Magnetic soft fiber robots have demonstrated significant potential in minimally invasive medicine due to their superior navigability in confined lumens. However, integrating functional end-effectors into these systems often leads to control coupling, where the actuation of distal modules inadvertently interferes with the robot's navigation posture. Herein, we propose a decoupled actuation strategy by integrating a photothermal MXene/reduced graphene oxide (RGO) gripper onto a magnetically steerable fiber robot. The distal gripper features a bilayer architecture, comprising a functional MXene@RGO/elastomer composite layer and a passive substrate layer. Leveraging the high photothermal conversion efficiency of MXene nanosheets, the gripper generates significant bending deformation driven by the thermal expansion mismatch under near-infrared (NIR) irradiation. This optical actuation mechanism is physically independent of the magnetic steering system, effectively eliminating signal crosstalk. We demonstrate that the fiber robot can perform precise magnetic navigation through complex tortuous paths and execute on-demand optical grasping of small objects without compromising its structural flexibility. This work presents a robust material interface-based solution for enabling multimodal control in soft robotics, expanding their capabilities for precise remote operations in restricted environments.

Drawing inspiration from the doubly reentrant microstructures on springtail skins, surfaces exhibiting repellency to liquids with very low surface tension, are well developed. However, utilizing doubly reentrant microstructures for controllable wettability switching, especially for liquids with low surface tensions, still remains a challenge. Herein, a strategy is presented involving two-photon lithography-assisted molding to fabricate doubly reentrant soft microstructures (DRSMs) with real-time magnetic responsiveness. Owing to the high spatial resolution enabled by two-photon absorption and the dissolvable molding template, the 3D reentrant features are well preserved in the DRSMs based on the magnetic elastomer. Accordingly, the fabricated magnetic DRSMs exhibit switchable repellency for nearly all commonly used solvents within 1 s. Furthermore, the additional doubly reentrant micro-fence design surrounding the doubly reentrant micropillars allows the DRSMs to switch wettability even when fully immersed in liquids. These DRSMs demonstrate sufficient abilities for on-demand analyte enrichment and drug release. This work may not only serve as a design strategy to enhance the responsiveness of DRSMs but also significantly simplify the wetting switching system, which is highly attractive across various fields in biomedical and microelectronic applications.

Magnetic soft robots with multimodal locomotion have demonstrated significant potential for target manipulation tasks in hard-to-reach spaces in recent years. Achieving universal manipulation between robots and their targets requires a nondestructive and easily switchable interaction with broad applicability across diverse targets. However, establishing versatile and dynamic interactions between diverse targets and robotic systems remains a significant challenge. Herein, a series of magnetic millirobots capable of universal target manipulation with magnetically switchable adhesion is reported. Through two-photon lithography-assisted molding, magnetic soft double-reentrant micropillar arrays with liquid repellency are fabricated on the robots. These micropillar arrays can serve as switchable adhesion units for the millirobots to effectively manipulate targets of various geometries (0D, 1D, 2D, and 3D) in both air and water. As proof-of-concept demonstrations, these adhesive robots can perform various complex tasks, including circuit repair, mini-turbine assembly, and high-speed underwater rotation of the turbine machine. This work may offer a versatile approach to magnetic manipulation of non-magnetic objects through amphibious adhesion, emerging as a new paradigm in robotic manipulation.

Highly programmable shape morphing of 4D-printed micro/nanostructures is urgently desired for applications in robotics and intelligent systems. However, due to the lack of autonomous holistic strategies throughout the target shape input, optimal material distribution generation, and fabrication program output, 4D nanoprinting that permits arbitrary shape morphing remains a challenging task for manual design. In this study, we report an autonomous inverse encoding strategy to decipher the genetic code for material property distributions that can guide the encoded modeling toward arbitrarily pre-programmed 4D shape morphing. By tuning the laser power of each voxel at the nanoscale, the genetic code can be spatially programmed and controllable shape morphing can be realized through the inverse encoding process. Using this strategy, the 4D-printed structures can be designed and accurately shift to the target morphing of arbitrarily hand-drawn lines under stimulation. Furthermore, as a proof-of-concept, a flexible fiber micromanipulator that can approach the target region through pre-programmed shape morphing is autonomously inversely encoded according to the localized spatial environment. This strategy may contribute to the modeling and arbitrary shape morphing of micro/nanostructures fabricated via 4D nanoprinting, leading to cutting-edge applications in microfluidics, micro-robotics, minimally invasive robotic surgery, and tissue engineering.

