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International audience; Bistable molecules represent a potential miniaturization limit for high-density information technologies. However, molecules exhibit memory effect typically at very low temperatures. This is the case of spin-crossover (SCO) complexes, where the concept of a molecular memory has not been considered due to the fast spin-state interconversion of all previous systems. Breaking this principle, here we report a slow relaxation process found in an SCO iron-triazole polyanionic complex. Multiple experimental evidences confirm the opening of a thermal hysteresis upon solid dilution and even in liquid solution. Density functional theory (DFT) calculations reveal the origin of this unexpected phenomenon to the appearance of an energy barrier that slows down the spin-state relaxation processes at the molecular level. These results show how SCO molecules may store information at room temperature, opening unique opportunities for molecular data storage.

Moving animal groups often spontaneously change their group structure and dynamics, but standard models used to explain collective motion in animal groups are typically unable to generate changes of this type. Recently, a model based on attraction, repulsion and asymmetric interactions designed for specific fish experiments was shown capable of producing such changes. However, the origin of the model’s ability to generate them, and the range of this capacity, remains unknown. Here we modify and extend this model to address these questions. We establish that its ability to generate groups exhibiting changes depends on the size of the blind zone parameter β. Specifically, we show that for small β swarms and mills are generated, for larger β polarized groups forms, and for a region of intermediate β values there is a bistability region where continuous switching between milling and polarized groups occurs. We also show that the location of the bistability region depends on group size and the relative strength of velocity alignment when this interaction is added to the model. These findings may contribute to advance the use of self-propelled particle models to explain a range of disruptive phenomena previously thought to be beyond the capabilities of such models.

As future energy-saving optoelectronics, bistable electrochromic (EC) materials/devices have high energy efficiency for potential applications as smart windows, displays, and information/energy sto...

The power capture performance of an adaptive bistable point absorber wave energy converter (WEC) in irregular waves is investigated in this paper. Based on the linear potential flow theory and Cummins equations, the equation of motion for the WEC is established in time domain. Then a parametric study is performed on the power capture performance of the WEC by considering the influences of different wave and system parameters such as the spring combination parameter, the stiffness of auxiliary springs and main springs, the original length value of the main spring, damping coefficient of the PTO systems and the significant wave height. The results show that in an irregular wave, each parameter will have a certain impact on the performance of the device. Appropriate device parameters need to be selected according to actual environmental parameters to ensure that the adaptive bistable WEC has better power capture performance than its linear and conventional bistable counterparts.

In this paper, we studied the homoclinic bifurcation and nonlinear characteristics of a bistable piezoelectric energy harvester while it is concurrently excited by galloping and base excitation. Firstly, the electromechanical model of the energy harvester is established analytically by the energy approach, the Kirchhoff's law and quasi-steady hypothesis. Then, by the Melnikov method, the threshold for underlying snap-through in the system is derived, and the necessary conditions for homoclinic bifurcation and chaos are presented. The threshold is a determinant for the occurrence of high-energy oscillation. The analysis results reveal that the wind speed and the distance between magnets could affect the threshold for inter-well chaos and high energy oscillation. Finally, numerical simulation and experiments are carried out. Both results from numerical simulation and experiment support the theoretical prediction from Melnikov theory. The study could provide a guideline for the optimum design of the bi-stable piezoelectric energy harvester for wind and vibration in practice.

Origami has been proved as a valuable tool to develop deployable, multifunctional, and tunable devices for diverse engineering applications. Inspired by the Kresling origami, this article presents a soft pneumatic actuator with vacuum control to realize the compound motion of twist and contraction. The twist direction varies as the crease angle changes and it offers pure contraction after combining two actuators with reverse creases. Our actuator can lift 180 folds of its weight and achieve the contraction ratio of 47%, while the response time is below 0.3 s. The origami-based actuator can realize an adjustable bistable property, leading to the possibility for external stimulus detection and mechanical memory devices, where the sensitivity can be regulated by the initial vacuum pressure. Through several actuators, we demonstrate the reconfigurable crawling robots capable of worm-like creep, alternating-step locomotion as well as obstacle detection. After activating all the actuators, the four-actuator robot with two working modes is validated to perform agilely for confined space navigation, showing our actuator has the potential in soft robotics applications.

