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We report THz induced ratchet photocurrent in AlGaN/GaN heterostructures superimposed with asymmetric dual-grating gate structure. The photocurrent shows giant magneto-oscillations in the regime of high magnetic fields. Peculiarly, the envelope of these oscillations exhibits large beatings as a function of the magnetic field. We demonstrate experimentally and theoretically that the beatings are caused by the spin-orbit interaction in GaN conduction band. Our results show how THz photoconductivity can be used for studies of spin dependent effects in GaN-based materials.

We report on the observation of terahertz radiation induced ratchet effects in HgTe/HgCdTe-based quantum well (QWs) structures with a comb-like dual-grating-gate (DGG) structures. For investigations, we used various HgTe QWs with thickness of the 8.0, 7.0, and 6.3 nm, corresponding to parabolic dispersion with inverted band structure (8.0 and 7.0 nm) and linear dispersion (6.3 nm).

We present world’s first ultra-wide spectral range quantum ratchet THz detector. It can detect the spectral range from 4 THz to 200 THz. The detector also shows evident photocurrent even at zero bias and presents a bias-tunable photoresponse characteristic. Additionally, the quantum ratchet detector exhibits pronounced rectification behavior at the temperature below 77 K owing to the ratchet effect, which makes it promising to improve the operation temperature.

We investigate the construction of ratchet band solar cells using InGaN quantum dots. The piezoelectric potentials can spatially separate electron and hole states in InGaN quantum dots. This spatial separation reduces both radiative and non-radiative recombination within the quantum dot, providing one of the key characteristics of a ratchet band system. Ratchet band solar cells have proven difficult to realize experimentally, and the piezoelectric potential in InGaN quantum dots could provide a spatial ratchet that can operate at room temperature with broadband absorption. We use a k.p model to calculate the electronic structure and absorptance of a superlattice of InGaN/GaN quantum dots. We present a new method to calculate the absorptance for the bound-to-continuum transition by using bulk k.p states to approximate the host material continuum states. We show an example of an InGaN quantum dot that could act as a ratchet band solar cell, using its spatially separated states to reduce recombination within the quantum dot.

In this study, a passive arm-support exoskeleton was designed to provide assistive aid for manufacturing workers. The exoskeleton has two operating states which can be altered using an unique ratchet bar mechanism with two blocks fixed on the ratchet bar. When the upper arm is elevated to the highest poiont, the pawl module will touch the lower block to allow the pawl separated, so that the arm can move freely without any resistance. When the upper arm is depressed to the lowest point, the pawl module will touch the upper block to make the pawl re-engaged, so that the upper arm can be locked at any vertical position. For purpose to improve the ergonomical property, the structural parameters of the exoskeleton were determined by particle swarm optimization. The designed exoskeleton was simulated in the Adams model to investigate its actual performance. A preliminary experimental study was conducted to evaluate the effectiveness of the designed exoskeleton on alleviating users’ physical loads in holding heavy tools; the muscular activities on the shoulder muscle groups involved in the weights bearing, elicited by the surface electromyography (EMG) over the shoulder, were significantly reduced from three healthy subjects who carried hand-held tools. The simulation and experiment results show that the designed exoskeleton could effectively relieve the shoulder burden by transferring the bearing load to the waist, where the motion of the arm was not obstructed.

A system of automatic adjustment of the volume of the receiving sleeve of the upper/lower limb with the possibility of memorizing the tightening force of the cables is proposed. The memory effort is embedded in the microprocessor based on the data obtained from determining the optimal loads on certain parts of the stump. The system consists of a motor unit with a microcontroller, which controls the tightening of the three cables, independently of each other, by means of ratchet mechanisms. The target group of amputees according to the type of surgical intervention to establish the proposed system of self-regulation is determined.

