Self-propelling Mechanism Research Articles

Self-Repeatable snapping liquid–crystal-elastomer actuator

Liquid crystal elastomers (LCEs) show potential for use in sensors and robotics owing to their reversible stimuli response. However, current actuators have limitations such as low power and slow recovery. Incorporating snap-through transitions induced by mechanical instability into motion can enhance the speed and power of soft actuators. However, the snap-through transitions’ single-shot motion response without external assistance at complicates their application to continuous and self-repeatable actuation. This study introduces a promising and simple approach for creating a rapid and self-repeatedly regulated snapping motion in an LCE actuator by confining the LCE film in a frame. We explore the confinement effect of a freestanding pre-curved LCE film that smoothly changes its bending direction and shows anticlastic buckling. Interestingly, a self-repeating snapping motion is generated by attaching a rigid film onto the LCE film, thereby inducing synclastic deformation. Remarkably, the up-and-down bending snapping motion occurs at a very high speed (within 30 ms) and is self-regulated depending on the temperature of the bottom surface. By utilizing this thermally responsive snapping LCE actuator, we successfully demonstrate an organic-based novel fire alarm and a self-propelled soft-walk mechanism.

Photoresponsive CHA-Integrated Self-Propelling 3D DNA Walking Amplifier within the Concentration Localization Effect of DNA Molecular Framework Enables Highly Efficient Fluorescence Bioimaging.

While three-dimensional (3D) DNA walking amplifiers hold considerable promise in the construction of advanced DNA-based fluorescent biosensors for bioimaging, they encounter certain difficulties such as inadequate sensitivity, premature activation, the need for exogenous propelling forces, and low reaction rates. In this contribution, a variety of profitable solutions have been explored. First, a catalytic hairpin assembly (CHA)-achieved nonenzymatic isothermal nucleic acid amplification is integrated to enhance sensitivity. Subsequently, one DNA component is simply functionalized with a photocleavage-bond to conduct a photoresponsive manner, whereby the target recognition occurs only when the biosensor is exposed to an external ultraviolet light source, overcoming premature activation during biodelivery. Furthermore, a special self-propelling walking mechanism is implemented by reducing biothiols to MnO2 nanosheets, thereby propelling forces that are self-supplied to a Mn2+-reliant DNAzyme. By carrying the biosensing system with a DNA molecular framework to induce a unique concentration localization effect, the nucleic acid contact reaction rate is notably elevated by 6 times. Following these, an ultrasensitive in vitro detection performance with a limit of detection down to 2.89 fM is verified for a cancer-correlated microRNA biomarker (miRNA-21). Of particular importance, our multiple concepts combined 3D DNA walking amplifier that enables highly efficient fluorescence bioimaging in live cells and even bodies, exhibiting a favorable application prospect in disease analysis.

Numerical analysis of a multistable capsule system under the delayed feedback control with a constant delay

The vibro-impact capsule system is a self-propelled mechanism that has abundant coexisting attractors and moves rectilinearly under periodic excitation when overcoming environmental resistance. In this paper, we study the control of coexisting attractors in this system by using a delayed feedback controller (DFC) with a constant delay. The aim of our control is to steer this complex system toward an attractor with preferable performance characteristics among multiple coexisting attractors, e.g., a periodically fast forward progression. For this purpose, we give an example of a feedback-controlled transition from a period-3 motion with low progression speed to a period-1 motion with high progression speed at the system parameters where both responses coexist. The effectiveness of this controller is investigated numerically by considering its convergence time and the required control energy input to achieve transition. We combine pseudo-spectral approximation of the delay, event detection for the discontinuities and path-following (continuation) techniques for non-smooth delay dynamical systems to carry out bifurcation analysis. We systematically study the dynamical performance of the controlled system when varying its control gain and delay time. Our numerical simulations show the effectiveness of DFC under a wide range of system parameters. We find that the desired period-1 motion is achievable in a range of control delays between a period-doubling and a grazing bifurcation. Therefore, two-parameter continuation of these two bifurcations with respect to the control delay and control gain is conducted to identify the delay-gain parameter region where the period-1 motion is stable. The findings of this work can be used for tuning control parameters in experiments, and similar analysis can be carried out for other non-smooth dynamical systems with a constant delay term.