The non-linear dynamics of large ion clouds ($N \geq 256 $ ions) trapped in radio-frequency traps and coupled to laser-cooling give rise to a bistable behaviour of the temperature. Numerical simulations of the free evolution of a large three-dimensional spherical cloud is used to characterise how the oscillating field amplitude and the ion number control the rf heating rate and the switching between the two stable states. We show that the heating rate does not significantly depends on the ion number but strongly depends on the oscillating field. This exhibits the major role played by the density of the ensemble. The competition between the radio-frequency heating and the laser cooling is also discussed. They are used to design scenarii to take advantage of the threshold effect to detect and quantify perturbations by an intruder., Comment: 5 pages, 3 figures

The preparation of intelligent-responsive materials with controllable topology structure has long been a significant objective for chemists in the field of materials science. In this paper, we designed and prepared a linear-cyclic reversible topological structure polymer based on the bistable [1]rotaxane molecular shuttle. A ferrocene-functionalized [1]rotaxane and naphthalimide fluorophore group are introduced into the both ends of the polymer, which exhibit distance-induced photo-electron transfer effect. The structural transformation between linear and cyclic state of polymer is demonstrated by simple acid-base stimuli, accompanying visual fluorescence changes. The transformation process was characterized by 1H NMR spectra and fluorescence spectra. This work provides a novel strategy to construct functionalized polymers with topological structure.

This study presents the design and test of a novel self-adaptive soft gripper, integrating pneumatic actuators and bistable carbon-fiber reinforced polymer laminates. The morphology was designed using the distinct structural characteristics of bistable structures; and the stable gripping configuration of the gripper was maintained through the bistability without continuous pressure application. The sufficient compliance of bistable structures makes the gripper versatile and adaptable to gripping deformable objects. First, a pneumatic-actuated method was introduced to achieve the reversible shape transition of the bistable structure. Next, three arrangement methods for actuators were analyzed with respect to the bistable transition and curvature, where it was found that the cross-arrangement is optimal. The effects of pneumatic actuators with different geometrical parameters on the response times are discussed, and the results show that the bistable structure can achieve shape transition within milliseconds under low pressure. Furthermore, the numerical and experimental results show good agreement between critical pressures and out-of-plane deformation. Furthermore, the shape retention function of the soft gripper was studied by using it to grasp objects of various sizes even when the pressure was reduced to the initial state. The bistable laminates exhibit sufficient compliance, and the deformed laminates can automatically accommodate the deformation of objects. The relationship between the weight and size of available gripping objects was studied; functional tests confirmed that the proposed soft gripper is versatile and adaptable for gripping objects of various shapes, sizes, and weights. This gripper has immense potential to reduce energy consumption in vacuum environments such as underwater and space.

The physical implementation of reservoir computing (RC), a brain-inspired computing framework, is attracting increasing attention in various research fields owing to its capability of quick learning and the relatively simple training process. Although several physical RC models have been envisaged and realized, most of them require additional peripherals; it leads to an increase in the power consumption of the system. In this study, we propose a novel RC model that is based on an overdamped bistable system and exhibits a counter-intuitive phenomenon called stochastic resonance, through which it can transfer noise energy to the information-carrying signal to realize learning with a comparatively low power consumption. The proposed model also possesses the functional capability of filtering and amplification and thus does not require additional peripheral equipment. In order to prove the feasibility and determine the desired operation mode of the system, two basic benchmark tests, namely short-term memory and parity check tasks, were employed to assess the proposed model. The results verify that this work will potentially act as a stepping stone towards realizing even better low-power-consumption physical RC.

[EN] The structurally simple complex {Fe-II[tren(6F-py)(3)]}(BF4)(2) [tren(6F-py)(3) = tris(3-aza-4-(6-fluoro-2-pyridyl)-3-butenyl)amine] undergoes an abrupt spin transition (ST) with the critical temperature T down arrow(1/2) = 243 K on cooling and T up arrow(1/2) = 281 K on heating, with a 38 K wide hysteresis, while the ClO4- congener shows ST spanning the room temperature region at T down arrow(1/2) = 267 K and T up arrow(1/2) = 295 K with a 28 K wide hysteresis. Calorimetric data confirm the occurrence of a highly energetic ST process, while multi-temperature single crystal X-ray structural studies identify a concerted symmetry-breaking P2(1)/n P2(1)/c as the origin of the rare strong cooperativity and the large hysteresis loop. The analysis of the experimental data discloses two distinct interdependent events, namely, the combination of a gradual ST and an induced crystallographic phase transition, which endows the material with strong bistability and makes it an excellent platform for investigating new generations of ST based electronic and spintronic devices., This work was supported by grant PID2019-106147GB-I00 funded by MCIN/AEI/10.13039/501100011033, Unidad de Excelencia Maria de Maeztu (CEX2019-000919-M); the Generalitat Valenciana through PROMETEO/2016/147 and EU Framework FET-OPEN project COSMICS (grant agreement 766726), by the grant of the Ministry of Education and Science of Ukraine for perspective development of a scientific direction "Mathematical sciences and natural sciences" at Taras Shevchenko National University of Kyiv. We thank Prof. Dr Eric Collet for invaluable comments and suggestions.

