Rotary Nanomotor Research Articles

The Viscosity-Propelled Rotary Nanomotor through the Solid-Liquid Interface

The Viscosity-Propelled Rotary Nanomotor through the Solid-Liquid Interface

A magnetically powered nanomachine with a DNA clutch.

Machines found in nature and human-made machines share common components, such as an engine, and an output element, such as a rotor, linked by a clutch. This clutch, as seen in biological structures such as dynein, myosin or bacterial flagellar motors, allows for temporary disengagement of the moving parts from the running engine. However, such sophistication is still challenging to achieve in artificial nanomachines. Here we present a spherical rotary nanomotor with a reversible clutch system based on precise molecular recognition of built-in DNA strands. The clutch couples and decouples the engine from the machine's rotor in response to encoded inputs such as DNA or RNA. The nanomotor comprises a porous nanocage as a spherical rotor to confine the magnetic engine particle within the nanospace (∼0.004 μm3) of the cage. Thus, the entropically driven irreversible disintegration of the magnetic engine and the spherical rotor during the disengagement process is eliminated, and an exchange of microenvironmental inputs is possible through the nanopores. Our motor is only 200 nm in size and the clutch-mediated force transmission powered by an embedded ferromagnetic nanocrystal is high enough (∼15.5 pN at 50 mT) for the in vitro mechanical activation of Notch and integrin receptors, demonstrating its potential as nano-bio machinery.

Precise control of CNT-DNA assembled nanomotor using oppositely charged dual nanopores.

Inspired by nature, nanomotors have been developed that have great potential in microfluidics and biomedical applications. The development of the rotary nanomotor, which is an important type of nanomotor, is an essential step towards intelligent nanomachines and nanorobots. Carbon nanotubes (CNTs) are a crucial component of rotary nanomotors because of their excellent mechanical properties and adaptability to the human body. Herein, we introduce a convenient manipulation method for controlling the rotation of a nanomotor assembled from CNT-DNA, which uses the electroosmosis effect within oppositely charged dual nanopores. The central components of this nanomotor consist of a double-walled carbon nanotube (DWCNT) and a circular single-stranded DNA (ssDNA), which acts as the driving element for the nanomotor. Selective ion transport through charged nanopores can generate a robust electroosmotic flow (EOF), which serves as the primary power for the movement of circular ssDNA. The tangential force on the ssDNA is transmitted via electrostatic adsorption to the outer surface of the CNT, known as the rotor, resulting in the rotation of the nanomotor. By simply adjusting the electric field and surface charge density of each nanopore, rotational variables including speed, output power and torque can be readily regulated in this work. This proof-of-concept research provides a promising foundation for the future development of the precise control of nanomotors.

Controlled Mass Transportation on Nanotubes by Strain and Thermal Gradient: A Molecular Dynamics Study

According to the motion style, a nanomotor can be classified into linear nanomotor and rotary nanomotor. Nanomotors, as the core components of nanomachine, have broad research prospects and applications. Here, a molecular dynamics method is used to simulate the linear nanomotor on a stretched carbon nanotube substrate. The results show that the nanomotor speed is well controlled by the temperature gradient, the axial strain of the substrate and the nanomotor size. When the nanomotor moves stably on the substrate carbon nanotube with a temperature difference of 200 K at both ends, the time required for the nanomotor to travel the same distance on the substrate carbon nanotube with 15% strain is about 62% longer than that without strain. The mechanism for the nanomotor movement and speed control is attributed to the thermophoretic force acting on the nanomotor. Specifically, the thermophoretic force increases with increasing substrate temperature gradient and decreases with increasing substrate strain. These results provide a novel method for controlling the speed of a nanomotor and inform nanomotor design and manufacture, as well as presenting a deeper understanding of the mechanism and movement law of the nanomotor.

CNT-motor driven by competition between thermal fluctuation and REF

Rotary nanomotors are essential components in nanomachines. This study proposes a carbon nanotube (CNT)-based nanomotor driven by two methods. In the first method, we set inwardly radial deviation (IRD) to some of the atoms at the edges of the CNT stators which confine and support the rotor tube. At finite temperatures, the IRD atoms will drive the rotor to rotate via the inter-tube collision. The other method is to apply a rotating electric field (REF) on the water box in which the bladed segment of the rotor sinks. The rotor's rotational acceleration is determined by driving moments from both the IRD atoms and or from the rotating water molecules, and the resistant moments from the environment of the rotor. Since the resistant moments increase with the rotor's rotational frequency, a stable rotational frequency (SRF) of the rotor can be obtained. Molecular dynamic simulation results demonstrate that the value of SRF depends on the number and size of the blades assembled on the rotor, the frequency of the REF, and the number of IRD atoms. This work provides a useful guideline for the design of CNT-based Brownian rotary nanomotor.

