磁场驱动柔性微纳机器人研究进展

 磁场驱动微纳机器人无需化学燃料,因而可以在水、血浆、组织液等多种液体环境中使用。它可以在生物体内进行无损伤远程调控,并易于进行运动控制,这些特点使得它在医疗领域具有广泛的应用前景。微纳机器人尺寸极小,处于低雷诺数环境中,需要克服高黏性力实现运动。磁场驱动微纳机器人有表面型、螺旋型和柔性驱动型3种。柔性的磁场驱动机器人通过外界磁场力产生周期性变形,在低雷诺数环境中实现推进,与微生物的推进方式类似,具有推进效率高、对磁场强度要求低的优点。本文综述了磁场驱动柔性微纳机器人的制备、驱动方式、运动性能和运动控制性能研究进展。     

Motile flagellar axonemes with a 9 + 1 microtubule configuration

Electron microscope (EM) studies of the eukaryotic flagellum reveal that the organelle contains a 9 + 2 arrangement of microtubules, the axoneme, with nine doublets surrounding two singlets enveloped by a membrane which is continuous with that of the cell; various linkages and projections are associated with the microtubules. Strong experimental evidence supports the idea that the forces required for bend formation on eukaryotic flagella are derived from active relative sliding of the peripheral doublets. Dynein arms, which project from each peripheral microtubule and possess ATPase activity, interact with a neighbouring doublet and undergo conformational changes which induce sliding. To form and propagate coordinated bends along a flagellum the sliding must be resisted in a controlled manner by structures within the axoneme. The regulatory mechanism responsible for the control of inter-doublet sliding is not known in detail, but ultrastructural studies suggest that interactions between the radial spokes attached to each doublet and the central complex of the axoneme may be involved. We report here the treatment of flagella with a 9 + 2 microtubular structure from the trypanosomid flagellate Crithidia oncopelti to produce motile axonemes with only one central microtubule. We conclude that the complete central complex is not involved in the conversion of microtubule sliding into axonemal bending, but may be both associated with the control of wave propagation and essential for bend initiation.     

超磁机器鱼游动数值模拟及其控制

针对管道中微小型机器人的研究和开发,提出一种利用外磁场驱动起小型机器鱼的研究方法.采用合金薄板模拟鱼尾骨架,贴在该薄板的超磁致伸缩材料模拟鱼体肌肉,建立了该问题的力学模型.通过研究机器鱼的游动机理,设计了一种机器鱼的超磁动力驱动器(GMMA).利用调整外界磁场频率,实现神经模拟以控制鱼尾摆动,即机器鱼的游动.结果表明,鱼尾摆动平均驱动力的大小取决于鱼尾的材料参数、几何参数和外磁场频率.特别是当外磁场频率接近系统固有频率时,该驱动力相对较大,该结论可作为鱼尾设计和控制的主要思路和依据.     

Polar and lateral flagellar motors of marine Vibrio are driven by different ion-motive forces.

Various species of marine Vibrio produce two distinct types of flagella, each adapted for a different type of motility. A single, sheathed polar flagellum is suited for swimming in liquid medium, and numerous unsheathed lateral flagella, which are produced only under viscous conditions, are suited for swarming over viscous surfaces. Both types of flagella are driven by reversible motors embedded in the cytoplasmic membrane. Here we report that the energy source for the polar flagellar motor of Vibrio parahaemolyticus is the sodium-motive force, whereas the lateral flagellar motors are driven by the proton-motive force. This is evidence that two distinct types of flagella powered by different energy sources are functionally active in one cell.     