Magnetic soft flapping milliswimmers hold significant potential for biomedical applications due to their flexible mobility and multifunctionality. However, advanced motion control tasks for such forms remain underexplored, hindering their flexible mobility and various biomedical applications. The multi-physics coupling inherent in the flapping swimming process presents substantial challenges for dynamics modeling and control. In this study, we fabricated a magnetic soft flapping millirobot and conducted dynamics analysis using rigid-body modeling and quasi-static wing-flapping analysis method. The resulting state-space model is employed to build a navigation control framework based on adaptive Model Predictive Control (MPC) method, realizing autonomous navigation and obstacle avoidance performances. To validate the effectiveness of the proposed control framework, the complex path-following task in 3D space is performed, demonstrating superior performance compared to geometry-based following methods. Furthermore, the robot's navigation ability in complex environments is evaluated in both physical and simulated setups featuring static and dynamics obstacles. The milliswimmer's 3D flexible mobility and its capability to operate effectively in challenging and intricate environments may reveal great potential for real-world biomedical and other advanced applications. Note to Practitioners-This paper is motivated by the problem of precise motion control task of the magnetic soft flapping milliswimmer but the method also applies to other magnetic torque driven swimmers. Existing literature has not fully investigated the modeling and control strategy for the magnetic driven flapping swimming motion. This paper suggests a modeling method to describe the magnetic field driven propulsion from body-environment interactions and proposed a control framework which is suitable for the mechanism. We then demonstrate the efficacy of the method with a series of experiments on advanced motion control tasks. In future research, we will explore how instantaneous magnetic actuation dynamics shape the robot's motion profile, with the goal of improving both the generalization capability and precision of the proposed approach.

The emergence of micro/nanorobotics stands poised to revolutionize various biomedical applications, given its potential to offer precision, reduced invasiveness, and enhanced functionality. In the face of such potential, understanding the mechanisms that drive these tiny robots, especially their actuation techniques, becomes critical. Although there is a surge in research dedicated to micro/nanorobotics, there exists a gap in consolidating the diverse actuation strategies and their suitability for biomedical applications. This comprehensive review seeks to bridge this gap by providing an in‐depth evaluation of the current actuation techniques employed by micro/nanorobots, particularly emphasizing their relevance and potential for clinical translation. The discussion starts by elucidating the different actuation strategies, ranging from magnetic, electric, acoustic, light‐based, to chemical and biological mechanisms. Then, various examples and meticulous assessment of each technique are offered, spotlighting their respective merits and limitations within a biomedical context. This review illuminates the transformative capabilities of these actuation methods in medicine. It not only highlights the progress made in this burgeoning field but also underscores the areas that require further exploration and development.

Reconfigurable and tunable holograms hold significant practical value in the fields of anti-counterfeiting, optical security, and information display due to their ability to reprogram holographic patterns and create variable visual effects. However, current encryption techniques face challenges in achieving rapid encryption/decryption and ensuring consistent methods. In this study, a method for producing a reconfigurable encryption hologram utilizing the deformation and recovery properties of micropillars in response to liquid is demonstrated. Micron-scale micropillars are fabricated using femtosecond laser two-photon polymerization. By exploiting the rapid deformation and recovery capabilities of micropillars with specific pitches and aspect ratios in response to liquids, micropillar structures and holograms are combined to construct reconfigurable holograms. The encrypted pattern information in the reconfigurable holograms is only readable following immersion in alcohol and laser irradiation. The proposed method offers a facile, reversible, reusable, and practical solution for information encryption, with significant potential in anti-counterfeiting and optical security. A method for producing reconfigurable encryption holograms using the deformation and recovery characteristics of the micropillar response to liquid is proposed. The specific pitch and aspect ratio design can flexibly adjust micropillars' rapid deformation and recovery ability of responses to liquid. The reconfigurable hologram designed based on the method can realize dual information encryption in an alcohol environment and laser irradiation. image

The field of laser fabrication technologies has seen remarkable advancements in recent years [...]

