Laser-Induced Graphene Tapes as Origami and Stick-On Labels for Photothermal Manipulation via Marangoni Effect

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.     

Multifunctional Carbon–Silica Nanocapsules with Gold Core for Synergistic Photothermal and Chemo‐Cancer Therapy under the Guidance of Bimodal Imaging

Carbon‐based nanomaterials have been developed for photothermal cancer therapy, but it is still a great challenge to fabricate their multifunctional counterparts with facile methods, good biocompatibility and dispersity, and high efficiency for cancer theranostics. In this work, an alternative multifunctional nanoplatform is developed based on carbon–silica nanocapsules with gold nanoparticle in the cavity (Au@CSN) for cancer theranostics. The encapsulated chemodrug doxorubicin can be released from the Au@CSN with mesoporous and hollow structure in a near‐infrared light and pH stimuli‐responsive manner, facilitating spatiotemporal therapy to decrease off‐target toxicity. The nanocapsules with efficient photothermal conversion and excellent biocompatibility achieve a synergistic effect of photothermal and chemotherapy. Furthermore, the nanocapsules can act as a multimodal imaging agent of computed tomography and photoacoustic tomography imaging for guiding the therapy. This new design platform can provide a promising strategy for precise cancer theranostics.     

Direct Laser Writing of Superhydrophobic PDMS Elastomers for Controllable Manipulation via Marangoni Effect

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.     

Biomimetic 4D-Printed Breathing Hydrogel Actuators by Nanothylakoid and Thermoresponsive Polymer Networks

Shape-morphing actuators, which can breathe with the accompany of morphology changes to mimic botanical events, are challenging to fabricate with soft hydrogel materials. Herein, 4D printed-smart hydrogel actuators are reported that can not only dynamically deform but also generate oxygen (O₂) upon external stimulations. The printed breathing actuators featured with spinach leaf-derived thylakoid membrane (nanothylakoid) for photothermal conversion and catalytical O₂ evolution, a poly(N-isopropylacrylamide) (PNIPA) thermoresponsive polymer network for generating deformation forces by swelling/shrinkage (rehydration/dehydration), and an asymmetric bilayer poly(N-isopropylacrylamide)/polyacrylamide (PNIPA/PAA) structure to amplify the mechanical motions. Upon thermal stimulation or laser irradiation, the actuator can reversibly bend/unbend because of the photothermal conversion of nanothylakoid and the printed thermoresponsive asymmetric bilayer structure. Additionally, the catalase-like property of nanothylakoid imparts the actuator with O₂ evolution capability to breathe for further mimicking botanical systems. Notably, 4D printing can greatly facilitate and simplify the actuator fabrication process, including adjusting the size and layer compositions. This artificial breathing actuator with photothermal and catalytical properties provides a strategy in designing intelligent hydrogel systems and proves to be a highly promising material candidates in the fields of 3D/4D printing, automated robotics, and smart biomedical devices.     

Hierarchically Structured Self‐Healing Actuators with Superfast Light‐ and Magnetic‐Response

Despite the tremendous advancement of intelligent robots, it remains a great challenge to integrate living organisms‐like multistimuli responsive actuation and excellent self‐healing ability into one single material system, which will greatly benefit and broaden the development of smart biomimetic materials. Herein, a novel self‐healable multistimuli responsive actuator is developed based on hierarchical structural design and interfacial supramolecular crosslinking. The resulting biomimetic actuator shows a record high photothermal efficiency (η_PT = 79.1%) and thermal conductivity (31.92 W m^?1 K^?1), and presents a superfast actuating response (near‐infrared light: 0.44 s; magnetic field: 0.36 s). In addition, the supramolecular crosslinking endows excellent self‐healing performance in both mechanical and actuating properties to the material. This biomimetic actuator with its hierarchical structure design provides great potential for various applications, such as artificial muscles, soft robotics, and biomedical microdevices.     

