Design Of Microrobot Research Articles

Simultaneous emergence of active turbulence and odd viscosity in a colloidal chiral active system

Active fluids display collective phenomena such as active turbulence or odd viscosity, which refer to spontaneous complex and transverse flow. The simultaneous emergence of these seemingly separate phenomena is here reported in experiment for a chiral active fluid composed of a carpet of standing and spinning colloidal rods, and in simulations for synchronously rotating hard discs in a hydrodynamic explicit solvent. Experiments and simulations reveal that multi-scale eddies emerge, a hallmark of active turbulence, with a power-law decay of the kinetic-energy spectrum, a feature of self-similar dynamics. Moreover, the particles are dragged to the centre of the vortices, a telltale sign of odd viscosity. The weak compressibility of the system enables an explicit measurement of the odd viscosity in bulk via the relation between local vorticity and excess density. Our findings are relevant for the understanding of biological systems and for the design of microrobots with collective self-organized behavior.

Acoustic Streaming-Induced Multimodal Locomotion of Bubble-Based Microrobots.

Acoustically-driven bubbles at the micron scale can generate strong microstreaming flows in its surrounding fluidic medium. The tunable acoustic streaming strength of oscillating microbubbles and the diversity of the generated flow patterns enable the design of fast-moving microrobots with multimodal locomotion suitable for biomedical applications. The acoustic microrobots holding two coupled microbubbles inside a rigid body are presented; trapped bubbles inside the L-shaped structure with different orifices generatevarious streaming flows, thus allowing multiple degrees of freedom in locomotion. The streaming pattern and mean streaming speed depend on the intensity and frequency of the acoustic wave, which can trigger four dominant locomotion modes in the microrobot, denoted as translational and rotational, spinning, rotational, and translational modes. Next, the effect of various geometrical and actuation parameters on the control and navigation of the microrobot is investigated. Furthermore, the surface-slipping multimodal locomotion, flow mixing, particle manipulation capabilities, the effective interaction of high flow rates with cells, and subsequent cancerous cell lysing abilities of the proposed microrobot are demonstrated. Overall, these results introduce a design toolbox for the next generation of acoustic microrobots with higher degrees of freedom with multimodal locomotion in biomedical applications.

Living Magnetotactic Microrobots Based on Bacteria with a Surface-Displayed CRISPR/Cas12a System for Penaeus Viruses Detection.

Bacterial microrobots are an emerging living material in the field of diagnostics. However, it is an important challenge to make bacterial microrobots with both controlled motility and specific functions. Herein, magnetically driven diagnostic bacterial microrobots are prepared by standardized and modular synthetic biology methods. To ensure mobility, the Mms6 protein is displayed on the surface of bacteria and is exploited for magnetic biomineralization. This gives the bacterial microrobot the ability to cruise flexibly and rapidly with a magnetization intensity up to about 18.65 emu g-1. To achieve the diagnostic function, the Cas12a protein is displayed on the bacterial surface and is used for aquatic pathogen nucleic acid detection. This allows the bacterial microrobot to achieve sensitive, rapid, and accurate on-site nucleic acid detection, with detection limits of 8 copies μL-1 for decapod iridescent virus 1 (DIV1) and 7 copies μL-1 for white spot syndrome virus (WSSV). In particular, the diagnostic results based on the bacterial microrobots remained consistent with the gold standard test results when tested on shrimp tissue. This approach is a flexible and customizable strategy for building bacterial microrobots, providing a reliable and versatile solution for the design of bacterial microrobots.

A review of magnetically driven swimming microrobots: Material selection, structure design, control method, and applications

Abstract Magnetically driven swimming microrobot is a typical one in the family of microrobots and they can achieve navigation and manipulation in low Reynolds number biomedical environments with an external magnetic drive strategy. This study reviews recent advances in material selection, structure design, fabrication techniques, drive control method, and applications for magnetically driven swimming microrobots. First, the materials used in magnetically driven swimming microrobots were introduced and the effect of material selection on performance was discussed. Second, structure design of swimming microrobots and manufacturing techniques are reviewed, followed by a discussion on the main advances in effective motion control, path planning, and path tracking. Then, the multi-applications of magnetically driven swimming microrobots including targeted drug delivery, cell manipulation, and minimally invasive surgery are summarized. Finally, the current challenges and future directions of the work on magnetically driven swimming microrobots are discussed.

