Artificial Motors Research Articles

Tuning the performance of an artificial protein motor

The Tumbleweed (TW) is a concept for an artificial, tri-pedal, protein-based motor designed to move unidirectionally along a linear track by a diffusive tumbling motion. Artificial motors offer the unique opportunity to explore how motor performance depends on design details in a way that is open to experimental investigation. Prior studies have shown that TW's ability to complete many successive steps can be critically dependent on the motor's diffusional step time. Here, we present a simulation study targeted at determining how to minimize the diffusional step time of the TW motor as a function of two particular design choices: nonspecific motor-track interactions and molecular flexibility. We determine an optimal nonspecific interaction strength and establish a set of criteria for optimal molecular flexibility as a function of the nonspecific interaction. We discuss our results in the context of similarities to biological, linear stepping diffusive molecular motors with the aim of identifying general engineering principles for protein motors.

Supramolecular Bola-Like Ferroelectric: 4-Methoxyanilinium Tetrafluoroborate-18-crown-6

Molecular motion is one of the structural foundations for the development of functional molecular materials such as artificial motors and molecular ferroelectrics. Herein, we show that pendulum-like motion of the terminal group of a molecule causes a ferroelectric phase transition. Complex 4-methoxyanilinium tetrafluoroborate-18-crown-6 ([C(7)H(10)NO(18-crown-6)](+)[BF(4)](-), 1) shows a second-order ferroelectric phase transition at 127 K, together with an abrupt dielectric anomaly, Debye-type relaxation behavior, and the symmetry breaking confirmed by temperature dependence of second harmonic generation effect. The origin of the polarization is due to the order-disorder transition of the pendulum-like motions of the terminal para-methyl group of the 4-methoxyanilinium guest cation; that is, the freezing of pendulum motion at low temperature forces significant orientational motions of the guest molecules and thus induces the formation of the ferroelectric phase. The supramolecular bola-like ferroelectric is distinct from the precedent ferroelectrics and will open a new avenue for the design of polar functional materials.

Conceptual Models for Synthetic Bipedal Motors

Biomolecular nano-motors have provided the inspiration for the design and construction of artificial nanoscale motors and machines based on several types of molecule including DNA. However, no synthetic nano-motors have yet been constructed from building blocks of protein-based material even though biomotors themselves are proteins. The HFSP motor group (1) are in the process of developing a bottom-up approach to the understanding of bio-motors by designing and constructing synthetic protein motors and numerically simulating their kinetic properties. One such concept is the “tripedal tumbleweed” motor (1) and another is the “Inchworm”. In this context we present the results of numerical simulations for a bipedal motor with two connected peptide legs and a simple model for the “inchworm” motor in terms of harmonic bonds. These motors walk on a one-dimensional track of periodically arranged binding sites. The sequence of binding sites on the track of each motor is AB-AB-AB..... and the motors are powered by a temporally periodic sequence of composite washes which modulate the ligand concentrations and the leg angles. The washes cause the motors to undergo directed motion by a hand-over-hand mechanism and an inchworm mechanism, respectively, on a track with asymmetric spacing between the AB and the BA binding sites. We will show simulation results for two-dimensional motor action which includes stepping diagrams, stall forces processivity and first passage times for a range of parameters. These motor has the following properties observed for biological molecular motors: binding, power stroke and diffusional search. Extensions of the model will also be discussed. 1. E. Bromley et al. HFSP Journal Vol. 3 pp.204-212, (2009).

Characterization and studies on grafting of ferroelectric liquid crystal onto polybutylacrylate

AbstractFerroelectric liquid crystalline (FLC) elastomer as a class of electroactive polymers, exhibiting high strain at very low voltage compared to other materials. This giant eletrostriction exploring new applications for ferroelectric materials and these materials are suitable candidates for designing nanoscale artificial muscles, sensors, actuators, pumps and motors. Due to these properties, considerable attention has been paid to these materials in recent years. In this study, ferroelectric liquid crystalline (FLC) monomer was synthesized in a mini reactor in a four‐step procedure. The synthesized materials were characterized with HNMR and FTIR in each step. Then the monomer in the presence of benzoylperoxide as an initiator and n‐butyl acetate as a solvent was grafted onto polybutylacrylate. Grafting was carried out in different processing conditions and products were characterized with HNMR and DSC. The level of initiator, method of initiator's injection to reactor, reaction time, and reactants concentration were part of parameters that were investigated. The analysis of results shows that the reaction time is an important parameter and appropriate grafting needs a long time. Components concentration illustrated important effect on the level of grafting and final structure of grafted chains.

