Jumping Mode Research Articles

An Active Strategy Based on Different Droplet Removal Modes on Polydimethylsiloxane Magnetic Microstructures.

The efficient removal of droplets on solid surfaces holds significant importance in the field of fog collection, condensation heat transfer, and so on. However, on current typical surfaces, droplets are characterized by a passive and single removal mode, contingent on the traction force (e.g., capillary force, Laplace pressure, etc.) generated by the surface's physics and chemistry design, posing challenges for enhancing the efficiency of droplet removal. In this paper, an effective active strategy based on different removal modes is demonstrated on magnetic responsive polydimethylsiloxane (PDMS) superhydrophobic microplates (RM-MPSM). By regulating the parameters of microplates and droplet volume, different effective departure modes (top jumping and side departure) can be induced to facilitate the removal of droplets. Moreover, the removal volume of droplets through the side departure mode exhibits a significant reduction compared to that observed in the top jumping mode. The exceptional removal ability of RM-MPSM demonstrates adaptability to diverse functional applications: efficient fog collection, removal of condensation droplets and micro-particles. The efficient modes of droplet removal demonstrated in this work hold significant implications for broadening its application in many fields, such as droplet collection, heat transfer, and anti-icing.

Light-powered sustained chaotic jumping of a liquid crystal elastomer balloon

Chaotic systems comprising of active materials have the capability to absorb energy directly from the external environment to preserve their own sustained motion, holding tremendous potential for utilization in diverse fields, for instance, controllable sensors, energy harvesting, motion behavior control of smart materials and more. In this paper, a sustained jumping system consisting of photosensitive liquid crystal elastomer (LCE) balloon is developed innovatively, in which the LCE balloon can transition from a static state to a sustained jumping state under periodic illumination. Given the dynamic constitutive model of LCE and Hertz contact theory, the nonlinear dynamics model of the sustained jumping LCE balloon system is established. Numerical calculations demonstrate the existence of two jumping modes for the LCE balloon, i.e., periodic jumping and chaotic jumping. The mechanism of sustained jumping that counterbalances the energy dissipation by the net work combining contact expansion and buoyancy variation, as well as the mechanism of chaotic phenomena, are revealed. In addition, the influences of vital parameters on the jumping mode of the balloon are examined, and the conversion of the jumping modes with parameters is illustrated by bifurcation diagrams. This work can broaden the knowledge of the dynamic behavior of smart materials, which is of guiding significance for the research on chaos control and chaotic system design.

Competitive Hydration Versus Migration of Pre‐hydrated Electrons for CO2 Reduction in Aqueous Solution Revealed by Ab Initio Molecular Dynamics Simulation

AbstractPhotoinjected excess electrons (EEs) can fulfill the direct reduction of CO2 (CO2R) in an aqueous solution. However, the underlying mechanism is still poorly understood, especially the EE dynamics, which govern reaction mechanisms. Here, using a hybrid functional‐based ab initio molecular dynamic simulation strategy, it accurately characterizes the dynamics details of CO2R by aqueous EEs in solution and uncovers the nature of how EEs migrate for efficient CO2R. The AIMD simulations reveal that the injected EEs undergo hydration with diverse hydrated forms (various pre‐hydrated/e−pre/e22−pre and hydrated/e−aq/e22−aq) and multiple reaction channels due to competition of hydration versus migration. Interestingly, all pathways go through the same relay state [CO22−]aq and reach the same product (HCOO−). The core process before [CO22−]aq is competitive electron hydration and possible e−pre‐migration featuring either slowly flowing or fast jumping mode, while that after [CO22−]aq is proton transfer catalyzed by H‐bonding network as a proton source. The nature is how the concerted hydration dynamics of EEs and target CO2 govern the reaction proceeding through modulating their energy gap . This study provides dynamics insights into CO2R in aqueous solution by diverse e−pre/e−aq and the proposed strategy can also be utilized to explore the reduction mechanisms based on pre‐solvated electrons in other media.

