Unidirectional Rotation Research Articles

Spatiotemporal rotational dynamics of laser-driven molecules

Molecular alignment and orientation by laser fields has attracted significant attention in recent years, mostly due to new capabilities to manipulate the molecular spatial arrangement. Molecules can now be efficiently prepared for ionization, structural imaging, orbital tomography, and more, enabling, for example, shooting of dynamic molecular movies. Furthermore, molecular alignment and orientation processes give rise to fundamental quantum and classical phenomena like quantum revivals, Anderson localization, and rotational echoes, just to mention a few. We review recent progress on the visualization, coherent control, and applications of the rich dynamics of molecular rotational wave packets driven by laser pulses of various intensities, durations, and polarizations. In particular, we focus on the molecular unidirectional rotation and its visualization, the orientation of chiral molecules, and the three-dimensional orientation of asymmetric-top molecules. Rotational echoes are discussed as an example of nontrivial dynamics and detection of prepared molecular states.

Tracking Longitudinal Rotation of Silicon Nanowires for Biointerfaces.

The rolling motion (i.e., longitudinal rotation) of nanomaterials may serve as a proxy to probe microscopic environments. Furthermore, nanoscale rotations in biological systems are common but difficult to measure. Here, we report a new tool that measures rolling motion of a nanowire with a short arm grown at one end. We present a particle detection algorithm with subpixel resolution and image segmentation with principal component analysis that enables precise and automated determination of the nanowire orientation. We show that the nanowires’ rolling dynamics can be significantly affected by their surroundings and demonstrate the probes’ ability to reflect different nanobio interactions. A non-cell-interacting nanowire undergoes rapid subdiffusive rotation, while a cell-interacting nanowire exhibits superdiffusive unidirectional rotation when the cell membrane actively interacts with the nanowire and slow subdiffusive rotation when it is fully encompassed by the cell. Our method can be used to yield insights into various biophysical and assembly processes.

Optical Imaging of Coherent Molecular Rotors

AbstractShort laser pulses are widely used for controlling molecular rotational degrees of freedom and inducing molecular alignment, orientation, unidirectional rotation, and other types of coherent rotational motion. To follow the ultrafast rotational dynamics in real time, several techniques for producing molecular movies have been proposed based on the Coulomb explosion of rotating molecules, or recovering molecular orientation from the angular distribution of high harmonics. The present work offers and demonstrates a novel nondestructive optical method for direct visualization and recording of movies of coherent rotational dynamics in a molecular gas. The technique is based on imaging the time‐dependent polarization dynamics of a probe light propagating through a gas of coherently rotating molecules. The probe pulse continues through a radial polarizer, and is then recorded by a camera. The technique is illustrated by implementing it with two examples of time‐resolved rotational dynamics: alignment–antialignment cycles in a molecular gas excited by a single linearly polarized laser pulse, and unidirectional molecular rotation induced by a pulse with twisted polarization. This method may open new avenues in studies on fast chemical transformation phenomena and ultrafast molecular dynamics caused by strong laser fields of various complexities.

Evaluation of power regeneration in primary suspension for a railway vehicle

To improve the fuel economy of rail vehicles, this study presents the feasibility of using power regenerating dampers (PRDs) in the primary suspension systems of railway vehicles and evaluates the potential and recoverable power that can be obtained. PRDs are configured as hydraulic electromagnetic-based railway primary vertical dampers and evaluated in parallel and series modes (with and without a viscous damper). Hydraulic configuration converts the linear behavior of the track into a unidirectional rotation of the generator, and the electromagnetic configuration provides a controllable damping force to the primary suspension system. In several case studies, generic railway vehicle primary suspension systems that are configured to include a PRD in the two configuration modes are modeled using computer simulations. The simulations are performed on measured tracks with typical irregularities for a generic UK passenger route. The performance of the modified vehicle is evaluated with respect to key performance indicators, including regenerated power, ride comfort, and running safety. Results indicate that PRDs can simultaneously replace conventional primary vertical dampers, regenerate power, and exhibit desirable dynamic performance. A peak power efficiency of 79.87% is theoretically obtained in series mode on a top-quality German Intercity Express track (Track 270) at a vehicle speed of 160 mile/h (∼257 km/h).