Conceptual Model for a Synthetic Bipedal Stepping Motor

Biomolecular nanomotors have provided the inspiration for the design and construction of artificial nanoscale motors and machines based on several types of molecule including DNA. However, no synthetic nano-motors have yet been constructed from building blocks of protein-based material even though biomotors themselves are proteins. The HFSP smotor group (1) are in the process of developing a bottom-up approach to the understanding of biomotors by designing and constructing synthetic protein motors and numerically simulating their kinetic properties. One such concept is the “tripedal tumbleweed” motor, which is described in (1). In this context we present the results of numerical simulations for a bipedal motor with two connected peptide legs and with some of the properties of the tumbleweed motor. This motor walks on a one-dimensional track of periodically arranged binding sites. The two “feet” at the end of the legs represent different ligand-gated binding proteins which can only bind to their specific binding sites on the track when the related ligands are themselves bound to the binding proteins. The sequence of binding sites on the track is AB-AB-AB…. and the motor is powered by a temporally periodic sequence of composite washes which modulate the ligand concentrations and the leg angles. The washes cause the motor to undergo directed motion by a hand-over-hand mechanism on a track with asymmetric spacing between the AB and the BA binding sites. We will show simulation results for both two-dimensional and three-dimensional motor action of our bipedal motor which will include stepping diagrams, stall forces and first passage times for a range of parameters. This motor has the following properties observed for biomolecular motors: binding, power stroke and diffusional search. Extensions of the model will also be discussed. 1. E. Bromley et al. HFSP Journal (2009)

The Tumbleweed: Towards a synthetic protein motor

Biomolecular motors have inspired the design and construction of artificial nanoscale motors and machines based on nucleic acids, small molecules, and inorganic nanostructures. However, the high degree of sophistication and efficiency of biomolecular motors, as well as their specific biological function, derives from the complexity afforded by protein building blocks. Here, we discuss a novel bottom-up approach to understanding biological motors by considering the construction of synthetic protein motors. Specifically, we present a design for a synthetic protein motor that moves along a linear track, dubbed the "Tumbleweed." This concept uses three discrete ligand-dependent DNA-binding domains to perform cyclically ligand-gated, rectified diffusion along a synthesized DNA molecule. Here we describe how de novo peptide design and molecular biology could be used to produce the Tumbleweed, and we explore the fundamental motor operation of such a design using numerical simulations. The construction of this and more sophisticated protein motors is an exciting challenge that is likely to enhance our understanding of the structure-function relationship in biological motors.

Artificial Brownian motors: Controlling transport on the nanoscale

In systems possessing spatial or dynamical symmetry breaking, Brownian motion combined with unbiased external input signals, deterministic and random alike, can assist directed motion of particles at submicron scales. In such cases, one speaks of ``Brownian motors.'' In this review the constructive role of Brownian motion is exemplified for various physical and technological setups, which are inspired by the cellular molecular machinery: the working principles and characteristics of stylized devices are discussed to show how fluctuations, either thermal or extrinsic, can be used to control diffusive particle transport. Recent experimental demonstrations of this concept are surveyed with particular attention to transport in artificial, i.e., nonbiological, nanopores, lithographic tracks, and optical traps, where single-particle currents were first measured. Much emphasis is given to two- and three-dimensional devices containing many interacting particles of one or more species; for this class of artificial motors, noise rectification results also from the interplay of particle Brownian motion and geometric constraints. Recently, selective control and optimization of the transport of interacting colloidal particles and magnetic vortices have been successfully achieved, thus leading to the new generation of microfluidic and superconducting devices presented here. The field has recently been enriched with impressive experimental achievements in building artificial Brownian motor devices that even operate within the quantum domain by harvesting quantum Brownian motion. Sundry akin topics include activities aimed at noise-assisted shuttling other degrees of freedom such as charge, spin, or even heat and the assembly of chemical synthetic molecular motors. This review ends with a perspective for future pathways and potential new applications.

A microrotary motor powered by bacteria

Biological molecular motors have a number of unique advantages over artificial motors, including efficient conversion of chemical energy into mechanical work and the potential for self-assembly into larger structures, as is seen in muscle sarcomeres and bacterial and eukaryotic flagella. The development of an appropriate interface between such biological materials and synthetic devices should enable us to realize useful hybrid micromachines. Here we describe a microrotary motor composed of a 20-mum-diameter silicon dioxide rotor driven on a silicon track by the gliding bacterium Mycoplasma mobile. This motor is fueled by glucose and inherits some of the properties normally attributed to living systems.