Dual asynchronous control for T‐S fuzzy semi‐Markov jump systems: A finite‐time design

AbstractThis paper addresses the control problem of Takagi–Sugeno fuzzy semi‐Markov jump systems (TFSMJSs) under the finite‐time analysis and synthesis framework. Due to the commonly used networked communication structure, the semi‐Markovian jumping modes and fuzzy premise variables cannot always perfectly match for system and controller among the whole system operation. More precisely, both asynchronous phenomena in fuzzy membership and jumping mode are taken into account, and then, mode‐dependent finite‐time controllers are developed with these features. By utilizing stochastic analysis and Lyapunov–Krasovskii stability theory, sufficient criteria are first established for the closed‐loop system in the context of mean‐square sense. Furthermore, feedback controller gains are captured by the matrix technique and parallel distributed compensation (PDC)‐related arguments. Eventually, a simulation example of an unmanned marine vehicle (UMV) is utilized to demonstrate the validity of the developed results.

Effect of Probe Lifting Height in Jumping Mode AFM for Living Cell Imaging

Atomic force microscopy (AFM) is one of the effective methods for imaging the morphological and physical properties of living cells in a near-physiological environment. However, several problems caused by the adhesion of living cells and extension of the cell membranes seriously affect the image quality during living cell imaging, hindering the study of living cells. In this work, jumping mode AFM imaging was used to image living cells at varied probe lifting heights to meet image quality requirements, and image quality related to the probe lifting height is discussed in detail. The jumping mode was divided into three parts based on the varying heights of the lifted probe, namely near-contact mode, half-jumping mode, and full-jumping mode, and the causes of their imaging drawbacks were analyzed. At an appropriate lifting height, the probe can be completely free from the influence of cell adhesion and self-excited oscillation, thus avoiding the occurrence of “trail” phenomena and invalid points in the imaging of living cells and improving the image quality. Additionally, this work provides a new approach to calculating the lateral force through the adhesion of trace and retrace scanning at a low height, which is important for studying the extension characteristics of the cell membrane.

Molecular Origin of Wetting Characteristics on Mineral Surfaces

Accurate determination of the wetting characteristics on mineral surfaces is critical for many natural processes and industrial applications where multiphase flow in porous media is involved. The wetting behaviors on mineral surfaces are controlled by water-mineral interactions, giving rise to various wetting characteristics, including contact line advancement, formation of precursor films, etc. However, a fundamental understanding of wetting characteristics on different mineral surfaces is still lacking at the molecular level. Here, utilizing a comprehensive set of molecular dynamics simulations, we investigate the wetting characteristics of water on various mineral surfaces and obtain the corresponding water-mineral interaction properties (including the areal density of water-mineral interaction energy and the work of adhesion of the water-mineral interface), mineral wettability, and structural and diffusion properties of water molecules near the surface. We show that the diffusion properties of water molecules on mineral surfaces play an important role in wetting characteristics. We find that the contact line tends to advance forward in the jumping mode or the rolling mode during the wetting process, which depends on the diffusion capacity of the water molecules on mineral surfaces. The corresponding evolution of the solid-liquid friction coefficient during dynamic spreading is also analyzed. We further demonstrate the strong impact of isomorphic substitution and charge-balancing counterions on wetting characteristics on the surfaces of clay minerals. It is shown that the introduction of charge-balancing counterions can shift the mineral surface from strongly hydrophilic to strongly hydrophobic and lead to completely different wetting characteristics. Our results provide a clearer picture of the molecular underpinnings in mineral wetting phenomena and deepen the understanding of the control of water-mineral interactions on the wetting properties.

Quantitative Characterization of Local Thermal Properties in Thermoelectric Ceramics Using "Jumping-Mode" Scanning Thermal Microscopy.