Triple-negative breast cancer (TNBC), characterized by its aggressive metastatic propensity and lack of effective targeted therapeutic options, poses a major challenge in oncological management. A proof-of-concept neoadjuvant strategy aimed at inhibiting TNBC tumor growth and mitigating metastasis through a localized delivery of chemotherapeutics is reported in this paper. This approach addresses the limitations in payload capacity and stimuli responsiveness commonly associated with microrobotics in oncology. A hydrogel-based system is developed for the immobilization of chemotherapeutic agents, subsequently encapsulated within magnetically responsive microrobots. This design leverages external magnetic fields to facilitate the precise navigation and localization of the therapeutic agents directly to the tumor site. The efficacy of this approach is demonstrated in an animal model, in which a significant 14-fold reduction in tumor size and suppression of metastasis to critical organs such as the liver and lungs are observed. Crucially, the drug release mechanism is engineered to be responsive to the tumor microenvironment and is regulated by the overexpression of the enzymatic activity of matrix metalloproteinases (MMP2 and MMP9) in TNBC tumors, triggering the degradation of the hydrogel matrix, leading to controlled release of the immobilized therapeutic drug. This ensures that the therapeutic action is localized, reducing systemic toxicity and enhancing treatment efficacy. These findings suggest that this neoadjuvant approach holds promise for broader applications in other cancer types.

AbstractSwitchable adhesion, a phenomenon characterized by the ability to transition between attachment and detachment states under external stimuli, has recently gained popularity in various advanced devices. The realization of the desired functionalities on such surfaces relies on intricate interfacial designs. A general understanding of the commonalities and distinctions among these designs can foster the development of refined switchable adhesion interfaces (SAIs). To address this, this review first examines adhesion interfaces by focusing on the fundamental interactions at the atomic/molecular level, adhesion models, and their correlation with the diverse forces/bonds that dominate the adhesion behaviors. The latest progress in SAIs based on various forces/bonds, including electrostatic force, van der Waals force, capillary force, chemical bond, and suction force, is then discussed with regard to their specific design strategies, such as structures, components, and triggers. Additionally, an extensive overview of the broad applications of SAIs in fields ranging from space to biomedicine is provided, along with an exploration of the prevailing challenges and potential opportunities. With the rapid progress that has been made in state‐of‐the‐art mechanisms and design strategies, SAIs are expected to undergo booming development in the foreseeable future.

Magnetic fiber robots have revealed great potential for future minimally invasive robotic surgery. However, with the miniaturization of fiber robots, the integration of functional microtools at the distal end becomes extremely challenging, since it requires assembling multifunctional structures on the curved surfaces of fiber ends, which typically have very small curvature radii. In this study, a submillimeter fiber robot with integrated micro-manipulation tool at the distal end is reported using a "Swiss roll" assembly strategy. This approach enables the one-step assembly of multiscale structures (mm-mu m) from a 2D film to a 3D tool on the curved surface of the fiber robot. The multiscale structure consists of a millimeter-scale (mm) magnetic thin film with integrated micrometer-scale (mu m) feature structures, which is inspired from the cat tongue covered by numerous little papillae. The fiber robot can perform multiple functions including endovascular clot grabbing, liquid delivery, and sampling under the manipulation of the magnetic field. The strategy provides a universal protocol for integrating and assembling functional components at the distal end of fiber robots, contributing significantly to the functionalization and miniaturization of interventional medical robots. Magnetic fiber robots reveal great potential in minimally invasive surgery. Assembling microtools on curved surfaces of fiber ends is challenging due to their small curvature radii. Herein, a submillimeter fiber robot with integrated micro-manipulation tools is reported using a "Swiss roll" method, allowing one-step assembly on the curved surface. The robot can perform various functions via magnetic manipulation.image

Biomimetic switchable adhesion interfaces (BSAIs) with dynamic adhesion states have demonstrated significant advantages in micro-manipulation and bio-detection. Among them, gecko-inspired adhesives have garnered considerable attention due to their exceptional adaptability to extreme environments. However, their high adhesion strength poses challenges in achieving flexible control. Herein, we propose an elegant and efficient approach by fabricating three-dimensional mushroom-shaped polydimethylsiloxane (PDMS) micropillars on a flexible PDMS substrate to mimic the bending and stretching of gecko footpads. The fabrication process that employs two-photon polymerization ensures high spatial resolution, resulting in micropillars with exquisite structures and ultra-smooth surfaces, even for tip/stem ratios exceeding 2 (a critical factor for maintaining adhesion strength). Furthermore, these adhesive structures display outstanding resilience, enduring 175% deformation and severe bending without collapse, ascribing to the excellent compatibility of the micropillar's composition and physical properties with the substrate. Our BSAIs can achieve highly controllable adhesion force and rapid manipulation of liquid droplets through mechanical bending and stretching of the PDMS substrate. By adjusting the spacing between the micropillars, precise control of adhesion strength is achieved. These intriguing properties make them promising candidates for various applications in the fields of microfluidics, micro-assembly, flexible electronics, and beyond.