This paper presents the effect of the twist rod angles on an inertial rotary electromagnetic energy harvester. Adopting a twist driving system and ratchet clutch system, the harvester can convert linear motion into inertial rotation. There is a remarkable increase of the output when the twist rod is designed with an angle of 50 degrees compared with that of 80 degrees. A power output of 6.2 mW is achieved on the 50 degrees harvester when the rod speed reaches 154.93 mm/s, while the power output is only 0.34 mW on the harvester of 80 degrees. Detailed study is made to investigate the rod speed, the rotor rotating speed, the output and force on the lid. Linearity is observed in the rod speed and the output. The curve related to the 50 degrees harvester has a largest slope among all harvesters.

It is noted that the use of reed switches makes it possible to solve the urgent problem of building relay protection devices without current transformers. It is emphasized that for their fastening and regulation of the response parameters of these devices by changing the position of the reed switches in the vicinity of live buses, special structures are necessary. Four new designs are offered for mounting reed switches close to AC and DC buses. The first of them differs from the known ones by the availability of a clamp covering the bus, a plate on which n reed switches are fixed and a strap fastened with this clamp. The second one differs by a double ear clamp and two rotary arcs with ratchet drums with a reed switch. The third one differs by a L-shaped plate with reed switches and mounting angles. The fourth one differs by two rectangular beams with four through holes. The article describes how to control the parameters of protections tripping on the reed switches using these structures.

This experimental, terrestrial study is part of a larger effort to dissipate increased heat fluxes through enhanced pool boiling in spacecraft electronics prior to an extensive study to be conducted on the International Space Station under pristine microgravity conditions. The absence of buoyancy forces in microgravity causes vapor bubbles to grow to a very large size, leading to premature critical heat flux (CHF). Using an engineered surface modification, namely an asymmetric sawtooth ratchet, to create mobility of the vapor mass can alleviate this problem. The stainless steel (SS 316L) test surfaces were fabricated using powder bed fusion, a metal additive manufacturing process. Vapor mobility was observed in the downward-facing configuration for the asymmetric sawtooth structure explored in the stud y. A thin liquid film was observed underneath the vapor bubbles as they slid along the microstructure. The asymmetric nature of this liquid film is explored using high-speed imaging at the crest and trough of the sawtooth. The proposed asymmetric saw-tooth microstructure is a potential technique to induce motion of vapor bubbles across electronic components when reduced buoyancy forces do not detach vapor bubbles from the surface.

In this paper, we present the design of a novel quasi-passive motor-free orthosis that realizing the compensation of knee joint supporting force during the weight acceptance phase and almost free motion during the swing phase. We explain that the normal knee landing motion is approximately a linear spring through the motion curve, so a suitable linear spring for the knee joint in parallel can achieve an approximate natural response. We show a compound mechanism based on ratchet and cam, which makes springs with different stiffness parallel in support and swing phases, and explain how to design mechanism parameters in switching process. This mechanism is a passive motor-free exoskeleton with automatic switching spring stiffness. It is lightweight and has no energy consumption.

We study the potential efficiency of a wurtzite InGaN/GaN quantum dot system as an intermediate band solar cell. We show that within the detailed balance formalism, efficiencies of quantum dot intermediate band solar cells are equivalent to a ratchet band system, which can be more efficient than a standard intermediate band solar cell. These detailed balance results provide targets for the ideal energy levels of the quantum dots. We use a k.p electronic structure model, including the effects of strain, to design the size and alloy fraction of dots to approach the optimal energy levels. Strain-driven piezoelectric fields tend to separate the electron and holes states inside the quantum dot, requiring small quantum dots in order to have significant optical absorptions. In this case of small dots, we find 1-sun optimal efficiencies up to 39% with a required indium fraction of 78%.

This paper demonstrates an AC electrowetting-on-dielectric (EWOD) based platform to manipulate water droplets using anisotropic patterning of electrodes, without the need of complex control circuits. Only two electrodes are required to transport the droplet. Different droplet sizes (5~15 μL) have been tested and the droplet transport speed can reach 20 mm/s for 15 μL at 20 Hz external AC frequency. By introducing DC EWOD electrodes, we can perform multiple droplet manipulating functionalities including droplet synchronizing, merging, and mixing, which provides potential applications including active self-cleaning surfaces and lab-on-chip instruments.

