Delivering Microrobots in the Musculoskeletal System

Disorders of the musculoskeletal system are the major contributors to the global burden of disease and current treatments show limited efficacy.Patients often suffer chronic pain and might eventually have to undergo end-stage surgery.Therefore,future treatments should focus on early detection and intervention of regional lesions.Microrobots have been gradually used in organisms due to their advantages of intelligent,precise and minimally invasive targeted delivery.Through the combination of control and imaging systems,microrobots with good biosafety can be delivered to the desired area for treatment.In the musculoskeletal system,microrobots are mainly utilized to transport stem cells/drugs or to remove hazardous substances from the body.Compared to traditional biomaterial and tissue engineering strategies,active motion improves the efficiency and penetration of local targeting of cells/drugs.This review discusses the frontier applications of microrobotic systems in different tissues of the musculoskeletal system.We summarize the challenges and barriers that hinder clinical translation by evaluating the characteristics of different microrobots and finally point out the future direction of microrobots in the musculoskeletal system.

A New Type of Hybrid Fish-like Microrobot

In order to develop a new type of fish-like microrobot with swimming, walking, and floating motions, in our past research, we developed a hybrid microrobot actuated by ionic conducting polymer film （ICPF） actuators. But the microrobot had some problems in walking and floating motions. In this paper, we propose a concept of hybrid microrobot （see Fig. 1）. The microrobot is actuated by a pair of caudal fins, a base with legs and an array of artificial swim bladders. We have developed a prototype of the base with legs and one artificial swim bladder, respectively, and carried out experiments for evaluating their characteristics. Experimental results show the base with legs can realize walking speed of 6 mm/s and rotating speed of 7.1 degrees/s respectively, and the prototype of the artificial swim bladder has a maximum floatage of 2.6 mN. The experimental results also indicate that the microrobot has some advantages, such as walking motion with 2 degrees of freedom, the walking ability on rough surface （sand paper）, the controllable floatage, etc. This kind of fish-like microrobot is expected for industrial and medical applications.

Development of ICPF Actuated Underwater Microrobots

It is our target to develop underwater microrobots for medical and industrial applications. This kind of underwater microrobots should have the characteristics of flexibility, good response and safety. Its structure should be simple and it can be driven by low voltage and produces no pollution or noise. The low actuating voltage and quick bending responses of Ionic Conducting Polymer Film （ICPF） are considered very useful and attractive for constructing various types of actuators and sensors. In this paper, we will first study the characteristics of the ICPF actuator used in underwater microrobot to realize swimming and walking. Then, we propose a new prototype model of underwater swimming microrobot utilizing only one piece of ICPF as the servo actuator. Through theoretic analysis, the motion mechanism of the microrobot is illustrated. It can swim forward and vertically. The relationships between moving speed and signal voltage amplitude and signal frequency is obtained after experimental study. Lastly, we present a novel underwater crab-like walking microrobot named crabliker-1. It has eight legs, and each leg is made up of two pieces of ICPF. Three sample processes of the octopod gait are proposed with a new analyzing method. The experimental results indicate that the crab-like underwater microrobot can perform transverse and rotation movement when the legs of the crab collaborate.

3D printed ultra-fast photothermal responsive shape memory hydrogel for microrobots

Hydrogels with stimuli-responsive capabilities are gaining more and more attention nowadays with prospective applications in biomedical engineering,bioelectronics,microrobot,etc.We develop a photothermal responsive hydrogel based on N-isopropylacrylamide that achieved a fast and reversible deformation manipulated only by near-infrared(NIR)light.The hydrogel was fabricated by the projection micro stereolithography based 3D printing technique,which can rapidly prototype complex 3D structures.Furthermore,with the variation of the grayscale while manufacturing the hydrogel,the deformation of the hydrogel structure can be freely tuned within a few seconds by losing and absorbing water through adjusting the intensity and the irradiation direction of the NIR light,showing a potential application in ultra-fast object grabbing and transportation.The present study provides a new method for designing ultrafast photothermal responsive hydrogel based microrobot working in water.

