Electrostatic Manipulation Research Articles

Catalyst Supraparticles: Tuning the Structure of Spray-Dried Pt/SiO2 Supraparticles via Salt-Based Colloidal Manipulation to Control their Catalytic Performance.

The structure of supraparticles (SPs) is a key parameter for achieving advanced functionalities arising from the combination of different nanoparticle (NP) types in one hierarchical entity. However, whenever a droplet-assisted forced assembly approach is used, e.g., spray-drying, the achievable structure is limited by the inherent drying phenomena of the method. In particular, mixed NP dispersions of differently sized colloids are heavily affected by segregation during the assembly. Herein, the influence of the colloidal arrangement of Pt and SiO2 NPs within a single supraparticulate entity is investigated. A salt-based electrostatic manipulation approach of the utilized NPs is proposed to customize the structure of spray-dried Pt/SiO2 SPs. By this, size-dependent separation phenomena of NPs during solvent evaporation, that limit the catalytic performance in the reduction of 4-nitrophenol, are overcome by achieving even Pt NP distribution. Additionally, the textural properties (pore size and distribution) of the SiO2 pore framework are altered to improve the mass transfer within the material leading to increased catalytic activity. The suggested strategy demonstrates a powerful, material-independent, and universally applicable approach to deliberately customize the structure and functionality of multi-component SP systems. This opens up new ways of colloidal material combinations and structural designs in droplet-assisted forced assembly approaches like spray-drying.

Quantum trapping and rotational self-alignment in triangular Casimir microcavities.

Casimir torque, a rotational motion driven by zero-point energy minimization, is a problem that attracts notable research interest. Recently, it has been realized using liquid crystal phases and natural anisotropic substrates. However, for natural materials, substantial torque occurs only at van der Waals distances of ~10 nm. Here, we use Casimir self-assembly with triangular gold nanostructures for rotational self-alignment at truly Casimir distances (100 to 200 nm separation). The interplay of repulsive electrostatic and attractive Casimir potentials forms a stable quantum trap, giving rise to a tunable Fabry-Pérot microcavity. This cavity self-aligns both laterally and rotationally to maximize area overlap between templated and floating flakes. The rotational self-alignment is sensitive to the equilibrium distance between the two triangles and their area, offering possibilities for active control via electrostatic screening manipulation. Our self-assembled Casimir microcavities present a versatile and tunable platform for nanophotonic, polaritonic, and optomechanical applications.

Triboelectric ‘electrostatic tweezers’ for manipulating droplets on lubricated slippery surfaces prepared by femtosecond laser processing

The use of ‘Electrostatic tweezers’ is a promising tool for droplet manipulation, but it faces many limitations in manipulating droplets on superhydrophobic surfaces. Here, we achieve noncontact and multifunctional droplet manipulation on Nepenthes-inspired lubricated slippery surfaces via triboelectric electrostatic tweezers (TETs). The TET manipulation of droplets on a slippery surface has many advantages over electrostatic droplet manipulation on a superhydrophobic surface. The electrostatic field induces the redistribution of the charges inside the neutral droplet, which causes the triboelectric charged rod to drive the droplet to move forward under the electrostatic force. Positively or negatively charged droplets can also be driven by TET based on electrostatic attraction and repulsion. TET enables us to manipulate droplets under diverse conditions, including anti-gravity climb, suspended droplets, corrosive liquids, low-surface-tension liquids (e.g. ethanol with a surface tension of 22.3 mN·m−1), different droplet volumes (from 100 nl to 0.5 ml), passing through narrow slits, sliding over damaged areas, on various solid substrates, and even droplets in an enclosed system. Various droplet-related applications, such as motion guidance, motion switching, droplet-based microreactions, surface cleaning, surface defogging, liquid sorting, and cell labeling, can be easily achieved with TETs.

Electrostatic Gating of Spin Dynamics of a Quasi-2D Kagome Magnet.