Design and Control of a Magnetically-Actuated Anti-Interference Microrobot for Targeted Therapeutic Delivery

Design and Control of a Magnetically-Actuated Anti-Interference Microrobot for Targeted Therapeutic Delivery

Microrobots for Biomedicine: Unsolved Challenges and Opportunities for Translation.

Microrobots are being explored for biomedical applications, such as drug delivery, biological cargo transport, and minimally invasive surgery. However, current efforts largely focus on proof-of-concept studies with nontranslatable materials through a "design-and-apply" approach, limiting the potential for clinical adaptation. While these proof-of-concept studies have been key to advancing microrobot technologies, we believe that the distinguishing capabilities of microrobots will be most readily brought to patient bedsides through a "design-by-problem" approach, which involves focusing on unsolved problems to inform the design of microrobots with practical capabilities. As outlined below, we propose that the clinical translation of microrobots will be accelerated by a judicious choice of target applications, improved delivery considerations, and the rational selection of translation-ready biomaterials, ultimately reducing patient burden and enhancing the efficacy of therapeutic drugs for difficult-to-treat diseases.

A 4D-Printing Inverse Design Strategy for Micromachines with Customized Shape-Morphing.

An active heterostructure with smart-response material used as "muscle" and inactive material as "skeleton" can deform over time to respond to external stimuli. 4D printing integrated with two-photon polymerization technology and smart material allows the material or characteristic distribution of active heterostructures to be defined directly at the microscale, providing a huge programmable space. However, the high degree of design freedom and the microscale pose a challenge to the construction of micromachines with customized shape morphing. Here, a reverse design strategy based on multi-material stepwise 4D printing is proposed to guide the structural design of biomimetic micromachines. Inspired by the piecewise constant curvature model of soft robot, a reverse design algorithm based on the Timoshenko model isdeveloped. The algorithm can approximate 2D features to a constant-curvature model and determine an acceptable material distribution within the explored printing range. Three Chinese "Long" (Chinese dragon heralds of good fortune) designed by the strategy candeform to the customized shape. In addition, a microcrawler printed using this method canimitate a real inchworm gait. These results demonstrate that this method can be an efficient tool for the action or shape design of bionic soft microrobots or micromachines with predetermined functions.

Bioinspired claw-engaged and biolubricated swimming microrobots creating active retention in blood vessels

Swimming microrobots guided in the circulation system offer considerable promise in precision medicine but currently suffer from problems such as limited adhesion to blood vessels, intensive blood flow, and immune system clearance-all reducing the targeted interaction. A swimming microrobot design with clawed geometry, a red blood cell (RBC) membrane-camouflaged surface, and magnetically actuated retention is discussed, allowing better navigation and inspired by the tardigrade's mechanical claw engagement, coupled to an RBC membrane coating, to minimize blood flow impact. Using clinical intravascular optical coherence tomography in vivo, the microrobots' activity and dynamics in a rabbit jugular vein was monitored, illustrating very effective magnetic propulsion, even against a flow of ~2.1 cm/s, comparable with rabbit blood flow characteristics. The equivalent friction coefficient with magnetically actuated retention is elevated ~24-fold, compared to magnetic microspheres, achieving active retention at 3.2 cm/s, for >36 hours, showing considerable promise across biomedical applications.

Morphological transformations of vesicles with confined flexible filaments

A fundamental understanding of cell shaping with confined flexible filaments, including microtubules, actin filaments, and engineered nanotubes, has been limited by the complex interplay between the cell membrane and encapsulated filaments. Here, combining theoretical modeling and molecular dynamics simulations, we investigate the packing of an open or closed filament inside a vesicle. Depending on the relative stiffness and size of the filament to the vesicle as well as the osmotic pressure, the vesicle could evolve from an axisymmetric configuration to a general configuration with a maximum of three reflection planes, and the filament could bend in or out of plane or even coil up. A plethora of system morphologies are determined. Morphological phase diagrams predicting conditions of shape and symmetry transitions are established. Organization of actin filaments or bundles, microtubules, and nanotube rings inside vesicles, liposomes, or cells are discussed. Our results provide a theoretical basis to understand cell shaping and cellular stability and to help guide the development and design of artificial cells and biohybrid microrobots.