Vibration-Driven Microrobot Positioning Methodologies for Nonholonomic Constraint Compensation

This paper presents the formulation and practical implementation of positioning methodologies that compensate for the nonholonomic constraints of a mobile microrobot that is driven by two vibrating direct current(DC) micromotors. The open-loop and closed-loop approaches described here add the capability for net sidewise displacements of the microrobotic platform. A displacement is achieved by the execution of a number of repeating steps that depend on the desired displacement, the speed of the micromotors, and the elapsed time. Simulation and experimental results verified the performance of the proposed methodologies.

Autonomous docking based on infrared sensors for mobile self-reconfigurable relay microrobots

A simple autonomous docking method based on infrared sensors for mobile self-reconfigurable relay microrobots is proposed in the paper.The IR guidance system composed of an IR receiver and four IR emitters is designed,analyzed and developed.The autonomous docking control method based on centering alignment and dynamic motion planning is adopted so that it has high efficiency and reliability.Two basic microrobot prototypes are developed,and related docking experiments are done to verify the feasibility of the approach.

A Piezoelectrically Driven Microrobot Using a Novel Monolithic Spatial Parallel Mechanism as Its Hip Joint

Inspired by the fast,agile movements of insects,we present a 1.9 g,4.5 cm in length,piezoelectrically driven,quadrupedal microrobot.This microrobot uses a novel spatial parallel mechanism as its hip joint,which consists of two spatially orthogonal slider-crank linkages.This mechanism maps two inputs of two independent actuators to the decoupled swing and lift outputs of a leg,and each leg can produce the closed trajectories in the sagittal plane necessary for robot motion.Moreover,the kinematics of the transmission are analyzed,and the parameters of the flexure hinges are designed based on geometrical constraints and yield conditions.The hip joints,legs and exoskeletons are integrated into a five-layer standard laminate for monolithic fabrication which is composed of two layers of carbon fiber,two layers of acrylic adhesive and a polyimide film.The measured output force(15.97 mN)of each leg is enough to carry half of the robot’s weight,which is necessary for the robot to move successfully.It has been proven that the robot can successfully perform forward and turning motions.Compared to the microrobot fabricated with discrete components,the monolithically fabricated microrobot is more capable of maintaining the original direction of locomotion when driven by a forward signal and has a greater speed,whose maximum speed is 25.05 cm/s.

Application of magnetotactic bacteria as engineering microrobots:Higher delivery efficiency of antitumor medicine

For a significant duration,enhancing the efficacy of cancer therapy has remained a critical concern.Magnetotactic bacteria(MTB),often likened to micro-robots,hold substantial promise as a drug delivery system.MTB,classified as anaerobic,aquatic,and gram-negative microorganisms,exhibit remarkable motility and precise control over their internal biomineralization processes.This unique ability results in the formation of magnetic nanoparticles arranged along filamentous structures in a catenary fashion,enclosed within a membrane.These bacteria possess distinctive biochemical properties that facilitate their precise positioning within complex environments.By harnessing these biochemical attributes,MTB could potentially offer substantial advantages in the realm of cancer therapy.This article reviews the drug delivery capabilities of MTB in tumor treatment and explores various applications based on their inherent properties.The objective is to provide a comprehensive understanding of MTB-driven drug delivery and stimulate innovative insights in this field.