Dealing with the Commonplace: Constantinos A. Doxiadis and the Zygos Technical Company

This paper deals with a largely unknown episode in the prolific career of the internationally renowned planner Constantinos A. Doxiadis (1913-1975). Between 1962 and 1974, he operated the construction company Zygos S.A. with a view to take advantage of the opportunities presented by the proliferation of the polykatoikìa (a characteristic mid-rise apartment building in Greece) via antiparochì (a popular land-for-flats contract)Αs this paper analyzes, the story of Zygos offers a unique opportunity to unpack a series of important issues regarding housing production and urbanization processes in postwar Greece—and potentially other countries—where housing was neither undertaken by centralized mechanisms, nor promoted by the welfare state. It discusses how the self-propelling mechanism of antiparochì both created and drew on a system of social and economic interdependencies that enjoyed broad support across the political spectrum, while boosting the growth of a speculative real estate market, where amateurish contractors and small construction companies thrived. In fact, the growth of such a market owes a lot to the regulatory measures launched by Doxiadis while being in charge of the Greek Reconstruction and Recovery programs (1945-1951). Altogether, the story of Doxiadis’s involvement in the Greek real estate market offers a striking example of how top-down incentives and bottom-up initiatives converged to create the conditions and framework within which Greek architects (including renowned ones) routinely operated. To contextualize the design and building process of polykatoikìes (a commonplace building type outside the realm of high architectural design), the paper draws on the concept of the “commonplace” as an umbrella term used to describe the socio-economic conditions evinced in the antiparochì mechanism and the everyday lived experience of a developing urban society.

Dynamic self-propelling condensed microdroplets over super-hydrophobic surface: An exceptional atmospheric corrosion inhibition strategy

Superhydrophobic surfaces (SHS) have potential application prospects in many fields for the lotus effect. The microdroplet self-propelling effect is a newly discovered mechanism of SHS phenomena, which provides more possibilities for SHS applications. In this study, the ZnO-nanoneedle array was designed and constructed by an electrodeposition method. Based on surface characterization and analysis, the nucleation, growth, and merging process of SHS surface droplets under simulated condensation conditions were studied. The correlation between the surface microstructure and the jumping behavior was established, and the self-propelling mechanism was analyzed from an energy perspective. Based on electrochemical data, the contribution of self-propelling behavior to the atmospheric corrosion protection performance of SHS was analyzed, which confirms that the droplet self-propelling behavior, as a new SHS atmospheric corrosion protection mechanism, has potential applications in atmospheric corrosion protection in the future.

“Self-Perpetuating Mechanism” in Experiences Stimulating Academic Teachers to Creative Didactic Work - Research Report

Abstract Objective: The main aim of paper is to present results from research concerning creative didactic work understood as consciously taken actions whose aim is to invent/implement and popularize new and valuable teaching strategies, methodical and organizational solutions. The paper presents an area of experiences that stimulate academic teachers to innovative didactic work. Methods: In a qualitative research conducted with the use of a theoretical-methodological approach of Gruber (1989) titled The Evolving Systems Approach to Creative Work (ESA). In it, the author applied a case study and conducted an Interpretative Phenomenological Analysis (IPA) to contents deriving from semistructured interviews carried out with 13 academic teachers-innovators that for at least 5 years invented/implemented new strategies/methods/techniques/programes/didactic aids in the process of teaching-learning with students. Results: Such experiences of didactic work as: positive emotions accompanying the process of inventing and implementing creative didactic solutions, good feedback from students, reaching educational goals, and encouragement from: students, co-workers, and significant persons make up the “self-propelling mechanism” for creativity in didactic work. Conclusions: Each stage of didactic work: from idea through implementation of the solution to its popularization is connected with pleasure and satisfaction taken by teachers. It makes them eager to continue their work in the form of various activities that create an internally related “weave of actions.” Thus, teaching in a creative way becomes a “self-propelling mechanism” thanks to which it is also subject to a process of continuous evolution of it.

