Electrical Modulation Research Articles

Thermal and Electron Plasma Effects on Phase Separation Dynamics Induced by Ultrashort Laser Pulses

During ultrafast laser-induced crystallization from glass with a non-congruent composition, a phase separation occurs. The morphology of the crystallized area, inside the heat-affected zone (HAZ), is spectacular showing a bouquet-like structure, under some specific conditions related to glass chemical composition and laser parameters. In this work, we investigate this HAZ along a written line through a set of high-resolution electron microscopy techniques to probe both the morphology and the chemical distribution at the nanoscale. Based on these findings, we demonstrate that the bouquet-like structure arises from poorly textured nanocrystals between two regions that have probably accumulated elastic strain. From that analysis, we also provide insights into the chemical separation process during this complex light-matter transformation in which the induced plasma structure guides the spatial distribution of SiO2 and LiNbO3. We suggest a model based on an electric field modulation produced by the inhomogeneous plasma electron trapping, that modifies the electrochemical potentials of the constituents.

An end-to-end big data analytics platform for IoT-enabled smart factories: A case study of battery module assembly system for electric vehicles

Within the concept of factories of the future, big data analytics systems play a critical role in supporting decision-making at various stages across enterprise processes. However, the design and deployment of industry-ready, lightweight, modular, flexible, and cost efficient big data analytics solutions remains one of the main challenges towards the Industry 4.0 enabled digital transformation. This paper presents an end-to-end IoT-based big data analytics platform that consists of five interconnected layers and several components for data acquisition, integration, storage, analytics and visualisation purposes. The platform architecture benefits from state-of-the-art technologies and integrates them in a systematic and interoperable way with clear information flows. The developed platform has been deployed in an electric vehicle battery module assembly automation system designed by the Automation Systems Group at the University of Warwick, the UK. The developed proof-of-concept solution demonstrates how a wide variety of tools and methods can be orchestrated to work together aiming to support decision-making and to improve both process and product qualities in smart manufacturing environments.

Parallel Microdispensing Method of High-Viscous Liquid Based on Electrostatic Force.

Parallel microdispensing of high-viscous liquid is a fundamental task in many industrial processes. Herein, a smart printing head is developed, including the probe array, the electric control module, the contact force measurement module, and the extra force balance module. The parallel dispensing of high-viscous liquid in nL level is achieved. The interacting effect between probes on the loading process is analyzed too. According to the result, the interacting effect between probes has a strong influence on the loading process. Therefore, the strategy of serial electrical loading and parallel transfer printing is utilized. Finally, the dependency of transfer printing volume on probe size, etc., is experimentally investigated. The volume of the loaded droplet can be controlled by the lifting velocity of the probe array, and the volume of the transferred droplet can be adjusted by the size of the probe instead of the contact force. The advantage of the proposed method is to realize the highly repeatable parallel dispensing of high-viscous liquid with a relatively simple device.

Development of FE Modeling Procedures for Laser Welded Aluminum Structures in An Electric Vehicle Battery Module and Validation by Test Data

<div class="section abstract"><div class="htmlview paragraph">High strength and thin materials are widely adopted in modern electric vehicles for lightweight design to achieve high energy efficiency. For battery modules, 5000 and 6000 aluminum are typically utilized as a structural material with a thickness range between 1 to 5 mm. Laser welding is one of the most optimum welding tools for joining such a thin material due to its unique advantages, e.g., high welding speed, high accuracy, high energy yet the smallest possible heat affect zone, etc.</div><div class="htmlview paragraph">This paper aims to develop a simplified yet effective FE modeling procedure to simulate the laser welding effects on the aluminum structures used in electric vehicle battery modules. A sequentially-coupled thermo-mechanical analysis procedure is developed to determine the softened zone size for aluminum weldments. Then a tie-rupture weld model incorporates the softened zone to predict the weld failure strength. The effectiveness of the developed modeling procedures is confirmed by a large number of coupon level weld strength tests. Finally, a module-level box pull test is simulated and validated by the test data with the knowledge obtained from the developed welding modeling procedure.</div></div>

Resolving Multi-Path Interference in Compressive Time-of-Flight Depth Imaging with a Multi-Tap Macro-Pixel Computational CMOS Image Sensor.