Versatile magnetic hydrogel soft capsule microrobots for targeted delivery

Maintaining the completeness of cargo and achieving on-demand cargo release during long navigations in complex environments of the internal human body is crucial. Herein, we report a novel design of magnetic hydrogel soft capsule microrobots, which can be physically disintegrated to release microrobot swarms and diverse cargoes with almost no loss. CaCl2 solution and magnetic powders are utilized to produce suspension droplets, which are put into sodium alginate solution to generate magnetic hydrogel membranes for enclosing microrobot swarms and cargos. Low-density rotating magnetic fields drive the microrobots. Strong gradient magnetic fields break the mechanical structure of the hydrogel shell to implement on-demand release. Under the guidance of ultrasound imaging, the microrobot is remotely controlled in acidic or alkaline environments, similar to those in the human digestion system. The proposed capsule microrobots provide a promising solution for targeted cargo delivery in the internal human body.

Accelerating the Design of Self-Guided Microrobots in Time-Varying Magnetic Fields.

Mobile robots combine sensory information with mechanical actuation to move autonomously through structured environments and perform specific tasks. The miniaturization of such robots to the size of living cells is actively pursued for applications in biomedicine, materials science, and environmental sustainability. Existing microrobots based on field-driven particles rely on knowledge of the particle position and the target destination to control particle motion through fluid environments. Often, however, these external control strategies are challenged by limited information and global actuation where a common field directs multiple robots with unknown positions. In this Perspective, we discuss how time-varying magnetic fields can be used to encode the self-guided behaviors of magnetic particles conditioned on local environmental cues. Programming these behaviors is framed as a design problem: we seek to identify the design variables (e.g., particle shape, magnetization, elasticity, stimuli-response) that achieve the desired performance in a given environment. We discuss strategies for accelerating the design process using automated experiments, computational models, statistical inference, and machine learning approaches. Based on the current understanding of field-driven particle dynamics and existing capabilities for particle fabrication and actuation, we argue that self-guided microrobots with potentially transformative capabilities are close at hand.

Design, Fabrication, and Characterization of a Helical Adaptive Multi-Material MicroRobot (HAMMR)

Adaptive locomotion is an advanced function of microrobots that can be achieved using smart materials. In this letter, a responsive hydrogel is utilized as a smart material and used to fabricate Helical Adaptive Multi-material MicroRobots (HAMMRs) with deformable tails to achieve adaptive locomotion capabilities. Moreover, a novel fabrication method is proposed to realize these types of helical microrobots with enhanced swimming performances by taking advantage of a strong magnetic head and deformable tail. The deformations of different tail designs and the fabricated microrobots are tested in different solvents. The swimming performances of the swimming microrobots are investigated experimentally under a rotating magnetic field and verified with theoretical calculations. The HAMMRs show significant deformations upon stimulation and changes in swimming performance which are in agreement with the scaled calculation result. Finally, the HAMMRs present an enhanced mobility with a highest published translational velocity for an adaptive swimming microrobot of 8.1 body length per second.

Propulsion of Homonuclear Colloidal Chains Based on Orientation Control under Combined Electric and Magnetic Fields

The remarkable efficiency and dynamics of micromachines in living organisms have inspired researchers to make artificial microrobots for targeted drug delivery, chemical sensing, cargo transport, and waste remediation applications. While several self- and directed-propulsion mechanisms have been discovered, the phoretic force has to be generated via either asymmetric surface functionalization or sophisticated geometric design of microrobots. As a result, many symmetric structures assembled from isotropic colloids are ruled out as viable microrobot possibilities. Here, we propose to utilize orientation control to actuate axially symmetric micro-objects with homogeneous surface properties, such as linear chains assembled from superparamagnetic microspheres. We demonstrate that the fore-and-aft symmetry of a horizontal chain can be broken by tilting it with an angle relative to the substrate under a two-dimensional magnetic field. A superimposed alternating current electric field propels the tilted chains. Our experiments and numerical simulation confirm that the electrohydrodynamic flow along the electrode is unbalanced surrounding the tilted chain, generating hydrodynamic stresses that both propel the chain and reorient it slightly toward the substrate. Our work takes advantage of external fields, where the magnetic field, as a driving wheel and brake, controls chain orientation and direction, while the electric field, as an engine, provides power for locomotion. Without the need to create complex-shaped micromotors with intricate building blocks, our work reveals a propulsion mechanism that breaks the symmetry of hydrodynamic flow by manipulating the orientation of a microscopic object.