Synchronized Unidirectional-Rotation and Helical-Motion of Kinesin-Bound Gold Nanorods Indicates Coupling of Torque and Lateral-Force Generations of Kinesin Heads

Kinesin has translational and rotational degrees of freedom and thus the kinesin motility is comprised of helical and rotational motions on a microtubule. However, the motility obtained by combination of helical and rotational motions remains elusive. Here we performed a comparative study of the multiple-motors motility of three plus-ended kinesins; processive single-headed KIF1A, weakly-processive double-headed ZEN-4 and non-processive single-headed kinesin-1 (sK1). Performing a gold-nanorod (GNR) motility assay, which enables us to measure the translational and rotational movements of kinesin-bound GNR around the suspended microtubule, we found that KIF1A-bound, ZEN-4-bound, and sK1-bound GNRs rotate 180° about the short axis of GNRs in one period of helical motion. The rotation-and-helix pitches were comparable between KIF1A-, ZEN-4- and sK1-GNRs (∼0.6 μm) while there were significant differences in their forward velocities. Theoretical analyses with the noise-driven 2D ratchet model indicates that the torque generation of kinesins is coupled to the force generation and that unidirectional rotation of the GNR driven by kinesins enhances biased sideward movement.

Optimum power analysis of a self-reactive wave energy point absorber with mechanically-driven power take-offs

This paper studies a self-reactive ocean wave energy converter (WEC) where energy is absorbed through the relative motion between a floating buoy on the ocean surface and a submerged body. Two types of direct-drive power take off (PTO) systems are examined. One adopts a ball screw system in inverse driving mode with mechanical motion rectifier (MMR) that converts the oscillating bi-directional input heave motion into unidirectional rotation to drive an electromagnetic generator, and another one uses a ball screw system to directly drive the generator (called non-MMR). Dynamic models for both types of PTOs are established and integrated with the overall WEC system model in both the time and frequency domains. Numerical simulation is used to investigate the dynamic performance of both PTOs. The influences of the PTO inerter, which is from the rotational inertia of the flywheel and generator, and the WEC drag damping coefficient are discussed and explored. The analytical closed-form solution for the optimum condition of the non-MMR system is derived based on the criterion of maximum power absorption, and numerical simulation yields the optimum condition for the MMR system. The results under regular and irregular waves show that the PTO inerter in the MMR system can improve the power absorption for small wave periods and maintain the same performance for large wave periods. The PTO inerter in the non-MMR system shifts the peak frequency. The WEC drag damping negatively influences the power absorption in both PTO systems, especially at large wave periods.

Predominantly unidirectional rotation of a viscous liquid with a free boundary

The problem is considered on a periodical of time motion of a viscous liquid bordering on a solid body and a gas. The liquid is affected by oscillatory influences which have no predominant direction in space. The new hydromechanical effect is revealed which consists in that the free parts of the hydro-mechanical system — liquid layers — perform unidirectional stationary rotational motion with the background of oscillations.

Supramolecular control of unidirectional rotary motion in a sterically overcrowded photoswitchable receptor

The induction of unidirectional rotary motion in an achiral, sterically overcrowded, photoswitchable receptor by binding of a chiral guest molecule is unequivocally established.

Direct imaging of direction-controlled molecular rotational wave packets created by a polarization-skewed double-pulse.

High-precision, time-resolved Coulomb explosion imaging of rotational wave packets in nitrogen molecules created with a pair of time-delayed, polarization-skewed femtosecond laser pulses is presented, providing insight into the creation process and dynamics of direction-controlled wave packets. To initiate unidirectional rotation, the interval of the double-pulse was set so that the second, polarization-tilted pulse hit the molecules at the time when molecules were aligned or antialigned along the polarization vector of the first pulse. During the revival period of the rotational wave packet, pulse intervals around both the full and half revival times were used. The observed molecular wave packet movies clearly show the signatures of quantum rotation, such as angular localization (alignment), dispersion, and revival phenomena, during the unidirectional motion. The patterns are quite different depending on the pulse interval even when the angular distribution at the second pulse irradiation is similar. The observed interval-dependence of the dynamics was analyzed on the basis of the real-time images, with the aid of numerical simulations, and the creation process of the packets was discussed. We show that the observed image patterns can be essentially rationalized in terms of rotational period and alignment parameter. Because the double-pulse scheme is the most fundamental in the creation of direction-controlled rotational wave packets, this study will lead to more sophisticated control and characterization of directional molecular motions.

A novel oscillating buoy wave energy harvester based on a spatial double X-shaped mechanism for self-powered sensors in sea-crossing bridges

With the sharp increase in the number of sea-crossing bridges, various sensors have been widely used in bridge monitoring systems in order to ensure safety and prevent accidents during the use of sea-crossing bridges. In this paper, an oscillating buoy wave energy harvester (WEH) based on a spatial double X-shaped mechanism is proposed for self-powered sensors in sea-crossing bridges. Fixed to the side of pillars in sea-crossing bridges, the proposed WEH can convert wave energy with high energy density into electricity. The system consists of four modules: wave energy capture module, transmission module, generator module, and energy storage module. The wave energy capture module collects wave energy through a cylindrical buoy. The transmission module converts the up and down motion of the buoy into a unidirectional rotational motion of the generator input shaft in the generator module to produce electricity. The super-capacitors in the energy storage module store this electrical energy, which is applied to the self-powered sensors. A max efficiency of 57% and an average efficiency of 46.17% can be obtained through MTS bench tests. In field tests, the system’s voltage can reach approximately 3 V, given wave excitation of 1.2 Hz frequency and 15 mm amplitude, which indicates that the proposed WEH is feasible and practical for generating energy used for self-powered sensors in sea-crossing bridges.