Microactuators can autonomously convert external energy into specific mechanical motions. With the feature sizes varying from the micrometer to millimeter scale, microactuators offer many operation and control possibilities for miniaturized devices. In recent years, advanced microfluidic techniques have revolutionized the fabrication, actuation, and functionalization of microactuators. Microfluidics can not only facilitate fabrication with continuously changing materials but also deliver various signals to stimulate the microactuators as desired, and consequently improve microfluidic chips with multiple functions. Herein, this cross-field that systematically correlates microactuator properties and microfluidic functions is comprehensively reviewed. The fabrication strategies are classified into two types according to the flow state of the microfluids: stop-flow and continuous-flow prototyping. The working mechanism of microactuators in microfluidic chips is discussed in detail. Finally, the applications of microactuator-enriched functional chips, which include tunable imaging devices, micromanipulation tools, micromotors, and microsensors, are summarized. The existing challenges and future perspectives are also discussed. It is believed that with the rapid progress of this cutting-edge field, intelligent microsystems may realize high-throughput manipulation, characterization, and analysis of tiny objects and find broad applications in various fields, such as tissue engineering, micro/nanorobotics, and analytical devices.

Femtosecond laser (FSL) technology has created an evolution in ophthalmic surgery in the last few decades. With the advantage of high precision, accuracy, and safety, FSLs have helped surgeons overcome surgical limits in refractive surgery, corneal surgery, and cataract surgery. They also open new avenues in ophthalmic areas that are not yet explored. This review focuses on the fundamentals of FSLs, the advantages in interaction between FSLs and tissues, and typical clinical applications of FSLs in ophthalmology. With the rapid progress that has been made in the state of the art research on FSL technologies, their applications in ophthalmic surgery may soon undergo a booming development.

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.

As a typical micro/nano processing technique, femtosecond laser fabrication provides the opportunity to achieve delicate microstructures. The outstanding advantages, including nanoscale feature size and 3D architecting, can bridge the gap between the complexity of the central nervous system in virto and in vivo. Up to now, various types of microstructures made by femtosecond laser are widely used in the field of neurobiological research. In this mini review, we present the recent advancement of femtosecond laser fabrication and its emerging applications in neurobiology. Typical structures are sorted out from nano, submicron to micron scale, including nanoparticles, micro/nano-actuators, and 3D scaffolds. Then, several functional units applied in neurobiological fields are summarized, such as central nervous system drug carriers, micro/nano robots and cell/tissue scaffolds. Finally, the current challenges and future perspective of integrated neurobiology research platform are discussed.

Optical systems provide a new and practical platform for studying Bloch oscillations. This study investigates the fundamental-mode propagation of polarization-dependent Bloch oscillations. By using the three-dimensional properties of femtosecond laser direct writing, we fabricate a polymer-based gradient waveguide array and determine the Bloch oscillations under different polarization inputs by using the birefringence gradient and the equivalent refractive index, thus exhibiting a polarization-dependent Bloch period. Our results provide a new, to the best of our knowledge, paradigm for two-dimensional optical Bloch modes and highlight the influence of optical polarization in the same system, which provides a possibility to observe richer physics related to Bloch oscillations in one structure.

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.

Natural musculoskeletal systems have been widely recognized as an advanced robotic model for designing robust yet flexible microbots. However, the development of artificial musculoskeletal systems at micro-nanoscale currently remains a big challenge, since it requires precise assembly of two or more materials of distinct properties into complex 3D micro/nanostructures. In this study, we report femtosecond laser programmed artificial musculoskeletal systems for prototyping 3D microbots, using relatively stiff SU-8 as the skeleton and pH-responsive protein (bovine serum albumin, BSA) as the smart muscle. To realize the programmable integration of the two materials into a 3D configuration, a successive on-chip two-photon polymerization (TPP) strategy that enables structuring two photosensitive materials sequentially within a predesigned configuration was proposed. As a proof-of-concept, we demonstrate a pH-responsive spider microbot and a 3D smart micro-gripper that enables controllable grabbing and releasing. Our strategy provides a universal protocol for directly printing 3D microbots composed of multiple materials.