A review on microrobots driven by optical and magnetic fields.

Due to their small sizes, microrobots are advantageous for accessing hard-to-reach spaces for delivery and measurement. However, their small sizes also bring challenges in on-board powering, thus usually requiring actuation by external energy. Microrobots actuated by external energy have been applied to the fields of physics, biology, medical science, and engineering. Among these actuation sources, light and magnetic fields show advantages in high precision and high biocompatibility. This paper reviews the recent advances in the design, actuation, and applications of microrobots driven by light and magnetic fields. For light-driven microrobots, we summarized the uses of optical tweezers, optoelectronic tweezers, and heat-mediated optical manipulation techniques. For magnetically driven microrobots, we summarized the uses of torque-driven microrobots, force-driven microrobots, and shape-deformable microrobots. Then, we compared the two types of field-driven microrobots and reviewed their advantages and disadvantages. The paper concludes with an outlook for the joint use of optical and magnetic field actuation in microrobots.

Carbon Quantum Dot-Decorated BiOBr/Bi2WO6 Photocatalytic Micromotor for Environmental Remediation and DFT Calculation

Efficient photocatalysts are crucial for degrading antibiotic pollutants in water and vital for environmental remediation. In this study, an efficient carbon quantum dot (CQD)-modified BiOBr/Bi2WO6 hybrid material was prepared by a mild hydrothermal method. Meanwhile, a visible-light-driven micromotor based on the photocatalyst was developed. The micromotor can achieve self-propelled motion powered by the photocatalytic degradation reaction. It exhibited remarkable photocatalytic activity toward common pollutants in water, such as sulfonamide, quinolone, and tetracycline antibiotics. Among them, 10CQD/BiOBr/Bi2WO6-4 (10CBBr-4) exhibited the highest photocatalytic activity, which was 2.8 and 5 times higher than those of BiOBr and Bi2WO6, respectively. The high activity is attributed to the decoration of CQDs, which promoted visible-light absorption. Additional contributions may be due to the specific Z-type electron transport mode and flower-like BiOBr inserted by two-dimensional (2D) Bi2WO6 nanosheets, which enriched the active reaction sites, facilitated the adsorption of antibiotic molecules, and promoted the final radical attack. Based on the theoretical calculation of molecular orbitals and the Fukui index, the possible intermediate products, degradation pathways, and photocatalytic mechanism were elucidated. This study suggests that structural engineering based on CQD modification effectively allows the design of self-propelled microrobots for antibiotic degradation.

Bionic morphological design and interface-free fabrication of halfmoon microrobots with enhanced motion performance

Micro/nanorobots with the ability to explore the microworld have attracted extensive research interest for the promising biomedical application. However, the extremely low motion stability and efficiency by active self-propulsion and remote control at the sub-micron scale greatly limit its practical application. The morphological structure of micro/nanorobots with high kinetic stability and efficiency needs to be designed and prepared. Here, inspired by halfmoon betta fish, the halfmoon Janus microrobots (HJMRs) with stable directional motion performance at the sub-micron scale were developed. Through modeling analysis, the halfmoon morphology was proved a better anti-interference ability to the fluid and irregular Brownian motion than other morphologies. An interface-free Janus preparation method was developed for the production of halfmoon Janus nanoparticles and asymmetric loading of platinum to prepare HJMRs. Benefiting from the bionic rational morphological design, HJMR showed enhanced directional motion performance under chemical propulsion. HJMR also presented programmable motion control and transformable swarm control using magnetic field. HJMR was further utilized as active catalytic carriers to execute tumor-targeted propulsion and trigger the tumor-selective cascade reaction for active tumor therapeutics. The rational morphological design of microrobots with enhanced motion performance and the universal interface-free Janus preparation holds considerable promise for the large-scale production of active Janus microrobots and practical biomedical applications.

Functional Chemical Motor Coatings for Modular Powering of Self-Propelled Particles.