Purpose The aim of this study is to investigate the implementation of the sliding-line technique (SLT) in a generic two-dimensional (2D) nonlinear adaptive magnetic equivalent circuit (MEC) model predicting the electromagnetic force evolution of a linear bistable electromagnetic actuator technology. Design/methodology/approach The developed MEC model considers the saturation effect and the auto-adjustability of the spatial discretisation. The connection between static and mobile zones is ensured by an approach known as “air-gap sliding-line technique”, which is widely used for rotary electric motor models. To the best of the author’s knowledge, that is the first time that the SLT is implemented on an electromagnetic structure with linear motion. Findings It was found that, in case of a linear actuator with a relatively small working stroke, the implementation of the SLT could lead to some non-negligible inaccuracies. Originality/value To solve the above-mentioned problem, it was proposed to investigate the implementation of a single SLT vs double SLT. The results of the MEC models were compared with the 2D finite-element analysis (FEA) as well as with the experimental test results. The developed semi-analytical models can be easily adapted to other topologies of linear electromagnetic machines.

This paper investigates friction-induced instability in a Single Degree-of-Freedom, pseudo-rigid-body representation of a bistable compliant mechanism composed of two sliders connected with a massless rigid link. The friction force is a function of the state variables through Stribeck effect and variable contact force due to the structural nonlinearity of the mechanism. A Constant normal force ensures the mass-belt contact during oscillation. It is shown that the steady-state response of the vibrating mechanism depends on the belt velocity, applied normal load, and stiffness. The applied normal force and belt velocity, as bifurcation parameters, are used to define the number and location of equilibrium points and their corresponding stability.

Soft robots made of elastic and compliant materials offer various advantages, such as safe interaction, adaptiveness, and easy fabrication. However, the highly dissipative nature of elastic materials intrinsically limits certain functions, such as force transmission, positioning accuracy, and load capability. Herein, we present a design approach for developing articulated soft robots with variable stiffness. We propose a bioinspired bistable articulated joint that consists of a rigid joint and bistable structures. We realize stiffness change through forming a locking function by triggering the bistable structure to switch between two stable states. The trigger force is generated by heating shape memory alloy springs connected to the bistable structures. After the locking function is triggered, the bending stiffness of the articulated joint is highly amplified. Moreover, the joint can be locked at different angles through mechanically preprograming bistable structures fabricated with a single 3D print. With this approach, we developed an articulated soft robot as a case study. The robot demonstrated variable stiffness, changeable configurations, and large workspace. Moreover, the approach proposed in this work provides valuable insights into the utilization of bistability for developing variable-stiffness robotic systems.

Stochastic resonance (SR) has been extensively utilized in the field of weak fault signal detection for its characteristic of enhancing weak signals by transferring the noise energy. Aiming at solving the output saturation problem of the classical bistable stochastic resonance (CBSR) system, a double Gaussian potential stochastic resonance (DGSR) system is proposed. Moreover, the output signal-to-noise ratio (SNR) of the DGSR method is derived based on the adiabatic approximation theory to analyze the effect of system parameters on the DGSR method. At the same time, for the purpose of overcoming the drawback that the traditional SNR index needs to know the fault characteristic frequency (FCF), the weighted local signal-to-noise ratio (WLSNR) index is constructed. The DGSR with WLSNR can obtain optimal parameters adaptively, thereby establishing the DGSR system. Ultimately, a DGSR method is proposed and applied in centrifugal fan blade crack detection. Through simulations and experiments, the effectiveness and superiority of the DGSR method are verified.

In this article, we experimentally demonstrate, for the first time, an all-optical bistable monolithically integrated photonic waveguide memory of distinctive simplicity, relying on two travelling waveguide Semiconductor Optical Amplifiers with Cross Gain modulation (SOA-XGM) phenomena. Experimental proof-of-principle memory operation and wavelength switching operation are demonstrated at 5Gb/s, featuring an Extinction Ratio of 6 dB and a 4.6 dB BER penalty, in the case of the memory operation, as well as a power penalty of 3.5 dB at 10−9 BER value, in the case of the wavelength switching. Being entirely designed and fabricated using standard library-based components, the proposed photonic memory fits within a 3.5 mm waveguide configuration of a generic monolithic InP platform, while its overall footprint is $3.5\times 2$ mm2 demonstrating a footprint reduction of 40% compared to previous hybrid SOA-MZI SR-FF architectures, holding the credentials for a fast photonic memory unit.

