Direct Electrical Control Research Articles

Electromechanical model for electro-ribbon actuators

The emerging field of soft actuators is anticipated to significantly impact areas that require enhanced adaptability and safe interaction including biomedical robotics. The electro-ribbon actuator, characterised by its compliance, lightweight, high efficiency, extensive scalability, and direct electrical control, emerges as a promising candidate for the future of soft robotics. Although the electro-ribbon actuator demonstrates efficient performance, a comprehensive understanding of its fundamental mechanics remains unexplored. To explain the impact of the actuation mechanism and the design parameters on the performance of the actuator, we have developed a mathematical model grounded in large deformation beam theory. As evidenced by our experimental results, this model accurately predicts the quasi-static behaviour of electro-ribbon actuators. Utilising this model, we establish a strategic road map for the development of electro-ribbon actuators with a range of passive stiffness tailored to achieve required output forces and displacement. This study provides a pivotal foundation for the model-based control and design optimisation of electro-ribbon actuators.

Direct electric current control of hyperchaotic packets of dissipative dark envelope solitons in a magnonic crystal active ring resonator

Direct electric current control of hyperchaotic packets of dissipative dark envelope solitons in a magnonic crystal active ring resonator

Overcoming Barriers in Photodynamic Therapy Harnessing Nanogenerators Strategies.

Photodynamic therapy (PDT) represents a targeted approach for cancer treatment that employs light and photosensitizers (PSs) to induce the generation of reactive oxygen species (ROS). However, PDT faces obstacles including insufficient PS localization, limited light penetration, and treatment resistance. A potential solution lies in nanogenerators (NGs), which function as self-powered systems capable of generating electrical energy. Recent progress in piezoelectric and triboelectric NGs showcases promising applications in cancer research and drug delivery. Integration of NGs with PDT holds the promise of enhancing treatment efficacy by ensuring sustained PS illumination, enabling direct electrical control of cancer cells, and facilitating improved drug administration. This comprehensive review aims to augment our comprehension of PDT principles, explore associated challenges, and underscore the transformative capacity of NGs in conjunction with PDT. By harnessing NG technology alongside PDT, significant advancement in cancer treatment can be realized. Herein, we present the principal findings and conclusions of this study, offering valuable insights into the integration of NGs to overcome barriers in PDT.

Electric control of spin transitions at the atomic scale

Electric control of spins has been a longstanding goal in the field of solid state physics due to the potential for increased efficiency in information processing. This efficiency can be optimized by transferring spintronics to the atomic scale. We present electric control of spin resonance transitions in single TiH molecules by employing electron spin resonance scanning tunneling microscopy (ESR-STM). We find strong bias voltage dependent shifts in the ESR signal of about ten times its line width. We attribute this to the electric field in the tunnel junction, which induces a displacement of the spin system changing the g-factor and the effective magnetic field of the tip. We demonstrate direct electric control of the spin transitions in coupled TiH dimers. Our findings open up new avenues for fast coherent control of coupled spin systems and expands on the understanding of spin electric coupling.

Integrated Soft Porosity and Electrical Properties of Conductive‐on‐Insulating Metal‐Organic Framework Nanocrystals

AbstractA one‐stone, two‐bird method to integrate the soft porosity and electrical properties of distinct metal–organic frameworks (MOFs) into a single material involves the design of conductive‐on‐insulating MOF (cMOF‐on‐iMOF) heterostructures that allow for direct electrical control. Herein, we report the synthesis of cMOF‐on‐iMOF heterostructures using a seeded layer‐by‐layer method, in which the sorptive iMOF core is combined with chemiresistive cMOF shells. The resulting cMOF‐on‐iMOF heterostructures exhibit enhanced selective sorption of CO2 compared to the pristine iMOF (298 K, 1 bar, S from 15.4 of ZIF‐7 to 43.2–152.8). This enhancement is attributed to the porous interface formed by the hybridization of both frameworks at the molecular level. Furthermore, owing to the flexible structure of the iMOF core, the cMOF‐on‐iMOF heterostructures with semiconductive soft porous interfaces demonstrated high flexibility in sensing and electrical “shape memory” toward acetone and CO2. This behavior was observed through the guest‐induced structural changes of the iMOF core, as revealed by the operando synchrotron grazing incidence wide‐angle X‐ray scattering measurements.