Multiresponsive Bidirectional Bending Actuators Fabricated by a Pencil‐on‐Paper Method

Recently, actuating materials based on carbon nanotubes or graphene have been widely studied. However, present carbon‐based actuating materials are mostly driven by a single stimulus (humidity, light, electricity, etc.), respectively, which means that the application conditions are limited. Here, a new kind of multiresponsive actuating material which can be driven by humidity, light, and electricity is proposed, so it can be used in various conditions. The fabrication is based on the simplest pencil‐on‐paper method, in which the pencil and paper are both low‐cost and easily obtained daily materials. The actuation effect is more remarkable due to a dual‐mode actuation mechanism, which leads to an ultralarge actuation (bending curvature up to 2.6 cm^?1). Elaborately designed, the actuator can further exhibit a bidirectional bending actuation, which is a significant improvement compared with previous reported thermal actuators. What is more, a colorful biomimetic flower and a smart curtain are also fabricated, fully utilizing the printable characteristic of the paper and multiresponsive characteristic of the actuator. It is assumed that the newly designed actuating material has great potential in the fields of lab‐on‐paper devices, artificial muscles, robotics, biomimics, and smart household materials.     

Supramolecular Photothermal Nanomaterials as an Emerging Paradigm toward Precision Cancer Therapy

The concept of the “supramolecular photothermal effects” refers to the collection property and photothermal conversion efficiency resulting from the supramolecular assembly of molecular photothermal sensitizers. This review considers organic supramolecular photothermal materials assembled at the nanoscale via various molecular self‐assembly strategies and associated with the organization of multiple noncovalent interactions. In these materials, the individual photosensitizer molecules are typically aggregated through self‐assembly in a certain form that exhibits enhanced biostability, increased photothermal conversion efficiency with photoluminescence quenching, and improved photothermal therapeutic effects in comparison with those of the monomeric photosensitizer molecules. These supramolecular photothermal effects are controlled or influenced by intermolecular noncovalent interactions, especially the hydrophobic effects, which are distinct from the mechanisms of conventional sensitizer molecules and polymers and inorganic photothermal agents. A focus lies on how self‐assembly strategies give rise to supramolecular photothermal effects, including polymer and protein fabrication, small molecule self‐assembly, and the construction of donor–acceptor binary systems. Emphases are placed on the rational design of supramolecular photothermal nanomaterials, drug delivery, and in vivo photothermal therapeutic effects. Finally, the key challenges and promising prospects of these supramolecular photothermal nanomaterials in terms of both technical advances and clinical translation are discussed.     

Plasmonic‐Assisted Graphene Oxide Films with Enhanced Photothermal Actuation for Soft Robots

Carbon‐based materials are widely used as light‐driven soft actuators relying on their thermal desorption or expansion. However, applying a passive layer in such film construction greatly limits the actuating efficiency, e.g., bending amplitude and speed. In this work, a dual active layer strengthened bilayer composite film made of graphene oxide (GO)–polydopamine (PDA)–gold nanoparticles (Au NPs)/polydimethylsiloxane (PDMS) is developed. In this film, the conventional passive layer is replaced by another AuNPs‐enhanced thermal responsive layer. When applying NIR light exposure, the whole film deforms controllably resulting from the water loss in the GO–PDA–Au NPs layer and thermal expansion in the PDMS layer. Benefiting from the dual active bilayer mechanism, the thin film's actuating efficiency is dramatically improved compared with that of conventional methods. Specifically, the bending amplitude is enhanced up to 173%, and the actuating speed is improved to 3.5‐fold. The soft actuator can act as an artificial arm with high actuating strength and can be used as a wireless gripper. Moreover, the film can be designed as soft robots with various locomotion modes including linear, rolling, and steering motions. The developed composite film offers new opportunities for biomimetic soft robotics as well as future applications.     

Greatly Enhanced Thermal Contraction at Room Temperature by Carbon Nanotubes

A crosslinked polyarylamide polymer exhibits novel photothermal behavior, that is, reversible giant contraction in response to near infrared irradiation in addition to normal thermal expansion. Such reversibility is seldom found in a polymeric system. Due to the amphiphilic nature of the benzocyclobutene‐containing triblock copolymer precursor with polyarylamide interacting strongly with few‐walled carbon nanotubes (FWCNTs), they are dispersed extremely well in the polymer solution at a loading up to at least 5 wt%. Also, strained carbon double bonds on FWCNTs can directly form covalent linkages with the benzocyclobutene groups on the polymer chains via cyclo‐addition. The incorporation of FWCNTs increases mechanical stiffness two‐fold. Exploiting the ability of FWCNTs to effectively convert photon energy into heat and to provide conductive pathways, the NIR‐induced unexpected contraction stress can be further increased dramatically. The systematic study suggests that there is an optimal CNT concentration. At 3 wt% FWCNTs, the enhancement factor for contraction stress is almost 24: 166 kPa with 3 wt% FWCNTs versus 7 kPa without FWCNTs. The colossal photothermal contraction stress generated by this new composite film at ambient condition upon NIR stimulation can lead to the development of new NIR actuators, for example, for biological applications, and create new material platforms for green energy conversion.     