Modeling and theoretical analysis of a novel ratcheting-type cam-based infinitely variable transmission system

An infinitely variable transmission (IVT) is a system that allows for a continuous (non-discrete) variation (including zero) in transmission ratio between two rotating elements. In this paper, a novel ratcheting-type IVT mechanism is presented and its geometrical design and kinematic analysis are studied in details. The proposed system contains two identical units. Each unit includes a cam with a follower, oscillatory slotted links pivoted at a shaft that can be moved vertically by a hydraulic ram (alterable transmission ratio), and a grooved wheel with an actuating rod. The input rotational motion is converted through each unit to an oscillatory angular motion of controlled amplitude. This resulting motion is rectified using a ratchet to get a unidirectional output rotational motion. Therefore, the system output motion will have a different velocity and acceleration than those of the system input. The kinematic analysis revealed that the transmission ratio can be varied continuously in a range from zero to infinity. The analysis also showed that, for particular transmission ratios, the system gives uniform output (angular velocity and acceleration) for a corresponding uniform input.

Acceleration and Deceleration of Unidirectional Molecular Rotation by a Femtosecond Laser Pulse

We report velocity controls of a directional molecular motion by a femtosecond intense laser pulse. A laser-induced, direction-controlled rotational wave packet in N2 molecules was subjected to a l...

Green light powered molecular state motor enabling eight-shaped unidirectional rotation

Molecular motors convert external energy into directional motions at the nano-scales. To date unidirectional circular rotations and linear motions have been realized but more complex directional trajectories remain unexplored on the molecular level. In this work we present a molecular motor powered by green light allowing to produce an eight-shaped geometry change during its unidirectional rotation around the central molecular axis. Motor motion proceeds in four different steps, which alternate between light powered double bond isomerizations and thermal hula-twist isomerizations. The result is a fixed sequence of populating four different isomers in a fully unidirectional trajectory possessing one crossing point. This motor system opens up unexplored avenues for the construction and mechanisms of molecular machines and will therefore not only significantly expand the toolbox of responsive molecular devices but also enable very different applications in the field of miniaturized technology than currently possible.

A high-efficiency regenerative shock absorber considering twin ball screws transmissions for application in range-extended electric vehicles

Abstract Renewable energy technologies, particularly in electric vehicles (EVs), have received significant attention in recent years. The wasted energy in a vehicle's shock absorber can be converted into an alternative energy source by regenerative shock absorbers. In this paper, a high-efficiency regenerative shock absorber considering twin ball screws transmissions is proposed for application in range-extended electric vehicles. The proposed regenerative shock absorber can convert vibrational kinetic energy, which is traditionally dissipated as heat in suspension systems, into electricity. The proposed system is divided into four modules: suspension vibration input module, transmission module, generator module and power storage module. Induced by road roughness, the irregular linear oscillations of the suspension are transmitted to the suspension vibration input module. The reciprocating vibrations are converted into unidirectional rotation of the generator by a pair of ball screws, gears, and two overrun clutches in the transmission module. The utilisation of different screw pitches leads to different damping coefficients for upward and downward progress, enabling the shock absorber to fully utilise elastic elements to improve vehicle comfort when compressed and quickly absorb vibrations when stretched. The electricity produced by the generator is stored in supercapacitors to charge the battery and extend the range of EVs. The mechanical properties of the full-scaled fabricated prototype were studied by utilising a mechanical testing and sensing fixture. An average power output of 3.701 W in 1Hz-3 mm sinusoidal vibration input and a peak efficiency of 51.1% and average efficiency of 36.4% were achieved in a bench tests. The range can be approximately extended by 1 mile per 100 miles when EV is driving on the road of class B with a speed of 60 km/h, demonstrating that the proposed high-efficiency regenerative shock absorber is beneficial for harvesting renewable energy, and practical and significant for extending the range of EVs.