Integrated Soft Porosity and Electrical Properties of Conductive-on-Insulating Metal-Organic Framework Nanocrystals.

A one-stone, two-bird method to integrate the soft porosity and electrical properties of distinct metal-organic frameworks (MOFs) into a single material involves the design of conductive-on-insulating MOF (cMOF-on-iMOF) heterostructures that allow for direct electrical control. Herein, we report the synthesis of cMOF-on-iMOF heterostructures using a seeded layer-by-layer method, in which the sorptive iMOF core is combined with chemiresistive cMOF shells. The resulting cMOF-on-iMOF heterostructures exhibit enhanced selective sorption of CO2 compared to the pristine iMOF (298 K, 1 bar, S from 15.4 of ZIF-7 to 43.2-152.8). This enhancement is attributed to the porous interface formed by the hybridization of both frameworks at the molecular level. Furthermore, owing to the flexible structure of the iMOF core, the cMOF-on-iMOF heterostructures with semiconductive soft porous interfaces demonstrated high flexibility in sensing and electrical "shape memory" toward acetone and CO2 . This behavior was observed through the guest-induced structural changes of the iMOF core, as revealed by the operando synchrotron grazing incidence wide-angle X-ray scattering measurements.

Non-Aqueous Electrodeposition of 2-D Layered MoS2 from a Tailored Single Source Precursor

2-D layered transition metal dichalcogenide (TMDC) materials have been intensively investigated in the past few years because of their remarkable properties such as semiconductivity, strong spin splitting, tunable band gaps etc.1, that make them ideal candidates for optoelectronic and electronics applications2-3. The flagship of TMDCs is MoS2 due to its unique electronic, optical and other features, including size-dependent band gap4. A number of techniques have been recently established for obtaining ultra-thin MoS2 films, however, improved processing methods for scalable production of the films are highly desirable. At present, the TMDCs are typically deposited by vapour deposition methods such as magnetron sputtering5 and chemical vapour deposition (CVD)6. However, these techniques are expensive and mostly involve constraining deposition conditions such as high temperature and high vacuum. On the other hand, electrodeposition, being a low cost alternative technique, has a number of key advantages that make it an interesting materials deposition process. First, electrodeposition is a ‘bottom-up’ growth technique where conformal deposition occurs via atom by atom growth over the exposed electrode surface. Secondly, electrodeposition is, in general, a low temperature technique that is mostly performed in ambient conditions and it is very efficient in use of materials. The deposition only occurs in areas defined by the electrical contact and is under direct electrical control during the growth. Thanks to these advantages, electrodeposition finds use in key high tech areas such as deposition of magnetic read-write heads and the copper interconnects in microprocessor chips7. Water is the most commonly employed solvent in electrodeposition, however, its narrow potential window induces limitations in depositing metals/compounds requiring large negative overpotentials, and also the water reduction and H2 evolution reactions introduce additional complexity to the experiments. Here, we employ an electrolyte system based on tetrabutylammonium tetrathiomolybdate as a single source precursor for MoS2, with compatible tetrabutylammonium halide supporting electrolyte and trimethylammonium chloride as proton source in a weakly coordinating, non-aqueous solvent, which provides the ability to deposit 2-D TMDC films with desired structures and properties. In the present study, we report on the electrodeposition of 2-D MoS2 films from dichloromethane. The electrodeposited MoS2 films were characterized by variety of methods including Scanning Electron Microscopy (SEM), Raman spectroscopy and X-ray diffraction. A detailed investigation on the electrochemical growth mechanism of MoS2 has been conducted using Electrochemical Quartz Crystal Microbalance (EQCM). The influence of various growth parameters on the structure and composition of the thin films will also be discussed. This work was funded by EPSRC grant reference EP/P025137/1. [1] Nature Chemistry, 2013. 5: 263. [2] Chemical Society Reviews, 2015. 44(21): 7715-7736. [3] Chemical Society Reviews, 2015. 44(9): 2664-2680. [4] Chemical Society Reviews, 2018. 47(16): 6101-6127. [5] Nanoscale, 2015. 7(6): 2497-2503. [6] Chemical Society Reviews, 2015. 44(9): 2744-2756. [7] IBM Journal of Research and Development, 1998. 42(5): 567-574.