Photothermal Bimorph Actuators with In‐Built Cooler for Light Mills,Frequency Switches,and Soft Robots

Photothermal bimorph actuators are widely used for smart devices, which are generally operated in a room temperature environment, therefore a low temperature difference for actuation without deteriorating the performance is preferred. The strategy for the actuator is assembling a broadband‐light absorption layer for volume expansion and an additional water evaporation layer for cooling and volume shrinkage on a passive layer. The response time and temperature‐change‐normalized bending speed under NIR, white, and blue light illumination are at the same level of high performance, fast photothermal actuators based on polymer or polymer composites. The classical beam theory and finite element simulations are also conducted to understand the actuation mechanism of the actuator. A new type of light mill is designed based on a wing‐flapping mechanism and a light‐modulated frequency switch. A fast‐walking robot (with a speed of 26 mm s^?1) and a fast‐and‐strong mechanical gripper with a large weight‐lifting ratio (≈2142), respectively, are also demonstrated.     

Non‐Equilibrium,Light‐Adaptive,Steady‐State Reconfiguration of Mechanical Patterns in Bioinspired Nanocomposites

Bioinspired nanocomposites have made great progress for the fabrication of mechanical high‐performance structural materials, but their properties have thus far been engineered with a focus on static behavior. This contrasts profoundly with the dynamic reconfiguration often observed in living tissues. Here, a first concept is introduced for steady‐state, light‐adaptive reconfiguration of mechanical patterns in bioinspired nanocomposites under dissipative out‐of‐equilibrium conditions. This is realized for green, waterborne cellulose nanofibril/polymer nanopapers by achieving a heterogeneous activation of a photothermal effect. To this end, predefined mechanical patterns are designed by top‐down lamination of bottom‐up engineered bioinspired nanocomposites containing thermoreversible hydrogen bonds, as well as spatially selectively incorporated single‐walled carbon nanotubes for photothermal response. Global irradiation leads to localized photothermal softening by cascading light to heat, and to the dynamization and breakage of the thermoreversible supramolecular bonds, leading to macroscopic reconfiguration and even inversion of mechanical stiff/soft patterns. The altered configuration is only stable in a dissipative steady state and relaxes to the ground state once light is removed. The strategy presents a new approach harnessing the capabilities from top‐down and bottom‐up structuring, and by interfacing it with non‐equilibrium adaptivity concepts, it opens avenues for hierarchical bioinspired materials with anisotropic response in global fields.     

Soft Optomechanical Systems for Sensing,Modulation, and Actuation

Soft optomechanical systems have the ability to reversibly respond to optical and mechanical external stimuli by changing their own properties (e.g., shape, size, viscosity, stiffness, color or transmittance). These systems typically combine the optical properties of plasmonic, dielectric or carbon-based nanomaterials with the high elasticity and deformability of soft polymers, thus opening the path for the development of new mechanically tunable optical systems, sensors, and actuators for a wide range of applications. This review focuses on the recent progresses in soft optomechanical systems, which are here classified according to their applications and mechanisms of optomechanical response. The first part summarizes the soft optomechanical systems for mechanical sensing and optical modulation based on the variation of their optical response under external mechanical stimuli, thereby inducing mechanochromic or intensity modulation effects. The second part describes the soft optomechanical systems for the development of light induced mechanical actuators based on different actuation mechanisms, such as photothermal effects and phase transitions, among others. The final section provides a critical analysis of the main limitations of current soft optomechanical systems and the progress that is required for future devices.     

Biocompatible D–A Semiconducting Polymer Nanoparticle with Light‐Harvesting Unit for Highly Effective Photoacoustic Imaging Guided Photothermal Therapy

The development of nanotheranostic agents that integrate diagnosis and therapy for effective personalized precision medicine has obtained tremendous attention in the past few decades. In this report, biocompatible electron donor–acceptor conjugated semiconducting polymer nanoparticles (PPor‐PEG NPs) with light‐harvesting unit is prepared and developed for highly effective photoacoustic imaging guided photothermal therapy. To the best of our knowledge, it is the first time that the concept of light‐harvesting unit is exploited for enhancing the photoacoustic signal and photothermal energy conversion in polymer‐based theranostic agent. Combined with additional merits including donor–acceptor pair to favor electron transfer and fluorescence quenching effect after NP formation, the photothermal conversion efficiency of the PPor‐PEG NPs is determined to be 62.3%, which is the highest value among reported polymer NPs. Moreover, the as‐prepared PPor‐PEG NP not only exhibits a remarkable cell‐killing ability but also achieves 100% tumor elimination, demonstrating its excellent photothermal therapeutic efficacy. Finally, the as‐prepared water‐dispersible PPor‐PEG NPs show good biocompatibility and biosafety, making them a promising candidate for future clinical applications in cancer theranostics.     