Inspired by the locomotion of semiaquatic insects, a variety of surface swimming microrobots propelled by surface tension Marangoni forces have been developed over the years. However, most Marangoni micromotor systems present limitations in their applications due to poor performance, short lifetime, low efficiency, and toxicity. We have developed a functional chemical motor coating consisting of protein microfilms with entrapped fuel to functionalize inactive substrates or particles. This motor material system generates large Marangoni propulsive forces with extremely small amounts of fuel due to a self-regulated fuel release mechanism based on dynamic nanostructural changes in the protein matrix, enhancing the lifetime and efficiency performance over other material systems and motors. These motor functional coatings offer great versatility as they can be coated on a wide array of substrates and materials across length scales, with opportunities as modular power sources for microrobots and small-scale devices. The synergy between the protein motor matrix and the chemical fuel enables the wider design of self-powered surface microrobots without previous limitations in their fabrication and performance, including the new design of hybrid microrobots with protein functional coatings as a modular power source.

Microrobots with Antimicrobial Peptide Nanoarchitectonics for the Eradication of Antibiotic‐Resistant Biofilms

AbstractBacterial biofilms are composed of a consortium of bacteria that communicate with each other through quorum sensing. Therefore, bacteria can form an extracellular matrix, which is a mucus composed of exopolysaccharides, peptidoglycans, and extracellular DNA, through these communication molecules. The matrix protects the community of bacteria from the adverse effects of the external environment, including antibiotics, biocides, and eradicating agents. Self‐propelled functional microrobots offer great promises in the biomedical field. The self‐propelled microrobots represent an innovative platform in microrobotic research, aiming to have an important role in the biomedical field. One of the potential applications is removal of bacterial biofilms. Herein, the specific design of multifunctional microrobots is demonstrated using antimicrobial‐designed peptides for eradication of methicillin‐resistant Staphylococcus aureus (MRSA)‐produced biofilms. The designed microrobots can perform various tasks, including autonomous navigation toward bacterial cells, mechanical entry into bacterial biofilms, and blockage of the replication of bacterial DNA by indolicidin peptides. The implemented design extends the microrobot applications not only to the removal of biological aggregates but also to the delivery and release of drugs or even target manipulation, demonstrating their great potential for use in biomedical research.

Magnet‐Driven Microwalker in Surface Motion Based on Frictional Anisotropy

Untethered magnet‐driven microrobots play an increasingly important role in various biomedical applications. Incorporating bionic technology into microrobot design is an emerging way to improve the work efficiency of microrobots. Herein, a magnetically powered and frictional anisotropy‐based microwalker that can be potentially used in in vivo nonliquid‐filled environment is proposed. The microwalker is constructed by two rigid segments with an equal length of 70 μm, connected by a rigid joint. Parallel gecko setae‐like tentacles are placed at the bottom of the segments as contact feet to generate friction with the contact surface. The microwalker is integrally fabricated from biocompatible materials with 3D laser lithography based on two‐photon polymerization. The microwalker can be well controlled to move in low‐Reynolds (Re)‐number regimes under an external oscillating magnetic field. In addition to moving in a liquid environment as existing microswimmers, the microwalker can move in surface in a nonliquid‐filled environment. It can also climb the slope driven by the planar magnetic field only. Several experiments were conducted to demonstrate good motion capability of the microwalker. This study provides a new solution to microrobot design for future biomedical applications.

Reversible morphology-resolved chemotactic actuation and motion of Janus emulsion droplets

We report, for the first time, a chemotactic motion of emulsion droplets that can be controllably and reversibly altered. Our approach is based on using biphasic Janus emulsion droplets, where each phase responds differently to chemically induced interfacial tension gradients. By permanently breaking the symmetry of the droplets’ geometry and composition, externally evoked gradients in surfactant concentration or effectiveness induce anisotropic Marangoni-type fluid flows adjacent to each of the two different exposed interfaces. Regulation of the competitive fluid convections then enables a controllable alteration of the speed and the direction of the droplets’ chemotactic motion. Our findings provide insight into how compositional anisotropy can affect the chemotactic behavior of purely liquid-based microswimmers. This has implications for the design of smart and adaptive soft microrobots that can autonomously regulate their response to changes in their chemical environment by chemotactically moving towards or away from a certain target, such as a bacterium.