Thermoelectric conversion may take a significant share in future energy technologies.Oxide-based thermoelectric composite ceramics attract attention for promising routes for control of electrical and thermal conductivity for enhanced thermoelectric performance. However, the variability of the composite properties responsible for the thermoelectric performance, despite nominally identical preparation routes, is significant, and this cannot be explained without detailed studies of thermal transport at the local scale. Scanning thermal microscopy (SThM) is a scanning probe microscopy method providing access to local thermal properties of materials down to length scales below 100 nm. To date, realistic quantitative SThM is shown mostly for topographically very smooth materials. Here, methods for SThM imaging of bulk ceramic samples with relatively rough surfaces are demonstrated. "Jumping mode" SThM (JM-SThM), which serves to preserve the probe integrity while imaging rough surfaces, is developed and applied. Experiments with real thermoelectric ceramics show that the JM-SThM can be used for meaningful quantitative imaging. Quantitative imaging is performed with the help of calibrated finite-elements model of the SThM probe. The modeling reveals non-negligible effects associated with the distributed nature of the resistive SThM probes used; corrections need to be made depending on probe-sample contact thermal resistance and probe current frequency.

Inhibition of condensation-induced droplet wetting by nano-hierarchical surfaces

Superhydrophobic nanostructured surfaces can enhance water condensation efficiency by facilitating droplet departure via coalescence-induced jumping. However, condensed droplets tend to transit from a mobile jumping mode to a highly pinned state at high condensation heat flux because excessive water nucleates within the nanostructures and anchors the condensed droplets. The large pinned droplets act as a thermal barrier and insulate the cooling surface, thus severely degrading its heat transfer efficiency. This work developed a nano-hierarchical structured surface by growing branched TiO2 nanorod arrays to prevent condensation-induced droplet pinning. After hydrophobization, the nano-hierarchical structure can spontaneously push the water out of nanostructures with an outward Laplace capillary pressure gradient when the droplet size is only at the nanoscale level. This effective de-wetting process maintains the high droplet mobility on the nano-hierarchical surface over a wide subcooling range, resulting in an up to ∼ 90 % increase in heat transfer coefficient at a high heat flux of 132 kW∙m−2 compared to the single-tier nanorod surface. Our investigation of how the nano-hierarchical structures fundamentally suppress the condensation-induced wetting on superhydrophobic surfaces represents a significant advance in understanding multiphase wetting phenomena and paves the way for the rational design of cooling surfaces.

Moving dynamics of a nanorobot with three DNA legs on nanopore-based tracks.

DNA nanorobots have garnered increasing attention in recent years due to their unique advantages of modularity and algorithm simplicity. To accomplish specific tasks in complex environments, various walking strategies are required for the DNA legs of the nanorobot. In this paper, we employ computational simulations to investigate a well-designed DNA-legged nanorobot moving along a nanopore-based track on a planar membrane. The nanorobot consists of a large nanoparticle as the robot core and three single-stranded DNAs (ssDNAs) as the robot legs. The nanopores linearly embedded in the membrane serve as the toeholds for the robot legs. A charge gradient along the pore distribution mainly powers the activation of the nanorobot. The nanorobot can move in two modes: a walking mode, where the robot legs sequentially enter the nanopores, and a jumping mode, where the robot legs may skip a nanopore to reach the next one. Moreover, we observe that the moving dynamics of the nanorobot on the nanopore-based tracks depends on pore-pore distance, pore charge gradient, external voltage, and leg length.

Fabrication of hierarchically textured aluminum-based superhydrophobic surfaces for anti-frosting application

Rational design of solid interfaces with an ability to prevent frost formation is crucial in many industrial systems such as refrigeration, air-conditioning, cryogenics, etc. In this work, we fabricated two hierarchically textured aluminum-based superhydrophobic surfaces by simple steps such as chemical etching and dip/spray coating. We used perfluorooctyltriethoxysilane (PFOTES) and commercial Glaco solution as a hydrophobic coating material. The fabricated substrates have shown excellent superhydrophobicity with a low contact angle hysteresis of below 5°. The frost formation on both the coatings was different despite having similar macroscopic wettability. We analyzed the surface topography and its effects on frost formation comprehensively. PFOTES coated substrate has shown a sweeping mode of drop drainage, whereas the Glaco coated substrate showed the droplet jumping mode. Rapid ejection of condensed microdroplets from the Glaco coated substrate is delayed the frost formation due to the significant reduction in the drop contact time. This study elucidates the dependence of nanostructured coatings over the microstructures during frost formation. The insights from this study are helpful for the fabrication of anti-frosting surfaces for industrial applications.