An analytical model for the design of Peano-HASEL actuators with drastically improved performance

The emerging field of soft robotics promises applications in areas such as human–machineinteraction, industrial automation, and biomedical devices. Electrohydraulic Peano-HASEL (hydraulically amplified self-healing electrostatic) actuators feature muscle-like linear contraction on activation, fast operation, and direct electrical control, which makes them a versatile actuator for soft robotics. To better understand the impact of geometry and materials on actuator performance, we develop an analytical model – based on minimizing the total energy of the actuator system – that accurately predicts the quasi-static behavior of the actuators without relying on fitting parameters. We present extensive experimental validation of this model for actuators with varying geometries, as well as actuators made from shell materials with different electrical and mechanical properties. Using these results, we identify design rules for the development of actuators with tunable force-strain characteristics. As a key result of this paper, we lay out a roadmap for creating Peano-HASELs with drastically improved specific energies. Specifically, we identify a combination of pouch geometry and an existing high-performance shell material for which the model predicts actuators that achieve a specific energy of over 10,000 J/kg, far exceeding maximum values reported for natural muscle (∼ 40 J/kg).

Direct Conversion of Electric Input Signals into Fluidic Output

Background: Fluid flow control techniques gained many advantages when, under the newly coined name fluidics, were found ways of operating without moving or deformed mechanical components. In particular, it became possible to handle fluid motion at very small scales and/or high frequencies. The control signals upon which this motion depends, are often produced by microelectronic devices, also operating without moving components. The transducers from electric to fluidic signals and actions, especially if the latter operate with air, however, cannot so far avoid two-stage indirect conversion, with intermediate mechanical motions of components which are difficult to manufacture, have limited life, and are slow due to mechanical parts inertia. Objective: Development of transducer for direct electric control of flow of air, circumventing the fact that air is electrically neutral and therefore not influenced by voltage or electric current and therefore not influenced by applied voltage or electric current. Methods: The solution is achieved by using ionic wind generated by non-thermal plasma discharge inside cavities the configuration of which correspond to a fluidic bistable diverter amplifier. By using the Coanda effect, the jet of air remains alternatively attached to one of the two attachment walls so that the ionic wind only briefly switches the jet between them. Results: Laboratory models of an electric-to-fluidic transducer were demonstrated to operate reliably with the input electric switching signal voltage increased in a transformer (inexpensive because mass produced for other purposes). The absence of inertia of mechanical components made it possible to operate at quite high switching frequency (above 100 Hz). Conclusion: Patent covering various alternative transducer configurations based on the ionic wind idea was recently grated to the present authors - unfortunately valid only within the boundaries of the Czech Republic. Keywords: Fluidics, plasma, ionic wind, dielectric barrier, fluidic amplifier, Coanda effect.

Full Electric Control of Exchange Bias at Room Temperature by Resistive Switching.

Electric control of exchange bias (EB) is of vital importance in energy-efficient spintronics. Although many attempts have been made during the past decade, each has its own limitations for operation and thus falls short of full direct and reversible electrical control of EB at room temperature. Here, a novel approach is proposed by virtue of unipolar resistive switching to accomplish this task in a Si/SiO2 /Pt/Co/NiO/Pt device. By applying certain voltages, the device displays obvious EB in the high-resistance-state while negligible EB in the low-resistance state. Conductive filaments forming in the NiO layer and rupturing near the Co-NiO interface are considered to play dominant roles in determining the combined resistive switching and EB phenomena. This work paves a new way for designing multifunctional and nonvolatile magnetoelectric random access memory devices.

Multiple p-n junction subwavelength gratings for transmission-mode electro-optic modulators

We propose a free-space electro-optic transmission modulator based on multiple p-n-junction semiconductor subwavelength gratings. The proposed device operates with a high-Q guided-mode resonance undergoing electro-optic resonance shift due to direct electrical control. Using rigorous electrical and optical modeling methods, we theoretically demonstrate a modulation depth of 84%, on-state efficiency 85%, and on-off extinction ratio of 19 dB at 1,550 nm wavelength under electrical control signals within a favorably low bias voltage range from −4 V to +1 V. This functionality operates in the transmission mode and sustainable in the high-speed operation regime up to a 10-GHz-scale modulation bandwidth in principle. The theoretical performance prediction is remarkably advantageous over plasmonic tunable metasurfaces in the power-efficiency and absolute modulation-depth aspects. Therefore, further experimental study is of great interest for creating practical-level metasurface components in various application areas.