International audience; Bistable spin-crossover molecules are particularly interesting for the development of innovative electronic and spintronic devices as they present two spin states that can be controlled by external stimuli. In this paper, we report the voltage-induced switching of the high spin/low spin electronic states of spin-crossover molecules self-assembled in dense 2D networks on Au(111) and Cu(111) by scanning tunneling microscopy at low temperature. On Au(111), voltage pulses lead to the nonlocal switching of the molecules from any─high or low─spin state to the other followed by a spontaneous relaxation toward their initial state within minutes. On the other hand, on Cu(111), single molecules can be addressed at will. They retain their new electronic configuration after a voltage pulse. The memory effect demonstrated on Cu(111) is due to an interplay between long-range intermolecular interaction and molecule/substrate coupling as confirmed by mechanoelastic simulations.

Nonlinear materials can exhibit bistability, namely support different possible outputs for the same input, depending on the excitation history. This property can find direct application to photonic memory devices, the vast majority of which operate by changing the amplitude of the incoming signals. In this work, we study impedance metasurfaces producing hysteresis responses with respect to impinging beam angle by keeping a fixed intensity profile; accordingly, the considered setups remember the history of illumination incidence. The reported findings may open new unexplored avenues toward the design of photonic systems supporting a wide range of fixed-power memory functionalities from switching and sensing to information storage and data writing.

A physical unclonable function (PUF) is a promising lightweight circuit that provides security and authentication capability for electronic devices with low computational resources. Among various PUFs, the bistable ring PUF (BR-PUF) is considered one of the robust configurations. However, it has been shown that the challenge-response pairs (CRPs) from BR-PUF are vulnerable to statistical machine learning (ML) attacks, such as k-junta learning, support vector machine (SVM), and logistic regression (LR). In this article, we first show that the k-junta attack can break CRPs from the BR-PUF. Then, we present a hybrid chaotic-BR-PUF structure that obfuscates the BR-PUF response with the nonlinearized chaotic response. The proposed PUF structure has been implemented and experimentally evaluated on Xilinx Artix-7 FPGA, and the PUF measurements were captured. The proposed PUF was tested with a powerful statistical method developed using k-junta-based learning to confirm its strength against such attacks and evaluated using CRPs collected. The proposed PUF provides better resistance against ML attacks and reduces the learning accuracy to 50%–60% compared with previously proposed PUFs.

Bistability is intrinsically connected to various decision making processes in living systems. The operating principles of a bistable switch, generated from a positive feedback loop, are well understood both in natural and synthetic settings. However, the fate of dynamic modularity of a positive feedback loop is unknown when it is connected to another dynamically modular signaling motif. In order to address this, here we investigate feed-forward signaling of a positive feedback loop to determine the fate of a bistable switch under such signaling. Using the potential energy based high-throughput bifurcation analysis method, we uncover that in addition to the conventional bistability the hybrid motifs generate various emergent bistable switches, namely mushroom and isola switches, which are not produced by the individual motifs. Using random parameter sampling, network perturbation, and phase plane analysis, we establish the design principles of such emergent behaviors. Incoherent feed-forward signaling of a positive feedback loop with distinct regulatory thresholds of the two arms of the feed-forward loop are the key requirements for such emergent behaviors. Our calculations show that the specific types of atypical bistable responses depend on the logic gate configuration of the signals. However, the emergent bistable behaviors of the hybrid networks do not depend on the nature of the positive feedback loop.

In recent years, several examples of materials combining the molecular bistability of spin crossover (SC) and fluorescent moieties have flourished in the literature. Fluorescence is a sensitive probe, and SC may provide modulation of the signal, thus affording systems in which physicochemical changes in the environment of the SC centers could be effectively detected. On the contrary, organic semiconductor polymers are of great interest and, furthermore, have been successfully applied in different optoelectronic devices, such as transistors, solar cells, and light-emitting devices. Herein, we report on the fabrication of composites comprising a fluorescent, organic semiconductor polymer (polyfluorene) and a spin crossover compound, an Fe(II)-triazole coordination polymer. A strong synergy was observed between the spin transition of the Fe(II) compound and variations in the fluorescence of the organic polymer. The fluorescence modulation was shown to be reversible, with an increase of ≤20% with respect to the original value.

In this work, a sufficiently simple model allows one to perform detailed analytic studies to gain insights for the dynamical mechanisms in the general model of gene expression. Through theoretical analysis and numerical simulation, we find that the transcription and translation delays as a bifurcation parameter can drive the system to undergo a Hopf bifurcation, thereby producing oscillation behavior. Meanwhile, the length of these delays can determine the amplitude and period of the oscillations. Moreover, an optimal rate of model parameters is also essential to induce the limit-cycle oscillations. In particular, the transcription factor concentration is called a signal that not only induces twice Hopf bifurcation, but also affects the role of the delay in the system, that is, the varying time delay leads to subcritical Hopf bifurcation and bistability under the small signal strength. On the contrary, supercritical Hopf bifurcation is generated. Furthermore, two-parameter diagram is drawn to further explore how time delay and signal strength coordinate to regulate the oscillation behavior of the system. In addition, the stability and the direction of periodic solutions bifurcating from Hopf bifurcations are determined through the explicit formulae and the global existence of periodic solutions is discussed to verify the authenticity of the simulation. These results may be helpful for us to fully grasp oscillation dynamics and provide clues for further exploring the molecular mechanism of biological rhythms.