MOF-based magnetic microrobot swarms for pH-responsive targeted drug delivery

Metal-organic frameworks(MOFs)hold significant potential as vehicles for drug delivery due to their expansive specific surface area,biocompatibility,and versatile attributes.Concurrently,magnetically actuated micro/nano-robots(MNRs)offer distinct advantages,such as untethered and precise manipulation.The fusion of these technologies presents a promising avenue for achieving non-invasive targeted drug delivery.Here,we report a MOF-based magnetic microrobot swarm(MMRS)for targeted therapy.Our approach overcomes limitations associated with a single MNR,including limited drug loading and the risk of loss during manipulation.We select Zeolitic Imidazolate Framework-8(ZIF-8)as the drug vehicle for its superior loading potential and p H-sensitive decomposition.Our design incorporates magnetic responsive components into the one-pot synthesis of Fe@ZIF-8,enabling collective behaviors under actuation.Tuning the yaw angle of alternating magnetic fields and nanoparticles'amount,the MMRSs with controllable size achieve instantaneous transformation among different configurations,including vortex-like swarms,chain-like swarms,and elliptical swarms,facilitating adaptation to environmental variations.Transported to the subcutaneous T24 tumor site,the MMRSs with encapsulated doxorubicin(DOX)automatically degrade and release the drug,leading to a dramatic reduction of the tumor in vivo.Our investigation signifies a significant advancement in the integration of biodegradable MOFs into microrobot swarms,ushering in new avenues for accurate and non-invasive targeted drug delivery.

Magnetically driven microrobots moving in a flow:a review

Magnetically driven microrobots hold great potential to perform specific tasks more locally and less invasively in the human body.To reach the lesion area in vivo,microrobots should usually be navigated in flowing blood,which is much more complex than static liquid.Therefore,it is more challenging to design a corresponding precise control scheme.A considerable amount of work has been done regarding control of magnetic microrobots in a flow and the corresponding theories.In this paper,we review and summarize the state-of-the-art research progress concerning magnetic microrobots in blood flow,including the establishment of flow systems,dynamics modeling of motion,and control methods.In addition,current challenges and limitations are discussed.We hope this work can shed light on the efficient control of microrobots in complex flow environments and accelerate the study of microrobots for clinical use.

微型胶囊机器人外壳的淹没式空化射流成形质量分析

目的针对微型胶囊机器人外壳成形的技术难题,提出了一种基于淹没式空化射流冲击箔材的微型机器人外壳成形方法,分析了微型外壳的成形质量。方法基于微型胶囊机器人外壳的特征尺寸设计模具,利用淹没式空化射流试验装置,完成了对T2铜箔的高能冲击成形试验,分析了淹没式空化射流的成形原理,讨论了微型外壳的成形深度、表面粗糙度、厚度减薄率以及纳米硬度。结果在空化射流冲击成形过程中,微型外壳成形深度的增长率随成形时间的延长而减小,最大成形深度可达291.4μm(模具最大深度为300μm);成形后微型外壳表面粗糙度Ra值由0.7897μm逐渐增加至1.0576μm,厚度减薄率为10%~25%,纳米硬度提高了21.78%~46.64%,最大硬度增长率出现在刃口处。结论在淹没式空化射流成形过程中,微型外壳的成形深度与模具的相当,微型外壳表面存在小幅度粗化现象,成形后减薄率降低,纳米硬度大幅提高,抵抗外界破坏能力提高。

Recent Developments in Metallic Degradable Micromotors for Biomedical and Environmental Remediation Applications

Synthetic micromotor has gained substantial attention in biomedicine and environmental remediation.Metal-based degradable micromotor composed of magnesium(Mg),zinc(Zn),and iron(Fe)have promise due to their nontoxic fuel-free propulsion,favorable biocompatibility,and safe excretion of degradation products Recent advances in degradable metallic micromotor have shown their fast movement in complex biological media,efficient cargo delivery and favorable biocompatibility.A noteworthy number of degradable metal-based micromotors employ bubble propulsion,utilizing water as fuel to generate hydrogen bubbles.This novel feature has projected degradable metallic micromotors for active in vivo drug delivery applications.In addition,understanding the degradation mechanism of these micromotors is also a key parameter for their design and performance.Its propulsion efficiency and life span govern the overall performance of a degradable metallic micromotor.Here we review the design and recent advancements of metallic degradable micromotors.Furthermore,we describe the controlled degradation,efficient in vivo drug delivery,and built-in acid neutralization capabilities of degradable micromotors with versatile biomedical applications.Moreover,we discuss micromotors’efficacy in detecting and destroying environmental pollutants.Finally,we address the limitations and future research directions of degradable metallic micromotors.

