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Effective sorting and extraction of tiny plastic objects is becoming increasingly important for manufacturing high-quality recycled plastics. Herein, we designed a manipulation device for tiny objects that can drive multiple target objects individually. This type of device has a potential to sort tiny pieces of a wide variety of materials, not strongly depending on their physical properties, by combining different detection meanings. In this study, two types of devices were tested as the basic components of the proposed device. One of them had a single object-holding point and the other had two of them. These holding points consisted of strip-shaped electrodes facing each other. The high voltage applied to the facing electrodes created forces heading toward the object-holding points caused by the heterogeneity of the electric field in the devices. The forces created in these devices were determined from the motion analysis of a glass sphere, which is a model for target objects, and a numerical simulation. The results indicate that dielectrophoretic forces are dominant at locations that are sufficiently remote from the holding point, and the Coulombic force caused by dielectric barrier discharge is dominant near the high-voltage electrodes with the holding point. Moreover, the transfer of a glass sphere from one holding point to an adjacent point was successfully demonstrated.

Recent years have witnessed an increased demand for a method for precise measurement of the microstructures of mechanical microparts, microelectromechanical systems, micromolds, optical devices, microholes, etc. This paper presents a measurement system for three-dimensional (3D) microstructures that use an optical fiber probe. This probe consists of a stylus shaft with a diameter of 2.5 µm and a glass ball with a diameter of 5 µm attached to the stylus tip. In this study, the measurement system, placed in a vacuum vessel, is constructed suitably to prevent adhesion of the stylus tip to the measured surface caused by the surface force resulting from the van der Waals force, electrostatic force, and liquid bridge force. First, these surface forces are analyzed with the aim of investigating the causes of adhesion. Subsequently, the effects of pressure inside the vacuum vessel on surface forces are evaluated. As a result, it is found that the surface force is 0.13 µN when the pressure inside the vacuum vessel is 350 Pa. This effect is equivalent to a 60% reduction in the surface force in the atmosphere.

Electrostatic force spectroscopy (EFS) is a method for monitoring the electrostatic force microscopy (EFM) phase with high resolution as a function of the electrical direct current bias applied either to the probe or sample. Based on the dielectric constant difference of graphene oxide (GO) sheets (reduced using various methods), EFS can be used to characterize the degree of reduction of uniformly reduced one-atom-thick GO sheets at the nanoscale. In this paper, using thermally or chemically reduced individual GO sheets on mica substrates as examples, we characterize their degree of reduction at the nanoscale using EFS. For the reduced graphene oxide (rGO) sheets with a given degree of reduction (sample n), the EFS curve is very close to a parabola within a restricted area. We found that the change in parabola opening direction (or sign the parabola opening value) indicates the onset of reduction on GO sheets. Moreover, the parabola opening value, the peak bias value (tip bias leads to the peak or valley EFM phases) and the EFM phase contrast at a certain tip bias less than the peak value can all indicate the degree of reduction of rGO samples, which is positively correlated with the dielectric constant. In addition, we gave the ranking of degree for reduction on thermally or chemically reduced GO sheets and evaluated the effects of the reducing conditions. The identification of the degree of reduction of GO sheets using EFS is important for reduction strategy optimization and mass application of GO, which is highly desired owing to its mechanical, thermal, optical and electronic applications. Furthermore, as a general and quantitative technique for evaluating the small differences in the dielectric properties of nanomaterials, the EFS technique will extend and facilitate its nanoscale electronic devices applications in the future.

Among metals, Ti and majority of its alloys exhibit excellent biocompatibility or tissue compatibility. Although their high corrosion resistance is a factor in the biocompatibility of Ti and Ti alloys, it is clear that other factors exist. In this review, the corrosion resistance and passive film of Ti are compared to those of other metallic biomaterials, and their band gap energies, E g s, are compared to discuss the role of E g in the reactivity with living tissues. From the perspective of the material's surface, it is possible to explain the excellent biocompatibility of Ti by considering the following factors: Ti ions are immediately stabilized not to show toxicity if it is released to body fluids; good balance of positive and negative charges by the dissociation of surface hydroxyl groups on the passive film; low electrostatic force of the passive film inducing a natural adsorption of proteins maintaining their natural conformation; strong property as n-type semiconductor; lower band gap energy of the passive film on Ti generating optimal reactivity; and calcium phosphate formation is caused by this reactivity. The results suggest that due to the passive oxide film, the optimal balance between high corrosion resistance and appropriate reactivity of Ti is the predominate solution for the excellent biocompatibility of Ti.