Bistable composite structures have a wide application prospect in the design of deformable structures. In this study, the snap behaviors of unsymmetric cross-ply bistable composites with different ...

Considering that the vibration signal of rolling bearing is very weak and difficult to be extracted under the working environment noise, a two-dimensional asymmetric bistable system (TDAB) is proposed. The system is coupled by two systems, and the weak signal is enhanced by adjusting the control system (monostable system) to adjust the controlled system (asymmetric bistable system). First, under the condition of adiabatic approximation system, the signal-to-noise ratio (SNR) is deduced, and analyzes the influence of different system parameters on the shape of potential function. Then the effects of each parameter on the SNR of the system are analyzed theoretically. Finally, combined with the adaptive intelligent algorithm, the parameters of the controlled system are optimized, and then the coupling coefficient and control system parameters are adjusted to obtain better system performance. The TDAB system obtained is applied to different bearing fault diagnosis and compared with different coupling systems. The experimental results show that the method can extract the characteristic frequency effectively and has good spectrum amplification performance and anti-noise capability. It is proved that the TDAB system can also have good detection effect in practical application.

On-platform pumping systems are a potentially critical technology for microphysiological systems (MPS) to control the pressure and flow of growth media. Supporting sufficient physiological tissue quantity in culture requires fluid flow rates on the order of microliters per second, which is larger than for typical microfluidic systems. Thus, a need exists for new types of pumping systems operating in this flow range while maintaining stringent sterility of the culture as well as enabling tight temperature control at ${37}^{\circ } {\rm C}$ . Flow rates and pressure also need to be readily computer-controlled, with a manageable set of connections into the culture incubator environment. This article describes a novel mesoscale electromagnetically driven pumping system designed to meet all these requirements. Our design achieves a very low energy dissipation of ${0.65}\,{\rm mJ}$ per switching event, which allows one pumping channel to operate at ${0.45}\,{{\rm {\mu } L} /{\rm s}}$ with an average power dissipation of 1.3 mW and ${0.04}\,{{^\circ } {\rm C}}$ temperature rise in each actuator. The actuator operates in a bistable, teeter-totter configuration with a latching force of ${4.5}\,{\rm N}$ , and a relatively large stroke of ${400}\,{{\mu } {\rm m}}$ at the actuator pole face. Preliminary operational pumping test results show the potential of this type of electromagnetic actuator for fluidic pumping. Due to their compact configuration and very high energy efficiency, these pumps can provide the foundation for multichannel, on-platform pumping for MPS platforms, as well as for a range of sterile, temperature-sensitive microflow devices such as portable, battery-operated insulin pumps.

Highlights •Mechanical stimuli-triggered optical responses of cholesteric liquid crystal devices are realized.•Self-powered bistable smart window and E-paper are demonstrated.•Self-powered optical switch is developed for remote control.Intelligent responsive devices are crucial for a variety of applications ranging from smart electronics to robotics. Electro-responsive cholesteric liquid crystals (CLC) have been widely applied in display panels, smart windows, and so on. In this work, we realize the mechanical stimuli-triggered optical responses of the CLC by integrating it with a triboelectric nanogenerator (TENG), which converts the mechanical motion into alternating current electricity and then tunes the different optical responses of the CLC. When the voltage applied on the CLC is relatively low (15–40 V), the TENG drives the switching between the bistable planar state and focal conic state of the CLC, which shows potential applications in self-powered smart windows or E-paper displays. When the voltage supplied by the TENG is larger than 60 V, a self-powered optical switch is demonstrated by utilizing the transformation between focal conic state and instantons homeotropic state of the CLC. This triboelectric-optical responsive device consumes no extra electric power and suggests a great potential for future smart electronics.

