Electrostatic Repulsive Forces Research Articles

Continuous Focusing of Particles by AC-Electroosmosis and Induced Dipole Interactions.

Continuous particle focusing by using microfluidics is an effective method for separating particles, cells, or droplets for analytical purposes. Previously, it was shown that an alternating current across rectangular microchannels with slightly deformed side walls results in vortex flow patterns caused by alternating current electroosmosis (AC-EOF) and could lead to particle focusing. In this work, we explore this mechanism by experimentally studying the particle focusing behavior for various fluid flow velocities through a microchannel. Since it is unlikely that the particles are kept in their focused position solely by convection, a theoretical force balance between the hydrodynamic and the induced dipole force was determined. In our experiments, it was found that there is no substantial effect of the pressure-driven fluid velocity on the particle focusing velocity within the studied range. From the theoretical force balance calculations, it was determined that while the addition of the induced dipole force can still not completely describe the experimentally observed particle focusing, the induced dipole can be strong enough to overcome the hydrodynamic force. Finally, it is hypothesized that under specific circumstances, including a repulsive electrostatic force between a particle and electrode wall can complete the theoretical particle focusing force balance. Alternative phenomena that could also play a role in particle focusing are proposed.

Interaction of charged magnetic nanoparticles with surfaces

The behavior of magnetic nanoparticles covering the surface with positive charges (MN), suspended in a continuous medium, was simulated by Brownian dynamics. Then, we studied the behavior of the MN in an aqueous-like suspension and their adsorption on a negatively charged surface, mimicking a mica surface. After several microseconds, particles are deposited onto the charged surface. Experimental results of ordered magnetic nanoparticles in surfaces are compared with the present simulation results of MN in two dimensions. We also demonstrate the effect of charged MN on the hexagonal structure when electrical repulsions dominate against magnetic dipole-dipole and van der Waals attractions. On one hand, the adsorption of MN on the surface depends on the electrostatic attraction force with the surface, while the surface organization of MN results from balancing electrostatic repulsion forces and magnetic attraction forces among particles. In magnetic nanoparticles simulated with a non-charged surface or weakly charged surface, dipole-dipole interactions dominate the particle-particle interactions, and the interactions between particles and a mica-like surface are conducted by van der Waals forces.

Evaluating the operational properties of concrete admixtures containing molecularly modified polycarboxylate superplasticizers

The objective of this study focused on the design and preparation of a molecularly modified polycarboxylate superplasticizer to develop concretes with enhanced engineering features. For this purpose, polyethylene glycol was chemically modified with maleic anhydride to give the mono polyethylene glycol maleate (MPEGM). Then, polycarboxylate superplasticizer comprising of isoprenyl oxy polyethylene glycol (TPEG) and acrylic acid (AA, PCE-1), and the synthesized MPEGM with TPEG and AA (PCE-2) were prepared through solution radical polymerization. Subsequently, concrete mixtures with different dosages (0, 0.1, 0.15, 0.2, 0.25, 0.3 wt%) of PCE-1 and PCE-2 were prepared. Chemical structure of the synthesized MPEGM and superplasticizers together with their copolymer composition were identified by FTIR and 1HNMR analyses. The molecular weights (Mw) and molecular weight distributions (PDI) of PCE-1 (8.74 × 104, 1.36) and PCE-2 (8.74 × 104, 2.19) were studied by GPC analysis, respectively. The zeta potential of cement particles (2.8 mV) becomes negative in the presence of 0.6 g/L of PCE-1 (− 7.8) and PCE-2 (− 9.5). This implies that electrostatic and steric hindrance forces of adsorbed superplasticizers synergistically provide a situation for appropriate dispersion of cement particles. The results of water-reducing percentage, fluidity, air content, bleeding water rate, initial and final setting times, wet density, flexural and compressive properties, and ultrasonic pulse velocity analyses exhibit significant enhancement on the features of concrete mixtures made of polycarboxylate superplasticizer. The superiority of PCE-2 to PCE-1 was connected to its adsorption-dispersibility potent induced by stronger electrostatic and steric repulsion forces, which result in quality and continuity enhancement in concretes.

Electrodynamic dust shield efficiency characterisation under UV in vacuum for lunar application

Dust mitigation is one of the most crucial aspects of extraterrestrial exploration. This paper presents a series of experiments on the electrodynamic dust shield (EDS) and how UV radiation affects its efficiency on selected lunar simulants (LHS-1 and LMS-1) across a range of particle sizes, quantities, and surface materials. In this experimental study, VUV is used with a 1500V AC electric field to mobilise the dust particles resting on either glass, Kapton, or Beta cloth inside a vacuum chamber at ∼10-6 mbar. The dust removal efficiency is characterised by two quantifying methods: weighing and solar array light transmission. The experimental results show that EDS activation under continuous UV exposure on the simulant particles improves the dust removal rate by 40 to 80 percentage points across all surfaces, with the exception of certain particle size ranges on Beta cloth. The primary force facilitating particle mobilisation was identified as the repulsive electrostatic force, enhanced by ionising mechanisms such as photoemission.