Carbon-nanotube Nanomotor Driven by Graphene Origami

Experiments have shown that graphene origami (GORI) can be formed by compressing a folio graphene ribbon. In this study, the GORI is introduced to a rotary nanomotor built from a double-walled carbon nanotube. By placing several cantilevered GORI around the long inner tube (rotor) of the nanomotor with their tips toward the rotor, the nonbonding interaction between the tips and the rotor becomes strong when their distance is less than 1 nm. Rotationally symmetrical layout of the GORI tends to induce nonzero unidirectional torque on the rotor. Thereout, the rotor is accelerated to rotate until a stable rotational frequency (SRF) is reached on the condition that the stators (short outer tubes) applying equal but opposite torque on the rotor. The molecular-dynamics simulation approach is adopted to verify the procedure of the proposed rotary nanomotor. Conclusions are drawn for fabrication of the present rotary nanomotor.

Atomically precise nanoclusters with reversible isomeric transformation for rotary nanomotors

Thermal-stimuli responsive nanomaterials hold great promise in designing multifunctional intelligent devices for a wide range of applications. In this work, a reversible isomeric transformation in an atomically precise nanocluster is reported. We show that biicosahedral [Au13Ag12(PPh3)10Cl8]SbF6 nanoclusters composed of two icosahedral Au7Ag6 units by sharing one common Au vertex can produce two temperature-responsive conformational isomers with complete reversibility, which forms the basis of a rotary nanomotor driven by temperature. Differential scanning calorimetry analysis on the reversible isomeric transformation demonstrates that the Gibbs free energy is the driving force for the transformation. This work offers a strategy for rational design and development of atomically precise nanomaterials via ligand tailoring and alloy engineering for a reversible stimuli-response behavior required for intelligent devices. The two temperature-driven, mutually convertible isomers of the nanoclusters open up an avenue to employ ultra-small nanoclusters (1 nm) for the design of thermal sensors and intelligent catalysts.

Effect of differing stator and rotor radii on a three-class rotation-transmission nanobearing driven by a gigahertz rotary nanomotor

Particularly critical for a transmission system is a control system that adjusts the output drive speed. Toward this end, we introduce herein a three-class rotation-transmission system. To obtain an effective down-converted rotation-transmission system, the coaxial rotary components are fabricated from carbon nanotubes (CNTs). At 300 K, a gigahertz nanomotor drives nanobearings and thereby changes the output rotation frequency. Considering the chirality of CNTs and the differing radii between stator and the rotor, 12 transmission models are established and tested by molecular dynamics simulations. The rotational-transmission ratio curves for the rotors give the dynamic response of the transmission systems. A down-converting transmission system is obtained when the radii of the stators and rotors differ by 0.3–0.4 nm. The dynamic response given by the rotational-transmission ratio curves for various models leads to useful conclusions about the design of such nanosystems.

A three-stage rotary transmission nanobearing driven by a gigahertz nanomotor

In a transmission system, the rotational speed of the output can be adjusted by the system. In this study, we introduce a three-stage rotational transmission nanosystem model that uses carbon nanotubes with excellent mechanical properties to fabricate coaxially distributed nanomotors with three nanobearings. Driven by a gigahertz nanomotor at 300 K, the nanobearings are changed to adjust the output rotational frequency. In view of the differences in chirality and radius of the carbon nanotubes, 17 transmission models are established and tested by molecular dynamics simulation. The rotor’s rotational transmission ratio curves show the dynamic response of the transmission system. A better down-converting transmission system can be obtained when the radius of the rotating component is between 0.58nm and 0.88nm or the difference in radii between the rotating components is greater than 0.2 nm. From the results obtained by molecular dynamics simulation, some key points are demonstrated for future deceleration of the rotary nanomotor.

Diamond Needles Actuating Triple-Walled Carbon Nanotube to Rotate via Thermal Vibration-Induced Collision.

A rotary nanomotor is an essential component of a nanomachine. In the present study, a rotary nanomotor from wedged diamonds and triple-walled nanotubes was proposed with the consideration of boundary effect. The outer tubes and mid-tubes were used as nanobearing to constrain the inner tube. Several wedges of the diamond were placed near the inner tube for driving the inner tube to rotate. At a temperature lower than 300 K, the inner tube as the rotor had a stable rotational frequency (SRF). It is shown that both the rotational direction and the value of SRF of the rotor depended on the temperature and thickness of the diamond wedges. The dependence was investigated via theoretical analysis of the molecular dynamics simulation results. For example, when each diamond wedge had one pair of tip atoms (unsaturated), the rotational direction of the rotor at 100 K was opposite to that at 300 K. At 500 K, the rotating rotor may stop suddenly due to breakage of the diamond needles. Some conclusions are drawn for potential application of such a nanomotor in a nanomachine.