Electrostatically actuated, bistable, curved micromechanical beams can exhibit latching, wherein the beams remain in two distinct stable states without an applied voltage. These structures could serve as building blocks in a variety of applications such as micromechanical logic elements, switches, non-volatile memories, and low power consumption sensors. However, the design of such devices is challenging since such structures are prone to symmetry breaking, which consequently inhibits latching. Generally, asymmetric responses may be circumvented by introducing a tailored axial compressive prestress. In this work we explore, both theoretically and experimentally, the influence of prestress on the single electrode, bidirectional dynamic switching of curved, latchable, single crystal Si $\approx 1000 \;\mu \text{m}$ long and $\approx 3.5\;\mu \text{m}$ wide beams. We use Joule heating to apply the necessary prestress required to eliminate symmetry breaking and ensure latching. In accordance with reduced-order model predictions, our experimental findings show that prestress plays a key role in the dynamic response of the beam. Our results demonstrate bidirectional operation using a single electrode, fostering a compact footprint device for tailoring the axial stress and dynamic conditions.

Micro aerial vehicles (MAVs) with multiple rotors, or multicopters, have many promising applications ranging from environmental monitoring, agricultural inspection, to package delivery. These applications, however, usually face a critical problem: the flight time of MAVs is limited due to the low aerodynamic efficiency and high energy consumption. One promising solution is to make them rest on desired objects using perching, an important capability in biological flyers (e.g., birds). In this article, we present the design and experimentation of a novel perching mechanism: a low cost, 3-D-printed gripper with bistability (i.e., two stable states). The gripper has two unique characteristics. First, using bistability, it can passively switch from open to closed state using the impact between the gripper and the perching object, alleviating the requirement for precise motion control. Second, the gripper has two perching methods for different objects. For objects with a small height, it can form a closed diamond shape to encircle the objects (encircling method). For objects with a large height, the gripper's two fingers can clip on each side of the objects to utilize the friction forces for perching (clipping method). We analyze the proposed gripper design to predict the required force for opening and closing the gripper. We also predict the size of objects that will allow for successful perching for the clipping method. All the theoretical analyses are experimentally verified. Finally, we integrate the gripper onto a palm-size quadcopter to enable a mechatronic system for perching, and demonstrate successful perching with both clipping and encircling methods as well as aerial grasping. Although our bistable gripper is used with a palm-size quadcopter, the design strategy can also be applied to large-size MAVs for both energy efficient perching and aerial grasping.

Magnetorheological (MR) fluids have unique characteristics that make them well-suited for soft robotic actuation systems. Two particularly interesting applications are bistable valves and force-amplified grippers, which only require power to switch states. These design topologies can not only make MR fluid actuation systems more efficient, but can also allow them to be constructed from entirely compliant materials. In this work, we describe new bistable valve mechanism concepts; the first design is constructed using traditional rigid components while the second design is composed of entirely compliant materials. This includes liquid metal coils, compliant magnetic composites, and silicone flexures. The MR valve concept is modeled using magnetic field theory and scaling laws are determined from MR fluid holding pressure experiments. Then, experimental results are used to show that rough tubing surfaces can withhold an average of 5× more pressure than smooth tubing surfaces. Both rigid and compliant valve topologies are then constructed and tested, showing the ability to hold up to 88 kPa and 37 kPa of pressure, respectively. These valves are then implemented for controlling a soft multi-fingered PneuNet gripper and a new force-amplified MR fluid gripper, which has the ability to provide up to 324 $\%$ higher load capacity than purely pressure-driven mechanisms (with the addition of a 25 mm diameter and 12.7 mm thick Nd-Fe-B magnet). Finally, we show how these bistable valves and grippers can be used for grasping and manipulation applications.

Bistable relays are widely used in both general and special purpose engineering. Such relays are subdivided according to the construction principle into two groups: bistable electromagnetic polarized relays and bistable electromagnetic latching relays. In the technical literature, there is practically no information on the design of the relay of the second group. This article highlights general issues of their design using the example of high-current relays of the DP-1 series for rated currents from 25 to 100 A, which have been used for a long time in autonomous power supply systems for military equipment. The descriptions of the distinctive features of the relay construction and the principle of its operation are given. The kinematic schemes of the main mechanism of the electromagnetic and contact systems are considered. The example of constructing the opposing characteristics of the relay is shown. The paper provides the replacement scheme for calculating of magnetic system on improved method of sections and assumptions, characteristic of the given relay construction.

Simple and light-weighted quasi-zero stiffness (QZS) isolators can be designed based on nonlinear and negative stiffness generated by the snap-through effect of bistable structures. Traditionally, the snap-through force of the bistable structure is limited which makes the weight which can be isolated based on this mechanism very low. This paper investigates increasing loading capacity of this kind of isolator by using an optimized and varying sectional profile. Numerical models were derived for the bistable structures with variable sectional distributions. Optimized sections’ alignment of the bistable beam was derived based on the numerical model which was consequently validated by experimental results. Influences of the bistable beams with a variable section on nonlinear stiffness characteristics and performance of the isolator were at last investigated with the harmonic balance method.