Flagellar motility is required for the viability of the bloodstream trypanosome

The 9 + 2 microtubule axoneme of flagella and cilia represents one of the most iconic structures built by eukaryotic cells and organisms. Both unity and diversity are present among cilia and flagella on the evolutionary as well as the developmental scale. Some cilia are motile, whereas others function as sensory organelles and can variously possess 9 + 2 and 9 + 0 axonemes and other associated structures. How such unity and diversity are reflected in molecular repertoires is unclear. The flagellated protozoan parasite Trypanosoma brucei is endemic in sub-Saharan Africa, causing devastating disease in humans and other animals. There is little hope of a vaccine for African sleeping sickness and a desperate need for modern drug therapies. Here we present a detailed proteomic analysis of the trypanosome flagellum. RNA interference (RNAi)-based interrogation of this proteome provides functional insights into human ciliary diseases and establishes that flagellar function is essential to the bloodstream-form trypanosome. We show that RNAi-mediated ablation of various proteins identified in the trypanosome flagellar proteome leads to a rapid and marked failure of cytokinesis in bloodstream-form (but not procyclic insect-form) trypanosomes, suggesting that impairment of flagellar function may provide a method of disease control. A postgenomic meta-analysis, comparing the evolutionarily ancient trypanosome with other eukaryotes including humans, identifies numerous trypanosome-specific flagellar proteins, suggesting new avenues for selective intervention.     

Abrupt changes in flagellar rotation observed by laser dark-field microscopy

Bacteria such as Escherichia coli and Salmonella typhimurium swim by rotating their flagella, each of which consists of an external helical filament and a rotary motor embedded in the cell surface. The function of the flagellar motor has been examined mainly by tethering the flagellar filament to a glass slide and observing the resultant rotation of the cell body. But under these conditions the motor operates at a very low speed (about 10 r.p.s.) owing to the unnaturally high load conditions inherent in this technique. Lowe et al. analysed the frequency of light scattered from swimming cells to estimate the average rotation speed of flagellar bundles of E. coli as about 270 r.p.s. To analyse motor function in more detail, however, measurement of high-speed rotation of a single flagellum (at low load) with a temporal resolution better than 1 ms is needed. We have now developed a new method--laser dark-field microscopy--which fulfils these requirements. We find that although the average rotation speed of S. typhimurium flagella is rather stable, there are occasional abrupt slowdowns, pauses and reversals (accomplished within 1 ms). These changes were frequently observed in mutants defective in one of the motor components (called the switch complex), suggesting that this component is important not only in switching rotational direction but also in torque generation or regulation.     

Micro-robot design based on swimming mechanism of bacterial flagella

Nanomachines are controllable machines at the nano meter or molecular scale that are composed of nano-scale components.They have their own mechanochemistry,dynamics,workspace,and usability and are composed of nature's building blocks:namely proteins,DNA,and other compounds.Some bacteria(i.e.Escherichia coli)swim by rotating helical flagella.The structure and motion character of the flagellum are introduced.Through the study,a micro-robot was designed and its mechanical structure was explained in this paper....     

Analysis and Design of Cylindrical Magnetorheological Fluid Brake

Magnetorheological (MR) fluids consist of stable suspensions of magnetic particles in a carrying fluid such as water or silicone oils. The magnetorheological response of MR fluids results from the polarization induced in suspended particles by application of an external magnetic field. The interaction between the induced dipoles causes the particles to form columnar structure, parallel to the applied field. These chain-like structures restrict the motion of fluids, thereby increasing the viscosity and yield...     

2020年光学超材料热点回眸

 光学超材料一直是超材料学科中的重要组成部分之一，是超材料在信息科学领域中应用的重要体现。2020年，光学超材料领域的研究涌现出了一大批非常优秀的科技成果。围绕非线性光学超材料、人工智能超材料与光学超表面等方面回顾了光学超材料在2020年的研究热点。     

Stabilization of sea urchin flagellar microtubules by histone H1.

Complex microtubule assemblies are essential components of eukaryotic cilia and flagella. They are extremely stable and are not affected by agents that normally induce polymer disassembly. The molecular basis of this microtubular stability is unknown, and it is not related to any feature of the constitutive tubulin. In sea urchin sperm flagella, axonemal microtubules are found to be stabilized by a protein identical to histone H1, a result that defines a new role for this histone and provides evidence for a concerted evolution of chromatin and microtubular structures.     

变化磁场环境下海森堡XXZ模型的热力学纠缠

研究了变化磁场环境下,海森堡XXZ模型的热力学纠缠性质.通过计算,得出热力学纠缠度解析表达式,由模拟表明,系统纠缠度对变化的磁场、各向异性参数、温度表现出不同的行为.为提高系统临界温度,给出了磁场强度范围和各向异性参数条件.     