Electrostatic gating has emerged as a powerful technique for tailoring the magnetic properties of two-dimensional (2D) magnets, offering exciting prospects including enhancement of magnetic anisotropy, boosting Curie temperature, and strengthening exchange coupling effects. Here, we focus on electrical control of the ferromagnetic resonance of the quasi-2D Kagome magnet Cu(1,3-bdc). By harnessing an electrostatic field through ionic liquid gating, significant shifts are observed in the ferromagnetic resonance field in both out-of-plane and in-plane measurements. Moreover, the effective magnetization and gyromagnetic ratios display voltage-dependent variations. A closer examination reveals that the voltage-induced changes can modulate magnetocrystalline anisotropy by several hundred gauss, while the impact on orbital magnetization remains relatively subtle. Density functional theory (DFT) calculations reveal varying d-orbital hybridizations at different voltages. This research unveils intricate physics within the Kagome lattice magnet and further underscores the potential of electrostatic manipulation in steering magnetism with promising implications for the development of spintronic devices.

Quantum-Tuned Cascade Multijunction Infrared Photodetector.

Emerging applications such as augmented reality, self-driving vehicles, and quantum information technology require optoelectronic devices capable of sensing a low number of photons with high sensitivity (including gain) and high speed and that could operate in the infrared at telecom windows beyond silicon's bandgap. State-of-the-art semiconductors achieve some of these functions through costly and not easily scalable doping and epitaxial growing methods. Colloidal quantum dots (QDs), on the other hand, could be easily tuned and are compatible with consumer electronics manufacturing. However, the development of a QD infrared photodetector with high gain and high response speed remains a challenge. Herein, we present a QD monolithic multijunction cascade photodetector that advances in the speed-sensitivity-gain space through precise control over doping and bandgap. We achieved this by implementing a QD stack in which each layer is tailored via bandgap tuning and electrostatic surface manipulation. The resulting junctions sustain enhanced local electric fields, which, upon illumination, facilitate charge tunneling, recirculation, and gain, but retain low dark currents in the absence of light. Using this platform, we demonstrate an infrared photodetector sensitive up to 1500 nm, with a specific detectivity of ∼3.7 × 1012 Jones, a 3 dB bandwidth of 300 kHz (0.05 cm2 device), and a gain of ∼70× at 1300 nm, leading to an overall gain-bandwidth product over 20 MHz, in comparison with 3 kHz of standard photodiode devices of similar areas.

High-defined and size-selective deposition of nanoparticles by their manipulation in an electrostatic field

This study combines numerical simulation with an experimental investigation of high-level designed nanostructured surfaces built from metal nanoparticles (NPs). The ultimate goal of this research is to prepare highly designed isotropic surfaces with high purity, defined size, homogeneous surface coverage, and high deposition rate, i.e., the properties appreciated e.g., in precise nanoengineering of microsensors and/or nanoelectronics, etc. The approach is based on manipulation of electrically charged nanoparticles, produced by a gas aggregation cluster source (GAS), in the electrostatic field propagated by two parallel electrodes mounted at the GAS output orifice. The model derived by numerical simulation enables prediction of the distribution and properties of the NPs across the (x, y) substrate plane as a function of the electrical potential superimposed by the charged NPs in the volume and the external electrical field. A good qualitative agreement was found between the model and the properties of GAS-deposited NPs onto the Si substrate (the deposited surface was analyzed by the atomic force microscopy (AFM) imaging), which reveals the electrostatic manipulation of the charged NPs beam as a promising tool for deposition of highly tailored nanostructures.

Synergistic electrostatic shielding manipulation of Na+ and desolvation effect of Zn2+ enabled by glycerol for long-lifespan and dendrite-free Zn anodes

The development of aqueous Zn-based energy storage devices is severely restricted by uncontrollable Zn dendrite growth, serious parasitic side-reactions, and poor low-temperature performance. In this work, we introduce glycerol (Gl) with an appropriate concentration of 2.1 M (mol L−1) as a synergistic manipulator and desolvater in the 1 M Zn(ClO4)2 and 0.5 M Na2SO4 electrolyte for zinc batteries. Theoretical calculations and experimental analysis confirm that the Gl-Na+ structure adsorbs onto the Zn anode during the plating process, which increases the electrostatic shielding area of negative charge on Zn dendrites and thus inhibit their growth. Meanwhile, the desolvation effect of Zn2+ enabled by Gl promotes the optimization of solvated structure, resulting in uniform deposition of Zn2+. Additionally, Gl suppresses parasitic side-reactions and coagulation of the electrolyte to ensure a homogeneous electrode surface and improve low-temperature performance. In the modified electrolyte, stable Zn plating-stripping has been achieved for 2930 h at 2 mA cm−2 and 1 mA h cm−2, which is about 7.5 times longer than that in the Gl-free electrolyte. Moreover, even at −10 ℃, the hybrid capacitor with activated carbon and V2O5//Zn full battery realizes 95.37% and 62.84% capacity retention after 30,000 and 3000 cycles, respectively. This work presents an effective strategy for the synergism of double additives to promote the stability of the Zn electrode for high-performance aqueous batteries.