Design of a self-propelled mechanism to be mounted on a capsule endoscope that made it possible to observe the stomach

Design of a self-propelled mechanism to be mounted on a capsule endoscope that made it possible to observe the stomach

A Self-Propelled Mechanism to Increase Range of Bistable Operation of a Piezoelectric Cantilever-Based Vibration Energy Harvester.

In our previous works, we presented a method to increase the harvested energy from vibrations using a piezoelectric cantilever and to increase the frequency range of operation by introducing bistability with the use of magnetic repulsion. However, for small excitations, the cantilever may not be able to overcome the magnetic repulsive force but vibrate at one of its two equilibrium positions with reduced amplitude. This work introduces a method of increasing the range of excitations over which the operation remains bistable. This is achieved by spring loading one of the magnets, previously on a fixed support, allowing motion in one dimension only, toward and away from the cantilever in the horizontal plane. Configured so, as the cantilever moves toward this magnet, the repulsion due to the cantilever-mounted magnet pushes the spring-loaded magnet away, increasing distance, and thus, reducing magnetic force between them, required to be overcome by external excitations for bistable operation. Similarly, as the cantilever moves away, the spring pushes the magnet closer to the cantilever-mounted magnet, increasing vibration amplitude. Thus, the spring introduces a negative feedback which favors bistable operation over an increased range of excitations. This completely mechanical method requires no additional energy cost. Peak power gains of up to 90 and a decrease in excitation voltage of up to 60% were observed over the fixed magnet.

Upon the Optimal Design of a Self-Propelled Double-Cone Mechanism

Upon the Optimal Design of a Self-Propelled Double-Cone Mechanism

Dynamics of the walking machines

In this paper we analyze the mechanisms which can be implemented on a structure of walking vehicle, vehicle which possesses mobility and stability on different types of soils with obstacles (even other than terrestrial). We present a mechanical model for a walking self-propelled mechanism with joints, for which we perform the kinematic and dynamic analysis. For the dynamic analysis the elements of the mechanism are modeled with solids in AutoCAD, obtaining thus the geometric and mechanic properties of the self-propelled structure. We adopt a dynamic model for which, with the aid of the determined mechanical parameters, we obtain the equation of motion of the machine. After the solving of the equation of motion one obtains the variation of the angular velocity at the driving element. In the end of the paper the authors present the conclusion resulted from the performed study.

Planar Self-Assembly of Submicron and Nanoscale Wires and Grooves on III–V(110) Surfaces

Metallic Ga and In submicron and nanowires (NWs) tens of microns long naturally form via a self-propelled mechanism on the (110) surfaces of GaAs and InAs, respectively, during noncongruent sublimation in ultrahigh vacuum. Under stringent conditions, low-energy electron microscopy uncovers GaAs and InAs(110) surfaces on the brink of decomposition rapidly assemble planar wires of their cations in the ⟨110⟩ direction. For InP(110), wire formation is unfavorable due to a smooth decomposing front but can be assisted by Au nanoparticles (NPs), which sacrifice themselves to form rough pits via solid–liquid–vapor etching. The resulting self-assembled and AuNP-assisted NWs grow crystallographically in a self-sustainable manner, unless they are obstructed and consumed by stationary microdroplets, leaving emptied grooves. The findings reveal a hitherto hidden natural process on the surfaces of binary crystals capable of producing elementary submicron and nanoscale wires without extrinsic materials, paving the way ...

Collective behavior of strongly confined suspensions of squirmers

We run numerical simulations of strongly confined suspensions of model spherical swimmers called “squirmers”. Because of the confinement, the Stokeslet dipoles generated by the particles are quickly screened and the far-field flow is dominated by the source dipole for all the different kinds of squirmers. However, we show that the collective behavior of the suspension still depends on the self-propelling mechanism of the swimmers as polar states can only be observed for neutral squirmers. We demonstrate that the near-field hydrodynamic interactions play a crucial role in the alignment of the orientation vectors of spherical particles. Moreover, we point out that the enstrophy and the fluid fluctuations of an active suspension also depend on the nature of the squirmers.