Multi-path interference causes depth errors in indirect time-of-flight (ToF) cameras. In this paper, resolving multi-path interference caused by surface reflections using a multi-tap macro-pixel computational CMOS image sensor is demonstrated. The imaging area is implemented by an array of macro-pixels composed of four subpixels embodied by a four-tap lateral electric field charge modulator (LEFM). This sensor can simultaneously acquire 16 images for different temporal shutters. This method can reproduce more than 16 images based on compressive sensing with multi-frequency shutters and sub-clock shifting. In simulations, an object was placed 16 m away from the sensor, and the depth of an interference object was varied from 1 to 32 m in 1 m steps. The two reflections were separated in two stages: coarse estimation based on a compressive sensing solver and refinement by a nonlinear search to investigate the potential of our sensor. Relative standard deviation (precision) and relative mean error (accuracy) were evaluated under the influence of photon shot noise. The proposed method was verified using a prototype multi-tap macro-pixel computational CMOS image sensor in single-path and dual-path situations. In the experiment, an acrylic plate was placed 1 m or 2 m and a mirror 9.3 m from the sensor.

Electrical modulation of transplanted stem cells improves functional recovery in a rodent model of stroke

Stroke is a leading cause of long-term disability worldwide, intensifying the need for effective recovery therapies. Stem cells are a promising stroke therapeutic, but creating ideal conditions for treatment is essential. Here we developed a conductive polymer system for stem cell delivery and electrical modulation in animals. Using this system, electrical modulation of human stem cell transplants improve functional stroke recovery in rodents. Increased endogenous stem cell production corresponds with improved function. Transcriptome analysis identified stanniocalcin 2 (STC2) as one of the genes most significantly upregulated by electrical stimulation. Lentiviral upregulation and downregulation of STC2 in the transplanted stem cells demonstrate that this glycoprotein is an essential mediator in the functional improvements seen with electrical modulation. Moreover, intraventricular administration of recombinant STC2 post-stroke confers functional benefits. In summation, our conductive polymer system enables electrical modulation of stem cells as a potential method to improve recovery and identify important therapeutic targets.

Modulation of vacancy-ordered double perovskite Cs2SnI6 for air-stable thin-film transistors

Vacancy-ordered halide double perovskites are promising non-toxic and stable alternatives for their lead- and tin (II)-based counterparts in electronic and optoelectronic applications. Despite extensive theoretical studies on this emerging family of materials, efforts devoted to the chemical modulation of their thin-film properties and their potential application in electronic devices remain rare. Here, we develop a facile one-step solution processing strategy to tune the film quality of cesium tin (IV) iodide (Cs 2 SnI 6 ) perovskite and demonstrate its feasibility in thin-film transistor (TFT) application. We reveal critical roles of precursor stoichiometric ratio and solvent engineering in achieving uniform and highly crystalline Cs 2 SnI 6 films with superior electron mobility. We further modulate the electronic properties by incorporating an external manganese (Mn 2+ ) dopant, achieving high-performance air-stable n-channel TFTs and all-perovskite complementary inverters. We anticipate that the present study would pave the way for expanding the environmentally friendly and stable perovskites toward widespread applications. • Precursor engineering for one-step solution deposition of Cs 2 SnI 6 thin films • Electrical modulation of the Cs 2 SnI 6 perovskite for transistor application • Integrated transistors exhibit appealing electrical performance with high stability Liu et al. report the deposition of eco-friendly vacancy-ordered double perovskite Cs 2 SnI 6 thin films using a one-step solution process. Subsequently, an external atomic doping is adopted to modulate the electrical property of the Cs 2 SnI 6 perovskite. The resulting transistors exhibit appealing electrical performance with highly stable characteristics.

High aspect ratio tilted gratings through local electric field modulation in plasma etching

The anisotropic nature of plasma etching is usually exploited to realize vertical nano-/micro- silicon structures by deep reactive ion etching. However, some applications require tilted instead of perpendicular profiles with respect to the substrate. Here, a controlled tilted etching is realized by introducing a set of metal electric field modulator(s), which modify the near sample surface potential. The ions from the plasma body are accelerated under the influence of the distorted electric field, and hit the silicon surface with a certain incident angle. A model is built with finite elements method, taking into account the geometry of the experiment and the chamber conditions during the etching process. The thickness and the inter-distance of Al slabs have been varied in a range of 0.5–3 mm and 10–25 mm, respectively. A tilt angle ranging from 0° to 22.6° has been measured and validates the simulation results, showing that a desired tilt profile can be achieved with a proper parameters tuning. Examples of 1D and 2D modulations are reported with linear and chessboard slanted gratings for X-ray imaging applications.