We present a novel atomizer using standing wave type surface acoustic wave nebulization (SAWN). Compared with progressive wave SAWN, the standing wave SAWN creates smaller drop sizes. We integrate droplet delivery control functionality with anisotropic ratchet conveyors (ARC) on top of the SAWN surface, which employs micro-sized hydrophilic patterns on hydrophobic Cytop coatings. By adopting Parylene-C as a stencil mask, the hydrophobicity of Cytop does not degrade during fabrication. Droplet movement, merging, mixing and nebulizing are demonstrated as a lab-on-chip platform.

During devices investigation for the purpose of high-accuracy measurement their parameters through the agency of vector network analyzer it is a high important to ratchet down systematic measurement error. Specifying the factors of systematic measurement error is meant to be used calibration of vector network analyzer, which is used in for control emerging inaccuracies and mathematical correction of measurements results. This article discloses the method of verification of the vector network analyzer allowing to conduct correct measurements of the microwave modules and also describes how work program of calibration verification.

Adaptive, underactuated and compliant robot systems have received an increased interest over the last decade. Possible applications of these systems range from the development of adaptive robot hands to tendon-driven, soft exosuits. Despite the significant progress in the field, some basic design issues such as the tendon termination and adjustment have not yet been addressed properly. In this paper, we focus on tendon-driven, underactuated systems and we propose a compact ratchet clutch mechanism that facilitates a fine tendon termination and adjustment. The proposed mechanism is experimentally compared with six common tendon termination solutions, using two different tests: i) an accuracy test to verify how precisely each mechanism can adjust the tendon length and ii) a tensile test to derive the strength limit of each mechanism. The experiments validate that the ratchet clutch system is a precise and robust mechanism that outperforms all the solutions compared. A cable driven finger was designed and built to accommodate the proposed mechanism and test its efficiency and applicability to devices that require compactness (e.g., adaptive robot hands). The design of the mechanism is disseminated in an open-source manner.

Development in biomechatronic technology has brought man-machine into close proximity. As the human-robot interaction has enhanced in past few decades, exoskeletons have started to emerge as a promising possibility for improving the human capabilities, assisting the ailing and supporting the heavy physical labour by reducing the fatigue. These systems are anthropomorphically designed so that they can be used in concomitance with human bodies natural structure, without hindering the movements. Our team has designed and created a proof of concept, ‘Passive Lower Body Exoskeleton’, In order to make this sophisticated technology, sustainable, durable and at the same time user-friendly. This Exoskeleton is using two way ratchets at various joints to facilitate the force transfer due to the payload. The weight carried by the wearer is transmitted to the ground without stressing the hips, knees and ankle joint. This passive lower body exoskeleton is not a power-enhancing or the augmentation device, it assists the wearer to transmit the load to the ground using locking and unlocking of ratchet at each joint. As the passive exoskeleton does not use the actuator for its working, minimum energy is required for actuating servo for locking and unlocking the joint reducing the battery consumption and increasing the operational period, while reducing the inertia of the device In this paper, we discuss the design of the mechanical system and electronic system architecture in the first half of the paper. We discuss the simulation and analysis of the system along with the parameter correlation and design of experiments simulation using ANSYS in the next half of the paper. Finally, we conclude the paper with opportunities in developing the exoskeleton further.

Electrical current standards based on the charge of the electron will become more important after the SI redefinition. Many of the best recent charge pump results have come in the one-gate ratchet pumping mode, but this mode is sometimes difficult to achieve. In this work, we discuss the likely reasons for this difficulty, and ways to overcome the difficulty.

Three fundamentally different approaches for the realization of a quantum ratchet intermediate band solar cell are compared. The quantum ratchet is a mechanism by which an energy loss of excited electrons is turned into an improvement in the efficiency of intermediate band solar cells by reducing carrier recombination in the system. The main requirement for this is to engineer forbidden transitions which can be achieved through vanishing spatial overlap of the wave-functions, spinselection rules or a momentum mismatch.