В данной статье предлагается взгляд на многозначность художественного текста через понятие бистабильности. Рассматриваются критерии бистабильности, а также структуры, на которых она реализуется. Сформулированная концепция демонстрируется на нескольких литературных примерах. This article offers a look at the polysemy of a literary text through the concept of bistability. Criteria for bistability are considered, as well as the structures on which it is realized. The formulated concept is demonstrated in several literary examples.

We develop two discrete models to study how supplemental releases affect the Wolbachia spreading dynamics in cage mosquito populations. The first model focuses on the case when only infected males are released at each generation. This release strategy has been proved to be capable of speeding up the Wolbachia persistence by suppressing the compatible matings between uninfected individuals. The second model targets the case when only infected females are released at each generation. For both models, detailed model formulation, enumeration of the positive equilibria and their stability analysis are provided. Theoretical results show that the two models can generate bistable dynamics when there are three positive equilibrium points, semi-stable dynamics for the case of two positive equilibrium points. And when the positive equilibrium point is unique, it is globally asymptotically stable. Some numerical simulations are offered to get helpful implications on the design of the release strategy.

Through a snap-through process, the bistable vibration energy harvester (EH) could undergo large amplitude motion and yield a large energy output. But realizing the transitions between the stable s...

Generation of mechanical oscillations is ubiquitous to a wide variety of intracellular processes ranging from activity of muscle fibres to oscillations of the mitotic spindle. The activity of motors plays a vital role in maintaining the integrity of the mitotic spindle structure and in generating spontaneous oscillations. While the structural features and properties of the individual motors are well characterized, their implications on the functional behaviour of motor-filament complexes is more involved. We show that force-induced allosteric deformations in dynein, which results in catchbonding behaviour, provide a generic mechanism to generate spontaneous oscillations in motor-cytoskeletal filament complexes. The resultant phase diagram of such motor-filament systems - characterized by force-induced allosteric deformations - exhibits bistability and sustained limit cycle oscillations in biologically relevant regimes, such as for catchbonded dynein. The results reported here elucidate the central role of this mechanism in fashioning a distinctive stability behaviour and oscillations in motor-filament complexes, such as mitotic spindles.

In this paper, tunable optical bistability that denotes the relationship between input intensity and output intensity is numerically investigated in the microwave frequency region based on the one-dimensional (1D) sandwich photonic structure consisting of a Kerr-type nonlinear material slab and two magnetized cold plasma layers. Results show that, in the case of TM-polarized electromagnetic wave, width and switching thresholds of the bistability loops are dependent on the working frequency, initial incidence angle, layer thickness, plasma density, and external magnetic field, which should be judiciously selected to obtain a required bistability behavior. Compared to the case of switch-down threshold, the switch-up threshold in the bistability loop is more sensitive to the changes of parameters. Through this study, the suggested 1D sandwich photonic structure is beneficial to the all-optical signal processing.

In this article, a novel nonlinear model is proposed to describe the permittivity of the plasma, and the nonlinear optical bistable phenomenon of the 1-D photonic crystals, which is composed of a nonlinear plasma defect layer, is theoretically investigated by the conventional transfer matrix method (TMM) under TM wave. It is figured out that the permittivity of nonlinear plasma exists in bistable state. Then, the tuning effects of the number of the photonic crystals’ (PCs) periodic layers, the incident frequency, the thicknesses of the nonlinear plasma layer, and the incident angle on the optical bistability (OB) have been emphatically studied. Additionally, the transmission and the reflectance under the influences of this bistable tuning are further proposed. The calculated results show that the adjustment of the OB can be achieved without changing the multi-layer material geometry. This multi-composite nonlinear plasma defect structure with the tunable bistable phenomenon can be applied to numerous valuable optical devices, such as novel optical power threshold devices, logic gates, and optical information memory.

Optical bistability (OB) is theoretically examined for a double quantum dot (QD) system placed in a ring cavity that is injected with a squeezed vacuum (SV) field. The SV field is injected at the output mirror of the cavity scheme to couple a one-photon transition of the atomic system. Interdot electron tunneling, which occurs between the two QDs, affects the steady-state behavior, from mono-to-multistable behaviors, of the system in the presence of SV field. We investigate the switching effects employing the SV field parameters, electron tunneling, and dispersive switching effects to demonstrate the one-way, two-way, and multiswitching processes. The electron tunneling strength of the dots injected with the SV field helps in designing an optical multiswitch. The SV-injected field exhibits more multiswitchings and larger bistable areas compared with the same intensities of coherent or thermal injected field case.