Electrically-modulated infrared absorption of graphene metamaterials via magnetic dipole resonance

To increase the absorption efficiency of graphene-based devices, we propose a metamaterial structure comprising of a square metal plate array on graphene, a dielectric spacer, and a metal substrate. This work numerically demonstrates enhancement of the near-infrared absorption of monolayer graphene via the magnetic dipole resonance in the metamaterial under normal-incidence. Furthermore, the absorption efficiency of graphene-based devices can reach up to 96% with proposed structures incorporating three layers of graphene when the Fermi energy is 0.6 eV. Varying the Fermi energy by varying the applied voltage, is shown to enable an increase of the absorption efficiency of graphene-based devices with a reduction of the Fermi energy. Therefore, the absorption wavelength exhibits a linear electrical modulation in a wide range from 1362 to 1787 nm. The designed graphene light absorber has potential applications in optoelectronic devices such as photodetectors and perfect absorbers. • A new resonance peak appeared by adding single layer graphene. • By increasing the number of graphene layers to three, the absorption efficiency can be increased from 32% to 96%. • By changing the Fermi energy of graphene, the maximum tunable wavelength range can reach 425 nm. • The absorption efficiency of all resonance peaks is more than 87%.

Edge modes and their conductance in narrow nanoribbons of 2D materials in a topological phase

Employing novel 2D materials with topologically protected current-carrying edge states is promising to boost the on-current in electronic devices. Using nanoribbons is essential to reduce the contribution of the 2D bulk states to the current. Making the nanoribbon widths narrower allows one to put more current-carrying edge states under the gate of a fixed width thus increasing the current. However, the edge states from opposite edges may start to interact in narrow nanoribbons. Based on an effective k∙p model, we analyze the topologically protected edge states and their conductance for several 2D materials as a function of the normal electric field. We compare the 2D materials MoS2, MoSe2, WS2, and WSe2 in the topological 1T′ phase and find the largest electric field-induced conductance modulation in MoS2 nanoribbons.

Flexible synaptic floating gate devices with dual electrical modulation based on ambipolar black phosphorus

SummaryTwo-dimensional van der Waals materials offer various possibilities for synaptic devices, matching the requirements of intelligent and energy-efficient computation. However, very few studies on robust flexible synaptic transistors have been reported, which hold great potential for soft robotics and wearable applications. Here a floating gate synaptic device based on ambipolar black phosphorus (BP) on a flexible substrate has been demonstrated with two working modes. The three-terminal mode, where the carriers are injected into the floating gate, shows a nonvolatile memory effect, whereas the two-terminal mode shows a quasi-nonvolatile memory effect. Remarkably, the synaptic device working on the three-terminal mode shows an excellent performance in the energy-efficient computation of sub-fJ/spike with a fast gate voltage response down to ∼10 ns. Furthermore, the flexible synaptic device exhibits good endurance under 5,000 bending cycles with a strain of ∼0.63%, suggesting great potential in flexible neuromorphic applications with low energy consumption.

Nonlinear Quantum Electrodynamics in Dirac Materials.

Classical electromagnetism is linear. However, fields can polarize the vacuum Dirac sea, causing quantum nonlinear electromagnetic phenomena, e.g., scattering and splitting of photons, that occur only in very strong fields found in neutron stars or heavy ion colliders. We show that strong nonlinearity arises in Dirac materials at much lower fields ∼1 T, allowing us to explore the nonperturbative, extremely high field limit of quantum electrodynamics in solids. We explain recent experiments in a unified framework and predict a new class of nonlinear magnetoelectric effects, including a magnetic enhancement of dielectric constant of insulators and a strong electric modulation of magnetization. We propose experiments and discuss the applications in novel materials.

Electrically modulated Josephson junction of light-dressed topological insulators

In a Josephson junction mediated by a two-dimensional irradiated topological insulator, the current-phase relation can be electrically modulated, including the 0-$\ensuremath{\pi}$ phase transition and the anomalous phase shift of the current. Qualitatively combining analyses and numerical simulations, we find that the $0\text{\ensuremath{-}}\ensuremath{\pi}$ phase transition and anomalous phase shift can be controlled by a gate voltage and a transverse electric field, respectively. These possible electrical modulations result from the photoinduced anisotropic helical edge states. Due to the anisotropy and spin-momentum locking nature in the edge channels, an effective Zeeman field is caused by an electrical potential whose orientation automatically matches the spin alignment of the edge modes. The photoinduced anisotropy provides potential applications in Flouqet engineering helical supercurrent and electrically modulated topological superconducting devices.