Decoupling Effects of Electrostatic Gating on Electronic Transport and Interfacial Charge-Transfer Kinetics at Few-Layer Molybdenum Disulfide.

The electronic properties of electrode materials play a crucial role in defining their electrochemical behavior in energy conversion and storage devices. The assembly of van der Waals heterostructures and fabrication into mesoscopic devices enable the dependence of an electrochemical response on electronic properties to be systematically interrogated. Here, we evaluate the effect of charge carrier concentration on heterogeneous electron transfer at few-layer MoS2 electrodes by combining spatially resolved electrochemical measurements with field-effect electrostatic manipulation of band alignment. Steady-state cyclic voltammograms and finite-element simulations reveal a strong modulation of the measured electrochemical response for outer-sphere charge transfer at the electrostatic gate voltage. In addition, spatially resolved voltammetric responses, obtained at a series of locations at the surface of few-layer MoS2, reveal the governing role of in-plane charge transport on the electrochemical behavior of 2D electrodes, especially under conditions of low carrier densities.

Room-temperature valley transistors for low-power neuromorphic computing

Valley pseudospin is an electronic degree of freedom that promises highly efficient information processing applications. However, valley-polarized excitons usually have short pico-second lifetimes, which limits the room-temperature applicability of valleytronic devices. Here, we demonstrate room-temperature valley transistors that operate by generating free carrier valley polarization with a long lifetime. This is achieved by electrostatic manipulation of the non-trivial band topology of the Weyl semiconductor tellurium (Te). We observe valley-polarized diffusion lengths of more than 7 μm and fabricate valley transistors with an ON/OFF ratio of 105 at room temperature. Moreover, we demonstrate an ion insertion/extraction device structure that enables 32 non-volatile memory states with high linearity and symmetry in the Te valley transistor. With ultralow power consumption (~fW valley contribution), we enable the inferring process of artificial neural networks, exhibiting potential for applications in low-power neuromorphic computing.

Electrostatic manipulation for saturated charging and orientating of recycled short-chopped carbon fibers based on dielectric polarization

Carbon fiber composites produce a large amount of scrap during their life cycle, to recycle and fully utilize these short-chopped carbon fibers (SCFs), present work proposes a method to disperse agglomerated SCFs using pure electrostatic forces, while using dielectric polarization to recycle and emit SCFs. SCFs are disorderly distributed or agglomerated into pellets in their natural state, and they need to be sufficiently charged and oriented for reliable collection. A novel plate-plate structure is proposed to maintain a higher load voltage to disperse and emit a larger amount of SCFs. The charging and orientation mechanisms of SCFs were investigated with high-speed camera. The dispersive characteristics of SCFs were statistically evaluated with Ripley's K function and Two-point spatial correlation. And SCFs were emitted by two different modes and the effects of embedment were studied. The results show that large-scale SCFs can be uniformly dispersed and sufficiently charged to 2 × 10−2C/kg in the electrostatic field and oriented to move under the driving of dielectric polarization. Moreover, the direction of embedded SCFs can be well controlled. This study describes the behavior pattern and motion characteristics of SCFs in the electrostatic field and provides a new method for the pollution-free, low-cost, efficient recycling of recycled fibers. It has broad application prospects in the field of carbon fiber reinforced polymer composites and is also significant for the pure electrostatic cross-scale control of micron-sized objects.

