Figure 2 - uploaded by Iram Adolfo de Nicolas
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shows the superimposed time series of oscillations for the controlled topological modes and the corresponding forcing signals. Figures 2(a) and 2(d) correspond to circular and triangular modes, respectively. On the other hand, Figs. 2(b) and 2(c)
Source publication
We report experimental results indicating entrainment of aperiodic and periodic oscillatory dynamics in the Mercury Beating Heart (MBH) system under the influence of superimposed periodic forcing. Aperiodic oscillations in MBH were controlled to generate stable topological modes, namely, circle, ellipse, and triangle, evolving in a periodic fashion...
Citations
... oscillations. 109 The forming and dissolving of a mercury sulfate film on the surface of the mercury droplet in conjunction with the variations in the surface tension of the droplet drives the system mechanically. 110,111 Understanding the oscillations of droplets is important from an academic point of view because of the complex nonlinear interaction involving the periodic and aperiodic dynamics and the macroscopic wave-particle duality characteristic of oscillating droplets. ...
The unique properties to combine the dual merits of both liquids and metals together make the gallium‐based liquid metal (LM) droplets a class of unconventional substitute which possess great potential for a group of newly emerging areas, such as stretchable electronics, soft devices, micro sensors and actuators. In addition, LM droplets are undoubtedly an intriguing target worth of pursuing in fundamental hydrodynamic investigations due to their extremely high surface tension nature compared to classical nonmetallic fluids. Since the discovery of the diverse transformation phenomena and self‐fueled droplet mollusks of LM that can move automatically in solution via single electricity or even without any external energy supply, tremendous attentions were attracted to this special fluidic object of LM droplets. Over the past decade, there has been a proliferation of explorations on LM droplet dynamics, while the involved contents are heterogeneous due to the interfacial physical/chemical activity of the LM and the diversity of the kinetic behaviors. To better understand and manipulate the droplet behavior and to promote further development of the LMs, this review is dedicated to summarize the latest progress and presents an overview on basic findings related to LM macro‐droplet dynamics. Firstly, the extended definition of LM droplets and the corresponding fabrication methods are given. Then, typical works on LM droplet dynamics are systematically interpreted based on their different behavior categories. Finally, the perspectives, main obstacles and challenges restricting the development of LM droplet dynamics are pointed out.
... These oscillations are often periodic with a regular cycle. Some natural oscillation cycles can be controlled by an aperiodic signal including non-biological [152] and biological systems [153][154][155]. Synthetic bacterial oscillators have been instrumental in exploring new frontiers of aperiodic controlled oscillators in biological systems [156]. ...
Bacterial proteases are a promising post-translational regulation strategy in synthetic circuits because they recognize specific amino acid degradation tags (degrons) that can be fine-tuned to modulate the degradation levels of tagged proteins. For this reason, recent efforts have been made in the search for new degrons. Here we review the up-to-date applications of degradation tags for circuit engineering in bacteria. In particular, we pay special attention to the effects of degradation bottlenecks in synthetic oscillators and introduce mathematical approaches to study queueing that enable the quantitative modelling of proteolytic queues.
... The excitatory nature of these chemo-mechanical oscillations makes this system an ideal tabletop system to demonstrate and verify a plethora of intriguing behaviors observed or predicted in such systems. A few examples are the entrainment [6,[12][13][14], synchronization [15,16], Kuramoto transition [17,18], quorum sensing [19][20][21] and cessation of oscillations [22][23][24][25][26]. ...
In this work, we report a quenching of oscillations observed upon coupling two chemomechanical oscillators. Each one of these oscillators consists of a drop of liquid metal submerged in an oxidizing solution. These pseudoidentical oscillators have been shown to exhibit both periodic and aperiodic oscillatory behavior. In the experiments performed on these oscillators, we find that coupling two such oscillators via an attenuated resistive coupling leads the coupled system towards an oscillation quenched state. To further comprehend these experimental observations, we numerically explore and verify the presence of similar oscillation quenching in a model of coupled Hindmarsh-Rose (HR) systems. A linear stability analysis of this HR system reveals that attenuated coupling induces a change in eigenvalues of the relevant Jacobian, leading to stable quenched oscillation states. Additionally, the analysis yields a threshold of attenuation for oscillation quenching that is consistent with the value observed in numerics. So this phenomenon, demonstrated through experiments, as well as simulations and analysis of a model system, suggests a powerful natural mechanism that can potentially suppress periodic and aperiodic oscillations in coupled nonlinear systems.
... A control of such aperiodic or chaotic dynamics is important because of its relevance to therapeutic treatments [13,14]. Aperiodic dynamics can be morphed into periodic dynamics with the help of an external periodic forcing [15][16][17], nonfeedback control [18], and even a time delay [19]. The modification of system dynamics using an external forcing typically leads to entrainment of the dynamics, wherein the oscillator phase is mode locked with the phase of the forcing. ...
We report experiments on an active camphor rotor. A camphor rotor is prepared by infusing camphor on a regular rectangular paper strip. It performs self-propelled motion at the air-water interface due to Marangoni driven forces. After some transient (periodic) dynamics, the rotor enters into the aperiodic bursting regime, which is characterized as an irregularly repeated rest (halt) and run (motion) of the rotor. Subsequently, this aperiodic (irregular) rotor is entrained to a periodic (regular) regime with the help of a suitable external periodic forcing. Furthermore, we conducted experiments on two such coupled aperiodic camphor rotors. In this set of experiments, synchronized bursting was observed. During this bursting motion, one rotor follows the movement of the other rotor. A numerical point particle model, incorporating excitable underlying equations, successfully replicated experimentally observed aperiodic bursting.