In this paper, a S-type memristor with tangent nonlinearity is proposed. The introduced memristor can generate two kinds of stable pinched hysteresis loops with initial conditions from two flanks of the initial critical point. The power-off plot verifies that the memristor is nonvolatile, and the DC V-I plot shows that the memristor is locally active with the locally active region symmetrical about the origin. The equivalent circuit of the memristor, derived by small-signal analysis method, is used to study the dynamics near the operating point in the locally active region. Owing to the bistable and locally active properties and S-type DC V-I curve, this memristor is called S-type BLAM for short. Then, a new Wien-bridge oscillator circuit is designed by substituting one of its resistances with S-type BLAM. It finds that the circuit system can produce chaotic oscillation and complex dynamic behavior, which is further confirmed by analog circuit experiment.

There are a number of situations in which rescaled interacting particle systems have been shown to converge to a reaction diffusion equation (RDE) with a bistable reaction term, see e.g., Cox et al. (Asterisque 349:1–127, 2013), Durrett (Ann Appl Prob 19:477–496, 2009, Electron J Probab 19:1–64, 2014), Durrett and Neuhauser (Ann Probab 22:289–333, 1994). These RDEs have traveling wave solutions. When the speed of the wave is nonzero, block constructions have been used to prove the existence or nonexistence of nontrivial stationary distributions. Here, we follow the approach in a paper by Etheridge et al. (Electron J Probab 22:1–40, 2017) to show that in a wide variety of examples when the RDE limit has a bistable reaction term and traveling waves have speed 0, one can run time faster and further rescale space to obtain convergence to motion by mean curvature. This opens up the possibility of proving that the sexual reproduction model with fast stirring has a discontinuous phase transition, and that in Region 2 of the phase diagram for the nonlinear voter model studied by Molofsky et al. (Theoret Pop Biol 55(1999):270–282, 1999) there were two nontrivial stationary distributions.

Stochastic resonance can detect weak periodic signals from strong background noise without loss of signal energy. However, the classical bistable stochastic resonance has the inherent outp...

The nonlinear energy sink (NES), which is proven to perform rapid and passive targeted energy transfer (TET), has been employed for vibration mitigation in many primary small- and large-scale structures. Recently, the feature of bistability, in which two nontrivial stable equilibria and one trivial unstable equilibrium exist, is utilized for passive TET in what is known as bistable NES (BNES). The BNES generates a nonlinear force that incorporates negative linear and multiple positive or negative nonlinear stiffness components. In this paper, the BNES is coupled to a linear oscillator (LO) where the dynamic behavior of the resulting LO-BNES system is studied through frequency–energy plots (FEPs), which are generated by analytical approximation using the complexification-averaging method and by numerical continuation techniques. The effect of the length and stiffness of the transverse coupling springs is found to affect the stability and topology of the branches and indicates the importance of the exact physical realization of the system. The rich nonlinear dynamical behavior of the LO-BNES system is also highlighted through the appearance of multiple symmetrical and unsymmetrical in- and out-of-phase backbone branches, especially at low energy levels. The superimposed wavelet frequency spectrums of the LO-BNES response on the FEP have verified the robustness of the TET mechanism where the role of the unsymmetrical NNM backbones in TET is clearly observed.

The photoelectric properties of thin films based on an organic composition of fullerene (C60), zinc phthalocyanine (ZnPc), and a ferroelectric copolymer of vinylidene fluoride with trifluoroethylene P(VDF–TrFE) are studied. Along with well-pronounced photoelectric properties (which are characteristic of fullerene–phthalocyanine mixtures), this material is shown to have ferroelectric properties as well. Ferroelectric switching of polarization is found to cause bistable switching of the photoelectric effect with a significant increase in the ampere–watt sensitivity in one of the polarized states. This effect is explained by a change in the built-in local electric field, which depends on the direction of the ferroelectric polarization vector and acts inside the cavities of the ZnPc/C60 molecular heterojunctions.

International audience; We report a study of an elastic buckled beam undergoing a contactless magnetic actuation of Laplace type. The beam model is based on the elastica beam theory including the beam extensibility. The Laplace force is produced by an electric current travelling along the beam placed in a magnetic induction. The magnitude of the electric current is the control parameter and by increasing the electric current the beam switches from one stable state to the other one for a given beam end-shortening. The main purpose of the study is to investigate the bistable response, more precisely, the diagram of the electric current as function of the midpoint vertical displacement of the beam according to the magnet location along the elastic beam. The model equations are established and they are numerically solved using an algorithm developed for nonlinear boundary value problem. A second part of the study is devoted to experimental validation of the model and comparisons with the results extracted from the numerical solutions to the model equations. Especially, the comparisons ascertain with good accuracy the approach of the proposed bistable beam model. In addition, the influence of the model parameters on the bistable response is clearly identified.