Polymeric nanoparticle system to target activated microglia/macrophages in spinal cord injury

The possibility to control the fate of the cells responsible for secondary mechanisms following spinal cord injury (SCI) is one of the most relevant challenges to reduce the post traumatic degeneration of the spinal cord. In particular, microglia/macrophages associated inflammation appears to be a self-propelling mechanism which leads to progressive neurodegeneration and development of persisting pain state. In this study we analyzed the interactions between poly(methyl methacrylate) nanoparticles (PMMA-NPs) and microglia/macrophages in vitro and in vivo, characterizing the features that influence their internalization and ability to deliver drugs. The uptake mechanisms of PMMA-NPs were in-depth investigated, together with their possible toxic effects on microglia/macrophages. In addition, the possibility to deliver a mimetic drug within microglia/macrophages was characterized in vitro and in vivo. Drug-loaded polymeric NPs resulted to be a promising tool for the selective administration of pharmacological compounds in activated microglia/macrophages and thus potentially able to counteract relevant secondary inflammatory events in SCI.

Selective Nanovector Mediated Treatment of Activated Proinflammatory Microglia/Macrophages in Spinal Cord Injury

Much evidence shows that acute and chronic inflammation in spinal cord injury (SCI), characterized by immune cell infiltration and release of inflammatory mediators, is implicated in development of the secondary injury phase that occurs after spinal cord trauma and in the worsening of damage. Activation of microglia/macrophages and the associated inflammatory response appears to be a self-propelling mechanism that leads to progressive neurodegeneration and development of persisting pain state. Recent advances in polymer science have provided a huge amount of innovations leading to increased interest for polymeric nanoparticles (NPs) as drug delivery tools to treat SCI. In this study, we tested and evaluated in vitro and in vivo a new drug delivery nanocarrier: minocycline loaded in NPs composed by a polymer based on poly-ε-caprolactone and polyethylene glycol. These NPs are able to selectively target and modulate, specifically, the activated proinflammatory microglia/macrophages in subacute progression of the secondary injury in SCI mouse model. After minocycline-NPs treatment, we demonstrate a reduced activation and proliferation of microglia/macrophages around the lesion site and a reduction of cells with round shape phagocytic-like phenotype in favor of a more arborized resting-like phenotype with low CD68 staining. Treatment here proposed limits, up to 15 days tested, the proinflammatory stimulus associated with microglia/macrophage activation. This was demonstrated by reduced expression of proinflammatory cytokine IL-6 and persistent reduced expression of CD68 in traumatized site. The nanocarrier drug delivery tool developed here shows potential advantages over the conventionally administered anti-inflammatory therapy, maximizing therapeutic efficiency and reducing side effects.

Strategic Analysis of Computer Waste Management Options: Game-Theoretic Approach

Computer waste has emerged as a critical issue globally because of the growing quantity of waste and problems arising out of its toxic nature. In India, it is estimated that 480,000 t of electronic waste (e-waste) is generated annually. Computer waste includes plastics and metals that have a good potential for recycling; however, if not managed properly, the additives and chemicals in plastic waste and traces of heavy metals raise concern for human health and the environment. Efficient e-waste management will require a strategy that offers a win-win situation for all the involved stakeholders. This paper uses a game-theoretic approach for analyzing the strategies by identifying the equilibrium points for various scenarios that can help in deciding the incentives and penalties for deriving the self-propelling market-based mechanism for efficient management of e-waste. Results suggest that applying take-back schemes with some incentives to the consumers and penalty to those who do not follow the prescribed procedure for discarding e-waste could be very useful to discourage the land disposal of computer waste. Nash-equilibrium implies that the recycler would prefer to collect the computer waste directly from the consumer only if the incentive return to the consumer is less than 15% of the price of the computer, the recycling fee is less than 5% of the price of the computer, and the price of the recycled material is more than 15% of the price of the computer; otherwise collect it through the producer. Also, for the producer, it would be preferable to take an extra fee from the consumer for end-of-life management of the desktop computer as an advance recovery fee (apparent fee) only up to 4.0% of the cost of the computer. If the producer had to take an extra fee more than 4.0%, it should be taken as an extended producer responsibility fee (hidden fee combined in the cost) so that computer sales are not affected.