In recent years, studies and developments of power devices are proceeding with the electric vehicles spreading. In this study, authors proposed an approach that considers fatigue characteristics to determine the lifetime of silver sintered materials for mounting SiC semiconductors. We obtained the Manson-Coffin rule from the thermal cycle test using the Si chip joined a substrate with the silver sintered material and the analysis under the same conditions as the test. We demand the lifetimetime predicted from the Manson-Coffin rule used analysis, however the result didn't agree with the test result. Then, improving the model for analysis and predicting the lifetimetime considering the ratchet phenomenon again, we obtained the result of lifetimetime close to the test result. The approach in this study promise to achieve the reliability evaluation of silver sintered materials more accurate.

We report on the development of a novel switchable clutched parallel elastic actuator (SCPEA), which is composed of active components, such as a brake and clutch, as well as passive components, such as a ratchet and one-way bearing. The proposed SCPEA can actively control the storing, preserving, and releasing of the spring potential energy to and from the input motor even when the motor is in operation, and it provides energy/torque to the output, thereby achieving the power/torque modulation of the actuator. Moreover, the controllability of the SCPEA allows the energy transfer between the motor and the spring to be planned in consideration of the energy efficiency, avoiding the motor to be operated in the low efficiency region where large amount of joule heat is produced. The proposed SCPEA is built and its performance is experimentally validated.

This paper describes an active self-cleaning surface where an optically flat and transparent anisotropic ratchet conveyor (ARC) guides a water droplet under orthogonal vibrations. Droplet transport speed is 32.9 mm/s at frequency 52 Hz and acceleration 4.8 g (g = 9.8 m/s2). ARC surfaces can work with a wide frequency bandwidth at 20∼500 Hz as well as with surface inclination angles up to 15°. Optical transmission measurements show that the loss due to ARC coating is within 1% at visible wavelengths. The self-cleaning surface has potential applications on photovoltaic module cover glass to remove dust accumulation and improve efficiency.

We report the first characterization of the transport velocity for droplets driven on ratchet conveyors. Through this study, we determined that the minimum vibration amplitude to initiate droplet transport does not occur at the largest movement of the droplet edges and is thus not simply a resonance effect. We have also discovered that the transport velocity is correlated with the vibration amplitude, but ultimately determined by the probability of the droplet edges advancing by a discrete number of steps.

We demonstrate a simple scattering quantum ratchet operating in terahertz regime. It is based on an asymmetrical quantum tunneling effect in two-dimensional electron gas with Rashba spin-orbit interaction (R2DEG).

The intermediate band solar cell (IBSC) concept aims to improve upon the Shockley-Queisser limit for single bandgap solar cells by also making use of below bandgap photons through sequential absorption processes via an intermediate band (IB). In order for this concept to be translated into more efficient solar cells there are still challenges to overcome; one of the most important is the increased recombination (radiative as well as non-radiative) associated with the additional states in the bandgap. A proposal to mitigate those recombination losses is the introduction of a photon ratchet into the IBSC, which effectively trades some of the energy of the excited electrons against these recombination losses. We show here that this can lead to substantial improvements even in the radiative limiting efficiency, where no non-radiative recombination is taken into account and that this advantage is especially prominent for IBSCs in which the transitions into and out of the IB are not very absorptive, a case commonly encountered for current IBSC proposals.

We describe the recent developments of an open-source project called RATCHET that can be used by groups of users to collectively construct attack trees. We present the RATCHET framework as well as a model for testing and evaluation of the produced attack trees. RATCHET has been tested in classroom settings with positive results and this paper presents the plans for expanding its outreach to the community at large and building attack trees through crowdsourcing. This paper gives an overview of RATCHET and an introduction to its use.

We report on a novel anisotropic ratchet conveyor (ARC) system that can transport liquid droplets using silicon dioxide (SiO2) patterns and applied vibrations. We have discovered that the threshold acceleration amplitude can be modulated by a transition in the duty cycle of recurring SiO2 features. From this observation we have developed ‘droplet gates’, or devices that can selectively pause droplet motion. These devices are essential for timing, synchronization, and mixing of droplets in automated ARC systems.