Performance of the NGX High‐Resolution Multiple Collector Noble Gas Mass Spectrometer

AbstractThis paper describes the design, setup, and performance of a new analytical system installed at Lancaster University, UK, to determine noble gas isotopes in gas samples using an NGX high‐resolution multiple collector noble gas mass spectrometer. The fixed position Faraday cups are configured to simultaneously measure all nine Xe isotopes whilst permitting all other noble gases, such as He, to be analyzed in peak jumping mode. The stability, sensitivity, and reproducibility of the measurements using this new noble gas analytical system were examined by repeating runs of atmospheric air. Reproducibility of the measurements obtained from 90 and 73 air standard runs are 4.2% and 0.4% for 3He/4He and 21Ne/20Ne, respectively. There is no significant difference in the 40Ar/36Ar ratio measurements with various 40Ar abundances, suggesting good sensitivity and pressure linearity of the NGX instrument. The standard errors for 124Xe/130Xe, 126Xe/130Xe, 128Xe/130Xe, 129Xe/130Xe, 131Xe/130Xe, 132Xe/130Xe, 134Xe/130Xe and 136Xe/130Xe in 46 air measurements are 0.782%, 0.804%, 0.053%, 0.029%, 0.029%, 0.029%, 0.030%, and 0.031%, respectively. In contrast, the corresponding reference values from Basford et al. (1973) are 0.342%, 0.505%, 0.148%, 0.139%, 0.153%, 0.076%, 0.156%, and 0.138%, respectively. This suggests that multicollection measurements of Xe isotopes on Faraday cups using the NGX have higher precision than the previous results except for 124Xe and 126Xe, where low abundances affect the measurement precision. Compared to traditional peak jumping single‐collector mass spectrometers, the NGX has significantly decreased analytical time in Xe analysis by allowing simultaneous measurements of all isotopes. As a consequence, high analytical precision can be achieved.

New System for Measuring Cosmogenic Ne in Terrestrial and Extra-Terrestrial Rocks

Cosmogenic Ne isotopes are used for constraining the timing and rate of cosmological and Earth surface processes. We combined an automated gas extraction (laser) and purification system with a Thermo Fisher ARGUS VI mass spectrometer for high through-put, high precision Ne isotope analysis. For extra-terrestrial material with high cosmogenic Ne concentrations, we used multi-collection on Faraday detectors. Multiple measurements (n = 26) of 1.67 × 10−8 cm3 air-derived 20Ne yielded an uncertainty of 0.32%, and 21Ne/20Ne = 0.17% and 22Ne/20Ne = 0.09%. We reproduced the isotope composition of cosmogenic Ne in the Bruderheim chondrite and Imilac pallasite in a sub-ten mg sample. For lower Ne amounts that are typical of terrestrial samples, an electron multiplier detector was used in peak jumping mode. Repeated analysis of 3.2 × 10−11 cm3 STP 20Ne from air reproduced 21Ne/20Ne and 22Ne/20Ne with 1.1% and 0.58%, respectively, and 20Ne intensity with 1.7% (n = 103) over a 4-month period. Multiple (n = 8) analysis of cosmogenic Ne in CREU-1 quartz yielded 3.25 ± 0.24 × 108 atoms/g (2 s), which overlaps with the global mean value. The repeatability is comparable to the best data reported in the international experiments performed so far on samples that are 2–5× smaller. The ability to make precise Ne isotope determinations in terrestrial and extra-terrestrial samples that are significantly smaller than previously analysed suggests that the new system holds great promise for studies with limited material.

