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MXene, which is known for its high electrical/thermal conductivity, surface hydrophilicity, excellent mechanical flexibility, and chemical stability, is a versatile and smart material for soft actuators. However, most MXene actuators are fabricated by combining MXene with other inert materials to form a bilayer or multilayer structure. Considering the strain mismatch at multimaterial interfaces under frequent deformation, MXene‐based actuators are generally associated with poor stability, which limits their practical applications. Herein, inspired by the natural quantum‐confined superfluidic (QSF) effect, a multiresponsive MXene actuator that can be driven by moisture, light, and electricity by engineering an asymmetric QSF structure on both sides of the MXene film is reported. The actuation mechanism of the MXene film can be attributed to nonuniform water adsorption, transport, and desorption within the asymmetric QSF channels under moisture, photothermal, and electrothermal stimuli. Interestingly, MXene actuators can be flexibly formed into various shapes under moisture‐assisted mechanical compression, which not only enhances their multiresponsive actuation, but also permits a more complex deformation. As proof‐of‐concept demonstrations, various intriguing applications including a dual‐role robot, a smart shielding curtain, and a dragonfly robot, are fabricated, revealing the potential of MXene actuators for soft robotics. [ABSTRACT FROM AUTHOR]

Recent advances in developing soft electronic devices have increased the demand for deformable storage devices. However, the fabrication of microsupercapacitors (MSCs) with satisfactory electrochemical performance and mechanical robustness remains a crucial challenge. In this work, deformable moisture-activated all-solid-state planar MSCs were designed and fabricated by an in situ laser reduction technology. The planar MSC shows a high areal-specific capacitance (∼4.7 mF cm−2 at 5 mV s−1) under high moisture (RH = 100%). Moreover, the tensile strength of the deformable planar MSC increased to 21 MPa. Moreover, the mechanical robustness of the planar MSC allows them to be folded into origami. The deformable moisture-activated all-solid-state planar MSC holds promises for soft storage devices. [ABSTRACT FROM AUTHOR]

Chemical Marangoni propulsion enables dynamic and untethered motion by generating surface tension gradient through chemical release, thereby having great potential for the development of insect‐scale self‐propelled robots. However, as the release and diffusion of chemical "fuels" are commonly uncontrollable, the Marangoni propulsion is unstable, thereby restricting robotic applications. Herein, the laser fabrication of superhydrophobic swimming robots to develop controllable Marangoni propulsion based on a photothermal composite of graphene and polydimethylsiloxane is reported. By combining the microfluidic channels with photothermal air chambers, a light‐triggered switch that can control the release of chemical "fuels" is proposed. Furthermore, a superhydrophobic surface is fabricated on the swimming robot by laser treatment, which reduced water resistance and promoted propulsion. On‐demand actuation and swimming route planning are realized by programming the alcohol/air segments in the releasing channels, on‐demand actuation and swimming route planning have been realized. As a proof‐of‐concept, a Marangoni swimming robot equipped with a miniature digital camera is used in an actual environment. Therefore, this study is expected to advance the practical applications of the chemical Marangoni effect in swimming robots. [ABSTRACT FROM AUTHOR]

Soft robots controlled by different actuation schemes are flourishing owing to the continued development of smart materials. However, most of the existing actuators are powered by a single source with predetermined mechanical properties and motion characteristics. Speed, power, and efficiency of these actuators are thus far inferior to their conventional counter parts. How to preload or alter the internal energy distribution and trigger rapid kinetic energy release combined with re‐programmability is a challenge and corresponding solutions will extend the practical use of soft robotics. Herein, a hybrid magnetically and photothermally responsive actuator with high degrees of freedom by using a coupled‐field manipulation strategy is proposed. As a proof‐of‐concept, a crab robot (CraBot) that contains uniformly distributed superparamagnetic particles and localized light‐responsive joints is produced. The spatial magnetic field exerts force on the robot, leading to real‐time adjustment of energy distribution within the entire robot. Meanwhile, the focused light field enables selective deformation of specific joints, releasing the accumulated energy into kinetic energy of motion for quick actuation. The directional accumulation and addressable release of elastic energy enables the CraBot to walk efficiently with improved power and speed. Such a hybrid‐field manipulation strategy holds great promise for sophisticated actuation of soft robots. [ABSTRACT FROM AUTHOR]

