Ion-Conducting Non-Flammable Liquid Crystal–Polymer Composites for High-Frequency Soft Actuators

High-frequency actuators are reported based on non-flammable lithium-ion conducting phosphate liquid crystal–polymer composite electrolytes, which exhibit a bending response at frequencies up to 80 Hz under an AC voltage of 2 V, owing to its high ionic conductivity reaching 10⁻⁴ S cm⁻¹ at room temperature. An equimolar complex of a phosphate-containing mesogenic molecule and lithium bis(trifluoromethylsulfonyl)imide through the ion-dipole interactions induced a room-temperature smectic A liquid-crystalline (LC) phase forming 2D ion-transport pathways comprising the 2D array of the phosphate moieties. A blend of 80 wt% LC electrolyte and 20 wt% polymers (poly(vinyl chloride) and poly(vinylidene fluoride-co-hexafluoropropylene)) formed a flexible, mechanically robust LC–polymer composite film. Scanning electron microscopy and white light interference microscopy revealed a microphase-segregated structure consisting of a continuous LC phase and a porous polymer matrix. In addition, the continuity of porous structure across the film is confirmed by permeation experiments of solvents thorough the membrane with a homemade filter in a dead-end filtration mode. The LC–polymer composite film sandwiched between two poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) electrodes is found to simultaneously exhibit high bending strain (0.63%) and high output force (0.35 mN), owing to the high ion migration into the composite electrolyte and electrode.     

Gallium-Based Liquid–Solid Biphasic Conductors for Soft Electronics

Soft and stretchable electronics have diverse applications in the fields of compliant bioelectronics, textile-integrated wearables, novel forms of mechanical sensors, electronics skins, and soft robotics. In recent years, multiple material architectures have been proposed for highly deformable circuits that can undergo large tensile strains without losing electronic functionality. Among them, gallium-based liquid metals benefit from fluidic deformability, high electrical conductivity, and self-healing property. However, their deposition and patterning is challenging. Biphasic material architectures are recently proposed as a method to address this problem, by combining advantages of solid-phase materials and composites, with liquid deformability and self-healing of liquid phase conductors, thus moving toward scalable fabrication of reliable stretchable circuits. This article reviews recent biphasic conductor architectures that combine gallium-based liquid-phase conductors, with solid-phase particles and polymers, and their application in fabrication of soft electronic systems. In particular, various material combinations for the solid and liquid phases in the biphasic conductor, as well as methods used to print and pattern biphasic conductive compounds, are discussed. Finally, some applications that benefit from biphasic architectures are reviewed.     

Polymer Chemistry for Haptics,Soft Robotics,and Human–Machine Interfaces

Progress in the field of soft devices—that is, the types of haptic, robotic, and human-machine interfaces (HRHMIs) in which elastomers play a key role—has its basis in the science of polymeric materials and chemical synthesis. However, in examining the literature, it is found that most developments have been enabled by off-the-shelf materials used either alone or as components of physical blends and composites. A greater awareness of the methods of synthetic chemistry will accelerate the capabilities of HRHMIs. Conversely, an awareness of the applications sought by engineers working in this area may spark the development of new molecular designs and synthetic methodologies by chemists. Several applications of active, stimuli-responsive polymers, which have demonstrated or shown potential use in HRHMIs are highlighted. These materials share the fact that they are products of state-of-the-art synthetic techniques. The progress report is thus organized by the chemistry by which the materials are synthesized, including controlled radical polymerization, metal-mediated cross-coupling polymerization, ring-opening polymerization, various strategies for crosslinking, and hybrid approaches. These methods can afford polymers with multiple properties (i.e., conductivity, stimuli-responsiveness, self-healing, and degradable abilities, biocompatibility, adhesiveness, and mechanical robustness) that are of great interest to scientists and engineers concerned with soft devices for human interaction.     

Modern Laboratory-Based Education for Power Electronics and Electric Machines

Students explore the class D audio amplifier by using a CD player to supply music as the modulating function and a moving coil speaker as the load. The quality is much higher than that attainable with the FET box and emphasizes all attributes of PWM as a high-quality power conversion control process.     