... The possibility of electrically forcing liquid metal oscillations along with their ability to generate alternating electrical signals of significant amplitude leads to a new research direction-studies in coupled electrochemical oscillators. There are numerous reports of coupling of mercury-based oscillators, [30][31][32][33][34][35]104,[143][144][145][146] but up to date, gallium-based systems were almost completely neglected. The behavior of gallium-based systems should be analogous to mercury-based systems, at least in terms of the dynamics and phenomenological description. ...
... Furthermore, such ensembles of coupled electrochemical oscillators show other features characteristic for neural networks (or other networks of coupled oscillators): explosive synchronization 144) and Kuramoto transitions. 35) Mercury-based weakly coupled oscillators are also prone to transition between periodic and aperiodic oscillations, 145,146) and show surprising sensitivity towards noise when maintained at specific oscillatory modes (e.g. triangular, cf. ...
The enormous amount of data generated nowadays worldwide is increasingly triggering the search for unconventional and more efficient ways of processing and classifying information, eventually able to transcend the conventional von Neumann-Turing computational central dogma. It is, therefore, greatly appealing to draw inspiration from less conventional but computationally more powerful systems such as the neural architecture of the human brain. This neuromorphic route has the potential to become one of the most influential and long-lasting paradigms in the field of unconventional computing. Memristive and the recently proposed memfractive systems have been shown to display basic features of neural systems such as synaptic-like plasticity and memory features, so that they may offer a diverse playground to implement synaptic connections. In this review, we address various material-based strategies of implementing unconventional computing hardware: (i) electrochemical oscillators based on liquid metals and (ii) mem-devices exploiting Schottky barrier modulation in polycrystalline and disordered structures made of oxide or perovskite-type semiconductors. Both items (i) and (ii) build the two pillars of neuromimetic computing devices, which we will denote as synthetic neural networks. We expect that the current review will be of great interest for scientists aiming at bridging unconventional computing strategies with specific materials-based platforms.
... [156][157] In this type of neural networks, due to the interplay between delays in signal transmission and plasticity, neurons of similar activity spontaneously self-organize into groups. 148 Mercury-based weakly coupled oscillators are also prone to transition between periodic and aperiodic oscillations, [149][150] and show surprising sensitivity towards noise when maintained at specific oscillatory modes (e.g., triangular, cf. Refs. ...
The enormous amount of data generated nowadays worldwide is increasingly triggering the search for unconventional and more efficient ways of processing and classifying information, eventually able to transcend the conventional von-Neumann-Turing computational central dogma. It is, therefore, greatly appealing to draw inspiration from less conventional but computationally more powerful systems such as the neural architecture of the human brain. This neuromorphic route has the potential to become one of the most influential and long-lasting paradigms in the field of unconventional computing. The material-based workhorse for current hardware platforms is largely based on standard CMOS technologies, intrinsically following the above mentioned von-Neumann-Turing prescription; we do know, however, that the brain hardware operates in a massively parallel way through a densely interconnected physical network of neurons. This requires challenging the intrinsic definition of the single units and the architecture of computing machines. (...)
... The external forcing of a single oscillator is discussed by Kumar et al. 30 for the interesting example of the "beating mercury heart," which refers to chemomechanical oscillations of a mercury drop in an electrolyte containing diluted sulfuric acid and dichromate ions. These oscillations arise from electrocapillarity (the dependence of the surface tension on the electrochemical potential) and have been known since the 19th century. ...
The heart beating phenomenon of room temperature liquid metal (LM) mercury has attracted much attention in the past years, but its research and application are limited because of the low vapor pressure and high toxicity. Here, a fundamental scientific finding is reported that the non-toxic eutectic gallium indium (EGaIn) alloy droplets beat periodically at a certain frequency based on a floating electrode under the stimulation of the direct current (DC) field. The essential characteristics of heart beating are the displacement and the projected area change of the LM droplet. The mechanism of this phenomenon is the self-regulation of interfacial tension caused by chemical oxidation, chemical corrosion, and continuous electrowetting. In this article, a series of experiments are also carried out to examine the effects of different factors on the heartbeat, such as voltage, the volume of the droplet, the droplet immersion depth, the electrolyte solution concentration, the distance of electrodes, and the type of floating electrode. Finally, the heartbeat state and application boundary of the LM droplet under different conditions are summarized by imitating the human life process. The periodic changes of the LM droplet under an external DC electric field provide a new method to simulate the beating of the heart artificially, and can be applied to the research of organ chip fluid pumping in the future.
Avalanche dynamics in an ensemble of self-propelled camphor boats is studied. The self-propelled agents are camphor infused circular paper disks moving on the surface of water. The ensemble exhibits bursts of activity in the autonomous state triggered by stochastic fluctuations. This type of dynamics have been previously reported in a slightly different system [Journal of the Physical Society of Japan 84, 034802 (2015)]. Fourier analysis of the autonomous ensemble’s average speed reveals a unimodal spectrum, indicating the presence of a preferred timescale in the dynamics. We, therefore, entrain such an ensemble to an external forcing by using periodic air perturbations on the surface of the water. This forcing is able to replace the stochastic fluctuations which trigger aburst in the autonomous ensemble, thus entraining the system. Upon varying the periodic forcing frequency, an optimal frequency is revealed at which the quality of entrainment of the ensemble by the forcing is augmented. This optimal frequency is found to be in the vicinity of the Fourier spectrum peak of the autonomous ensemble’s average speed. This indicates the existence of an underlying deterministic component in the apparent aperiodic bursts of motion of the autonomous ensemble of active particles. A qualitative reasoning for the observed phenomenon is presented.