A coupled transport model of Brownian motors driven by two periodic forces is established. The effects of the two periodic forces on the cooperative transport behaviours of Brownian motors are investigated, including the frequencies and intensities. The results show that when the frequencies of periodic forces are all too large or too small, the directed transport of the motors system can't appear, and appropriate frequencies can promote the transport. Otherwise, with increasing the intensities of periodic forces, the directed transport is more and more obvious. In addition, the effect of a constant force is discussed. It is found that the constant force on the non ratchet potential can't offer effective energy for the directed transport of system, but the constant force on the ratchet potential can offer.

This paper reports a new design for an electrostatic actuated microgripper with a ratchet self-locking mechanism. The self-locking mechanism enables long-time gripping without continuously applying the external driving signal, such as an electrical, thermal or magnetic field, which significantly reduces the effect and damage on the gripped micro-scale objects that are induced by the external driving signals. The microgripper is fabricated using a silicon-on-insulator (SOI) wafer with a 30µm device layer. The jaw gap is 100 µm, and the ratchet locking interval is 10 µm. A metal wire is successfully gripped to demonstrate the feasibility of the ratchet self-locking mechanism.

This research describes an investigation of nonuniform electric field for dielectrophoretic forces (F DEP ) application in particles and cells manipulation. In an electro kinetics occurrence, a miniaturized array and ratchet type microelectrodes has been simulated. The study of optimal F DEP behavior on the electric field distribution for both type microelectrodes was characterized and optimized by finite element method, (FEM). A set of array and ratchet type microelectrode are biased to generate asymmetric electric field distribution. Normalization of microelectrode simulation result shows that array and ratchet type produced a comparable electric field strength and direction. Deployment of additional dimension for array type electrode, three poles produced the highest of electric field strength of 7.513 e7 V/m and displacement field direction of 2.758 e−3 C/m2. Simulation results are used to design a higher sensitive and selective of a dielectrophoretic (DEP) microelectrode for selection, collection and processing of particle and cell using optimal F DEP that determination advancement in the development of dielectrophoretic a lab-on-a-chip. Ultimately, the findings of this work is possible to contribute in medical sciences research for the enrichment of stem cell from bone narrow and peripheral blood form via integration DEP into a lab on a chip, (DLOC) concept application.

Piezo actuators are usually found in applications where high precision, high stiffness, but small displacement are required. This makes them the actuation principle of choice for many microand nano-positioning applications. In contrast, animal and human muscles have a comparatively small stiffness, but long displacements. Their force is generated by a ratchet-type mechanism of the actin and myosin cross-bridges. In this paper, we will present a piezohydraulic “ratchet” design, using two valves to mimic the actin-myosin cross-bridges. The actuator is thus able to realize very long linear actuator displacements. The mechanism will be analyzed, and it will be shown that force-velocity and power characteristics of this type of actuator design are highly adaptable, and comparable to muscle tissue. When designing robots for human-robot collaboration, or social machines operating in close proximity to humans, this makes them inherently safe, even when control fails. Measurements from a prototype actuator are shown, demonstrating the practical feasibility of the design.

Micro-nano robots intended for application to various fields are developed. However, motors, which are robot's power, are not yet practical. In this paper, to realize the motor, which can be applied to micro-nano robot's power source, we established bio-motor by using surface swarming of Vibrio alginolyticus. We succeeded in controlling movement of surface swarming by ratchet shape micro channel and then driving the micro gear in the closed micro channel. As a next step, to transmit power of rotational movement, we fabricated the open micro channel and micro object (floating pillar, micro gear etc.) and succeeded in driving the object in the open micro channel. In addition, we revealed that rotational power of floating pillar by deformation of nano probe. Finally, we assembled the micro gear with shaft like crank. Therefore, it became possible transmitting the power from rotational movement to outside. Thus, we achieved to construct base of bio-motor.