Two-photon polymerization-based 4D printing and its applications

Two-photon polymerization(TPP)is a cutting-edge micro/nanoscale three-dimensional(3D)printing technology based on the principle of two-photon absorption.TPP surpasses the diffraction limit in achieving feature sizes and excels in fabricating intricate 3D micro/nanostructures with exceptional resolution.The concept of 4D entails the fabrication of structures utilizing smart materials capable of undergoing shape,property,or functional changes in response to external stimuli over time.The integration of TPP and 4D printing introduces the possibility of producing responsive structures with micro/nanoscale accuracy,thereby enhancing the capabilities and potential applications of both technologies.This paper comprehensively reviews TPP-based 4D printing technology and its diverse applications.First,the working principles of TPP and its recent advancements are introduced.Second,the optional4D printing materials suitable for fabrication with TPP are discussed.Finally,this review paper highlights several noteworthy applications of TPP-based 4D printing,including domains such as biomedical microrobots,bioinspired microactuators,autonomous mobile microrobots,transformable devices and robots,as well as anti-counterfeiting microdevices.In conclusion,this paper provides valuable insights into the current status and future prospects of TPP-based4D printing technology,thereby serving as a guide for researchers and practitioners.

锥形螺旋微机器人的结构设计与三维运动控制

为模拟微机器人在生物体内执行靶向给药、血管疏通等复杂操作,设计了锥形螺旋微机器人。锥形螺旋微机器人主要由圆柱体头部、锥形螺旋尾部和钕铁硼永磁铁组成。针对锥形螺旋微机器人在低雷诺数液体环境中的三维运动控制需求,基于空间矢量叠加原理设计万向旋转磁场发生装置,通过有限元分析方法对万向旋转磁场发生装置的磁场强度及磁场均匀性进行优化。制作锥形螺旋微机器人,并搭建磁驱动系统,进行锥形螺旋微机器人三维运动控制操控实验,实验结果表明,锥形螺旋微机器人在甘油中的最大运动速度为1 mm/s,能够实现稳定的二维及三维运动控制,并完成穿越迷宫的复杂操作。

一种基于惯性致动的四足压电移动机器人研究

设计了一种基于压电双晶梁的L型压电驱动器,基于模块化设计思想将L型压电驱动器应用于压电移动机器人的研制。压电移动机器人由4个周向分布的L型压电驱动器和连接平台组成,结构简单紧凑,可实现2自由度平面内大范围高精运动。对压电移动机器人进行加工和装配,并搭建测试平台对压电移动机器人的运动输出特性进行实验研究。测试结果表明,压电移动机器人具有兼顾高精度、快速度、高稳定性和强承载能力的良好综合性能,其运动分辨率为1μm,最大运动速度可达46 mm/s,承载能力可达75 g,在微纳操作、晶圆缺陷检测和超精密加工领域具有广阔的应用前景。

抗体工程化微型机器人清除水中新型冠状病毒的研究

由于严重急性呼吸系统综合征冠状病毒2型(简称“新型冠状病毒”)(SARS-CoV-2)可在水中保持长时间的稳定性和高度传染性,因此,清除水中的新型冠状病毒成为遏制及阻断其传播的重要途径。该研究采用“点击化学”反应将新型冠状病毒S蛋白的中和抗体P2C-1F11修饰在具有自驱动特性的枯草芽孢杆菌表面,构建了一种抗体工程化微型机器人(antibody functionalized bacteria microrobot,AB-robot)。AB-robot通过P2C-1F11对新型冠状病毒S蛋白的高效靶向作用,对水中新型冠状病毒进行捕获和清除。结果表明,AB-robot在饮用水和自来水等水介质中展示了快速的自驱动能力。以新型冠状病毒假病毒为病毒污染物模型,使用AB-robot后,水介质中病毒清除率高达95%。扫描电镜表征结果显示,AB-robot表面结合了大量的病毒颗粒,进一步表明AB-robot能高效捕获病毒。综上,AB-robot的快速运动和病毒靶向性能促进了其对新型冠状病毒假病毒的即时捕获和高效清除,对防止和阻断水中新型冠状病毒的传播具有重要应用价值。

