Unidirectional Rotor Research Articles

A rotational energy harvester with a semi-flexible one-way clutch for capturing low-frequency vibration energy

Renewable vibration energy is widely distributed in our living environment, but the low-frequency and irregular features impede its efficient exploitation and practical applications. To solve this issue, this paper proposes an innovative semi-flexible one-way clutch (OWC) and an OWC-based rotational energy harvester (OWC-REH) to achieve high and useable electric power out of low-frequency (<5 Hz) vibrations. The OWC consists of a pendulum equipped with a flexible thruster and a rotor designed with zigzag-shaped bulges on its surface. Through the interaction between the thruster and the bulges, the conversion of the bi-directional pendulum swing to the uni-directional rotor rotation can be realized. When excited by vibrations with an amplitude of 12 mm, the rotor achieves a fast speed of 240 rpm and the OWC-REH can generate high output power of 4.3 mW at 2.4 Hz. The energy conversion efficiency of the OWC-REH reaches a high value of 36.2%. When the OWC-REH is fastened to human limbs, the harvested energy from human motions can maintain the normal operation of portable electronic devices. This study proposes a promising strategy for utilizing the pervasive low-frequency vibrations as the sustainable energy for low-power electronics.

A Nanocar and Rotor in One Molecule.

Depending on its adsorption conformation on the Au(111) surface, a zwitterionic single-molecule machine works in two different ways under bias voltage pulses. It is a unidirectional rotor while anchored on the surface. It is a fast-drivable molecule vehicle (nanocar) while physisorbed. By tuning the surface coverage, the conformation of the molecule can be selected to be either rotor or nanocar. The inelastic tunneling excitation producing the movement is investigated in the same experimental conditions for both the unidirectional rotation of the rotor and the directed movement of the nanocar.

Photo‐responsive Helical Motion by Light‐Driven Molecular Motors in a Liquid‐Crystal Network

AbstractControlling sophisticated motion by molecular motors is a major goal on the road to future actuators and soft robotics. Taking inspiration from biological motility and mechanical functions common to artificial machines, responsive small molecules have been used to achieve macroscopic effects, however, translating molecular movement along length scales to precisely defined linear, twisting and rotary motions remain particularly challenging. Here, we present the design, synthesis and functioning of liquid‐crystal network (LCN) materials with intrinsic rotary motors that allow the conversion of light energy into reversible helical motion. In this responsive system the photochemical‐driven molecular motor has a dual function operating both as chiral dopant and unidirectional rotor amplifying molecular motion into a controlled and reversible left‐ or right‐handed macroscopic twisting movement. By exploiting the dynamic chirality, directionality of motion and shape change of a single motor embedded in an LC‐network, complex mechanical motions including bending, walking and helical motion, in soft polymer materials are achieved which offers fascinating opportunities toward inherently photo‐responsive materials.

Photo-responsive Helical Motion by Light-Driven Molecular Motors in a Liquid-Crystal Network.

Controlling sophisticated motion by molecular motors is a major goal on the road to future actuators and soft robotics. Taking inspiration from biological motility and mechanical functions common to artificial machines, responsive small molecules have been used to achieve macroscopic effects, however, translating molecular movement along length scales to precisely defined linear, twisting and rotary motions remain particularly challenging. Here, we present the design, synthesis and functioning of liquid‐crystal network (LCN) materials with intrinsic rotary motors that allow the conversion of light energy into reversible helical motion. In this responsive system the photochemical‐driven molecular motor has a dual function operating both as chiral dopant and unidirectional rotor amplifying molecular motion into a controlled and reversible left‐ or right‐handed macroscopic twisting movement. By exploiting the dynamic chirality, directionality of motion and shape change of a single motor embedded in an LC‐network, complex mechanical motions including bending, walking and helical motion, in soft polymer materials are achieved which offers fascinating opportunities toward inherently photo‐responsive materials.

Experimental Studies on Savonius Wind Turbine with Unidirectional Rotor House for High Speed Application

Experimental Studies on Savonius Wind Turbine with Unidirectional Rotor House for High Speed Application

Asymmetric Synthesis of Second-Generation Light-Driven Molecular Motors.