We report on the observation of terahertz radiation induced photocurrents in single-layer graphene samples subjected to an in-plane magnetic field. The photosignal is observed for both, linearly and circularly polarized radiation. A remarkable effect is that the current inverts its sign not only by switching the magnetic field direction, but as well by changing the radiation helicity from left- to right-handedness. We demonstrate that the photocurrent stems from strong structure inversion asymmetry (SIA) of samples originating from the presence of substrate and/or adatoms on graphene. The analysis shows that the observed effect represents a new type of ratchet effects: magnetic field induced ratchets. A microscopic theory of the observed effect is developed being in a good qualitative agreement with the experiment. Furthermore, the experiments open a promising access to the investigation of SIA which is of particular interest for the understanding of graphene properties as well as applications.

This paper studies open-loop operation of flashing ratchets, which refer to mechanisms that enable motion of particles under diffusion and possibly drag forces along a preferred direction through alternating turning on and off of specifically designed ratchet potentials. Flashing ratchets are used to model certain transport mechanisms of molecular motors and are of special interest to biologists and biophysicists. Mathematically they are are modeled by stochastic hybrid systems. For an open-loop design of on-times and off-times, we derive, under certain practical assumptions, an exact probability density function that reflects the spatial distribution of particles in space after the ratchet has flashed a given number of times, and find an optimal off-time that maximizes the transport velocity for a specific ratchet potential. Validation of the underlying assumptions is also presented. Simulation results show that these open-loop designs achieve as good or better average velocities for particles over certain well known existing feedback strategies in literature.

A means to passively effect liquid motion parallel to the surface through surface modifications is presented. The geometry considered is that of repeated array of silicon ratchets with reentrant cavities located on the shallow face of each ratchet. The surface is heated on the bottom side using a thin-film serpentine heater. Experiments were performed using deionized water at atmospheric pressures and subcoolings of 5°C and 20°C. High-speed videos were used to resolve bubble behavior near the surface. A preferential non-vertical bubble growth and departure direction was observed for both subcooling conditions. Tracking of bubbles was accomplished using a custom algorithm, which resolved instantaneous component of velocity of bubbles parallel to the surface in excess of 600 mm/s immediately following departure in the high subcooling condition. Mean horizontal component of velocities of bubbles farther from the surface, which were tracking the liquid velocity, were resolved in the range of 25 and 35 mm/s. A semi-empirical model based on bubble growth is presented to predict the observed liquid velocities.

Recently, micro-nano robots intended for application to various fields are developed. However, motors which are robot's power are not yet practical. In this paper, to realize the motor which can be applied to micro-nano robot's power source, we established bio-motor by using surface swarming of Vibrio alginolyticus. First, we succeeded in driving the micro gear in the closed micro channel. Next, to transmit power of rotational movement, we fabricated the open micro channel, and succeeded in driving the gear in the open micro channel similarly. In addition, we revealed that ratchet type gear rotated faster than other type. Finally, we assembled the micro gear with shaft. Therefore, it became possible transmitting the power from rotational movement to outside. Thus, we achieved to construct base of bio-motor.

In this paper, we established the driving systems for micro structures by using surface swarming of Vibrio alginolyticus. First, we succeeded in causing rotational movement using ratchet shape micro channel. Next, To rectify rotational movement, we fabricated center prior in the micro channel. We succeeded in smooth rotational movement using this new design micro channel. Furthermore, we succeeded in driving micro gear in the micro channel.

In nature, several animals and insects use jumping locomotion in rough terrains. Jumping locomotion is useful for ground robots as jumping provide high speed movement with enhanced energy efficiency. It also helps in overcoming obstacles relatively larger than their body sizes. Jumping needs coordination and large instantaneous forces within a very short duration. In this paper, a method of jumping by using a four-bar spring/linkage mechanism integrated with spool winding and ratchet release mechanism has been presented. Inspired by the frogs, we have modeled and simulated a simple and efficient four legged jumping frog robot.