Tailoring neuroplasticity in flexible perovskite QDs-based optoelectronic synaptic transistors by dual modes modulation

For the achievement of robust neuromorphic computing with simple device integration and low energy consumption, the development of artificial synaptic devices incorporating multiple excitation modes has attracted wide interests. In this regard, a multi-functional and energy-efficient CsPbBr3 quantum dots-based optoelectronic synaptic transistor is designed capable of realizing required synaptic plasticity with both photonic and electric modulation modes in one device. Important synaptic behaviors, including excitatory post-synaptic current and paired-pulse facilitation, are simulated utilizing both photonic and electric stimulations. Furthermore, the transition of short-term plasticity (STP) to long-term plasticity (LTP) can also be implemented through either the adjustment of input photonic pulses or the co-modulation of photonic and electric operations. The excellent tunability between STP and LTP of the synaptic device further leads to the STP-based “Morse-code” optical decoding scheme and LTP-based simulation of visual object recognition. More significantly, the synergistic modulation of photonic and electric operations enables the implementation of logic functions. The multi-functional optoelectronic synaptic transistors are also mechanically flexible, and no distinct synaptic performance variation is observed even when the bending radius of the devices is down to 1 mm. This work suggests a new path for developing flexible and multifunctional neuromorphic electronics.

Multiscale Analysis and Safety Assessment of Fresh and Electrical Aged Lithium-Ion Pouch Cells Focusing on Mechanical Behavior

Analyzing the impact of electrical aging on the lithium-ion cell’s mechanical behavior and safety is an important factor to assess the crash safety of electric vehicles during their lifetime. In this study, fresh and electrical aged state-of-the-art NCM pouch cells were investigated. Aged cells, which were cycled electrically to 90% state of health, under laboratory conditions in electric vehicle battery modules were used. The used charging/discharging strategy represents real customer behavior based on accelerated driving profiles. First, it is shown that electrical aging has a significant influence on the anodes’ and separators’ mechanical properties, which had a lower mechanical strength and stiffness under tension. Additionally, quasi-static cylindrical indentation and three-point bending tests were performed to investigate aging effects on cell level at varying state of charge (SOC). Aged cells with 0% SOC showed a right-shifted force–displacement curve and a 29% lower maximum force compared to fresh cells. Fully charged, aged cells reached a similar maximum force to fresh cells, but faster temperature increase and higher temperature peaks after internal short circuit. Inductively coupled plasma optical emission spectrometry analyses confirmed an increased lithium content on the anode surface, which is indicated in literature as a reason for the increased exothermic reaction of the aged cells. The results indicate a higher safety risk for the aged investigated pouch cells under mechanical loads based on their changed mechanical properties and thermal runaway behavior.

Light-stimulated artificial photonic synapses based on solution-processed In-Sn-Zn-O transistors for neuromorphic applications

Artificial photonic synapse devices (PSDs) hold great promise for the realization of next-generation artificial vision systems and processing units through a synergistic combination of brain-inspired neuromorphic computing and high levels of parallelism. Here, we demonstrate artificial PSDs based on solution-processed In-Sn-Zn-O (indium-tin-zinc oxide, ITZO) thin films capable of mimicking various neuromorphic functions. In particular, a transistor structure was adopted for PSDs to enable a facile control of the photo-response characteristics by gate biasing. With optimized gate bias condition, enhanced electrical conductance modulation was possible which can improve the energy efficiency of PSDs. In addition, we investigated the dependency of photo-response characteristics on light pulse waveforms to find out the correlation between various pulse parameters and the photo-current generation. Based on these findings, we demonstrated the emulation of associative learning which is one of the important cognitive functions of the brain. Moreover, to verify the translation of optically derived synaptic behaviors of ITZO PSDs into artificial neuromorphic computing, pattern recognition of handwritten digit patterns was demonstrated showing an accuracy up to 90.3%.

Blood Pressure Regulation by the Carotid Sinus Nerve: Clinical Implications for Carotid Body Neuromodulation.

