Soft robots have the appealing advantages of being highly flexible and adaptive to complex environments. However, the low‐stiffness nature of the constituent materials makes soft robotic systems incompetent in tasks requiring relatively high load capacity. Despite recent attempts to develop stiffness‐tunable soft actuators by employing variable stiffness materials and structures, the reported stiffness‐tunable actuators generally suffer from limitations including slow responses, small deformations, and difficulties in fabrication with microfeatures. This work presents a paradigm to design and manufacture fast‐response, stiffness‐tunable (FRST) soft actuators via hybrid multimaterial 3D printing. The integration of a shape memory polymer layer into the fully printed actuator body enhances its stiffness by up to 120 times without sacrificing flexibility and adaptivity. The printed Joule‐heating circuit and fluidic cooling microchannel enable fast heating and cooling rates and allow the FRST actuator to complete a softening–stiffening cycle within 32 s. Numerical simulations are used to optimize the load capacity and thermal rates. The high load capacity and shape adaptivity of the FRST actuator are finally demonstrated by a robotic gripper with three FRST actuators that can grasp and lift objects with arbitrary shapes and various weights spanning from less than 10 g to up to 1.5 kg.

Miniature soft robots offer excellent safety and deformability, which are highly desirable in applications such as navigation in confined areas or the manipulation of microscale objects. However, it is difficult to manufacture such robots using traditional processes due to the complexity of their design. While rapidly advancing 3D printing technologies offer manufacturing flexibility, it is still challenging to fabricate soft pneumatic robots on millimeter scales due to the difficulty in making microscale voids and channels, which are essential for pneumatic actuation. A generic process flow for systematic and efficient tailoring of the material formulation and key processing parameters for digital light processing‐based 3D printing of miniature pneumatic actuators for soft robots is presented. The process flow includes selection of photoabsorber and material performance characterization to determine the appropriate material formulation and characterizations for curing depth and XY fidelity to identify the combination of exposure time and sliced layer thickness. By applying the tailored results to a self‐built multimaterial 3D printing system, an assortment of miniature soft pneumatic robots with various structures and morphing modes are printed. Furthermore, potential applications of printed miniature actuators are exemplified by a soft debris remover that navigates in a confined space and collects small objects in a hard‐to‐reach position.

Vitrimers, a type of dynamically crosslinked polymers that combine the solventand heat-resistance of thermosets with the reprocessability of thermoplastics, offer a new solution to the problem of plastic pollution. However, the current recycling approaches of vitrimers greatly constrain the shapes of recycled vitrimers to simple geometries, thus significantly limiting the application scopes of recycled vitrimers. Here, a simple but universal method for upcycling vitrimer wastes is reported by developing a UV curable recycling (UVR) solution system. Conventional unprintable vitrimer powders can be mixed with the UVR solution, and the resulting mixture is compatible with digital light processing based 3D printing to fabricate 3D structures with high resolution (up to 20 µm) and high geometric complexity. Heat treatment triggers bond exchange reactions in the printed structures, and greatly enhances the mechanical properties. This method allows to cyclically print vitrimer wastes multiple times. Moreover, the UVR-vitrimer mixture solution can work as an adhesive to bond printed small parts together to build a larger and more complex structure which cannot be printed. The upcycling method reported in this work extends the application scope of recycled vitrimers and provide a practical solution to address environmental challenges associated with plastic pollution.

In article number 2007772, Xiaoyang Zhu, Hongbo Lan, and co‐workers develop a maskless, templateless, and plating‐free fabrication approach for high‐performance flexible transparent electrodes with an embedded silver mesh by combining electric‐field‐driven microscale 3D printing and hybrid hot‐embossing. The fabricated flexible, transparent electrode exhibits excellent photoelectric properties, remarkable mechanical stability, and environmental adaptability.

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