Efficient electrical control of thin-film black phosphorus bandgap

Recently rediscovered black phosphorus is a layered semiconductor with promising electronic and photonic properties. Dynamic control of its bandgap can allow for the exploration of new physical phenomena. However, theoretical investigations and photoemission spectroscopy experiments indicate that in its few-layer form, an exceedingly large electric field in the order of several volts per nanometre is required to effectively tune its bandgap, making the direct electrical control unfeasible. Here we reveal the unique thickness-dependent bandgap tuning properties in intrinsic black phosphorus, arising from the strong interlayer electronic-state coupling. Furthermore, leveraging a 10 nm-thick black phosphorus, we continuously tune its bandgap from ∼300 to below 50 meV, using a moderate displacement field up to 1.1 V nm−1. Such dynamic tuning of bandgap may not only extend the operational wavelength range of tunable black phosphorus photonic devices, but also pave the way for the investigation of electrically tunable topological insulators and semimetals.

Direct electrical control of IgG conformation and functional activity at surfaces.

We have devised a supramolecular edifice involving His-tagged protein A and antibodies to yield surface immobilized, uniformly oriented, IgG-type, antibody layers with Fab fragments exposed off an electrode surface. We demonstrate here that we can affect the conformation of IgGs, likely pushing/pulling electrostatically Fab fragments towards/from the electrode surface. A potential difference between electrode and solution acts on IgGs’ charged aminoacids modulating the accessibility of the specific recognition regions of Fab fragments by antigens in solution. Consequently, antibody-antigen affinity is affected by the sign of the applied potential: a positive potential enables an effective capture of antigens; a negative one pulls the fragments towards the electrode, where steric hindrance caused by neighboring molecules largely hampers the capture of antigens. Different experimental techniques (electrochemical quartz crystal microbalance, electrochemical impedance spectroscopy, fluorescence confocal microscopy and electrochemical atomic force spectroscopy) were used to evaluate binding kinetics, surface coverage, effect of the applied electric field on IgGs, and role of charged residues on the phenomenon described. These findings expand the concept of electrical control of biological reactions and can be used to gate electrically specific recognition reactions with impact in biosensors, bioactuators, smart biodevices, nanomedicine, and fundamental studies related to chemical reaction kinetics.

Quantum dot materials for terahertz generation applications

AbstractCompact and tunable semiconductor terahertz sources providing direct electrical control, efficient operation at room temperatures and device integration opportunities are of great interest at the present time. One of the most well‐established techniques for terahertz generation utilises photoconductive antennas driven by ultrafast pulsed or dual‐wavelength continuous wave laser systems, though some limitations, such as confined optical wavelength pumping range and thermal breakdown, still exist. The use of quantum dot‐based semiconductor materials, having unique carrier dynamics and material properties, can help to overcome limitations and enable efficient optical‐to‐terahertz signal conversion at room temperatures. Here we discuss the construction of novel and versatile terahertz transceiver systems based on quantum dot semiconductor devices. Configurable, energy‐dependent optical and electronic characteristics of quantum‐dot‐based semiconductors are described, and the resonant response to optical pump wavelength is revealed. Terahertz signal generation and detection at energies that resonantly excite only the implanted quantum dots opens the potential for using compact quantum dot‐based semiconductor lasers as pump sources. Proof‐of‐concept experiments are demonstrated here that show quantum dot‐based samples to have higher optical pump damage thresholds and reduced carrier lifetime with increasing pump power. image

Electrical generation and control of the valley carriers in a monolayer transition metal dichalcogenide.