Multimodal soft jumping robot with self-decision ability

The next generation of soft robots should have self-decision ability to judge reasonable responses adaptively according to external stimulation and without human assistance. However, few of the current soft robots have brains to think independently; rather, they have integrated sensors and actuators, similar to animals having skin and muscles. In this paper, a bistable soft jumping robot with self-decision ability is reported, which is manufactured by 4D printing of composites with continuous fibers. The snap-through triggered by temperature stimulation resulted in the jumping motion of the robot, and its jumping mode is controlled by a programmed continuous fiber pattern. This robot able to take decisions can change from the initial state to the final state via different deforming pathways when snap-through occurs, resulting in multiple jumping motion modes. This soft robot can realize (1) different jumping modes, including forward, rotational, lateral, and overturn movements; (2) self-decision function of motion modes responding to external stimuli; and (3) continuous movement, by repeatedly jumping under periodic temperature stimulation. This research will provide a new scheme for soft robotics to achieve the integration of sensation, actuation, and decision.

Study on droplet nucleation position and jumping on structured hydrophobic surface using the lattice Boltzmann method

In this study, droplet nucleation and jumping on the conical micro-structure surface is simulated using the lattice Boltzmann method. The nucleation and jumping laws of the droplet on the surface are summarized. The numerical results suggest that the height and the gap of the conical micro-structure exhibit a significant influence on the nucleation position of the droplet. When the ratio of height to the gap of the micro-structure (H/D) is small, the droplet tends to nucleate at the bottom of the structure. Otherwise, the droplet tends to nucleate to-wards the side of the structure. The droplet grown in the side nucleation mode possesses better hydrophobicity than that of the droplet grown in the bottom nucleation mode and the droplet jumping becomes easier. Apart from the coalescence of the droplets jumping out of the surface, jumping of individual droplets may also occur under certain conditions. The ratio of the clearance to the width of the conical micro-structure (D/F) depends on the jumping mode of the droplet. The simulation results indicate that when the D/F ratio is greater than 1.2, the coalescence jump of droplets is likely to occur. On the contrary, the individual jump of droplets is easy to occur.

The effect of jumping modes on various automata models

Recently, new types of non-sequential machine models have been introduced and studied, such as jumping automata and one-way jumping automata. We study the abilities and limitations of (finite, pushdown and linear bounded) automata with these 2 jumping modes of tape heads with respect to how they affect the class of accepted languages. We provide adapted versions of pumping lemmas and other methods to determine whether a language is accepted by a machine with jumping mode. Using these methods we establish the inclusion or incomparability relationships among the classes of languages defined by the new machines and their classical counterparts. We also study the closure properties of the resulting language classes and show that under most fundamental language operations, these classes are not closed.

Two-way deterministic automata with jumping mode

The recently introduced one-way jumping automata are strictly more powerful than classical finite automata (FA) while maintaining decidability in most of the important cases. We investigate the extension of the new processing mode to two-way deterministic finite automata (2DFA), resulting in deterministic finite automata which can jump to the nearest letter which they can read, with jumps allowed in either direction. We show that two-way jumping automata are strictly more powerful than one-way jumping ones and that alternative extensions of 2DFA with this jumping mode lead to equivalent machines. We also prove that the class of languages accepted by the new model is not closed under the usual language operations. Finally we show how one could change the model to terminate on every input by using non-erasable end markers.