The surface tension of ethanol and n-decane based nanofluid fuels containing suspended aluminum (Al), aluminum oxide (Al2O3), and boron (B) nanoparticles as well as dispersible multi-wall carbon nanotubes (MWCNTs) were measured using the pendant drop method by solving the Young-Laplace equation. The effects of nanoparticle concentration, size and the presence of a dispersing agent (surfactant) on surface tension were determined. The results show that surface tension increases both with particle concentration (above a critical concentration) and particle size for all cases. This is because the Van der Waals force between particles at the liquid/gas interface increases surface free energy and thus increases surface tension. At low particle concentrations, however, addition of particles has little influence on surface tension because of the large distance between particles. An exception is when a surfactant was used or when (MWCNTs) was involved. For such cases, the surface tension decreases compared to the pure base fluid. The hypothesis is the polymer groups attached to (MWCNTs) and the surfactant layer between a particle and the surround fluid increases the electrostatic force between particles and thus reduce surface energy and surface tension.

Purpose The purposes of this research were to: (1) establish new analytical kinetic equation for describing the effect of strong electrostatic force on adsorption; (2) experimentally determine if it is a strong or weak electrostatic force adsorption process; and (3) evaluate the adsorption energies of the strong and weak force adsorptions based on the proposed new theory of cation adsorption kinetics. Materials and methods The constantly charged material-montmorillonite was used in the experiment. The montmorillonite was saturated with two Cation species: K⁺ and Ca²⁺, respectively, using KNO₃ or Ca(NO₃)₂ before it was used for the experiment. The miscible displacement technique under a steady flow condition was adopted to the kinetic studies of Mg²⁺ (Mg(NO₃)₂) adsorption. In the experiment, 0.5000 g of K⁺- or Ca²⁺-saturated montmorillonite was layered on the exchange column, the thickness of sample layer was approximately 0.2-0.3 mm, the cross-sectional area of the column (sample area) was 15 cm². The concentration of Mg²⁺ in the flowing liquid was 10⁻⁴ mol L⁻¹. The flow velocity of the flowing liquid was 1.0 mL·min⁻¹. Effluent was collected at 10-min intervals. Results and discussion Firstly, new and exact rate models for describing ion adsorption have been advanced. Secondly, based on the experiments of Mg²⁺/K⁺ and Mg²⁺/Ca²⁺ exchange in K⁺ and Ca²⁺-saturated montmorillonites, Mg²⁺ adsorption in K⁺-saturated sample appeared zero-order kinetic process in the initial stage of the strong force adsorption for t = 0-405 min, and then the adsorption process converted to the first-order kinetics of the weak force adsorption, which agrees with the theoretical prediction. However, for the Ca²⁺-saturated sample, merely first-order kinetic process appeared for Mg²⁺ adsorption. Either for Mg²⁺/K⁺ exchange or Mg²⁺/Ca²⁺ exchange, the quantities of Mg²⁺ by weak force adsorption at equilibrium were almost the same. Thirdly, several important dynamic and thermodynamic parameters can be theoretically calculated based on the new theory in describing cation adsorption. Conclusions For Mg²⁺/K⁺ exchange, both strong and weak electrostatic force adsorptions exist, but for Mg²⁺/Ca²⁺ exchange only the weak electrostatic force adsorption occurs. The strong and weak force adsorption processes can be quantitatively described by the new analytical kinetic equations of the zero- and the first-order kinetics, respectively. Because each parameter in the analytical kinetic equations has its definitive physical meaning, several important dynamic and thermodynamic parameters in cation exchange can be theoretically estimated.