Fuel-Powered Artificial Muscles

Artificial muscles and electric motors found in autonomous robots and prosthetic limbs are typically battery-powered, which severely restricts the duration of their performance and can necessitate long inactivity during battery recharge. To help solve these problems, we demonstrated two types of artificial muscles that convert the chemical energy of high-energy-density fuels to mechanical energy. The first type stores electrical charge and uses changes in stored charge for mechanical actuation. In contrast with electrically powered electrochemical muscles, only half of the actuator cycle is electrochemical. The second type of fuel-powered muscle provides a demonstrated actuator stroke and power density comparable to those of natural skeletal muscle and generated stresses that are over a hundred times higher.

DNA Molecular Motor Driven Micromechanical Cantilever Arrays

The unique ability of living systems to translate biochemical reactions into mechanical work has inspired the design of synthetic DNA motors which generate nanoscale motion via controlled conformational change. However, while Nature has evolved intricate mechanisms to convert molecular shape change into specific micrometer-scale mechanical cellular responses, the integration of artificial DNA motors with mechanical devices presents a major challenge. Here we report the direct integration between an ensemble of DNA motors and an array of microfabricated silicon cantilevers. The forces exerted by the precise duplex to nonclassical i-motif conformational change were probed via differential measurements using an in-situ reference cantilever coated with a nonspecific sequence of DNA. Fueled by the addition of protons, the open to close stroke of the motor induced 32 +/- 3 mN/m compressive surface stress, which corresponds to a single motor force of approximately 11 pN/m, an order of magnitude larger than previous classical hybridization studies. Furthermore, the surface-tethered conformational change was found to be highly reversible, in contrast to classical DNA motors which typically suffer rapid system poisoning. The direction and amplitude of motor-induced cantilever motion was tuneable via control of buffer pH and ionic strength, indicating that electrostatic forces play an important role in stress generation. Hybrid devices which directly harness the multiple accessible conformational states of dynamic oligonucleotides and aptamers, translating biochemical energy into micromechanical work, present a radical new approach to the construction of "smart" nanoscale machinery and mechano-biosensors.

Unidirectional rotary motion in a liquid crystalline environment: color tuning by a molecular motor.

Life could not exist without motion induced by a variety of molecular motors. The construction of artificial motors by chemical synthesis, which can power motions that lead to macroscopic detectable effects in a system, is a major endeavor in contemporary science. To move toward this goal, a host-guest system, composed of a nematic liquid crystal film doped with a chiral light-driven molecular motor, is assembled. Irradiation of the film results in unidirectional rotary motion of the molecular motor, which induces a motion of the mesogenic molecules leading to a molecular reorganization and, as a consequence, a change in the color of the film. In this way, by control of the rotary motion at the molecular level, color tuning over the entire visible spectrum is achieved. These findings demonstrate that a molecular motor can exert a visually observable macroscopic change in a material.

Synchronized Self-Motion of Two Camphor Boats

The synchronized self-motion of two camphor boats was investigated on a circular water route. Two kinds of synchronization, phase-locking and phase-oscillatory modes, could be produced by changing the temperature, the radius of the circular cell, and the mass of each boat. The nature of the synchronization is discussed in relation to the distribution of the camphor layer, which is an important factor in the driving force of self-motion. The essential features of synchronized motion were reproduced by a numerical calculation regarding the spatial distribution of the camphor layer at the air/water interface. We believe that the present results may be useful for realizing artificial motors or chemomechanical transducers, which mimic motor organs or organelles in living organisms under nonlinear and isothermal conditions.

Improving management effectiveness through the use of computer systems in food service operations

This study investigated energy saving effects of published papers related to energy management system (EMS), building energy management system (BEMS), industrial, company and factory energy management system (I/C/F/EMS); and EMS for heating, ventilation, air conditioning (HVAC) and refrigerating equipment, artificial lighting systems, motors and others (EMS for equipment). From 1976 to 2014, management performance reported by 305 EMS cases (105 BEMS cases, 103 I/C/F EMS cases and 97 cases of EMS for equipment) is analyzed to evaluate varied energy saving effects. Statistical results show that saving effects of BEMS increased from 11.39% to 16.22% yearly. Inversely, saving effects of I/C/F EMS decreased from 18.89% to 10.35%. Regarding to EMS for equipment, there is no obvious trend but only the averaged saving effect can be reported. EMS for artificial lighting systems has the highest saving effect up to 39.5% in average. For HVAC and other equipment, energy saving effects are around 14.07% and 16.66% respectively. These energy saving performances are correlated with developed EMS functions. The key EMS functions could be identified from their developing progress for effective energy savings. Based on the quantitative analysis, the future trends of EMS are discussed.