Modern Laboratory-Based Education for Power Electronics and Electric Machines

Power electronics and motor drives are appropriate subjects for an advanced undergraduate or beginning graduate course. The subject is largely application-driven but draws from a broad knowledge base including basic circuits and electronics, control systems, power systems, and semiconductor devices. For many students, a power electronics laboratory can provide an early experience in synthesis, requiring them to use knowledge across their full curriculum with close attention to detail.     

Modern Laboratory-Based Education for Power Electronics and Electric Machines

C. Example Experiment： AutomaticBattery Charger The flexibility of the SCR blue box allows closed-loop applications. To demonstrate feedback control, a simple 24-V battery charger was implemented. The circuit is a simple 3-phase half Bridge rectifier connected to the battery by an inductor. A simple control circuit monitors the battery voltage. Fig. 5 shows typical test waveforms for the circuit. When the prescribed battery voltage is reached, the control signal goes high and charging is stopped. Hysteresis ensures that charging will not resume until the battery voltage dips sufficiently.     

Solid–Liquid Composites for Soft Multifunctional Materials

Soft materials with a liquid component are an emerging paradigm in materials design. The incorporation of a liquid phase, such as water, liquid metals, or complex fluids, into solid materials imparts unique properties and characteristics that emerge as a result of the dramatically different properties of the liquid and solid. Especially in recent years, this has led to the development and study of a range of novel materials with new functional responses, with applications in topics including soft electronics, soft robotics, 3D printing, wet granular systems and even in cell biology. Here a review of solid–liquid composites, broadly defined as a material system with at least one, phase-separated liquid component, is provided and discussed their morphology and fabrication approaches, their emergent mechanical properties and functional response, and the broad range of their applications.     

Techniques and Apparatus for Measuring Rotational Core Losses of Soft Magnetic Materials

In many situations such as the cores of a rotating electrical machine and the T joints of a multiphase transformer, the local flux density varies with time in terms of both magnitude and direction, i.e. the flux density vector is rotating. Therefore, the magnetic properties of the core materials under the rotating flux density vector excitation should be properly measured, modeled and applied in the design and analysis of these electromagnetic devices. This paper presents an extensive review on the development of techniques and apparatus for measuring the rotational core losses of soft magnetic materials based on the experiences of various researchers in the last hundred years.     

Cobalt–Polymer Nanocomposite Dielectrics for Miniaturized Antennas

Cobalt–polymer magnetic nanocomposites have been synthesized and characterized for their microstructure and properties such as permeability, permittivity, dielectric and magnetic losses from 100 MHz to 2 GHz to study their suitability as antenna dielectrics. Oxide-passivated cobalt nanoparticles were dispersed in epoxies to form nanocomposite toroids and thin-film resonator structures on organic substrates. Permeabilities of 2.10 and 2.65 were measured up to 500 MHz, respectively, with 25-nm to 50-nm and 5-nm nanoparticles in the nanocomposites. The loss tangent ranged from 0.02 to 0.04 at these frequencies. A combination of stable permeability of ～2 at 1 GHz to 2 GHz and permittivity of ～7 was achieved with nanocomposites having 5-nm nanoparticles. The magnetic nanomaterials described in this paper can overcome the limitations from domain-wall and eddy-current losses in microscale metal–polymer composites, leading to enhanced frequency stability. The paper also demonstrates integration of metal–polymer nanocomposites as thin-film build-up layers with two-metal-layer structures on organic substrates.     

Structural,Electrical, and Magnetic Properties of Ferrite–Polymer Composites

Six samples consisting of polypyrrole (PPy), pure NiFe₂O₄ ferrite, and their composites at ratio of 1:4 (PF1), 1:2 (PF2), 3:4 (PF3), and 1:1 (PF4) have been prepared by a coprecipitation method and their structural, electrical, dielectric, and magnetic properties measured experimentally. The direct-current (DC) resistivity was enhanced with increasing ferrite content, while the dielectric constant and loss decreased. The magnetic properties of all the composites and the ferrite revealed a narrow loop, confirming their soft nature. The saturation magnetization, remanence, and coercivity values increased with increasing ferrite content. The obtained parameter values suggest that such materials might be suitable for use in high-frequency applications.     