Directional droplet transport on smart surfaces with superwettabilities arouse extensive attentions from both the scientific community and industry due to the exciting applications in healthcare, environmental protection, and energy harvesting. The past decades have witnessed the progress and achievements in mechanism disclosure, device preparation, and applied investigation. Herein, various droplet transport schemes are summarized, such as electrohydrodynamic strategy, self‐propelled droplet on anisotropic surfaces, gravity driven droplet on slippery lubricant impregnated porous surfaces (SLIPS), and other engineering strategies. Accordingly, the basic mechanism of droplet manipulation, devices configuration, and key features are presented. The recent cutting‐edge applications of directional droplet transport, including digital microfluidics, electric energy harvesting, fag/water collection, and oil‐water separation are also reviewed. At the end, current challenges and future perspectives in this field are discussed. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO), which has many oxygen functional groups, is a promising candidate for use in moisture‐responsive sensors and actuators due to the strong water–GO interaction and the ultrafast transport of water molecules within the stacked GO sheets. In the last 5 years, moisture‐responsive actuators based on GO have shown distinct advantages over other stimuli‐responsive materials and devices. Particularly, inspired by nature organisms, various moisture‐enabled soft robots have been successfully developed via rational assembly of the GO‐based actuators. Herein, the milestones in the development of moisture‐responsive soft robots based on GO are summarized. In addition, the working mechanisms, design principles, current achievement, and prospects are also comprehensively reviewed. In particular, the GO‐based soft robots are at the forefront of the advancement of automatable smart devices. [ABSTRACT FROM AUTHOR]

Photoreduction of graphene oxide (GO) holds great potential for developing graphene-based electrodes for high-performance supercapacitors (SCs). However, the insufficient micro-nanostructure on photoreduced GO (PRGO) restricts its electrochemical performance. Here, a hierarchically structured PRGO-based planar SC is reported by combining two-beam-laser-interference with the masking technique. The hierarchical structures improve the surface area between PRGO and electrolyte and contribute to format electric double-layer capacitors. Planar device structures with PRGO-based interdigital finger current collectors are beneficial for rapid ion diffusion paths. As a result, the hierarchically structured PRGO-based planar SC achieves an areal capacitance of 3.97 mF cm−2 at 10 mV s−1. The proposed strategy of employing hierarchically structured PRGO in the planar SC design offers a new route for manufacturing high-performance integrated energy storage devices. [ABSTRACT FROM AUTHOR]

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]

Oil water separation plays a vital role in a series of industrial applications, such as petroleum industry and sewage treatments. However, traditional separation methods often suffer from non‐adjustable separation efficiency and solid impurities blockage. To solve this problem, we modify a commercially available stretchable textile with superwetting materials, including graphene oxide (GO) and polytetrafluoroethylene (PTFE), for tunable oil‐water separation. After GO coating, the stretchable textile shows superhydrophilicity in air and superoleophobicity underwater, which is further applied to tunable oils‐water separation via mechanical stretching. Interestingly, the superwetting textile is workable within a certain stretching degree. By tuning the pore size of the textile via stretching, the permeation rate increased by three times. The stretching property not only promotes the separation rate, but also imparts the self‐dredging property that can avoid solid impurities clogging in real case separation. The stretchable oil‐water separation textiles hold great potential for practical applications in sewage treatments. [ABSTRACT FROM AUTHOR]

Graphene-based actuators featuring fast and reversible deformation under various external stimuli are promising for soft robotics. However, these bimorph actuators are incapable of complex and programmable 3D deformation, which limits their practical application. Here, inspired from the collective coupling and coordination of living cells, we fabricated a moisture-responsive graphene actuator swarm that has programmable shape-changing capability by programming the SU-8 patterns underneath. To get better control over the deformation, we fabricated SU-8 micropattern arrays with specific geometries and orientations on a continuous graphene oxide film, forming a swarm of bimorph actuators. In this way, predictable and complex deformations, including bending, twisting, coiling, asymmetric bending, 3D folding, and combinations of these, have been achieved due to the collective coupling and coordination of the actuator swarm. This work proposes a new way to program the deformation of bilayer actuators, expanding the capabilities of existing bimorph actuators for applications in various smart devices. [ABSTRACT FROM AUTHOR]

