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Living things in nature have evolved with unique morphologies, structures, materials, behaviors, and functions to survive in complex natural environments. Nature has inspired the design ideas, preparation methods, and applications of versatile micro/nanomotors. This review summarizes diverse nature-inspired micro/nanomotors, which can be divided into five groups: (i) natural morphology-inspired micro/nanomotors, whose shapes are designed to imitate the morphologies of plants, animals, and objects in nature. (ii) Natural structure-inspired micro/nanomotors, which use structures from plants, red blood cells, and platelet cells as components of micro/nanomotors, or directly use sperm cells and microorganisms as the engines of micro/nanomotors. (iii) Natural behavior-inspired micro/nanomotors, which are proposed to mimic natural behaviors such as motion behavior, swarm behavior, and communication behavior between individuals. (iv) Micro/nanomotors inspired by both natural morphology and behavior. Nature makes it possible for synthetic micro/nanomotors to possess interesting morphologies, novel preparation methods, new propulsion modes, innovative functions, and broad applications. The nature-inspired micro/nanomotors could provide a promising platform for various practical fields.

Microscale intestinal perforation can cause considerable mortality and is very difficult to treat using conventional methods owing to the numerous challenges associated with microscale operations, which require the development of new body-friendly and effective treatment methods. Swarming micro- and nanomotors have shown great potential in biomedical applications in complex and hard-to-reach environments. Herein, we present a wheel-like magnetic-driven microswarm (WLM) with a band-aid imitation to patch microscale intestinal perforations by pasting on the perforation point in mucus-filled environments. A method called "packing under rolling" was applied to make the formed microswarms denser and rounder. Microswarms with variable aspect ratios can be fabricated by tuning the frequency and strength of the external magnetic field. Actuation and navigation in a confined complex environment, locomotion on three-dimensional surfaces, and multiple switchable motion modes have been realized by combining AC and DC magnetic fields. Moreover, we demonstrated WLM controllable navigation, movement, and microscale perforation patching in the chicken intestines

To improve the recovery rate of oil in the formation, oil recovery technology has been continuously studied. Considering the experimental cost and data measurement in oil recovery research, laborat...

Micropump systems show great potential on the micropatterning process as a result of remarkable performance and functionality. However, existing micropumps cannot be employed as direct writing tools to perform the complex micropatterning process because of their lacking motility and controllability. Here, we propose a motile micropump system based on the combination of a water-driven ZnO/Ni/polystyrene Janus micromotor with a traditional immobilized micropump. This novel motile micropump system can translate the trajectory of Janus micromotors into predefined micropatterns by pumping away passive silica particles around the micromotor under the effect of diffusiophoresis. The resolution and efficiency of the micropatterning process can be regulated by controlling the diameters of Janus micromotors. Diverse surface micropatterns can be fabricated though remote magnetic control of the motile micropump system. Such ability to transform the versatile motile micropump into predetermined surface micropatterns creates new opportunities for mask-free micropatterning.

Interaction behaviors are a crucial, distinctive feature of organisms in ecological systems. Inspired by nature, micro-/nanorobots also show interaction behaviors with a significant number of novel and advanced functionalities. The micro-/nanoscale size and self-driven abilities of micro-/nanorobots have attracted considerable attention for potential applications. The mission of micro-/nanorobots has evolved from basic mechanical transfer or assistance to a diverse range of complex tasks, such as targeted drug delivery, biosensing, and environmental remediation. Herein, we focus on the interaction behavior of coexisting cooperative cognitive (Tri-Co) micro-/nanorobots, summarize recent research, and classify the interactions into three broad types: with the environment, with robot peers, and with human external control.

As visible light accounts for a larger proportion of solar energy and is harmless to living organisms, it has the potential to be the energy source of micro/nanomotors, which transform visible-light energy into mechanical motion, for different applications, especially in environmental remediation. However, how to precisely control the motion of visible-light-driven micro/nanomotors (VLD-MNMs) and efficiently utilize the weak visible-light photon energy to acquire rapid motion are significant challenges. This review summarizes the most critical aspects, involving photoactive materials, propulsion mechanisms, control methods, and applications of VLD-MNMs, and discusses strategies to systematically enhance the energy-harvesting efficiency and adaptation. At first, the photoactive materials have been divided into inorganic and organic photoactive materials and comprehensively discussed. Then, different propulsion mechanisms of the current VLD-MNMs are presented to explain the improvement in the actuation force, speed, and environmental adaptability. In addition, considering the characteristics of easy control of VLD-MNMs, we summarized the direction, speed, and cluster control methods of VLD-MNMs for different application requirements. Subsequently, the potential applications of VLD-MNMs, e.g., in environmental remediation, micropumps, cargo delivery, and sensing in microscale, are presented. Finally, discussions and suggestions for future directions to enhance the energy-harvesting efficiency and adaptation of VLD-MNMs are provided.