Revisiting the protomotive vectorial motion of F0-ATPase

The elucidation of the detailed mechanism used by F0 to convert proton gradient to torque and rotational motion presents a major puzzle despite significant biophysical and structural progress. Although the conceptual model has advanced our understanding of the working principles of such systems, it is crucial to explore the actual mechanism using structure-based models that actually reproduce a unidirectional proton-driven rotation. Our previous work used a coarse-grained (CG) model to simulate the action of F0 However, the simulations were based on a very tentative structural model of the interaction between subunit a and subunit c. Here, we again use a CG model but with a recent cryo-EM structure of cF1F0 and also explore the proton path using our water flooding and protein dipole Langevin dipole semimacroscopic formalism with its linear response approximation version (PDLD/S-LRA) approaches. The simulations are done in the combined space defined by the rotational coordinate and the proton transport coordinate. The study reproduced the effect of the protomotive force on the rotation of the F0 while establishing the electrostatic origin of this effect. Our landscape reproduces the correct unidirectionality of the synthetic direction of the F0 rotation and shows that it reflects the combined electrostatic coupling between the proton transport path and the c-ring conformational change. This work provides guidance for further studies in other proton-driven mechanochemical systems and should lead (when combined with studies of F1) to a complete energy transduction picture of the F0F1-ATPase system.

Experimental Study of a Lift-Type Wave Energy Converter Rotor in a Freewheeling Mode

AbstractIn pursuit of energy harvesting from ocean waves, our recent progress on studying wave interaction with a lift-type rotor is discussed in this paper. The particular focus is on the characterization of the rotor's unidirectional responsiveness in waves. The rotor consists of six hydrofoil blades in two sets. One blade set has three blades laid out as a vertical-axis wind turbine of the Darrieus type. The other blade set has three blades configured like a Wells turbine. In combination, the formed rotor can be driven by flows in any direction to perform a unidirectional rotation about its vertically mounted shaft. This unidirectional responsiveness of the rotor also holds in waves, making the rotor an effective device for wave energy conversion. For the parametric study of the rotor, hydrofoil blades using different cross-sectional profiles and chord lengths have been employed to configure the rotor. The rotor was then tested in a wave flume under various wave conditions in a freewheeling mode. Experimental results were analyzed and discussed. The yielded research findings will greatly enhance the fundamental understanding of the rotor performance in waves and effectively guide the prototype rotor development for practical applications.

Synthesis, spectroscopy and QM/MM simulations of a biomimetic ultrafast light-driven molecular motor.

A molecular motor potentially performing a continuous unidirectional rotation is studied by a multidisciplinary approach including organic synthesis, transient spectroscopy and excited state trajectory calculations. A stereogenic center was introduced in the N-alkylated indanylidene-pyrroline Schiff base framework of a previously investigated light-driven molecular switch in order to achieve the unidirectional C[double bond, length as m-dash]C rotary motion typical of Feringa's motor. Here we report that the specific substitution pattern of the designed chiral molecule must critically determine the unidirectional efficiency of the light-induced rotary motion. More specifically, we find that a stereogenic center containing a methyl group and a hydrogen atom as substituents does not create a differential steric effect large enough to fully direct the motion in either the clockwise or counterclockwise direction especially along the E→Z coordinate. However, due to the documented ultrafast character and electronic circular dichroism activity of the investigated system, we find that it provides the basis for development of a novel generation of rotary motors with a biomimetic framework and operating on a picosecond time scale.

Using Unidirectional Rotations to Improve Vestibular System Asymmetry in Patients with Vestibular Dysfunction

Using Unidirectional Rotations to Improve Vestibular System Asymmetry in Patients with Vestibular Dysfunction

A chiral molecular propeller designed for unidirectional rotations on a surface

Synthetic molecular machines designed to operate on materials surfaces can convert energy into motion and they may be useful to incorporate into solid state devices. Here, we develop and characterize a multi-component molecular propeller that enables unidirectional rotations on a material surface when energized. Our propeller is composed of a rotator with three molecular blades linked via a ruthenium atom to a ratchet-shaped molecular gear. Upon adsorption on a gold crystal surface, the two dimensional nature of the surface breaks the symmetry and left or right tilting of the molecular gear-teeth induces chirality. The molecular gear dictates the rotational direction of the propellers and step-wise rotations can be induced by applying an electric field or using inelastic tunneling electrons from a scanning tunneling microscope tip. By means of scanning tunneling microscope manipulation and imaging, the rotation steps of individual molecular propellers are directly visualized, which confirms the unidirectional rotations of both left and right handed molecular propellers into clockwise and anticlockwise directions respectively.

A thermomechanical coupling in cholesteric liquid crystals: Unidirectional rotation of double-twist cylinders driven by heat flux.

We made aggregates of cholesteric liquid crystalline Cylinders with Double-Twist orientational structure (DTC) and investigated their rigid-body rotation under a temperature gradient, focusing on how the rotational speed should depend on the cylinder size. The experimental results showed that the angular velocity of the DTC aggregates linearly increased with the height of the cylinders and was inversely proportional to the base area. With a phenomenological equation, we analyzed the torque caused by the heat flux and its balance with the viscous friction, and found that the simple analysis well explained the size-dependence of the rotation of the DTC aggregates. The coupling constant between the heat flux and the torque to drive the rigid-body rotation was in the same order of magnitude as that for the director rotation.