Materials with Janus structures have attracted significant attention in recent years.

Although Janus films of different compositions have been commonly utilized to develop moisture actuators due to the different capabilities of swelling in materials, a sole material with a distinct structural design is also able to provide moisture-actuation. In this study, we simply used graphene oxide (GO) to fabricate a sole GO film with an asymmetric structure which consisted of a wavy layer and a smooth layer. Due to the asymmetric structure and excellent hygroscopicity of the GO material, the asymmetric graphene oxide (AGO) film (2.5 × 0.5 cm2) was responsive to moisture and showed a maximum bending angle change of ≈1800° as the relative humidity (RH) changed. Compared with other reports about moisture actuators, the AGO film exhibited a superior bending capability. Furthermore, we propose a novel mechanism for moisture actuation of the AGO film based on our detailed observations, and a wavy structure has been introduced for showing great potential in bending deformation. Finally, the AGO film was used as a grabber to grab a leaf and it exhibited good capability to twine around a plastic rod. This work provides a novel pathway for the development of moisture-responsive materials for potential applications in robotics, artificial muscles and switches.

In recent years, Janus materials have become a research hotspot in the field of materials science; however, fabricating inorganic Janus-like nanofibers (NFs) is still a challenge. Herein, we report novel ZnO/NiO Janus-like NFs with efficient photocatalytic performance via an electrospinning method followed by calcination treatment. The morphology, structure, chemical composition and crystallinity of ZnO/NiO Janus-like NFs were studied in detail via SEM, TEM, HRTEM, EDS, FT-IR, XPS and XRD, indicating that the NFs had a perfect Janus-like structure composed of ZnO and NiO. A series of photocatalytic experiments were carried out in aqueous organic dye solutions under 365 nm UV radiation for 1 h, with the degradation rate of malachite green able to reach 96%, proving that the NFs have great potential in the field of organic dye degradation. Furthermore, a reasonable catalytic mechanism for the ZnO/NiO Janus-like NFs was proposed, which was discussed from the view of electron-hole pairs and p-n junctions. In short, the method in our work is expected to become a new way of effectively preparing functional inorganic Janus-like NFs.