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Direct light‐to‐work conversion enables remote actuation through a non‐contact manner, among which the photothermal Marangoni effect is significant for developing light‐driven robots because of the diversity of applicable photothermal materials and light sources, as well as the high energy conversion efficiency. However, the lack of nanotechnologies that enable flexible integration of advanced photothermal materials with actuators of complex configurations significantly restricts their practical applications. In this paper, laser‐induced graphene (LIG) tape is reported as stick‐on photothermal labels for developing light‐driven actuators based on the Marangoni effect. With the help of direct laser writing technology, graphene patterns with superior photothermal properties are prepared on the PI tape. The patterned LIG tape can be stuck on any desired objects and generates an asymmetric photothermal field under light irradiation, forming a photothermal Marangoni actuator. Additionally, the PI tape with LIG patterns can be folded into 3D origami actuators that permit photothermal Marangoni actuation including both translation and rotation. The graphene‐based photothermal Marangoni actuators feature biocompatibility, which is confirmed by MDA‐MB‐231 cells proliferation experiments. Owing to the excellent photothermal property of LIG patterns, the as‐produced photothermal actuators can be manipulated by a variety of light sources, holding great promise for developing light‐driven soft robots. [ABSTRACT FROM AUTHOR]

Abstract: Actuators that can convert environmental stimuli into mechanical work are widely used in intelligent systems, robots, and micromechanics. To produce robust and sensitive actuators of different scales, efforts are devoted to developing effective actuating schemes and functional materials for actuator design. Carbon‐based nanomaterials have emerged as preferred candidates for different actuating systems because of their low cost, ease of processing, mechanical strength, and excellent physical/chemical properties. Especially, due to their excellent photothermal activity, which includes both optical absorption and thermal conductivities, carbon‐based materials have shown great potential for use in photothermal actuators. Herein, the recent advances in photothermal actuators based on various carbon allotropes, including graphite, carbon nanotubes, amorphous carbon, graphene and its derivatives, are reviewed. Different photothermal actuating schemes, including photothermal effect–induced expansion, desorption, phase change, surface tension gradient creation, and actuation under magnetic levitation, are summarized, and the light‐to‐heat and heat‐to‐work conversion mechanisms are discussed. Carbon‐based photothermal actuators that feature high light‐to‐work conversion efficiency, mechanical robustness, and noncontact manipulation hold great promise for future autonomous systems. [ABSTRACT FROM AUTHOR]

We report herein the engineering of the surface/interface properties of graphene oxide (GO) films by controllable photoreduction treatment. In our recent works, typical photoreduction processes, including femtosecond laser direct writing (FsLDW), laser holographic lithography, and controllable UV irradiation, have been employed to make conductive reduced graphene oxide (RGO) microcircuits, hierarchical RGO micro-nanostructures with both superhydrophobicity and structural color, as well as moisture-responsive GO/RGO bilayer structures. Compared with other reduction protocols, for instance, chemical reduction and thermal annealing, the photoreduction strategy shows distinct advantages, such as mask-free patterning, chemical-free modification, controllable reduction degree, and environmentally friendly processing. These works indicate that the surface and interface engineering of GO through controllable photoreduction of GO holds great promise for the development of various graphene-based microdevices. [ABSTRACT FROM AUTHOR]

Inspired from butterfly wings that exhibit unique dewetting properties and brilliant structural color synchronously, we reported here the preparation of biomimetic few-layer graphene films through a template-directed chemical vapor deposition method using laser-structured Cu foil as substrates. Hierarchical micronanostructures, including microscale stripes derived from the laser scanning and nanoscale laser-induced periodic surface structures (LIPSS), formed on Cu foil after a simple femtosecond laser treatment. By tuning the laser power, the surface roughness of the resultant Cu foils can be well controlled. Using the laser structures Cu foil as templates, biomimetic few-layer graphene films with both iridescence and superhydrophobicity have been successfully prepared. The present work may open up a new way to design and prepare structured graphene film in a biomimetic manner, and we deem that the bioinspired few-layer graphene films may find broad applications in the near future. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Reported here is a bioinspired fabrication of superhydrophobic graphene surfaces by means of two-beam laser interference (TBLI) treatment of graphene oxide (GO) films. Microscale grating-like structures with tunable periods and additional nanoscale roughness are readily created on graphene films due to laser induced ablation effect. Synchronously, abundant hydrophilic oxygen-containing groups (OCGs) on GO sheets can be drastically removed after TBLI treatment, which lower its surface energy significantly. The synergistic effect of micro-nanostructuring and the OCGs removal endows the resultant graphene films with unique superhydrophobicity. Additionally, dual TBLI treatment with 90° rotation is implemented to fabricate superhydrophobic graphene films with two-dimensional grating-like structures that can effectively avoid the anisotropic hydrophobicity originated from the grooved structures. Moreover, the superhydrophobic graphene films become conductive due to the laser reduction effect. Unique optical characteristics including transmission diffraction and brilliant structural color are also observed due to the presence of periodic microstructures. As a mask-free, chemical-free, and cost-effective method, the TBLI processing of GO may open up a new way to biomimetic graphene surfaces, and thus hold great promise for the development of novel graphene-based microdevices. [ABSTRACT FROM AUTHOR]

Graphene is emerging as one of the most useful electrode materials for various organic optoelectronic devices because of its outstanding properties such as high optical transparency, excellent mechanical flexibility, good electrical conductivity, and environmental stability. Numerous synthesis and transfer techniques used to obtain large‐area and high‐quality graphene materials are demonstrated, aiming at high‐performance graphene‐based organic optoelectronic devices such as solar cells, light‐emitting diodes, and field‐effect transistors. The properties, synthesis, and transfer processes of graphene are first introduced. Recent research progress on organic optoelectronic devices with graphene bottom, top, and full electrodes is then reviewed. Finally, graphene composite electrodes integrated with other conductive materials are also summarized. All these advanced works represent important steps in the evolution of graphene electrodes and indicate a bright future for their application in organic optoelectronic devices. [ABSTRACT FROM AUTHOR]

As the demand for display technology in consumer electronics and lighting panels increases, thin, light, high‐quality, and more cost‐effective light‐emitting devices are required. Organic light‐emitting devices (OLEDs), satisfying the criteria exactly, have been considered the most promising next‐generation display and lighting technique. In particular, an OLED based on flexible substrate enables the device to be applied to curved displays, electronic newspapers, wearable displays, and conceptual lighting panels, has been always in the spotlight both in science and industry. Great advances on flexible OLEDs (FOLEDs) have been made over the past three decades. The fundamental elements of FOLEDs including substrates, electrodes, fabrication and encapsulation techniques, as well as the strategies of efficiency improvement are discussed herein. Moreover, emerging electrodes such as graphene, carbon nanotubes, metal nanowire network and their composite, flexible perovskite light emitting devices, and stretchable light emitting devices are also considered. Finally, the future challenges and prospects for these devices are put forward. The fundamental elements of flexible organic light‐emitting devices including substrates, electrodes, fabrication and encapsulation techniques, as well as the strategies of efficiency improvement are discussed. Moreover, emerging electrodes such as graphene, carbon nanotubes, metal nanowire network and their composites, flexible perovskite light emitting devices, and stretchable light emitting devices are also considered. Finally, the challenges and prospects for the future are put forward. [ABSTRACT FROM AUTHOR]