宽颊纹潜叶蜂触角的分布和超微形态

利用扫描电镜对宽颊纹潜叶蜂Kaliofenusa genata雌蜂触角的形态特征、感觉器的类型及分布特点进行了观察.结果表明,宽颊纹潜叶蜂雌蜂触角呈丝状,由基节、柄节、梗节、鞭节组成.其中,鞭节由7鞭小节组成.触角上着生有6种感觉器,分别是毛形感觉器(Ⅰ型、Ⅱ型、Ⅲ型和IV型)、锥形感觉器(Ⅰ型和Ⅱ型)、刺形感觉器、锥形乳突状感觉器、芽形感觉器和Bhm氏鬃毛.其中,毛形感觉器I广泛分布在除基节以外的其他各节上;毛形感觉器II和III主要分布在柄节和梗节上;毛形感觉器IV主要分布在鞭小节的端部.刺形感觉器、芽形感觉器以及锥形感觉器I主要分布在鞭节的末端鞭小节上.腔锥形乳突状感觉器和锥形感器II主要分布在除第1鞭小节以外的其他鞭小节上.Bhm氏鬃毛仅分布在基节中部.结合相关研究报道,对宽颊纹潜叶蜂雌蜂触角各种感觉器可能的功能进行了探讨.     

Micro-robot design based on swimming mechanism of bacterial flagella

Nanomachines are controllable machines at the nano meter or molecular scale that are composed of nano-scale components. They have their own mechanochemistry, dynamics, workspace, and usability and are composed of natures building blocks: namely proteins, DNA, and other compounds. Some bacteria (i. e. Escherichia coli) swim by rotating helical flagella. The structure and motion character of the flagellum are introduced. Through the study, a micro-robot was designed and its mechanical structure was explained in this paper. In the future, the bionic micro-robot is expected tobe built, which can travel inside the human body and carry out a host of complex operations such as minimally invasive surgery, highly localized drug delivery, and screening for diseases that are in their very early stages. It is important to medicine and could be applied in other areas, including space exploration, electronics and military.     

Anisotropic thermal conductivity of magnetic fluids

Considering the forces acting on the particles and the motion of the particles, this study uses a numerical simulation to investigate the three-dimensional microstructure of the magnetic fluids in the presence of an external magnetic field. A method is proposed for predicting the anisotropic thermal conductivity of magnetic fluids. By introducing an anisotropic structure parameter which characterizes the nonuniform distribution of particles suspended in the magnetic fluids, the traditional Maxwell formula is modified and extended to calculate anisotropic thermal conductivity of the magnetic fluids. The results show that in the presence of an external magnetic field the magnetic nanoparticles form chainlike clusters along the direction of the external magnetic field, which leads to the fact that the thermal conductivity of the magnetic fluid along the chain direction is bigger than that along other directions. The thermal conductivity of the magnetic fluids presents an anisotropic feature. With the increase of the magnetic field strength the chainlike clusters in the magnetic fluid appear to be more obvious, so that the anisotropic feature of heat conduction in the fluids becomes more evident.     

Magnetic phase control by an electric field

The quest for higher data density in information storage is motivating investigations into approaches for manipulating magnetization by means other than magnetic fields. This is evidenced by the recent boom in magnetoelectronics and 'spintronics', where phenomena such as carrier effects in magnetic semiconductors and high-correlation effects in colossal magnetoresistive compounds are studied for their device potential. The linear magnetoelectric effect-the induction of polarization by a magnetic field and of magnetization by an electric field-provides another route for linking magnetic and electric properties. It was recently discovered that composite materials and magnetic ferroelectrics exhibit magnetoelectric effects that exceed previously known effects by orders of magnitude, with the potential to trigger magnetic or electric phase transitions. Here we report a system whose magnetic phase can be controlled by an external electric field: ferromagnetic ordering in hexagonal HoMnO3 is reversibly switched on and off by the applied field via magnetoelectric interactions. We monitor this process using magneto-optical techniques and reveal its microscopic origin by neutron and X-ray diffraction. From our results, we identify basic requirements for other candidate materials to exhibit magnetoelectric phase control.     