Dielectric Loss in the Polymer–Semiconductor–Composite System with Allowance for Nonlinear Dependence of Electric Characteristics on Temperature Resulting from Microwave Irradiation

An electrothermophysical model that makes it possible to estimate dielectric loss and predict energy-dissipation characteristics in dielectric materials is proposed. Heat and mass transfer is numerically simulated in the presence of microwave irradiation of an electronic device (polymer–semiconductor–composite system) with allowance for local heat liberation and nonlinear dependence of dielectric characteristics on temperature. Distributions of permittivity and tangent of dielectric loss with respect to thickness of the system under study are presented for a typical interval of variations in the parameters of electromagnetic radiation. It is demonstrated that dissipation of electromagnetic energy leads to a significant (by a factor of 1.6) increase in the tangent of dielectric loss.     

Mechanics property Study for Interface Bim Composite of Zinc Alloy ZAS35/Carbon Steel

1 .Introduction　　Thezinc -alluminiumalloyhasagoodmechanicsproperty ,anantifrictionandawearingresis tance.Itcanbeusedunderthecertainworkingconditionandisadesiredsubstitutematerialoftinbronzebecauseitsrawmaterialischeaper.Inordertoreducethecostanddecreasethematerialquanti tyofalloyZAS3 5,themanufactureofbimetalcompositeisaneweffectivemethodwhenthepartialal loyZAS3 5issubstitutedbytakingthecheapcarbonsteelasabase.　　Thelasermoireinterferometryisanon -contactaccuratelyopticaltesttechnologywi…     

Molecular-level Designed Polymer Electrolyte for High-Voltage Lithium–Metal Solid-State Batteries

In solid polymer electrolytes (SPEs) based Li–metal batteries, the inhomogeneous migration of dual-ion in the cell results in large concentration polarization and reduces interfacial stability during cycling. A special molecular-level designed polymer electrolyte (MDPE) is proposed by embedding a special functional group (4-vinylbenzotrifluoride) in the polycarbonate base. In MDPE, the polymer matrix obtained by copolymerization of vinylidene carbonate and 4-vinylbenzotrifluoride is coupled with the anion of lithium-salt by hydrogen bonding and the “σ-hole” effect of the C F bond. This intermolecular interaction limits the migration of the anion and increases the ionic transfer number of MDPE (t_Li⁺ = 0.76). The mechanisms of the enhanced t_Li⁺ of MDPE are profoundly understood by conducting first-principles density functional theory calculation. Furthermore, MDPE has an electrochemical stability window (4.9 V) and excellent electrochemical stability with Li–metal due to the CO group and trifluoromethylbenzene (ph-CF₃) of the polymer matrix. Benefited from these merits, LiNi_0.8Co_0.1Mn_0.1O₂-based solid-state cells with the MDPE as both the electrolyte host and electrode binder exhibit good rate and cycling performance. This study demonstrates that polymer electrolytes designed at the molecular level can provide a broader platform for the high-performance design needs of lithium batteries.     

Universal Design Rules for Flory–Huggins Polymer Photonic Vapor Sensors

Multilayered photonic sensors that rely on polymer-solvent Flory–Huggins interactions are drawing increasing interest owing to their broad-band selectivity, even among mixtures, without the need for chemical targeting. Moreover, these sensors provide simple colorimetric responses, and easy, quick fabrication both on laboratory and industrial scales. However, complex optical responses and slow response times are limiting their development. In this work, the behavior of different photonic sensor architectures is analyzed to speed up response time and define a strategy to simplify their spectral behavior. To this end, the effect of interfaces, materials order, and thickness on the diffusion kinetics of a single reference analyte in the multilayered sensors is studied to design the optimal structure.     