The enantiomeric homogeneity of light-driven molecular motors based on overcrowded alkenes is crucial in their application as either unidirectional rotors or as chiral multistate switches. It was challenging to obtain these compounds as single enantiomers via the established synthetic procedures due to loss of optical purity in the key step, i.e., the Barton–Kellogg olefination reaction. Searching for strategies to avoid racemization, a new class of light-driven molecular motors was designed, synthesized, and studied. The stereochemical integrity was fully preserved throughout the synthesis, and on the basis of photochemical and kinetic studies using UV/vis, CD, and 1H NMR spectroscopy, it was established that they still function properly as unidirectional molecular motors.

Enantiopure Functional Molecular Motors Obtained by a Switchable Chiral-Resolution Process.

Molecular switches, rotors, and motors play an important role in the development of nano-machines and devices, as well as responsive and adaptive functional materials. For unidirectional rotors based on chiral overcrowded alkenes, their stereochemical homogeneity is of crucial importance. Herein, a method to obtain new and functionalizable overcrowded alkenes in enantiopure form is presented. The procedure involves a short synthesis of three steps and a solvent-switchable chiral resolution by using a readily available resolving agent. X-ray crystallography revealed the mode of binding of the motor with the resolving agent, as well as the absolute configuration of the motor. (1) H NMR and UV/Vis spectroscopy techniques were used to determine the dynamic behavior of this molecular motor. This method provides rapid access to ample amounts of enantiopure molecular motors, which will greatly facilitate the further development of responsive molecular systems based on chiral overcrowded alkenes.

Light-driven molecular motors: imines as four-step or two-step unidirectional rotors.

Chiral N-alkyl imines undergo unidirectional rotation induced by light and heat, thus providing a new class of molecular motors. Depending on the conformational flexibility of the stator part (the carbonyl residue) and the nitrogen inversion barrier of the rotor part (the amine residue) in the molecule, the operation mode of the motor can be controlled as either a four- or a two-step cycling motion of the rotor part.

Biologically inspired molecular machines driven by light. Optimal control of a unidirectional rotor

We investigate the extent to which unidirectional intramolecular torsional motion can be created in an oriented bicyclic model system driven solely by laser light. We apply the machinery of quantum control via specifically tailored laser pulses to induce such motion, eliminating the need for the thermally constrained steps conventionally used in molecular motor systems. Our approach does not rely on specific details of the potential surfaces to create a preferred direction. Rather, we use matter–field interaction and the tools of coherent optimal control to create a wave packet with nonzero angular momentum among unbound torsional states on an excited electronic surface. Analysis of the results of the control algorithm provides general insight into when and how optimal control theory can find solutions that could not be generated through simple intuitive schemes. We find that, under constrained polarization, the control algorithm reduces to a simple intuitive coherent control strategy wherein a first IR pulse creates a non-stationary wave packet on the ground surface and a subsequent UV pulse transfers it to the excited state. Allowing for polarization shaping, however, we find new control routes that go beyond the intuitive scheme.

Mechanical twisting of a guest by a photoresponsive host

Molecular analogues of a variety of mechanical devices such as shuttles, brakes, unidirectional rotors and tweezers have been created. But these 'molecular machines' have not yet been used to mechanically manipulate a second molecule in a controlled and reversible manner. Here we show that light-induced scissor-like conformational changes of one molecule can give rise to mechanical twisting of a non-covalently bound guest molecule. To realize this coupling of molecular motions, we use a previously designed system: a ferrocene moiety with an azobenzene strap, each end of which is attached to one of the two cyclopentadienyl rings of the ferrocene unit, acts as a pivot so that photoisomerization of the strap rotates the ferrocene rings relative to each other and thereby also changes the relative position of two 'pedal' moieties attached to the ferrocene rings. We translate this effect into intermolecular coupling of motion by endowing the pedals with binding sites, which allow the host system to form a stable complex with a bidentate rotor molecule. Using circular dichroism spectroscopy, we show that the photoinduced conformational changes of the host are indeed transmitted and induce mechanical twisting of the rotor molecule. This design concept, which significantly extends the successful coupling of motion beyond the intramolecular level seen in synthetic allosteric receptors, might allow for the remote control of molecular events in larger interlocked molecular systems.