Gap effect on stable rotation of a carbon nanotube nearby diamond needles

A rotary nanomotor from carbon nanotube (CNT) and diamond is conceptually proposed, and the condition for stable rotation of the rotor is investigated. By putting several diamond needles (DNs) nearby a CNT, the tube can be driven to rotate at finite temperature. At finite temperature, thermal vibration of atoms in the CNT rotor and DNs leads to collision when their distance, i.e., Gap, is close to 0.34 nm, which is the equilibrium stance between neighbor sp2 carbon nanostructures, e.g., graphene or CNT. The fixed DNs provide the rotor repulsion via their tip atoms during collision. If the repulsion can generate a torque moment with unchanged direction, the rotor will be accelerated to rotate. After a period of acceleration, the stable rotational frequency (SRF) of the rotor can be obtained when Gap is no more than 0.34 nm. Numerical results demonstrate that the rotational direction depends on the value of Gap when each DN has only one pair of tip atoms; the temperature has a significant effect on the value of SRF but little effect on the rotational direction; and the rotation of the rotor becomes unstable due to breakage of DNs when Gap is higher than 0.34 nm.

A two-class rotation transmission nanobearing driven by gigahertz rotary nanomotor

For a vehicle, its speed can be adjusted via a transmission system. In this study, we propose a model of two-class rotation transmission nanosystem to adjust the input rotation via a gigahertz rotary nanomotor. To obtain an efficient rotation transmission system, carbon nanotubes, which have super-high in-shell strength but extremely low inter-shell friction, are adopted to build the coaxially rotary components. Besides 200 GHz motor, the other two components are the rotor1 in the class-1 nanobearing, and the rotor2 in the class-2 bearing, respectively. Considering both the chirality and radii differences of the rotary components, 27 types of transmission models are built and tested via molecular dynamic simulations. When the transmission ratio of the rotational frequency of the rotor2 and the input frequency is between 0.1 and 0.9, a successful transmission system is obtained. According to the rotation transmission ratios (RTRs) of both rotors in each model, some conclusions are drawn for potential design of such nanodevice. Besides, temperature can also influence the output rotation of the rotor2. It implies another way to adjust the output rotation from the same transmission system.

Dynamic behavior of a rotary nanomotor in argon environments

When argon is used as a protecting gas in the fabrication or working environment of a nanodevice, absorption of some argon atoms onto the surface of the device lead to different responses. In this work, the rotation of the rotor in a carbon nanotube (CNT)-based rotary nanomotor in argon environment is investigated. In the rotary nanomotor, two outer CNTs act as the stator and are used to constrain the inner CNT (i.e., the rotor). The rotor is driven to rotate by the stator due to their collision during thermal vibration of their atoms. A stable rotational frequency (SRF) of the rotor occurs when the rotor reaches a dynamic equilibrium state. The value of the SRF decreases exponentially with an increase in the initial argon density. At dynamic equilibrium date, some of the argon atoms rotate synchronously with the rotor when they are absorbed onto either internal or external surface of the rotor. The interaction between the rest of the argon atoms and the rotor is stronger at higher densities of argon, resulting in lower values of the SRF. These principles provide insight for future experimentation and fabrication of such rotary nanomotor.

Friction effect of stator in a multi-walled CNT-based rotation transmission system

The rotation transmission system (RTS) made from co-axial multi-walled nanotubes (MWNTs) has the function of regulating the input rotation from a nanomotor. The mechanism for the regulation is that the friction among the tubes during rotation governs the rotation of the rotors in the nanosystem. By integrating a rotary nanomotor and a nanobearing into an MWNT-based RTS, it is discovered that the stator (outer tube) provides relatively greater friction on the rotors by penetrating the motor tube, which has a higher stable rotational frequency. And the output rotation of the rotors in the system depends significantly on the temperature of the system, as the rotor tubes are slightly longer than the motor tube. Briefly, at low temperatures, say 8 K, the rotors rotate synchronously with the motor. However, at high temperatures, the rotors rotate slower than the motor with a bigger difference between their rotational frequencies. Hence, the output rotational frequencies can be adjusted by changing the temperature as well as the input rotational frequency.

Spectrum of Temperature-Dependent Rotational Frequency of the Rotor in a Thermally Diven Rotary Nanomotor

By fixing of the outer tube of double-walled carbon nanotubes, a thermally driven rotary nanomotor can be obtained one or more carbon atoms at the end of the stator have an obvious inward radial deviation. Due to the asymmetry of the potential field of the stator, a collision between two tubes leads to the axial component of angular momentum that drives the rotation of the rotor. Relative sliding between the two tubes is resisted due to the roughness of the potential field of stators. Hence, the rotational frequency of the rotor has a maximal value in the balanced state. The spectrum of rotational frequency with respect to temperatures from 8 to 2000 K is presented by means of molecular dynamics simulation. The temperature interval is divided into five zones on the basis of the characteristics of the spectrum. In the robust zone, the nanomotor exhibits stationary rotation. In the controllable zone, the rotational frequency of rotor can be adjusted by varying the temperature. In particular, if a rotating r...

