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.

Inspired from fish scales that exhibit unique underwater superoleophobicity because of the presence of micronanostructures and hydrophilic slime on their surface, we reported here the facile fabrication of underwater superoleophobic membranes by coating a layer of graphene oxide (GO) on commercially available wire meshes with tunable pore sizes. Using the wire mesh as a ready-made mask, GO-embellished mesh with open apertures (GO@mesh) could be readily fabricated after subsequent O2 plasma treatments from the back side. Interestingly, the congenital microstructures of the crossed microwires in combination with the abundant hydrophilic oxygen-containing groups of the GO layer endow the resultant GO@mesh with unique underwater superoleophobic properties. The antioil tests show that the underwater contact angles of various oils including both organic reagents (undissolved in water) and vegetable oil on GO@mesh exceed 150°, indicating the superoleophobic nature. In a representative experiment, a mixture of bean oil and water that imitates culinary sewage has been well separated with the help of our GO@mesh. GO-embellished wire meshes may find broad applications in sewage purification, especially for the treatment of oil contaminations.

ease of preparation. As a pioneer of this field, Gracias' group has proposed several impressive bilayer actuators. For instance, a thermoresponsive theragripper with photopatternable poly(propylene fumarate) (PPF)/poly(N-isopropylacrylamide-coacrylic acid) (pNIPAM-AAc) bilayer structure has been developed for drug delivery. [28] Besides, Yang and co-workers have successfully fabricated stimuliresponsive actuators including an intelligent spring, a smart gripper, and a new type of "microrobot" based on the singlewall carbon nanotube (SWCNT) and polyvinylidene fluoride (PVDF) bilayer structure. [29] Zhu and co-workers reported novel soft electrothermal bimorph actuators made of polyimide (PI) and silver nanowire (AgNW)/polydimethylsiloxane (PDMS), which could be used in selfwalkers and soft grippers. [30] Despite a rapid progress has been made in this field, continuous efforts have been devoted to exploring new functional materials for further promotion of their performance.Graphene oxide (GO) that features ultrafast water adsorption/desorption capability, tunable physical/chemical properties, and tractable solution processing property holds great promise for developing smart bimorph actuators. Significantly, there exist plenty of oxygen-containing groups (OCGs) on GO sheets, which make GO a very hydrophilic material. [31] Water molecules can be adsorbed by GO easily and transferred freely among the GO multilayers. In this case, GO is very promising for moisture-responsive actuators. Additionally, the OCGs on GO sheets can be selectively removed or modified through various chemical/physical strategies, which can endow the resultant materials with conductivity, light absorption property, and high electrothermal and photothermal conversion efficiency. [32] Therefore, bimorph actuators based on GO or its derivatives, for instance reduced GO (RGO), also enable light and electrical actuation. Recently, GO has emerged as a versatile material for actuator design. For example, Liu and coworkers prepared an electromechanical ring-shaped actuator by combining an RGO layer with a PDMS layer, in which the RGO layer serves as an electric-heated layer in the electrothermal actuator. [33] Tang et al. combined thermally expanding microspheres (TEMs) with RGO to fabricate an RGO-TEM-PDMS/ PDMS bilayer actuator. They realized remote construction of 3D structures upon light irradiation, and the photothermal effect Graphene oxide (GO) with tunable physical/chemical properties is a versatile material for smart bimorph actuators. Using GO or its derivatives (e.g., reduced GO, RGO) as an active material, actuators can be manipulated under various external stimuli including moisture, light, temperature, and electricity. However, most of these GO-based actuators respond to a solo stimulus, which limits its cutting-edge applications in soft robotics. Here, the programmable patterning of RGO/GO Janus paper using a threshold-controlled direct laser writing (DLW) technology is reported. By combining the RGO/GO Janus paper with a common thermal...