The acid-base environment of the biological digestive system is formed with the help of hydrogen ions and bicarbonate. At the same time, the chloride capacity in the blood is not ignorable. These ionic environments provide a new horizon for the medical application of bubble-propelled micromotors. Herein, a Janus Mg-based micromotor is reported as a novel ultrasonic contrast agent and its potential advantages in medical imaging are explored. With the capability of being powered by the magnetic field, these micromotors could be navigated to the corresponding ionic environment, and then they would rapidly generate continuous bubbles. These bubbles achieve an efficient and guided propulsion of micromotor, also provide support for contrast-enhanced ultrasound imaging. Besides owning the dual functions of imaging and targeted transport, the micromotors present aggregation response under the action of ultrasound, which is helpful for local reinforcement of the imaging effect. Such multi-response biocompatible Janus micromotor provides a new perspective for medical imaging and diagnosis.

Conventional methods for manipulating heat flow are restricted by a trade-off between tunable capability and efficient thermal conductivity. Herein, we report a novel method to manipulate thermal fields by using a reconfigurable two-phase thermal metamaterial composed of a translucent liquid and controllable micro magnetic particles. The thermal behavior as a function of the components of two-phase media is predicted on the basis of coupled radiative and conductive theory. The response of the thermal field can be efficiently tuned by the radial distribution of discrete microparticles. Precise and reconfigurable thermal coding/decoding information transmission is demonstrated by using multiple thermal particles regulating units. Our work should lead to the development of platforms for manipulating physical fields with multi-scale and multi-domain applications, which can be analogized to optics and acoustics. This work pioneers physical manipulations and should aid in the development of smart functional devices with micromanipulators for multiple physical environments.

Multiphysics-driven synthetic micro/nanomotors can convert chemical or other types of energies, such as magnetic, electrical, photochemical, thermal, acoustic energies into mechanical energies in terms of motion and velocity. Significant efforts have been dedicated to preparing micro/nanomotors as well as the applications of micro/nanomotors. This paper provides a comprehensive review on the research for a large variety of micro/nanomotors recently investigated in China. Three types of propulsion mechanisms are proposed for multiphysics-driven synthetic micro/nanomotors, i.e., chemical propulsion, external-physical-fields propulsion and hybrid propulsion. It is shown that chemical propelled micro/ nanomotors can convert the chemical energy caused by the redox reactions into mechanical energy, such as concentration- gradient propelled micro/nanomotors, self-electrophoresis micro/nanomotors and bubble-propelled micro/nanomotors. Among the diverse chemical propelled micro/nanomotors, the micro/nanomotors prepared by rolled-up or eletrodeposition technique show a higher velocity and a more controllable motion. External-physical-fields propelled micro/nanomotors can transfer light, magnetic energy, ultrasonic energy into mechanical energy. There is no need to require any additional chemical fuel which is harmful to human body such as hydrogen peroxide, strong acid, alkaline, Br2, or I2 solutions, for the micro/nanomotors propelled by external-physical-fields. Therefore, it has better biocompatibility and broader applications than the chemical propelled micro/nanomotors. Hybrid propelled micro/nanomotors can combine the chemical propulsion mechanisms with external-physical-fields propulsion mechanisms simultaneously. The hybrid propelled micro/nanomotors not only can move in the chemical fuel, but also can be propelled by light, magnetism or ultrasonic energy. It has more powerful applicability and a broader application than that propelled by the other two propulsion mechanisms. Although the existed researches of micro/nanomotors are still of limitations, such as ambiguous propulsion mechanisms, low velocity, imprecise motion control and poor biocompatibility, the Chinese researchers have made significant progress and breakthroughs in recent years. The micro/nanomotors, which move autonomously in fluids, are studied for a growing number of applications that include targeted drug delivery, separation, biosensor, and fabrication of active biomimetic systems, environmental remediation and other emerging applications. The micro/ nanomotors can be used as adsorbent of microscale particle to achieve reversible swarming and separation of micro/ nanomotors, eliminate the pollutants in environment and the toxin in human body. In recent years, the micro/nanomotors can also be used as microscale sensor to measure micro-fluid viscosity, search and repair the microcracks. In addition, the micro/nanomotors can be applied for drug carrier to pick up and deliver the drug particles to targeted locations and can effectively control-release drug molecules to avoid drug accumulation. Nowadays, the micro/nanomotors also can be applied to control and assemble the microparticles and this technique is expected to be applied for biological single-cell analysis system. Although the micro/nanomotors can be applied in different fields, the real application of micro/ nanomotors is still far away to reach, especially to be used in human body. In conclusion, various propulsion mechanisms have been demonstrated in this review. Furthermore, typical applications in various fields are also presented. The prospects, challenges and future trends of the investigation on micro-and nanomotors are discussed. It is helpful for researches who are working in micro/nano motors research area as well as in engineering applications.