Electrically controlling the flow of charge carriers is the foundation of modern electronics. By accessing the extra spin degree of freedom (DOF) in electronics, spintronics allows for information processes such as magnetoresistive random-access memory. Recently, atomic membranes of transition metal dichalcogenides (TMDCs) were found to support unequal and distinguishable carrier distribution in different crystal momentum valleys. This valley polarization of carriers enables a new DOF for information processing. A variety of valleytronic devices such as valley filters and valves have been proposed, and optical valley excitation has been observed. However, to realize its potential in electronics it is necessary to electrically control the valley DOF, which has so far remained a significant challenge. Here, we experimentally demonstrate the electrical generation and control of valley polarization. This is achieved through spin injection via a diluted ferromagnetic semiconductor and measured through the helicity of the electroluminescence due to the spin-valley locking in TMDC monolayers. We also report a new scheme of electronic devices that combine both the spin and valley DOFs. Such direct electrical generation and control of valley carriers opens up new dimensions in utilizing both the spin and valley DOFs for next-generation electronics and computing.

Linkage Control Security Research of the Mechanical Smoke Exhaust System in Large Space Buildings

Abstract When the large space buildings are in the event of fire, the mechanical smoke exhaust system must start safely and reliably with the smoke spreading quickly. A former analysis to the linkage control of the mechanical smoke exhaust system showed that the control of exhaust fans is safe and reliable with multiple redundant control. but the control security of exhaust ports in the large space buildings is very poor. According to the recent research, reliability of the linkage control of exhaust ports set in large space areas is the key to improve the reliability of the exhaust system's linkage control in large space buildings. We should set on-site mechanical control devices, remote multiple manual direct control devices and on-site electric control switch devices for exhaust ports in large space buildings. And the linked switches of exhaust ports should also be able to multiple interlocks control the exhaust fans.

Bioinspired Electrochemically Tunable Block Copolymer Full Color Pixels

By controlling absorption, reflection, and body surface texture cephalopods display an incredible ability to manage and manipulate light – a goal of modern display technology. With these and several other aquatic species, tunable, structural color plays a fundamental role in creating vivid and eye-catching color, which is produced in part by using and modulating 1D reflectors known as iridophores. The color change of the light reflected from these tunable Bragg reflectors is accomplished by the local introduction of chemical neurotransmitters that either change the spacing between high refractive index platelets or change the thickness (and possibly the refractive index) of the platelets themselves. Efficient, refined mechanisms of visual communication and disruptive coloration – such as iridophores are key to cephalopod survival. The next generation of display materials could benefit from the lessons learned over millions of years of evolution in order to produce inexpensive, robust, low-energy, high-contrast displays. Here we present a bioinspired, electrochemically tunable, full-color pixel based on a self-assembling block copolymer (BCP). Imitating cephalopod reflectin proteins, which form layered, highly reflective structures, the lamellar structure of these BCPs exhibits a periodic refractive index. Such structures are commonly known as 1D photonic crystals and yield photonic stop bands which reflect incident electromagnetic radiation of a wavelength range dependent on the angle of incidence of light, the index of refraction of the respective layers, and their periodicity. Partial color tunability has been demonstrated in numerous photonic crystal systems which have been intensely investigated due to their inherent passive structural color which negates the need for light-absorbing color filters and backlights common in emissive technologies. A number of types of photonic crystals based on cholesteric liquid crystals, synthetic opals, and diffraction gratings have attained full color tunability using direct or indirect electrical control. Tailored absorption using electrochromic materials has also achieved full color tunability in recent years. Electrical control is highly sought after for display applications because of the ease with which it can supply a local stimulus. Previously, BCPs have been used as photonic crystals but with limited tunability arising from changes in temperature and homopolymer or solvent concentration. Recently we reported a highly tunable, structural-color reflector based on a hydrophilic/hydrophobic block copolymer (polystyreneb-poly(2-vinylpyridine)PS-P2VP) that achieved substantial tunability (over 575%) of the primary stop band from ultraviolet (350 nm) to near infrared wavelengths (1600 nm) by changing the concentration of salt in the solvent. Here we employ the same block copolymer to create our biomimetic, full-color pixel. The lamellar structure of this block copolymer and the behavior of the electrically stimulated hydrophilic gel block mimic the type of optical response of the reflectin proteins found in certain cephalopod species. These cephalopods have the ability to change the iridescent colors reflected from their skin in real time by the secretion of the common neuromodulator acetylcholine, which alters the periodic spacing of the lamellar iridophore structure. In our work, we couple the structure-forming ability of a block copolymer with an electrically induced chemical tunability of the spacing and refractive index of the gel layers to obtain a tunable, reflectin-like structure. Polyelectrolyte polymer gels are well known for their stimuli responsiveness and have been shown to react to electric fields and changes in pH caused by electric fields. By selecting a diblock copolymer that incorporates a glassy domain (polystyrene) to limit the gel forming domain (poly 2-vinylpyridine) to expansion only in the direction normal to the layers, we control the swelling behavior of the gel andmagnify the response of the periodic dielectric stack to external stimuli. We use a modest molecular weight (102 kg/mol–97 kg/mol), PS-P2VP block copolymer in combination with a simple electrochemical cell to produce red, green, and blue color through electrochemical stimulation. Our biomimetic color pixel is based on a simple electrochemical cell in which the local chemical environment at the electrode/electrolyte interface can be changed by applying sufficient voltage to induce electrochemical oxidation or reduction. Because polymeric gels can undergo significant shape change in response to changes in their chemical environments, this chemical stimulus at the electrode can have major effects on the swelling behavior of the gel, as is the case in color changing iridophores in nature. Fish such as the blue damselfish, neon tetra, and paradise whiptail all employ 1D photonic crystals