• A complementary strategy can work as a universal design principle for dual-responsive actuators. • Combining moisture-active/alkane-inert GO with alkane-active/moisture-inert PDMS enables dual-responsive actuation. • GO and PDMS bimorph features fast and reversible response to both moisture and alkane. Smart actuators that enable deforming in a predictable manner under external stimuli have revealed great potential for both traditional and emerging industries. Generally, an asymmetric bilayer structure with one layer active and the other inert to a certain stimulus is essential to realize bending behavior. However, towards the development of dual- or multi-responsive actuators, it still lacks universal and effective strategies for rational design and fabrication of such devices through the simplest way. In this paper, we report a complementary strategy to produce dual-responsive bilayer actuators by combining the moisture-active/alkane-inert graphene oxide (GO) layer with the alkane-active/moisture-inert polydimethylsiloxane (PDMS) layer. The GO@PDMS bimorph actuator can switch its active and inert layers in response to moisture and alkane, respectively, realizing dual-responsive deformation under different actuations. Typical dual-responsive actuators, including a selective air valve and a grip and hook smart claw, are successfully fabricated, demonstrating the capability of effective gases and objects transmission. The complementary bimorph actuator may hold great promise for developing intelligent devices and portable delivery systems. [ABSTRACT FROM AUTHOR]

Here, we report embedded spiral zone plates (SZPs) processed by tightly focused femtosecond pulses, inducing a refractive index change in a sapphire crystal. The change in the index is investigated both experimentally and theoretically and found to be 0.93% lower than that before the laser irradiation. Benefiting from the investigation of the photorefraction, a high diffractive efficiency of up to 78% is achieved for the SZPs. In addition, the SZPs are embedded under the surface of the sapphire, which ensures that the components possess stable optical properties in the case of external refractive index changes. The high-performance elements having a high diffractive efficiency and stable optical performance will have tremendous applications in optical communication and optical manipulation. [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]

The combination of surface-enhanced Raman spectroscopy (SERS) technology with microfluidics makes it possible to diagnose genetic disease through label-free on-chip DNA detection. However, open problems including the integration of SERS substrate with microfluidic devices, controllable trapping and releasing of target molecules are still challenging. Here we demonstrate a facile laser scribing method to fabricate silver nanoparticles (AgNPs) and graphene oxide (GO) based biochips as a reusable SERS sensor for DNA detection. Programmable laser scribing of the AgNPs@GO composite film enables direct patterning of sensitive SERS channels that consist of graphene supported AgNPs by exfoliating the composites into hierarchical porous structures. Integrating the SERS-active patterns with a microfluidic chip forms a biochip for allowing SERS detection of DNA. The noncovalent interactions between DNA and graphene mediated controllable trapping and releasing of DNA sequences, enabling efficient on-chip SERS detection and the regeneration of the biochip. The simple, green and cost-effective fabrication of the SERS-active biochips reveals great potential for biomolecular sensing and genetic engineering applications. [ABSTRACT FROM AUTHOR]

Abstract: Flexible smart surfaces with tunable wettability are promising for emerging wearable uses. However, currently, wearable superhydrophobic surfaces with dynamic wetting behaviors are rarely reported. Here, a skin‐like superhydrophobic elastomer surface with switchable lotus leaf and rose petal states is reported. Direct laser writing technique is employed for one‐step, programmable, large‐scale fabrication of monolithic and hierarchical micro‐nanostructures on elastomer, leading to strong water repellence. The surface topography can be finely regulated in a rapid and reversible manner by simple stretching, providing the feasibility of controlling the surface wettability by simple body motions. The ability to switch wetting states enables the surface to capture and release multiple droplets in parallel. Furthermore, the active surface can be applied to the joints of fingers and operate as a droplet manipulator under finger motions without requiring energy supply or external appliance. In this work, dynamic tuning of wetting properties is integrated into the design of skin‐like wearable surfaces, revealing great potential in versatile applications such as wearable droplet manipulator, portable actuator, adaptive adhesion control, liquid repellent skin, and smart clothing. [ABSTRACT FROM AUTHOR]