Enhanced assembly stability for amine-based cationic glycolipid

Glycolipids incorporating positive charges, mediated by an imidazolium cation, have shown potential for effective formulation of vesicular drug carriers, reflecting repulsive electrostatic forces, promoting the formation of nanosized assemblies and preventing unwanted Oswald ripening (Goh et al. (2019), ACS Omega 4, 17,039). Our continuous development of an assembly-based drug delivery system prompted us to investigate a pH-sensitive analogue, leading to the synthesis of a 6-amino-Guerbet glycoside. However, in contrast to the imidazolium counterpart, the amine-mediated charge increased the intermolecular cohesions, furnishing bigger assemblies instead, which further increased upon introduction of acid. Moreover, assemblies exhibited a significantly reduced positive charge density. It is concluded that strong proton-initiated hydrogen bonding between amino groups provide cohesive head group interactions overcompensating possible repulsive charge interactions. While this behavior invalidates the application of the amino-glucoside as dispersing agent for the formulation of small vesicles, it potentially paves a route towards enhanced vesicle stability.

The decisive role of filtration reducers’ surface charge in affecting drilling fluid filtration performance

To elucidate the effects of filtration reducers’ surface charge on drilling fluid filtration performance, three kinds of SiO2@polymer nanoparticles with different surface charges are prepared. When these nanoparticles are added into bentonite-based drilling fluids as filtration reducers, the negatively charged nanoparticles show the best filtration reduction performance while the positively charged nanoparticles show the most inferior filtration reduction performance. Moreover, more negative charges induce better filtration reduction performance. Conversely, more positive charges induce more inferior filtration reduction performance. The filtration performance of drilling fluids is decided by the compactness of the filter cake. And the interactions among the particles in the drilling fluids play an important role in affecting the compactness of filter cake. The electrostatic attraction forces between the positively charged nanoparticles and negatively charged bentonite particles promoted the aggregation before the formation of incompact filter cake, and the electrostatic repulsion forces between the negatively charged nanoparticles and negatively charged bentonite particles slowed down the aggregation of particles to form more compact filter cakes. These findings demonstrate the decisive role of surface charge of filtration reducers, which could provide guidance for searching suitable filtration controlling additives for drilling fluids in the future.

Electro-responsive OCNT/PPy membrane for efficient irreversible-fouling control through electroregulation of electrostatic and fluid interaction forces

Membrane-based separation process has been proven to be a powerful strategy for low-energy-consumption and high-efficiency water purification. However, the practical application is still subjected to serious membrane fouling. In this study, an impressive approach to alleviate membrane fouling is proposed using an electro-conductive oxygenated carbon nanotube/polypyrrole (OCNT/PPy) membrane combining electrically-regulated electrostatic and fluid forces. Benefiting from the negative potential (−1.18 V vs. SCE) applied on the membrane, the electric polarization effects significantly enhance the repulsive electrostatic force on contaminant. The transmembrane pressure increases at an ignorable rate during the filtration process. Meanwhile, for accumulated irreversible membrane fouling after multi-cycle filtrations, the positive potential (+1.19 V vs. SCE) exerted on OCNT/PPy membrane can decrease the fluid resistances of backwash flow. As a result, the electrically-regulated hydraulic backwash achieves a thorough recovery rate of permeance at 99.1 %. The numerical analysis of the antifouling mechanism reveals that the mitigation of irreversible membrane fouling is mainly attributed to rapid formation of a loose cake layer under electrical assistance. Moreover, the computational fluid dynamics verifies that the reduction of water-channel resistance enhances the elimination of foulants in membrane pores. This work motivates a new thought for membrane fouling control through electroregulation of electrostatic and fluid forces at the membrane-water interface.

Effect of nitrogen/oxygen ratios on surface charge distributions generated by repetitive surface dielectric barrier discharges

Studies on the dielectric surface parameters and dielectric barrier discharges (DBD) characteristics considering the influence of gases in DBD on the surface charge distribution are scarce. Thus, to overcome this research gap, this study measured the potential distributions of AC-driven surface DBD in oxygen (O2), synthetic air and nitrogen (N2) as background gases using the Pockels effect. The results showed that the patterns of the filamentary discharges generated during the positive voltage polarity phase differed depending on the O2 ratio. In addition, the electrostatic repulsion forces between the residual charge and the newly created filament were analysed from the measured potential distribution and the greatest effect was observed in air, rather than in N2 and O2. The potential distribution was transformed into a charge density distribution and compared with the discharge luminescence in air and N2. The results showed that the shape of the filament tip differed between the charge density and discharge luminescence only in the case of air, which was attributed to the effect of attachment reactions on the formation of residual charge. The measurements showed that in a surface discharge, similar to the case in a volume discharge, the photoionisation and ionisation coefficients significantly affected the geometrical properties of the discharges.