Significance tests on the output power of a thermally driven rotary nanomotor

Many factors can have a significant influence on the output power of a thermally driven rotary nanomotor made of carbon nanotubes (CNTs). Making use of a computational molecular dynamics approach, we evaluate for the first time the output power of a nanomotor, considering some of the main factors including temperature, the diameter of the rotor and the number of IRD atoms (N) on the stator. When applying extra-resistant torque to the rotor to let the stable value of the rotational frequency of the rotor fluctuate near zero, the value of the resistant torque can be considered as the output power of the rotor. The effects of these factors on the output power of a motor are roughly predicted via a fitting approach. Using stepwise regression analysis, we discover that N has the greatest influence on the output power. The second and the third main factors that affect the output power of a nanomotor are the diameter of the rotor, and the interaction between N and the diameter, respectively. To improve the output power of a nanomotor, one can place more IRD atoms in the system and/or employ CNTs with larger diameters.

Nanoscale-length control of the flagellar driveshaft requires hitting the tethered outer membrane.

The bacterial flagellum exemplifies a system where even small deviations from the highly regulated flagellar assembly process can abolish motility and cause negative physiological outcomes. Consequently, bacteria have evolved elegant and robust regulatory mechanisms to ensure that flagellar morphogenesis follows a defined path, with each component self-assembling to predetermined dimensions. The flagellar rod acts as a driveshaft to transmit torque from the cytoplasmic rotor to the external filament. The rod self-assembles to a defined length of ~25 nanometers. Here, we provide evidence that rod length is limited by the width of the periplasmic space between the inner and outer membranes. The length of Braun's lipoprotein determines periplasmic width by tethering the outer membrane to the peptidoglycan layer.

Robust rotation of rotor in a thermally driven nanomotor

In the fabrication of a thermally driven rotary nanomotor with the dimension of a few nanometers, fabrication and control precision may have great influence on rotor’s stability of rotational frequency (SRF). To investigate effects of uncertainty of some major factors including temperature, tube length, axial distance between tubes, diameter of tubes and the inward radial deviation (IRD) of atoms in stators on the frequency’s stability, theoretical analysis integrating with numerical experiments are carried out. From the results obtained via molecular dynamics simulation, some key points are illustrated for future fabrication of the thermal driven rotary nanomotor.

An experimental study of the putative mechanism of a synthetic autonomous rotary DNA nanomotor.

DNA has been used to construct a wide variety of nanoscale molecular devices. Inspiration for such synthetic molecular machines is frequently drawn from protein motors, which are naturally occurring and ubiquitous. However, despite the fact that rotary motors such as ATP synthase and the bacterial flagellar motor play extremely important roles in nature, very few rotary devices have been constructed using DNA. This paper describes an experimental study of the putative mechanism of a rotary DNA nanomotor, which is based on strand displacement, the phenomenon that powers many synthetic linear DNA motors. Unlike other examples of rotary DNA machines, the device described here is designed to be capable of autonomous operation after it is triggered. The experimental results are consistent with operation of the motor as expected, and future work on an enhanced motor design may allow rotation to be observed at the single-molecule level. The rotary motor concept presented here has potential applications in molecular processing, DNA computing, biosensing and photonics.

Dynamic behavior of a black phosphorus and carbon nanotube composite system

A double walled nanotube composite is constructed by placing a black-phosphorene-based nanotube (BPNT) in a carbon nanotube (CNT). When driving the CNT to rotate by stators in a thermal driven rotary nanomotor, the BPNT behaves differently from the CNT. For instance, the BPNT can be actuated to rotate by the CNT, but its rotational acceleration differs from that of the CNT. The BPNT oscillates along the tube axis when it is longer than the CNT. The results obtained indicate that the BPNT functions with high structural stability when acting as a rotor with rotational frequency of ~20 GHz at 250 K. If at a higher temperature than 250 K, say 300 K, the rotating BPNT shows weaker structural stability than its status at 250 K. When the two tubes in the rotor are of equal length, the rotational frequency of the BPNT drops rapidly after the BPNT is collapsed, owing to more broken P–P bonds. When the black-phosphorene nanotube is longer than the CNT, it rotates synchronously with the CNT even if it is collapsed. Hence, in the design of a nanomotor with a rotor from BPNT, the working rotational frequency should be lower than a certain threshold at a higher temperature.