Liquid Alloy Enabled Solid-State Batteries for Conformal Electrode–Electrolyte Interfaces

Recent research efforts on solid-state alkali-metal batteries are pushing the limit of energy density to a higher level. However, the development of solid-state batteries is still hindered by many intrinsic limitations, among which the incompatibility between the solid electrolyte and the metal anode is a critical issue attracting massive research attention. A Na–K liquid alloy electrode is designed to form a conformal electrode–electrolyte interface with a solid electrolyte. Much enhanced electrode–electrolyte interfacial contact electrically and physically is observed with liquid metal anodes than solid alkali metals on solid electrolytes. Symmetric cells of the liquid metal electrolytes show much lower overpotential as well as better cyclability than the alkali-metal electrodes. Excellent cyclability over 500 cycles with reasonable capacity decay and good rate performance of full cells with the sodium rhodizonate and a ferricyanide potassium-ion cathode are both achieved. By adjusting salt and filler species in the polymer electrolyte, the wettability of liquid metal on the electrolyte can be further improved, and the raised ionic conductivity can further improve the battery performance of such a design.     

Recent Progress of Flexible Photodetectors Based on Low-Dimensional II–VI Semiconductors and Their Application in Wearable Electronics

Flexible photodetectors exhibit many advantages such as a good bendability, foldability, and even stretchability as well as weight light, which have triggered a widely concerned in wearable electronics including wearable monitoring, wearable image sensing, self-powered integrated electronics, etc. Recently, various II–VI semiconductor nanostructures have become promising candidates in flexible photodetectors due to their unique characteristics, such as direct bandgap semiconductors, excellent optical and electric properties, high quantum efficiency, and inherent mechanical flexibility. Herein, the most recent progress on low-dimensional (0D, 1D, 2D, and related heterostructures) II–VI semiconductors based flexible photodetectors and their application in wearable electronic is reviewed. First, a brief introduction of the main sensing mechanisms and key figures of merits for photodetectors is presented. Then, the recent progresses on flexible photodetectors are provided, in which the functional materials synthesis methods are also discussed. More importantly, the applications of the flexible photodetectors are summarized, including wearable monitoring sensors, image sensors, and self-powered integrated wearable electronics. Finally, the challenges and the future research direction of the flexible photodetectors are discussed, meanwhile the outlook for the development of flexible photodetectors in the future integration of wearable electronic is also provided.     

Using Analog Predistortion for Linearizing Class A–C Power Amplifiers

An analog 5th order, complex-valued polynomial predistortion IC has been built to linearize the behavior of RF power amplifiers. The predistorter can be used either at baseband or low IF frequencies and it was tested using a simple IF amplifier that could be biased to operate in classes A, AB, B and C. Intermodulation products can be reduced by 20 to 30 dB in classes A and AB over a bandwidth of several MHz. In classes B and C the shape of nonlinearity is such that a low-order polynomial predistortion function is not sufficient for linearizing them.     

Technology for Producing Schottky Contacts Based on an IrSi–Si Composite

Russian Microelectronics - In this study, in order to obtain Schottky contacts based on an IrSi–Si composite, n- and p-type silicon wafers doped, respectively, with boron and phosphorus with...     

MoxWx–1S2 Nanotubes for Advanced Field Emission Application

Transition metal dichalcogenide (TMDC) nanotubes complement the field of low-dimensional materials with their quasi-1D morphology and a wide set of intriguing properties. By introducing different transition metals into the crystal structure, their properties can be tailored for specific purpose and applications. Herein, the characterization and a subsequent preparation of single-nanotube field emission devices of Mo_xW_x-1S₂ nanotubes prepared via the chemical vapor transport reaction is presented. Energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray diffraction  indicate that the molybdenum and tungsten atoms are randomly distributed within the crystal structure and that the material is highly crystalline. High resolution transmission electron microscopy  and electron diffraction (ED) patterns further corroborate these findings. A detailed analysis of the ED patterns from an eight-layer nanotube reveal that the nanotubes grow in the 2H structure, with each shell consists of one bilayer. The work function of the nanotubes is comparable to that of pure MoS₂ and lower of pure WS₂ NTs, making them ideal candidates for field emission applications. Two devices with different geometrical setup are prepared and tested as field emitters, showing promising results for single nanotube field emission applications.