Development of a Magnetostrictive Linear Motor for Microrobots Using Fe-Ga (Galfenol) Alloys

This paper presents a unique magnetostrictive linear motor using Fe-Ga (Galfenol) alloys. The actuator is driven by a novel self-propelling mechanism that takes advantage of friction and inertial force. We describe in detail the driving principle and simply analyze it. We also present several experimental results regarding the performance of the fabricated magnetostrictive linear motor and verify the validity of the design of the actuator by these experimental results.

The inflammatory response in the MPTP model of Parkinson’s disease is mediated by brain angiotensin: relevance to progression of the disease

The neurotoxin MPTP reproduces most of the biochemical and pathological hallmarks of Parkinson's disease. In addition to reactive oxygen species (ROS) generated as a consequence of mitochondrial complex I inhibition, microglial NADPH-derived ROS play major roles in the toxicity of MPTP. However, the exact mechanism regulating this microglial response remains to be clarified. The peptide angiotensin II (AII), via type 1 receptors (AT1), is one of the most important inflammation and oxidative stress inducers, and produces ROS by activation of the NADPH-oxidase complex. Brain possesses a local angiotensin system, which modulates striatal dopamine (DA) release. However, it is not known if AII plays a major role in microglia-derived oxidative stress and DA degeneration. The present study indicates that in primary mesencephalic cultures, DA degeneration induced by the neurotoxin MPTP/MPP(+) is amplified by AII and inhibited by AT1 receptor antagonists, and that protein kinase C, NADPH-complex activation and microglial activation are involved in this effect. In mice, AT1 receptor antagonists inhibited both DA degeneration and early microglial and NADPH activation. The brain angiotensin system may play a key role in the self-propelling mechanism of Parkinson's disease and constitutes an unexplored target for neuroprotection, as previously reported for vascular diseases.

Development of a stair-climbing robot using springs and planetary wheels

This paper presents a self-propelled travelling mechanism capable of climbing stairs without a sensor or judging algorithm. The developed leg-wheeled mobile robot, which is a type of mechanism to be adaptable to obstacles and to overcome the gravity, uses springs and planetary wheels. The spring is effective when the front wheels start climbing a stair and the planetary wheels with the functions to roll, walk, and jump, thereby passing through stairs and obstacles. A detail design has been performed and a test model has been constructed with a vast range of simulation analysis results. Also, the validity of the constructed test model has been verified through the experiments in climbing the stairs of high step.

Elasticity-driven droplet movement on a microbeam with gradient stiffness: A biomimetic self-propelling mechanism

Directional movement of liquid droplets is of significance not only for certain physiological processes in nature but also for design of some microfluidic devices. In this study, we report a novel way to drive directional movement of liquid droplets on a microbeam with a varying or gradient stiffness. We use the energy method to theoretically analyze the interaction between a droplet and the elastic microbeam. The system tends to have the minimum potential energy when the droplet moves to the softer end of the beam. Therefore, a gradient change of the bending stiffness may be utilized to help the directional motion of droplets. Similarly, one can also drive droplets to move in a designed direction by varying the cross sectional geometry of the beam. Finally, some possible applications of this self-propelling mechanism are suggested.

An Initial and Boundary Value Problem Modeling of Fish-like Swimming

In this paper we consider an initial and boundary value problem that models the self-propelled motion of solids in a bidimensional viscous incompressible fluid. The self-propelling mechanism, consisting of appropriate deformations of the solids, is a simplified model of the propulsion mechanism of fish-like swimmers. The governing equations consist of the Navier–Stokes equations for the fluid, coupled to Newton’s laws for the solids. Since we consider the case in which the fluid–solid system fills a bounded domain we have to tackle a free boundary value problem. The main theoretical result in the paper asserts the global existence and uniqueness (up to possible contacts) of strong solutions of this problem. The second novel result of this work is the provision of a numerical method for the fluid–solid system. This method provides a simulation of the simultaneous displacement of several swimmers and is tested on several examples.