here we report a welding technique to strategically construct complex and heterogeneous 3D CAN structures by utilizing a solder doped with magnetic nanoparticles. The solder is able to induce a bond exchange reaction at the interface between the to-be-welded pieces. Using this method, not only CAN bulks with the same materials can be welded to form complex geometries, distinctive bulks with different physical properties and chemical compositions can also be connected to fabricate multimaterial devices. Besides, this method can be used to repair damaged CAN materials and efficiently recycle scrap CAN materials, which can effectively save resources and protect the environment. The universality and robustness of this strategy is expected to promote CAN application in broader functional polymer fields.

Liquid-crystalline elastomers (LCEs) are excellent soft actuator materials for a wide range of applications, especially the blooming area of soft robotics. For entirely soft LCE robots to exhibit high dexterity and complicated performance, several components are typically required to be integrated together in one single robot body. Here, we show that seamless multicomponent/multimaterial three-dimensional (3D) LCE robots can be created via simultaneously welding and aligning LCE materials with different chemical compositions and physical properties without other additives such as tapes and glues (just like metal welding). Both welding and aligning of the LCE materials rely on thermal polymerization of preformed LCE films with reactive acrylate groups. This method provides an easy way to robustly fabricate arbitrary 3D desirable geometries with strongly stable reversible actuations and multifunctionalities, which greatly enlarges and benefits the future applications and manufacturing of LCE soft robots.

Conductive structures determine the functions and actuation modes of electrically responsive soft actuators. The rewritability of conductive structures is highly desirable but has not been realized in electro‐driven actuators. Typically, once conductive pathways are established, they can hardly be modified; thus, the function of the actuator is permanently fixed. In this study, poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is developed as a rewritable conductive coating for actuators composed of liquid crystalline elastomers (LCEs). This enables reconfigurable, adaptive, and precisely controllable electro‐driven motions and the repeated use of the same actuator for various purposes without disposal. Moreover, different PEDOT:PSS layers can be coated onto different regions, thus enabling the assembly of different actuation behaviors in a monolithic actuator under a single input voltage. Unlike all previously reported soft actuators that respond to electricity and light, opposite shape changes in an actuator with a series circuit can be performed under these two stimuli. Furthermore, when combining LCEs with dynamic covalent bonds, the PEDOT:PSS‐coated LCE (PEDOT:PSS‐LCE) actuator can be reprogrammed based on two different mechanisms: rewriting the conductive PEDOT:PSS patterns and re‐aligning the LCEs. This versatile method can be adapted to other types of actuators. [ABSTRACT FROM AUTHOR]

Thermal reprogrammability is essential for new-generation large dry soft actuators, but the realization sacrifices the favored actuation performance. The contradiction between thermal reprogrammability and stability hampers efforts to design high-performance soft actuators to be robust and thermally adaptable. Now, a strategy has been developed that relies on repeatedly switching on/off thermal reprogrammability in liquid-crystalline elastomer (LCE) actuators to resolve this problem. By post-synthesis swelling, a latent siloxane exchange reaction can be induced in the common siloxane LCEs (switching on), enabling reprogramming into on-demand 3D-shaped actuators; by switching off the dynamic network by heating, actuation stability is guaranteed even at high temperature (180 °C). Using partially black-ink-patterned LCEs, selectively switching off reprogrammability allows integration of completely different actuation modes in one monolithic actuator for more delicate and elaborate tasks., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)