Synergistic Effect of Photothermal Conversion in MXene/Au@Cu2−xS Hybrids for Efficient Solar Water Evaporation

A three-plasmon hybrid, in which core–shell Au@Cu_2−xS hybrids are bonded with ultrathin Ti₃C₂T_x MXene, is prepared for high-efficiency photothermal conversion and membrane-based solar water evaporation for the first time. The MXene/Au nanorod@Cu_2−xS hybrids display excellent photothermal conversion efficiency under irradiation of an 808 laser, causing by the three-plasmon-induced synergistic plasmonic absorption and heating effects as well as the multichannel charge transfer between the components. Then, Au nanosphere@Cu_2−xS and Au nanorod@Cu_2−xS hybrids are mixed and combined with MXene to serve as the membrane material, which shows excellent light absorption ranging from ultraviolet to near-infrared region. By transferring the membrane materials on a hydrophilic cotton piece, the as-prepared photothermal membrane displays a high evaporation rate of 2.023 kg m⁻² h⁻¹ and light-to-heat conversion efficiency of 96.1% under 1-sun irradiation due to the synergistic photothermal conversion and over 96% of solar light absorption efficiency. Furthermore, a home-made solar evaporation device enabling automatic inflow of untreated water and outflow of evaporated water is designed based on the principles of liquid pressure and connectors. The seawater desalination and sewage treatment experiments performed on the device and membrane indicate the great potential in solar-light-driven water purification and drinkable water generation.     

Light‐Fueled,Spatiotemporal Modulation of Mechanical Properties and Rapid Self‐Healing of Graphene‐Doped Supramolecular Elastomers

Gaining spatially resolved control over the mechanical properties of materials in a remote, programmable, and fast‐responding way is a great challenge toward the design of adaptive structural and functional materials. Reversible, temperature‐sensitive systems, such as polymers equipped with supramolecular units, are a good model system to gain detailed information and target large‐scale property changes by exploiting reversible crosslinking scenarios. Here, it is demonstrated that coassembled elastomers based on polyglycidols functionalized with complementary cyanuric acid and diaminotriazine hydrogen bonding couples can be remotely modulated in their mechanical properties by spatially confined laser irradiation after hybridization with small amounts of thermally reduced graphene oxide (TRGO). The TRGO provides an excellent photothermal effect, leads to light‐adaptive steady‐state temperatures, and allows local breakage/de‐crosslinking of the hydrogen bonds. This enables fast self‐healing and spatiotemporal modulation of mechanical properties, as demonstrated by digital image correlation. This study opens pathways toward light‐fueled and light‐adaptive graphene‐based nanocomposites employing molecularly controlled thermal switches.     

Spiky Fe3O4@Au Supraparticles for Multimodal In Vivo Imaging

Nanomaterials with high biocompatibility and efficient photothermal conversion have drawn tremendous attention for tumor diagnosis and treatment. In this study, spiky Fe₃O₄@Au supraparticles (SPs) are used as phototherapy and multimodal imaging agents. The SPs show excellent photothermal and photodynamic therapeutic effects, with a photothermal conversion efficiency of 31%, and allow tumor‐targeted imaging, including computed tomographic, photoacoustic, and magnetic resonance imaging. The SPs show excellent biocompatibility both in vitro and in vivo. Furthermore, because of their remarkable absorption at near‐infrared region, the SPs obliterate a tumor under 808 nm irradiation. With their capacity for highly integrated multimodal imaging and multiple therapeutic functions, SPs are a promising agent for application to clinical practice.     