Direct light-to-work conversion enables manipulating remote devices in a contactless, controllable, and continuous manner. Although some pioneering works have already proven the feasibility of controlling devices through light-irradiation-induced surface tension gradients, challenges remain, including the flexible integration of efficient photothermal materials, multifunctional structure design, and fluidic drag reduction. This paper reports a facile one-step method for preparing light-driven floating devices with functional surfaces for both light absorption and drag reduction. The direct laser writing technique is employed for both arbitrary patterning and surface modification. By integrating the functional layer at the desired position or by designing asymmetric structures, three typical light-driven floating devices with fast linear or rotational motions are demonstrated. Furthermore, these devices can be driven by a variety of light sources including sunlight, a filament lamp, or laser beams. The approach provides a simple, green, and cost-effective strategy for building functional floating devices and smart light-driven actuators. [ABSTRACT FROM AUTHOR]

Graphene is a promising sensing material that has been widely used for high-performance sensors. However, the development of graphene-based sensing device is limited by complex manufacturing procedures. Here, we report a facile fabrication of humidity sensors by flash reduction of graphene oxides (GO) with the help of a photographic camera flash. The flash treatment triggers a drastic deoxygenation of oxygen functional groups (OCGs) from the GO sheets, which not only restores its conductivity partly but also induces the formation of a highly porous structure. The reduced GO sensor shows high sensitivity at the relative humidity atmosphere of 11%–95%, small hysteresis, rapid response, and enhanced durability. The sensitive mechanism was discussed through the investigation of complex impedance plots. This facile flash reduction strategy holds great promise for chemical-free production of graphene-based sensing devices. [ABSTRACT FROM PUBLISHER]

This paper demonstrates femtosecond laser direct writing mediated flexible integration of plasmonic Ag/Pd alloy nanostructures that can be potentially used as a robust surface‐enhanced Raman spectroscopy substrate inside the microfluidic chip. Silver–palladium alloy with controllable composition ratio can be patterned into plasmonic nanostructures due to two‐photon absorption induced coreduction of silver/palladium double metal ions. Since the alloy structures can effectively protect the silver from oxidation, thus they can facilitate the stable on‐chip detection devices with long lifetime. The as‐fabricated silver–palladium alloy substrate with 18% content of palladium maintains a relatively high enhancement factor of about 2.62 × 108 while at the same time demonstrating the best stability against aerobic oxidation, as it is stable for up to 20 d under ambient aerobic conditions, exhibiting a significant improvement compared to those unprotected silver substrates which have a limited lifetime of only 3 or 4 d. [ABSTRACT FROM AUTHOR]

Hydrogels such as poly(ethylene glycol) diacrylate are a class of cross-linked polymers that have the ability to absorb water and change volume. Here, a humidity responsiveness of hydrogel film fabricated by the photopolymerization of poly(ethylene glycol) diacrylate (PEG-DA) monomer is reported. This kind of film could be driven by a small humidity gradient, thus spontaneous deformation and motion can be achieved by placing the film onto a moist filter paper. The influence factors of humidity response sensitivity such as the exposure time and number-average molecular weight of PEG-DA monomer used during the fabrication are investigated. Under different relative humidity, the film displays different degrees of pink color and the intensities of fluorescence under 365 nm illumination are also different, which renders the film to be used as a 'humidity test strip.' A humidity-driven walking device is fabricated and the walking velocity is about 3 mm min−1 under the actuating water vapor. Vapor of volatile polar solvents could also drive the actuator to achieve fast deformation and shows the variety of the film responsivity. [ABSTRACT FROM AUTHOR]

In the development of microfluidic chips, conventional 2D processing technologies contribute to the manufacturing of basic microchannel networks. Nevertheless, in the pursuit of versatile microfluidic chips, flexible integration of multifunctional components within a tiny chip is still challenging because a chip containing micro-channels is a non-flat substrate. Recently, on-chip laser processing (OCLP) technology has emerged as an appealing alternative to achieve chip functionalization through in situ fabrication of 3D microstructures. Here, the recent development of OCLP-enabled multifunctional microfluidic chips, including several accessible photochemical/photophysical schemes, and photosensitive materials permiting OCLP, is reviewed. To demonstrate the capability of OCLP technology, a series of typical micro-components fabricated using OCLP are introduced. The prospects and current challenges of this field are discussed. [ABSTRACT FROM AUTHOR]