Honeybee-inspired electrostatic microparticle manipulation system based on triboelectric nanogenerator

Electrostatic manipulation of particles or droplets has raised huge interests across many fields including biomedical analysis, microchemistry and microfabrication/patterning, because of its merits of simple configuration and easy operation. However, traditionally applied bulky high voltage sources for electrostatic manipulation not only have potential safety risk to the operator and the devices, but also limit the portability. Here, we proposed an electrostatic microparticle manipulation system (EMMS) based on a triboelectric nanogenerator (TENG). Inspired from the pollen collection principle of honeybees, the EMMS featured a simple pin-to-plate electrodes system, which was electrostatically powered by the high voltage of the TENG. Different manipulation modes, including contact manipulation and noncontact manipulation were systematically studied. With a sliding displacement of 5 cm, the TENG delivered an output voltage of ± 3.2 kV, which could manipulate dielectric microparticles with weights of 1.7 mg, 0.9 mg and 13.3 mg at contact manipulation mode, noncontact manipulation (vertical lift) and noncontact manipulation (parallel move) mode, respectively. Manipulation mechanisms for both dielectric and conductive microparticles under different configurations of the pin-to-plate electrodes system were investigated. Finally, potential applications including micropatterning, dust remove and drug release/microchemistry were demonstrated to show the great prospects of the proposed TENG-based EMMS.

"Did you eat a MOLEcule today?" An Interactive Demonstration of Molecular Weight with Real-Time Breath Analysis Using Mass Spectrometry for All Ages.

Although mass spectrometry is a widely used analytical tool, age-appropriate, interactive outreach activities for laboratory visitors, especially children, are lacking. The presented interactive demonstration, "Did you eat a MOLEcule today?", introduces all ages to molecular weight concepts and mass spectrometry in a research laboratory, while connecting the concepts to real-world applications. Through real-time breath analysis, participants explore the concepts of molecular weight, electrostatic field manipulation of charged molecules, and analyte identification by mass analysis. This module is rapid and highly adaptable for outreach activities but also includes age- or classroom-appropriate variations to decrease or increase difficulty levels. The presented interactive demonstration has repeatedly been implemented, with over 2300 participants during six annual "Take Our Daughters & Sons to Work Day" and two corporate "Family Day" outreach activities, successfully engaging, exciting, and educating both kids and parents.

Controllable electrostatic manipulation of structure building blocks in noble metal aerogels

An electrostatic manipulation method has been presented by directly mixing oppositely charged noble metal nanoparticle solutions to prepare the corresponding noble metal hydrogels without introducing additional reagents.

A new method for the electrostatic manipulation of droplet movement by triboelectric nanogenerator

In view of the limitations of the current water droplet manipulation technology in liquid environment, a new polyaniline and polyvinylidene fluoride nanowire-based triboelectric nanogenerator (NW-TENG) is assembled to form two self-powered electrostatic manipulation systems (EMSs). Changes in the output signal of the TENG affect the strength, form, frequency, and other parameters of the electric field and result in different droplet motion behaviors because of the change in force. The unique polarization deformation mechanism of droplets in the double-electrode EMS is studied. In addition, the alternating electric field of TENG is applied to realize the reciprocating movement of the macro-charged droplets. The result shows that droplets have a shorter movement period than ordinary DC-regulated electric field (from 7.30 s to 3.67 s), and no electrical breakdown occurs. Thus, the EMS is practical and safe. The versatility of the EMS is proved by the controllable reciprocating motion of microscopic droplets (6.37 µm). Finally, a single-electrode EMS is applied to switch the adsorption and ejection of the droplets on the electrode, and an interesting step-by-step chemical reaction is realized. This work proposes a new method for manipulating the motion behavior of micro-droplets in liquid environment, which has promising potential applicability in microfluidic systems, biochemical reactions, targeted transportation and other applications.

Electrostatic Manipulation of Phase Behavior in Immiscible Charged Polymer Blends

Microphase separation in a binary blend of oppositely charged polymers can in principle be stabilized electrostatically without the need for connected block polymer architectures. This provides a r...

Recent Progress in the Manipulation of Molecules with DC Electric Fields.