An Autonomous Soft Actuator with Light‐Driven Self‐Sustained Wavelike Oscillation for Phototactic Self‐Locomotion and Power Generation

Mimicking the intelligence of biological organisms in artificial systems to design smart actuators that act autonomously in response to constant environmental stimuli is crucial to the construction of intelligent biomimetic robots and devices, but remains a great challenge. Here, a light‐driven autonomous carbon‐nanotube‐based bimorph actuator is developed through an elaborate structural design. This curled droplet‐shaped actuator can be simply driven by constant white light irradiation, self‐propelled by a light‐mechanical negative feedback loop created by light‐driven actuation, time delay in the photothermal response along the actuator, and good elasticity from the curled structure, performing a continuously self‐oscillating motion in a wavelike fashion, which mimics the human sit‐up motion. Moreover, this autonomous self‐oscillating motion can be further tuned by controlling the intensity and direction of the incident light. The autonomous actuator with continuous wavelike oscillating motion shows immense potential in light‐driven biomimetic soft robots and optical‐energy‐harvesting devices. Furthermore, a self‐locomotive artificial snake with phototaxis is constructed, which autonomously and continuously crawls toward the light source in a wave‐propagating manner under constant light irradiation. This snake can be placed on a substrate made of triboelectric materials to realize continuous electric output when exposed to constant light illumination.     

Extrusion Printing of Flexible Electrically Conducting Carbon Nanotube Networks

Carbon nanotube networks in biopolymer solutions are explored as potential ink systems for the extrusion printing of conducting structures. The biopolymer gellan gum is found to act as an excellent dispersant of multiwalled carbon nanotubes and has the appropriate flow properties to act as a thickener for the controlled dispensing of carbon nanotube networks. Absorbing substrates are found to improve the resolution and the flexibility of the printed structures. These printed conducting carbon nanotube networks exhibit interesting mechanical and electrical characteristics, which are applied to demonstrate their actuating and strain gauging capabilities.     

Solar-Powered High-Performance Lignin-Wood Evaporator for Solar Steam Generation

Recent research on wood-based solar evaporators has made great progress and significant breakthroughs have been made in using lignin as a photothermal material; however, the intensity change mechanism regarding the conjugate structure of lignin is almost never mentioned. This study innovatively proposes a mechanism to explain the changes in conjugate intensity that occur before and after lignin dissolution and fabricates a lignin/wood-based solar evaporator (LWE) using an all-wood-based material that is salt-tolerant and has long-term serviceability. Lignin in the evaporator serves not only as a photothermal material for converting light energy into heat energy but also as a reinforcement for the evaporator's structural strength. Adding lignin changes the original structure of balsa wood, increasing the proportion of intermediate water in the LWE, thereby lowering the enthalpy of water evaporation. The optimized LWE with an enhanced desalination capability, dye removal property, and high stability exhibits full-spectrum solar absorption of about 83.6%, a photothermal conversion efficiency of 91.74%, and an evaporation efficiency of 1.93 kg m⁻² h⁻¹, which surpasses most wood-based evaporators. This study demonstrates that all-wood-based materials can be used to prepare evaporators with excellent performance, providing a new approach to address freshwater depletion.     

Reversible and Rapid Laser Actuation of Liquid Crystalline Elastomer Micropillars with Inclusion of Gold Nanoparticles

It is highly desirable for liquid crystal elastomer (LCE) based microactuators to activate and actuate in a highly controlled fashion without perturbing the surrounding environment. To reach this goal, in this study, a novel experimental protocol is developed to successfully incorporate gold nanosphere (AuNS) and gold nanorod (AuNR) into polyacrylate based LCE elastomer to fabricate LCE/AuNR and LCE/AuNS micropillars or microactuators. The effect of gold nanoparticle inclusion has been studied by spectroscopy (UV–vis‐near‐infrared), microscopy (transmission electron microscopy), thermal analysis (differential scanning calorimetry and thermogravimetric analysis), and x‐ray scattering (wide‐angle x‐ray scattering and small‐angle x‐ray scattering). Finite element analysis is performed to examine the feasibility of utilizing the photothermal effect of AuNR/AuNS to enable photothermal actuation of LCE/AuNR and LCE/AuNS micropillars. The comparative experimental studies on the thermal and photothermal actuation behavior of the LCE, LCE/AuNS, and LCE/AuNR micropillar suggested that AuNR is an excellent candidate for developing high‐performance LCE actuators with photothermal actuation capability. With inclusion of less than 1 wt% of AuNR, the very high maximum actuation strain (30%) and rapid response (a few seconds) have been achieved in LCE/AuNR micropillar actuators under 635 nm laser irradiation.