This study explores the conceptual understanding of electromagnetism among physics professors at the Aeronautical University in Querétaro, Mexico. While student misconceptions in electromagnetism have been extensively studied, research on professors' understanding and its potential impact remains limited (Pardhan & Bano, 2001). This research aims to address this gap by focusing on the core concepts of electrostatic force, electric field, and electric potential. Eight professors participated in the study. Their academic background, electromagnetism course history, and teaching experience were documented. A three-tier diagnostic test, based on Vergnaud's theory of conceptual fields, was then used to assess their conceptualisation of these concepts and their interrelationships. The analysis revealed that only one professor consistently demonstrated correct understanding across all three concepts. Interestingly, this professor was also the one with the most extensive teaching experience in the subject. The results suggest a potential connection between teaching experience and a deeper conceptual understanding of electromagnetism. Further research is needed to explore this connection and its implications for mitigating student misconceptions through effective teaching practices.

Dust aerosols are produced by wind erosion, and it is widely accepted that dust aerosols can be produced only if the wind speed exceeds a certain threshold velocity, which is largely controlled by soil moisture content. The relative humidity (RH) in the air could affect soil moisture content, thereby impacting dust production indirectly. However, it is not clear if the RH can directly change dust aerosol production. Here we simulated dust production and show that the RH does play a direct role in affecting the production of dust aerosol in a quite complicated way, which can be explained by a hypothesis that the RH affects both the electrostatic forces and wet‐bonding forces between soil particles in opposite directions. The current formula for dust aerosol production flux does not include the direct RH effect, and this study strongly suggests that it could lead to significant errors in estimating dust production. Plain Language Summary Dust is a critical source of atmospheric particulate matter, which can exert significant influences on climate and human health. Strong wind can drive the soil particles to collide with each other and shake off small particles, which could be lifted up into the air and form dust aerosols. It is now generally accepted that humidity in the air could indirectly impact dust aerosol production through affecting soil moisture. However, in this study, it is found that relative humidity can directly influence dust aerosol production, possibly through affecting the electrostatic forces and wet‐bonding forces between soil particles. Our study suggests that the modeling of dust generation should include air humidity to better predict dust aerosol production. Key Points Humidity in the air can directly affect the production of dust aerosol in a complicated way Humidity may change the electrostatic forces and wet‐bonding forces between soil particles Humidity should be included in the source functions of dust aerosol production

In this paper, we present a compressive study on the design and development of a MEMS ring resonator and its dynamic behavior under electrostatic force when supported by twin circular curve beams. Finite element analysis (FEA)-based modeling techniques are used to simulate and refine the resonator geometry and transduction. In proper FEA or analytical modeling, the explicit description and accurate values of the effective mass and stiffness of the resonator structure are needed. Therefore, here we outlined an analytical model approach to calculate those values using the first principles of kinetic and potential energy analyses. The natural frequencies of the structure were then calculated using those parameters and compared with those that were simulated using the FEA tool ANSYS. Dynamic analysis was performed to calculate the pull-in voltage, shift of resonance frequency, and harmonic analyses of the ring to understand how the ring resonator is affected by the applied voltage. Additional analysis was performed for different orientations of silicon and assessing the frequency response and frequency shifts. The prototype was fabricated using the standard silicon-on-insulator (SOI)-based MEMS fabrication process and the experimental results for resonances showed good agreement with the developed model approach. The model approach presented in this paper can be used to provide valuable insights for the optimization of MEMS resonators for various operating conditions.

Strong confinement of charges in few-electron systems such as in atoms, molecules, and quantum dots leads to a spectrum of discrete energy levels often shared by several degenerate states. Because the electronic structure is key to understanding their chemical properties, methods that probe these energy levels in situ are important. We show how electrostatic force detection using atomic force microscopy reveals the electronic structure of individual and coupled self-assembled quantum dots. An electron addition spectrum results from a change in cantilever resonance frequency and dissipation when an electron tunnels on/off a dot. The spectra show clear level degeneracies in isolated quantum dots, supported by the quantitative measurement of predicted temperature-dependent shifts of Coulomb blockade peaks. Scanning the surface shows that several quantum dots may reside on what topographically appears to be just one. Relative coupling strengths can be estimated from these images of grouped coupled dots.