The structure and reactivity of a molecule in the condensed phase are governed by its intermolecular interactions with the surrounding environment. The multipole expansion of each molecule in the condensed phase indicates that the intermolecular interactions are essentially electrostatic (e.g., ion-dipole, dipole-dipole, dipole-quadrupole, dipole-induced dipole). The electrostatic field is a fundamental language of intermolecular communications. Therefore, understanding the influence of the electrostatic field on a molecule, that is, the mechanisms by which an electrostatic field manipulates a molecule, from the perspective of molecular structure, energy states, and dynamics is indispensable for illustrating and, by extension, controlling the chemistry in molecular systems.In this Account, we describe the recent progress made in manipulation of molecular processes using an external DC electrostatic field. An electrostatic field with unprecedentedly high strength (≤4 × 108 V/m) was applied in a controlled manner across a molecular film sample using the ice film nanocapacitor method. This field strength is comparable in magnitude to that of weak intermolecular interactions such as van der Waals interactions in the condensed phases. The samples were prepared using a thin film growing technique in vacuum to obtain the desired chemically tailored molecular systems. The examples of prepared systems included small molecules and molecular clusters isolated in cryogenic Ar matrices, frozen molecular films in amorphous or crystalline phase, and interfaces of multilayered molecular films. The response of the molecules to the external field was monitored by reflection-absorption infrared spectroscopy. This approach allowed us to investigate a variety of molecular systems with various intermolecular strength and environments under the influence of strong electrostatic fields. The range of observed molecular behaviors includes the manipulation of molecular orientation, intramolecular dynamics, and proton transfer reactions as an example of stereodynamic control of chemical reactivity. These observations improve our understanding of molecular behaviors in strong electric fields and broaden our perspective on electrostatic manipulation of molecules. This information is also relevant to a variety of research topics in physical and biological sciences where electric fields play a role in molecular and biological functions.

Insight into Manipulation Mechanism of Ion Transport through Angström-Scale Channels in Ti3C2Tx Membrane by Controlling Surface Potential Using Electrochemical Quartz Crystal Microbalance with Dissipation

A lamellar membrane assembled by parallel restacking of two-dimensional nanosheets provides a novel platform for studying the electrostatic manipulation of ion mobility under angstrom-scale confine...

Electrostatic Manipulation of Triblock Terpolymer Nanofilm Compartmentalization during Aqueous Photoinitiated Polymerization-Induced Self-Assembly

Electrostatic manipulation of triblock terpolymer nanofilm compartmentalization has been achieved via visible light-initiated reversible addition–fragmentation chain transfer aqueous dispersion pol...

Analysis of the effects of positive ions and boundary layer temperature at various hypersonic speeds on boundary layer density

Vehicles traveling at hypersonic speeds ionize the air around them. This ionization leads to the possibility of utilizing an induced positive surface charge to lower the density of the boundary layer flow electrostatically. Reducing the boundary layer's density would have several positive effects, such as lowering the drag and heat transfer. The study's goal was to identify the Mach numbers for which the electrostatic drag and heat transfer manipulation would be most applicable inside the stratosphere. We hypothesized that the potential to use induced positive surface charge repulsion to lower boundary layer density would increase with speed, and there will be greater (>10%) potential to decrease boundary layer density at a lower bound estimate of Mach 18-19. We also explored the extent to which extrapolation through a quadratic model based on Dr. Jesse R. Maxwell's data in Morphing Waveriders for Atmospheric Entry could be used to approximate maximum boundary layer temperature values. The experiments were conducted using computational fluid dynamics software. The study demonstrated that, on average, higher Mach speeds resulted in a considerably higher potential decrease in density. Also, as predicted by the hypothesis, a significant potential reduction in density occurred near Mach 19. The study also supported using the quadratic model based on Maxwell's data for approximating the maximum boundary layer temperature up to at least Mach 26. This study highlights that further research on the surface charge method is warranted as we seek to explore higher hypersonic speeds within the stratosphere.

Electric modulation of magnetic anisotropy on the granule/matrix interface of a permalloy/PZT composite

In this work, the electric modulation of magnetic anisotropy is investigated on a granule/matrix interface of a Py/PZT composite. Outside the Py/PZT interface, the electric polarization is derived through the Thomas-Fermi model and mean field approximation. Inside the Py/PZT interface, the magnetizing energy is derived through the spin-split model and spherical shell approximation. As the Py volume fraction varies from 0.0% to 0.8%, the electric polarization evolves from radiationlike to vortexlike distribution, while the magnetizing energy evolves from symmetric-type to asymmetric-type distribution. Under downward and upward polarization, parallel and perpendicular magnetization are preferred, respectively. As the granule diameter or matrix thickness is varied, the downward polarization induces unstable parallel magnetic anisotropy, while the upward polarization induces stable perpendicular magnetic anisotropy. This work is beneficial for achieving electrostatic manipulation of a magnetic vortex.