Non-extension movements inducing over half the mechanical energy directly contributing to jumping height in human running single-leg jump

The running single-leg jump (RSLJ), including certain non-extension movements (movements not induced by lower-limb extension works), is the highest jumping mode in humans. Here, we show the substantial contributions of non-extension movements, in generating mechanical energy directly contributing to the jumping height (Evert) in RSLJ. We determined the component of increase in Evert due to each segment movement in RSLJs by 13 male high-jumpers. The stance-leg shank forward rotation (rotation opposite to the actions of the knee extensors and ankle plantar flexors on the shank), increased Evert (0.76 ± 0.70 J/kg). Evert due to the stance-leg thigh forward rotation (4.39 ± 0.57 J/kg) was substantially larger than the inflowing energy into the thigh (difference: 2.36 ± 0.42 J/kg). These results suggest that the forward rotations of the shank and thigh transformed horizontal kinetic energy (Ehori) to Evert.Evert was increased by the elevation of the free-leg side of the pelvis (0.53 ± 0.22 J/kg) and rotation of free-leg thigh (1.52 ± 0.26 J/kg). The non-extension movements contributed to over half (59 ± 6%) the increase in Evert during the take-off phase. Human-specific morphologies are essential for the contributions of non-extension movements; fully extensible knee joints and relatively longer legs with respect to body mass for the transformation from Ehori to Evert by shank and thigh rotations, and a wide and short pelvis for increasing Evert by pelvic elevation. This study provides quantifiable evidence to indicate how substantially non-extension movements contribute to higher RSLJ.

Kubits: Solid-State Self-Reconfiguration With Programmable Magnets

Even though many prototypes of 3D self-reconfiguring modular robots (SRMRs) have been developed in recent years, a demonstration involving 1'000 modules remains a challenge. This is largely due to complex mechanics needed to achieve connection, disconnection and especially actuation in such a system. This work introduces 'Kubits,' which is, to the best of our knowledge, the first SRMR that achieves these functionalities without moving parts, i.e. in solid-state. Each module contains a kind of programmable magnet whose magnetization can be controlled. The simultaneous control of touching magnet pairs of two modules is used to create attraction (connection), neutrality (disconnection) and actuation (repulsion), which results in self-reconfiguration by a cube pivoting around an edge. We detail the design of the system and demonstrate a series of successful flips, including a jumping mode. The energy-efficient, lightweight and robust (both in terms of mechanics and control) method in Kubits is a promising path for scalable self-reconfiguration.

Reliable H∞ Control on Stochastic Delayed Markovian Jump System with Asynchronous Jumped Actuator Failure

This paper studies the reliable H∞ control on stochastic delayed Markovian jump systems (SDMJSs) with asynchronous jumped actuator failure and uncertain transition rates (TRs). It is assumed that the actuator failure occurs randomly under a Markov process with its jumping mode different from the system’s one. A generalized functional Ito’s formula for the closed-loop SDMJSs with mixed asynchronous Markovian jump modes (AMJMs) is successfully established. By the generalized functional Ito’s formula and the mixed-mode-dependent Lyapunov functionals, a sufficient delay-dependent condition of the reliable H∞ controller design for the SDMJSs with mixed AMJMs is proposed via matrix manipulation and a relaxation method. Finally, an example on VTOL (vertical take-off and landing) helicopter system is given to demonstrate the feasibility and effectiveness of the presented controller design scheme.

Effect of Substrates' Compliance on the Jumping Mechanism of Locusta migratoria.

Locusts generally live and move in complex environments including different kind of substrates, ranging from compliant leaves to stiff branches. Since the contact force generates deformation of the substrate, a certain amount of energy is dissipated each time when locust jumps from a compliant substrate. In published researches, it is proven that only tree frogs are capable of recovering part of the energy that had been accumulated in the substrate as deformation energy in the initial pushing phase, just before leaving the ground. The jumping performances of adult Locusta migratoria on substrates of three different compliances demonstrate that locusts are able to adapt their jumping mode to the mechanical characteristics of the substrate. Recorded high speed videos illustrate the existence of deformed substrate's recoil before the end of the takeoff phase when locusts jump from compliant substrates, which indicates their ability of recovering part of energy from the substrate deformation. This adaptability is supposed to be related to the catapult mechanism adopted in locusts' jump thanks to their long hind legs and sticky tarsus. These findings improve the understanding of the jumping mechanism of locusts, as well as can be used to develop artifact outperforming current jumping robots in unstructured scenarios.