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A facile and cost-effective preparation of moisture-responsive graphene bilayer paper by focused sunlight irradiation is reported. The smart graphene paper shows moisture-responsive properties due to selective adsorption of water molecules, leading to controllable actuation under humid conditions. In this way, graphene-based moisture-responsive actuators including a smart claw, an orientable transporter, and a crawler paper robot are successfully developed.

Inspired by natural autonomous systems that demonstrate controllable shape, appearance, and actuation under external stimuli, a facile preparation of moisture responsive graphene‐based smart actuators by unilateral UV irradiation of graphene oxide (GO) papers is reported. UV irradiation of GO is found to be an effective protocol to trigger the reduction of GO; however, due to the limited light transmittance and thermal relaxation, thick GO paper cannot be fully reduced. Consequently, by tuning the photoreduction gradient, anisotropic GO/reduced GO (RGO) bilayer structure can be easily prepared toward actuation application. To get better control over the responsive properties, GO/RGO bilayer paper with a certain curvature and RGO patterns are successfully prepared for actuator design. As representative examples, smart humidity‐driven graphene actuators that mimic the cilia of respiratory tract and tendril climber plant are successfully developed for controllable objects transport.

Reported here is femtosecond laser mediated bandgap tailoring of graphene oxides (GOs) for direct fabrication of graphene-based microdevices. When femtosecond laser pulses were used to reduce and pattern GO, oxygen contents in the reduced region could be modulated by varying the laser power. In this way, the bandgap of reduced GO was precisely modulated from 2.4 to 0.9 eV by tuning the femtosecond laser power from 0 to 23 mW. Through the first-principle study, the essence of GO bandgap tailoring is proved to be femtosecond laser reduction induced oxygen-content modulation. As representative illustrations, bottom-gate graphene FETs were fabricated in situ by using femtosecond laser reduced GO as the channel material, and an optimized room temperature on–off ratio of 56 is obtained. The controlled reduction of GO by femtosecond laser contributes great potential for bandgap tailoring and microdevices patterning of graphene toward future electronics.

4595 www.MaterialsViews.com wileyonlinelibrary.comsurfaces such as self-cleaning, anti-icing, anti-corrosion, and drag reduction, [ 3 ] great efforts have been devoted to the manufacturing of superhydrophobic surfaces based on a wide range of materials, including metal, metal oxides, polymer, carbon and even biomaterials. [4][5][6][7] It is well known that two factors govern the wettability of solid surfaces, one is geometrical microstructure, and the other one is chemical composition. [ 8,9 ] According to this basic principle, artifi cial superhydrophobic surfaces have been readily prepared by the combination of the as-mentioned two factors. Generally, the microstructuring with respect to hierarchical roughness could be realized with the help of various micronanofabrication techniques, represented by classical "bottom-up" approaches (e.g., Langmuir-Blodgett technique, Layer-by-layer assembly) [10][11][12] and "top-down" method (e.g., lithography, tip-technique); [ 13,14 ] while the tuning of surface energy with respect to the surface chemical composition usually resorts to covalent grafting of guest molecules (e.g., fl uorinated silane) or coating with low-surface-energy materials. [ 15 ] To date, despite the fact that artifi cial superhydrophobic surfaces have already revealed a cornucopia of both fundamental research and practical applications, continued efforts in endowing novel materials with unique dewetting property are still highly required to realize their structural and functional integrity.Considering the fact that graphene exhibits outstanding electrical, optical, thermal, and mechanical properties, [16][17][18] which are promising for a wide range of scientifi c fi elds, [ 19,20 ] fabrication of micro-structured graphene fi lms with unique superhydrophobicity is of great interest from the viewpoint of both experimental research and practical applications. Notably, the combination of graphene with superhydrophobicity would not only bring new opportunities for the development of novel graphene-based devices with remarkable performance, but also enable additional applications such as micro-droplet manipulation, anti-biofouling substrates, responsive switching and sensitive surface protection. [ 21 ] The attractive prospect of this dynamic fi eld has motivated considerable efforts to develop superhydrophobic graphene fi lms that feature refi ned control over surface wettability. For instance, Koratkar et al., successfully tune the Reported here is a bioinspired fabrication of superhydrophobic graphene surfaces by means of two-beam laser interference (TBLI) treatment of graphene oxide (GO) fi lms. Microscale grating-like structures with tunable periods and additional nanoscale roughness are readily created on graphene fi lms due to laser induced ablation effect. Synchronously, abundant hydrophilic oxygencontaining groups (OCGs) on GO sheets can be drastically removed after TBLI treatment, which lower its surface energy signifi cantly. The synergistic effect of micro-nanostructuring and the OCGs removal en...

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Silver microflower arrays constructed by upright nanoplates and attached nanoparticles were fabricated inside a microfluidic channel, thus a robust catalytic microreactor for allowing in situ SERS monitoring was proposed. On-chip catalytic reduction shows that the silver microflowers have high catalytic activity and SERS enhancement.

The wonderful world of graphene! A simple one‐step fabrication of biomimetic graphene surfaces that possess both superhydrophobicity and bright structural color is presented. By using two‐beam laser interference, construction of periodic grating microstructures and removal of hydrophilic oxygen groups were realized at the same time.