Chronic carotid sinus nerve (CSN) electrical modulation through kilohertz frequency alternating current improves metabolic control in rat models of type 2 diabetes, underpinning the potential of bioelectronic modulation of the CSN as a therapeutic modality for metabolic diseases in humans. The CSN carries sensory information from the carotid bodies, peripheral chemoreceptor organs that respond to changes in blood biochemical modifications such as hypoxia, hypercapnia, acidosis, and hyperinsulinemia. In addition, the CSN also delivers information from carotid sinus baroreceptors—mechanoreceptor sensory neurons directly involved in the control of blood pressure—to the central nervous system. The interaction between these powerful reflex systems—chemoreflex and baroreflex—whose sensory receptors are in anatomical proximity, may be regarded as a drawback to the development of selective bioelectronic tools to modulate the CSN. Herein we aimed to disclose CSN influence on cardiovascular regulation, particularly under hypoxic conditions, and we tested the hypothesis that neuromodulation of the CSN, either by electrical stimuli or surgical means, does not significantly impact blood pressure. Experiments were performed in Wistar rats aged 10–12 weeks. No significant effects of acute hypoxia were observed in systolic or diastolic blood pressure or heart rate although there was a significant activation of the cardiac sympathetic nervous system. We conclude that chemoreceptor activation by hypoxia leads to an expected increase in sympathetic activity accompanied by compensatory regional mechanisms that assure blood flow to regional beds and maintenance of hemodynamic homeostasis. Upon surgical denervation or electrical block of the CSN, the increase in cardiac sympathetic nervous system activity in response to hypoxia was lost, and there were no significant changes in blood pressure in comparison to control animals. We conclude that the responses to hypoxia and vasomotor control short-term regulation of blood pressure are dissociated in terms of hypoxic response but integrated to generate an effector response to a given change in arterial pressure.

Electrical Impedance of Surface Modified Porous Titanium Implants with Femtosecond Laser.

The chemical composition and surface topography of titanium implants are essential to improve implant osseointegration. The present work studies a non-invasive alternative of electrical impedance spectroscopy for the characterization of the macroporosity inherent to the manufacturing process and the effect of the surface treatment with femtosecond laser of titanium discs. Osteoblasts cell culture growths on the titanium surfaces of the laser-treated discs were also studied with this method. The measurements obtained showed that the femtosecond laser treatment of the samples and cell culture produced a significant increase (around 50%) in the absolute value of the electrical impedance module, which could be characterized in a wide range of frequencies (being more relevant at 500 MHz). Results have revealed the potential of this measurement technique, in terms of advantages, in comparison to tiresome and expensive techniques, allowing semi-quantitatively relating impedance measurements to porosity content, as well as detecting the effect of surface modification, generated by laser treatment and cell culture.

Efficient silicon and side-cladding waveguide modulator with electro-optic polymer.

Efficient electro-optic (EO) modulation can be generated in the hybrid silicon modulator with EO polymer in the form of an in-plane coplanar waveguide and electrode structure. Strong confinement of the optical field in the hybrid structure is critical to performing efficient electric poling and modulation of the EO polymer. The waveguide consists of silica-based side claddings and an EO core for increasing the integral of the optical field and the overlap interaction between the optical field and the modulated electric field within the EO polymer. We discuss in detail the volume resistivity dependence of the efficiency of electric poling and modulation for various side-cladding materials. In a Mach-Zehnder interferometer modulator, the measured half-wave-voltage length product (VπL) is 1.9 V·cm at an optical communication wavelength of 1,550 nm under the TE optical mode operation. The high-speed signaling of the device is demonstrated by generating on-off-keying transmission at signal rates up to 52 Gbit/s with a Q factor of 6.1 at a drive voltage of 2.0 Vpp.

Electrical property modulation of Au/Ba0.6Sr0.4TiO3/La0.7Sr0.3MnO3 structure by continuous composition spread Mn doping

Composition spread Mn-doped Ba0.6Sr0.4Ti1-xMnxO3 (BSTMx, 0 ≤x ≤ 0.05) thin films were prepared on La0.7Sr0.3MnO3/SrTiO3 (LSMO/STO) layer by combinatorial pulsed laser deposition. When x is less than 3.3%, the BSTMx films are single phase according to X-ray diffraction data, and the Au/BSTMx/LSMO structure presents asymmetric transport properties. The asymmetry of the transport property gets weak with increasing Mn doping concentration. The reverse-bias current density of the Au/BSTMx/LSMO structure remains at a low value of 10−7 A/cm2, and the forward-bias current density reduces rapidly with the ascending doping content (x ≤ 1.8%). Further increasing the Mn content, the differences between the positive and reverse current densities become smaller, and almost vanish when the Mn content is greater than 3.8%, indicating the disappearance of the asymmetry of the transport property. The effects of the LSMO electrode, Au/BSTMx Schottky junction, BSTMx thin film, and BSTMx/LSMO interface on the whole electrical transport properties are discussed by virtue of the experimental and fitted impedance spectrums. Our results are helpful for insight into the doping mechanisms in perovskite oxides.