液晶弹性体微结构及其应用

液晶弹性体因其可编程的形变与高达400%的应变而在微型医用机器人、可调控表面微结构、微流控等微观尺度领域有着重要的潜在应用。液晶弹性体微结构的制作需要同时兼顾高分辨率分子取向和高精度微米尺度结构,对分子取向和微纳加工技术有着很高的要求。本文综述了液晶弹性体分子取向的方法和微结构的先进加工技术,总结了其在微驱动器、人工肌肉纤维、可调控表面等方向的应用进展,并展望了液晶弹性体微结构在微型医用机器人领域的未来发展趋势。

Review of photoacoustic imaging for microrobots tracking in vivo [Invited]

Microrobots-assisted drug delivery and surgery have been always in the spotlight and are highly anticipated to solve the challenges of cancer in situ treatment. These versatile small biomedical robots are expected to realize direct access to the tumor or disease site for precise treatment, which requires real-time and high-resolution in vivo tracking as feedback for the microrobots’ actuation and control. Among current biomedical imaging methods, photoacoustic imaging(PAI) is presenting its outstanding performances in the tracking of microrobots in the human body derived from its great advantages of excellent imaging resolution and contrast in deep tissue. In this review, we summarize the PAI techniques, imaging systems, and their biomedical applications in microrobots tracking in vitro and in vivo. From a robotic tracking perspective,we also provide some insight into the future of PAI technology in clinical applications.

Micro Manipulation Using Magnetic Microrobots

When developing microscale robotic systems it is desired that they are capable of performing microscale tasks such as small scale manipulation and transport. In this paper, we demonstrate the transport of microscale objects using single or multiple microrobots in low Reynolds number fluidic environment. The microrobot is composed of a ‘U＇ shaped SU-8 body, coated on one side with nickel. Once the nickel coating is magnetized, the motion of the microrobots can be driven by external magnetic fields. To invoke different responses from two microrobots under a global magnetic field, two batches of microrobots were fabricated with different thicknesses of nickel coating as a way to promote heterogeneity within the microrobot population. The heterogeneity in magnetic content induces different spatial and temporal responses under the same control input, resulting in differences in movement speed. The nickel coated microstructure is manually controlled through a user interface developed using C＋＋. This paper presents a control strategy to navigate the microrobots by controlling the direction and strength of ex- ternally applied magnetic field, as well as orientation of the microrobots based on their polarity. In addition, multiple micro- robots are used to perform transport tasks.

Moving Mechanism of a High-speed Insect-scale Microrobot via Electro-magnetically Induced Vibration

This paper presents the moving mechanism of a high-speed insect-scale microrobot via electromagnetically induced vibration of two simply supported beams.The microrobot,which has a body length of 12.3 mm and a total mass of 137 mg,can achieve reciprocating lift motion of forelegs without any intermediate linkage mechanisms due to the design of an obliquely upward body tilt angle.The gait study shows that the body tilt angle prevents the forelegs from swinging backward when the feet contact the ground,which results in a forward friction force applied on the feet.During forward movement,the microrobot utilizes the elastic deformation of the simply supported beams as driving force to slide forward and its forelegs and rear legs work as pivots alternatively in a way similar to the movement of soft worms.The gait analysis also indicates that the moving direction of the microrobot is determined by whether its body tilt angle is obliquely upward or downward,and its moving speed is also related to the body tilt angle and as well as the body height.Under an applied AC voltage of 4 V,the microrobot can achieve a moving speed at 23.2 cm s1(18.9 body lengths per second),which is comparable to the fastest speed(20 cm s-1 or 20 body lengths per second)among the published insect-scale microrobots.The high-speed locomotion performance of the microrobot validates the feasibility of the presented actuation scheme and moving mechanism.