No abstract

Nastic movements in plants that occur in response to environmental stimuli have inspired many man-made shape-morphing systems. Tendril is an exemplification serving as a parasitic grasping component for the climbing plants by transforming from a straight shape into a coiled configuration via the asymmetric contraction of internal stratiform plant tissues. Inspired by tendrils, this study using a three-dimensional (3D) printing approach developed a class of soft grippers with preprogrammed deformations being capable of imitating the general motions of plant tendrils, including bending, spiral, and helical distortions for grasping. These grippers initially in flat configurations were tailored from a polymer-paper bilayer composite sheet fabricated via 3D printing a polymer on the paper substrate with different patterns. The rough and porous paper surface provides a printed polymer that is well-adhered to the paper substrate which in turn serves as a passive strain-limiting layer. During printing, the melted polymer filament is stretched, enabling the internal strain to be stored in the printed polymer as memory, and then it can be thermally released, which will be concurrently resisted by the paper layer, resulting in various transformations based on the different printed geometries. These obtained transformations were then used for designing grippers to grasp objects with corresponding motions. Furthermore, a fully equipped robotic tendril with three segments was reproduced, where one segment was used for grasping the object and the other two segments were used for forming a tendril-like twistless spring-like structure. This study further helps in the development of soft robots using active polymer materials for engineered systems.

Li−O 2 batteries provide high-capacity energy storage, but for aprotic Li−O 2 batteries, it is reported that the charge−discharge efficiency is ultimately limited by the crystal growth of insoluble Li 2 O 2 on the porous cathode. Catalysts have been reported to improve the nucleation and morphology of Li 2 O 2 , which helps achieve high energy densities. We provide a new insight into the catalytic mechanism of the oxygen reduction reaction (ORR) in aprotic Li−O 2 batteriesthe oxygen sites on the surface play a more important role than the exposed metal sitesvia a study based on the density functional theory (DFT) examining α-MnO 2 surfaces. Lithium ions from electrolytes are found to interact with the surface oxygen sites and form surface lithium sites, facilitating further growth of Li 2 O 2 . A larger number of initial growth points with uniform distribution makes Li 2 O 2 well dispersed, forming small particles, which benefit both the ORR and oxygen evolution reactions (OER). This design concept for oxygen sites has been successfully validated by the real Li−O 2 cell experiments with α-MnO 2 nanowire cathodes.

The beam steering mechanism has been a key element for various applications ranging from sensing and imaging to solar tracking systems. However, conventional beam steering systems are bulky and complex and present significant challenges for scaling up. This work introduces the use of soft deployable reflectors combining a soft deployable structure with simple kirigami/origami reflective films. This structure can be used as a macroscale beam steering mechanism that is both simple and compact. This work first develops a soft deployable structure that is easily scalable by patterning of soft linear actuators. This soft deployable structure is capable of increasing its height several folds by expanding in a continuous and controllable manner, which can be used as a frame to deform the linearly stretchable kirigami/origami structures integrated into the structure. Experiments on the reflective capability of the reflectors are conducted and show a good fit to the modeling results. The proposed principles for deployment and for beam steering can be used to realize novel active beam steering devices, highlighting the use of soft robotic principles to produce scalable morphing structures.

This study introduces a facile and novel route to synthesize the N + Ni codoped anatase TiO2 nanocrystals with exposed {001} facets through two‐step hydrothermal reaction. The microstructures, chemical compositions, and photocatalytic properties of the codoped TiO2 were characterized using X‐ray diffractometer, high‐resolution transmission electron microscopy, X‐ray photoelectron spectroscopy, UV‐vis spectrometry, and photoluminescence emission spectra. The experimental results revealed that (i) the elements N and Ni have been successfully codoped into the anatase TiO2 with exposed {001} facets; (ii) the size of the TiO2 reached to a narrow range of 5–15 nm; (iii) the codoped TiO2 exhibited an additional visible light absorption band from 400 to 500 nm, which greatly improved the photocatalytic activity. The theoretical calculations for band structure and total energy also provided a good explanation for the experimental results.