This paper designed a ratchet mechanism of a pastry slicer. In the first place, this discourse used SolidWorks software to model the ratchet mechanism, then imported the three-dimensional model into ADAMS by the nicer interface between SolidWorks and ADAMS to build a virtual machine and simulated it. The kinematic simulation result of ADAMS not only showed that the ratchet mechanism could fulfill the anticipative design requirements, but also offered the references to design and produce physical prototype of ratchet mechanism. The virtual prototype could be used to do a deeper analysis according to different requirements.

In this paper, we present a novel computing paradigm using a non-equilibrium electronic ratchet which is capable of driving current in the absence of an applied drain bias. By using a time varying, spatially asymmetric potential, we demonstrate that it is possible to create a net current from drift-diffusion processes of charge carriers. This is especially useful in reducing static dissipation encountered in conventional logic circuits. In addition, since the electronic ratchet acts as voltage-controlled current source, we find that the dynamic dissipation associated with charging/discharging of load capacitors is also decreased. Furthermore, we show that the ratchet device is naturally amenable to a dissipation reduction technique known as adiabatic clocking. Because of the unique charging mechanism of the ratchet, timing constraints on logic inputs—an important drawback of conventional adiabatic circuits—are not needed to achieve adiabatic computation.

A novel microfluidic device is described that can detect the chemotactic response of motile bacterial cells (Escherichia coli) that swim toward a preferred nutrient with high resolution by sorting and concentrating them. The device consists of the typical Y-shaped microchannels that have been widely used in chemotaxis studies to attract cells toward a high concentration and a concentrator array integrated with arrow head-shaped ratchet structures beside the main microchannel to trap and accumulate them. Since the number of accumulated cells in the concentrator array continuously increases with time, the device makes it possible to amplify the chemotactic responses of the cells to 10 times greater than that in the typical Y-shaped channels in 60 min. In addition, the device can characterize the chemotactic sensitivity of chemoreceptors to chemoeffectors by comparing the number of cells in the concentrator array at different distances from the channel junction. Since the device allows the analysis of the chemotactic responses and sensitivity of chemoreceptors with high resolution, we believe that not only can the device be broadly used for various microbial chemotaxis assays but it also can further the advancement of microbiology and even synthetic biology.

Ratchet effect might be responsible for the unidirectional movement of a couple of systems. The theoretical study of ratchet mechanism usually focuses on the particle or state properties on a prescribed ratchet potential. In contrast, this work starts with a real system and shows how one can manipulate the system setup to have a ratchet potential for the system state. The model consists of a rotor surrounded by several drivers on a 2D plane. Both the rotor and drivers are furnished with electric dipoles, through which they can interact with each other. During the rotational fluctuations of the driver dipoles between two states, the rotor may rotate unidirectionally, independent of whether the driver fluctuations are periodic or completely random. If the driver fluctuations come from the conformational change of certain protein subunits consuming ATP, the rotor behavior would be similar to the rotation of the central γ subunit of F 0 F 1 -ATPase in mitochondria. We compare the rotational properties of our model with that of the flashing ratchet and F 0 F 1 -ATPase. This model provides a feasible way for harvesting non-equilibrium energy from ambient noise, which could be used to design microscopic artificial machines.

Present day CMOS transistors operate by thermionic emission of electrons over a gate tunable barrier. The fundamental switching energy for each such switching event can be derived from equilibrium thermodynamic considerations. While clever ways can sometimes mitigate the power budget, more often than not, this involves trade-offs with short channel effects (variability), on-off ratio (reliability) and mobility (switching speed). We discuss switching paradigms that venture beyond the near-equilibrium operation of transistors involving the absence or presence of charges as the digital switching bits. To this end, a few case studies are presented. Dipolar switching is invoked as an example to show how gating non-electronic degrees of freedom can reduce the subthreshold swing below the textbook limit by acting as an added cut-off filter on the current. We discuss how new state variables may be engineered into a CMOS platform to enable such non-electronic switching. Another, completely different direction involves non-equilibrium switching, such as a ratchet that allows us to move charges unidirectionally without a drain bias, by using instead an always present AC clock signal adiabatically coupled with the gate.