Micro-robot design based on swimming mechanism of bacterial flagella

Nanomachines are controllable machines at the nano meter or molecular scale that are composed of nanoscale components. They have their own mechanochemistry, dynamics, workspace, and usability and are composed of natures building blocks: namely proteins, DNA, and other compounds. Some bacteria (i. e. Escherichia coli) swim by rotating helical flagella. The structure and motion character of the flagellum are introduced. Through the study, a microrobot was designed and its mechanical structure was explained in this paper. In the future, the bionic microrobot is expected tobe built, which can travel inside the human body and carry out a host of complex operations such as minimally invasive surgery, highly localized drug delivery, and screening for diseases that are in their very early stages. It is important to medicine and could be applied in other areas, including space exploration, electronics and military.     

Magnetic particles in the liver: a probe for intracellular movement

Previous studies have used magnetic particles to estimate the viscosity of cell cytoplasm in vitro 1-4. Here we describe how magnetic Fe2O3 particles can be used to estimate non-invasively the motion of organelles in hepatic macrophages in intact animals. We report that when these particles are injected intravenously (i.v.), most are phagocytosed by hepatic macrophages (Fig. 1)5. When an external magnetic field is applied to the rabbit, these particles become magnetized and aligned. After removal of the field, the particles collectively produce a remanent magnetic field which can be measured at the body surface. This field decreases with time due to particle rotation (relaxation) 6,7. As the particles are contained in phagosomes or secondary lysosomes, we conclude that motions of these organelles are responsible for the particle rotation and relaxation.     

Inner-arm dynein c of Chlamydomonas flagella is a single-headed processive motor.

Axonemal dyneins are force-generating ATPases that produce movement of eukaryotic cilia and flagella. Several studies indicate that inner-arm dyneins mainly produce bending moments in flagella and that these motors have inherent oscillations in force and motility. Processive motors such as kinesins have high duty ratios of attached to total ATPase cycle (attached plus detached) times compared to sliding motors such as myosin. Here we provide evidence that subspecies-c, a single-headed axonemal inner-arm dynein, is processive but has a low duty ratio. Ultrastructurally it is similar to other dyneins, with a single globular head, long stem and a slender stalk that attaches to microtubules. In vitro studies of microtubules sliding over surfaces coated with subspecies-c at low densities (measured by single-molecule fluorescence) show that a single molecule is sufficient to move a microtubule more than 1 microm at 0.7 microm s(-1). When many motors interact the velocity is 5.1 microm s(-1), fitting a duty ratio of 0.14. Using optical trap nanometry, we show that beads carrying a single subspecies-c motor move processively along the microtubules in 8-nm steps but slip backwards under high loads. These results indicate that dynein subspecies-c functions in a very different way from conventional motor proteins, and has properties that could produce self-oscillation in vivo.     

仿Morpho蝴蝶翅膀微纳结构的优化设计

鉴于Morpho蝴蝶翅膀呈耀眼蓝色光泽与蝶翅表面的微纳结构有密切联系,提出了一种服务于仿生微纳制造的优化设计方法.根据生物结构的形状与尺寸,结合微纳制造中的工艺约束,建立了便于制造的仿生模型.使用严格耦合波分析对仿生模型进行光学仿真计算.在此基础上,以提高仿生结构的蓝光波段（特征波长为470nm）反射率为目标,利用遗传算法对仿生模型进行了优化设计.所得到的最优结构反射率波峰均位于470nm附近,且反射率明显高于仿生结构.为了分析最优结构的蓝光波段高反射率机理,研究了不同层数最优结构的几何特征,计算了部分结构的磁场强度分布,确定了结构中影响反射率的主要参数.     

基于磁光材料的磁可调石墨烯多带吸收特性

为了改善石墨烯的吸收性能,基于石墨烯的磁光效应,提出了一种采用磁性材料构成的光子晶体异质结构。该光学结构可使石墨烯实现多带吸收。吸收带的数目可通过改变光子晶体的周期数来调节。利用4×4传输矩阵法数值研究了该光子晶体异质结构的相关参数对石墨烯吸收率的影响。结果表明:石墨烯的吸收特性表现出一定的磁圆二色性。但通过调节费米能量,在外磁场的作用,左旋圆偏振光和右旋圆偏振光均可具有较高的吸收率。研究结果为偏振光学领域石墨烯基新型光子学器件的设计制作提供了理论依据。