Field-Effect Modulation of Seebeck Coefficient in Single PbSe Nanowires

In this Letter, we present a novel strategy to control the thermoelectric properties of individual PbSe nanowires. Using a field-effect gated device, we were able to tune the Seebeck coefficient of single PbSe nanowires from 64 to 193 microV x K(-1). This direct electrical field control of sigma and S suggests a powerful strategy for optimizing ZT in thermoelectric devices. These results represent the first demonstration of field-effect modulation of the thermoelectric figure of merit in a single semiconductor nanowire. This novel strategy for thermoelectric property modulation could prove especially important in optimizing the thermoelectric properties of semiconductors where reproducible doping is difficult to achieve.

Mode-locked quantum-dot lasers

Semiconductor lasers are convenient and compact sources of light, offering highly efficient operation, direct electrical control and integration opportunities. In this review we describe how semiconductor quantum-dot structures can provide an efficient means of amplifying and generating ultrafast (of the order of 100 fs), high-power and low-noise optical pulses, with the potential to boost the repetition rate of the pulses to beyond 1 THz. Such device designs are opening up new possibilities in ultrafast science and technology.

Nervous control of ciliary beating by Cl-, Ca2+ and calmodulin inTritonia diomedea

In vertebrates, motile cilia line airways, oviducts and ventricles. Invertebrate cilia often control feeding, swimming and crawling, or gliding. Yet control and coordination of ciliary beating remains poorly understood. Evidence from the nudibranch mollusc, Tritonia diomedea, suggests that locomotory ciliated epithelial cells may be under direct electrical control. Here we report that depolarization of ciliated pedal epithelial (CPE) cells increases ciliary beating frequency (CBF), and elicits CBF increases similar to those caused by dopamine and the neuropeptide, TPep-NLS. Further, four CBF stimulants (zero external Cl(-), depolarization, dopamine and TPep-NLS) depend on a common mode of action, viz. Ca(2+) influx, possibly through voltage-gated Ca(2+) channels, and can be blocked by nifedipine. Ca(2+) influx alone, however, does not provide all the internal Ca(2+) necessary for CBF change. Ryanodine receptor (RyR) channel-gated internal stores are also necessary for CBF excitation. Caffeine can stimulate CBF and is sensitive to the presence of the RyR blocker dantrolene. Dantrolene also reduces CBF excitation induced by dopamine and TPep-NLS. Finally, W-7 and calmidazolium both block CBF excitation by caffeine and dopamine, and W-7 is effective at blocking TPep-NLS excitation. The effects of calmidazolium and W-7 suggest a role for Ca(2+)-calmodulin in regulating CBF, either directly or via Ca(2+)-calmodulin dependent kinases or phosphodiesterases. From these results we hypothesize dopamine and TPep-NLS induce depolarization-driven Ca(2+) influx and Ca(2+) release from internal stores that activates Ca(2+)-calmodulin, thereby increasing CBF.