Three-dimensional elastic contact model of the automobile gasoline economizer of the one-way gear devices is analyzed on the base of FEM. The work condition is calculated, and the stable stress distribution, strain distribution and the deformation of the outer ratchet, inside core and pawl are obtained. With the FEA analysis results, the intensity reliability of each part is checked based on maximum shearing stress criterion and criterion of the strain energy density corresponding to distortion. The results indicate that the device is safety.

Automobile gasoline economizer of the one-way gear device is a simple, effective and low cost saving device, which consists of inside core, pawl and outer ratchet. The 3d contact model is established on the base of elastic contact theory and then the practical work process is simulated by ANSYS software. In the end, the contact area, the stress distribution and strain are analyzed. This work may lay a foundation for optimization design.

A power module, which includes an insulating plate soldered to a heatsink, is called a direct-cooled power module. There are several packaging technologies to improve a direct-cooled power module in terms of not only reduction of thermal resistance but also elongation of lifetime. Among those approaches, this paper describes optimization of heatsink thickness and prevention of ratchet deformation. The calculation results show that a thicker heatsink is better to avoid liquid leakage although thicker heatsink provides shorter solder-lifetime. A heatsink with Vickers hardness of greater than 60 MPa is expected to prevent ratchet deformation under the condition of thermal cycling between -40oC and 125oC. and hardness is verified as an effective approach to produce reliable direct-cooled power modules.

We report on a Flat Surface Ratchet, capable of achieving droplet transport using curved hydrophilic rungs patterned onto a hydrophobic surface. These periodic asymmetric wetting barriers can be fabricated easily on a wide variety of surfaces. Transport of a 10 µl droplet is achieved by an electromagnetic speaker with vertical sinusoidal vibrational amplitudes as low as 37 µm at 82 Hz, making this technology implementable for a wide range of discrete microfluidic applications.

We report a performance comparison between different techniques for enhancing and controlling the ratchet effect recently observed in arrays of asymetric antidots . Under microwave linear polarized radiation, the effect was observed in a high mobility two dimensional electron gas based on AlGaAs/GaAs heterojunction, with periodic array of artificial semi-discs shaped antidots. The uniformity of the incident electric field polarization, the uniformity of the incident power density, as well as the amount of the incident power flow across the surface of the semiconductor sample are the important parameters for choosing the suitable millimeter-wave illumination technique. Several techniques based on the use of horn antenna, dielectric lens or planar dielectric multilayer structures are analyzed in this communication. A comparative study based on full wave electromagnetic simulation allows us to identify the most suitable techniques for improving the original setup used for ratchet experiments. To our knowledge, this opens new possibilities of high frequency detectors based on ratchet effect in the millimeter and sub-millimeter wave region.

We report on the successful experimental realization of a quantum ratchet for ultracold atoms in a driven spatially asymmetric optical lattice. Ratchets are usually considered as a tool, which rectify an otherwise undirected, for instance oscillating or fluctuating, motion of particles or objects. In order to observe a directed transport of atoms one has to break the space-time symmetry of the system [1–3]. Here, we report on the realization of a quantum ratchet in the absence of dissipative processes (Hamiltonian regime) within the interaction time.

This paper presents comprehensive improvements of micro motion transmission systems (MTS), which driven by electrostatic comb-drive actuators through ratchet mechanism to move micro objects unidirectionally in straight, curved and rotational paths. The first MTS is the tangential driving MTS, in which the driven objects are moved by tangential force. A rotational gearing MTS and micro conveyance system (MCS) based on this driving mode will be presented. Thanks to the new designs of directional guider of the micro containers and new turning module, the containers can move in both straight and curved paths in the tangential MCS. The second MTS is the perpendicular driving MCS, which drives micro containers by the perpendicular driving force, i.e. the moving direction of the container is perpendicular to the actuation direction. Movement velocities of the containers can be controlled by changing the driving frequency.