Recent strides in micro- and nanomanufacturing technologies have sparked the development of micro-/nanorobots with enhanced power and functionality. Due to the advantages of on-demand motion control, long lifetime, and great biocompatibility, magnetic propelled micro-/nanorobots have exhibited considerable promise in the fields of drug delivery, biosensing, bioimaging, and environmental remediation. The magnetic fields which provide energy for propulsion can be categorized into rotating and oscillating magnetic fields. In this review, recent developments in oscillating magnetic propelled micro-/nanorobot fabrication techniques (such as electrodeposition, self-assembly, electron beam evaporation, and three-dimensional (3D) direct laser writing) are summarized. The motion mechanism of oscillating magnetic propelled micro-/nanorobots are also discussed, including wagging propulsion, surface walker propulsion, and scallop propulsion. With continuous innovation, micro-/nanorobots can become a promising candidate for future applications in the biomedical field. As a step toward designing and building such micro-/nanorobots, several types of common fabrication techniques are briefly introduced. Then, we focus on three propulsion mechanisms of micro-/nanorobots in oscillation magnetic fields: (1) wagging propulsion; (2) surface walker; and (3) scallop propulsion. Finally, a summary table is provided to compare the abilities of different micro-/nanorobots driven by oscillating magnetic fields.

In order to increase the velocity and propulsion efficiency, an accelerated microrocket with a biomimetic lotus-leaf-like surface is proposed through an electrodeposition technique along with a self-assembly technique. The microrocket is propelled by the thrust of hydrogen bubbles generated from a redox reaction in a strong acidic solution. A low-surface-energy (LSE) layer along with rough structures is constructed at the outer surface of the microrocket to reduce the drag force resulting from the environmental fluid. Physical insights on the drag force reduction and the corresponding acceleration are identified. The decrease of drag reduction is achieved. A comparison of the average velocity of the microrockets with and without a LSE hydrophobic layer is performed. As we found, the average velocity of the microrocket is increased after being self-assembled with a biomimetic hydrophobic surface.

While chemical communication plays a key role in diverse natural processes, the intelligent chemical communication between synthetic nanomotors remains unexplored. Here we demonstrate the design and operation of bio-inspired synthetic nanomotors capable of chemical communication among themselves that influences their propulsion behavior. The chemical message is sent from a moving 'activator' motor to a nearby 'activated' (receiver) one, and involves release of silver ions from a Janus PS/Ni/Au/Ag 'activator' motor to the 'activated' Janus SiO2/Pt nanomotor. The transmitted silver signal is translated rapidly into a dramatic speed change associated with the enhanced catalytic activity of 'activated' motors. The concept of establishing chemical communication between different synthetic nanomotors paves the way to intelligent nanoscale robotic systems that are capable of cooperating with each other.

One emerging and exciting topic in robotics research is the design of micro-/nanoscale robots for biomedical operations. Unlike industrial robots that are developed primarily to automate routine and dangerous tasks, biomedical nanorobots are designed for complex, physiologically relevant environments, and tasks that involve unanticipated biological events. Here, a biologically interfaced nanorobot is reported, made of magnetic helical nanomotors cloaked with the plasma membrane of human platelets. The resulting biomimetic nanorobots possess a biological membrane coating consisting of diverse functional proteins associated with human platelets. Compared to uncoated nanomotors which experience severe biofouling effects and hence hindered propulsion in whole blood, the platelet-membrane-cloaked nanomotors disguise as human platelets and display efficient propulsion in blood over long time periods. The biointerfaced nanorobots display platelet-mimicking properties, including adhesion and binding to toxins and platelet-adhering pathogens, such as Shiga toxin and Staphylococcus aureus bacteria. The locomotion capacity and platelet-mimicking biological function of the biomimetic nanomotors offer efficient binding and isolation of these biological threats. The dynamic biointerfacing platform enabled by platelet-membrane cloaked nanorobots thus holds considerable promise for diverse biomedical and biodefense applications.

Self-propelled micro- and nanoscale robots represent a rapidly emerging and fascinating robotics research area. However, designing autonomous and adaptive control systems for operating micro/nanorobotics in complex and dynamically changing environments, which is a highly demanding feature, is still an unmet challenge. Here we describe a smart microvehicle for precise autonomous navigation in complicated environments and traffic scenarios. The fully autonomous navigation system of the smart microvehicle is composed of a microscope-coupled CCD camera, an artificial intelligence planner, and a magnetic field generator. The microscope-coupled CCD camera provides real-time localization of the chemically powered Janus microsphere vehicle and environmental detection for path planning to generate optimal collision-free routes, while the moving direction of the microrobot toward a reference position is determined by the external electromagnetic torque. Real-time object detection offers adaptive path planning in response to dynamically changing environments. We demonstrate that the autonomous navigation system can guide the vehicle movement in complex patterns, in the presence of dynamically changing obstacles, and in complex biological environments. Such a navigation system for micro/nanoscale vehicles, relying on vision-based close-loop control and path planning, is highly promising for their autonomous operation in complex dynamic settings and unpredictable scenarios expected in a variety of realistic nanoscale scenarios.

Recent strides in micro- and nanofabrication technology have enabled researchers to design and develop new micro- and nanorobots for biomedicine and environmental monitoring. Due to its non-invasive remote actuation and convenient navigation abilities, magnetic propulsion has been widely used in micro- and nanoscale robotic systems. In this article, a highly efficient Janus microdimer swimmer propelled by a rotating uniform magnetic field was investigated experimentally and numerically. The velocity of the Janus microdimer swimmer can be modulated by adjusting the magnetic field frequency with a maximum speed of 133 &mu, m&middot, s&minus, 1 (&asymp, 13.3 body length s&minus, 1) at the frequency of 32 Hz. Fast and accurate navigation of these Janus microdimer swimmers in complex environments and near obstacles was also demonstrated. This efficient propulsion behavior of the new Janus microdimer swimmer holds considerable promise for diverse future practical applications ranging from nanoscale manipulation and assembly to nanomedicine.

The swimming locomotion of fish involves a complex interplay between a deformable body and induced flow in the surrounding fluid. While innovative robotic devices, inspired by physicomechanical designs evolved in fish, have been created for underwater propulsion of large swimmers, scaling such powerful locomotion into micro-/nanoscale propulsion remains challenging. Here, a magnetically propelled fish-like artificial nanoswimmer is demonstrated that emulates the body and caudal fin propulsion swimming mechanism displayed by fish. To mimic the deformable fish body for periodic shape changes, template-electrosynthesized multisegment nanowire swimmers are used to construct the artificial nanofishes (diameter 200 nm; length 4.8 μm). The resulting nanofish consists a gold segment as the head, two nickel segments as the body, and one gold segment as the caudal fin, with three flexible porous silver hinges linking each segment. Under an oscillating magnetic field, the propulsive nickel elements bend the body and caudal fin periodically to generate travelling-wave motions with speeds exceeding 30 μm s-1 . The propulsion dynamics is studied theoretically using the immersed boundary method. Such body-deformable nanofishes exhibit a high swimming efficiency and can serve as promising biomimetic nanorobotic devices for nanoscale biomedical applications.

Considerable efforts have been devoted to self-propelled microrockets during the past decades for its diverse potential applications, ranging from targeted drug delivery to environmental remediation. Particularly attention has been given to the chemical-driven rockets which are analogous to actuators and can convert chemical energy into mechanical energy to achieve a certain propulsion velocity or force. Since the drag force on the surface of microrockets dominates the resistance in the microfluidic systems, it is of interest to decrease the drag force for efficient propulsion. A new microrocket with lower drag force is proposed with a hydrophobic molecular layer, 1-Dodecanethiol layer, on the outer polyaniline surface of the rockets by using self-assembly technology. The contact angle and the velocity of microrockets are determined before and after surface modification to quantify the drag force reduction. The findings of the research indicate that reducing drag force is a promising way for comprehensive application.Copyright © 2015 by ASME