Enhancing proton transport in polyvinylidenedifluoride membranes and reducing biofouling for improved hydrogen production in microbial electrolysis cells

Hydrophilic porous membranes, exemplified by polyvinylidene fluoride (PVDF) membranes, have demonstrated significant potential for replacing ion exchange membranes in microbial electrolysis cells (MECs). Membrane fouling remains a major challenge in MECs, impeding proton transport and consequently limiting hydrogen production. This study aims to investigate a synergistic antifouling strategy for PVDF membrane through the incorporation of a coating composed of polydopamine (PDA), polyethyleneimine (PEI), and silver nanoparticles (AgNPs). The PDA-PEI-Ag@PVDF membrane not only effectively mitigates fouling through steric and electrostatic repulsion forces, but also amplifies ion transport by facilitating water diffusion and electromigration. The PDA-PEI-Ag@PVDF membrane exhibited a reduced membrane resistance of 1.01 mΩ m2 and PDA-PEI-Ag modifying PVDF membrane was found to be effective in enhancing the proton transportation of PVDF membrane. Therefore, the enhanced hydrogen production rate of 2.65 ± 0.02 m3/m3/d was achieved in PDA-PEI-Ag@PVDF-MECs.

In situ acid production by organic matter induced with trace homogeneous Fenton reagent for membrane fouling control

The homogeneous Fenton process involves both coagulation and oxidation, but it requires added acidity, so it is rarely used to control membrane fouling. This work found that the pH of neutral simulated wastewater sharply declined to 4.1 after pre-treatment with 0.1 mM Fenton reagent (Fe2+:H2O2=1:1) without added acidity. This occurred mainly because the trace homogeneous Fenton reagent induced in situ acid production by organic matter in the wastewater, which supplied the acidic conditions required for the Fenton reaction and ensured that the reaction could proceed continuously. Then, oxidation during the pre-Fenton process enhanced the electrostatic repulsion forces and effectively weakened the hydrogen bonds of organic matter at the membrane surface by altering the net charge and hydroxyl content of organic matter, while coagulation caused the foulants to gather and form large aggregates. These changes diminished the deposition of foulants onto the membrane surface and resulted in a looser fouling layer, which eventually caused the membrane fouling rate to decline from 83 % to 24 % and the flux recovery rate to increase from 44 % to 98 % during 2 h of filtration. This membrane fouling mitigation ability is much superior to that of pre-H2O2, pre-Fe2+ or pre-Fe3+ processes with equivalent doses.

Negatively charged hydrochar from Aesculus indica waste: A sustainable material for enhanced Li-S batteries performance

This study presents a negatively charged hydrochar from Aesculus indica waste, employing a microwave-assisted hydrothermal carbonization (HTC) method at very low temperatures (120∼200 °C). The research shows the utilization of these negatively-charged-oxygen-containing hydrochars in lithium-sulfur (Li-S) batteries effectively mitigates polysulfide shuttling through electrostatic repulsive forces and simultaneously facilitate uniform lithium-ion transportation, leading to substantial improvement in battery performance. Through detailed investigations into the HTC reaction mechanism, the concentration of the negatively charged oxygen functional groups is tunable by controlling the carbonization process, which could further improve the enhancement effects. Furthermore, negatively-charged-oxygen-containing hydrochars were utilized as modified separator in Li-S batteries to enhance the electrochemical performance. The batteries assembled with hydrochar modified separator, has an initial discharge capacity of 1216 mAh g−1 at 0.1 C, and after 200 cycles at 1 C, its reversible discharge capacity was still 800 mAh g−1 with more than 80 % capacity retention. This research not only provides an efficient method for the utilization of waste biomass, but also offers a new approach for the preparation of negatively charged carbon for lithium-sulfur batteries.

Impact of silt chemical composition on deflocculation and coagulation of clay-rich paste

This paper investigates the impact of the chemical composition of two silts, quartz and limestone, on the deflocculation/coagulation process for poured earth application. The driving mechanisms behind the evolution of the rheological behavior after the addition of sodium hexametaphosphate are highlighted through zeta potential measurementand the chemical changes with ICP-OES and 31P MAS NMR spectroscopy. The first results show that adding sodium hexametaphosphate into the quartz silt modifies its inter-particle forces through electrostatic repulsion forces induced by the adsorption of phosphate anions onto the quartz structure. For limestone paste, the deflocculation mechanism is affected by the dissolution of the calcite. This dissolution leads to a release of Ca2+ cations and an increase in the paste's pH, reducing the paste deflocculation rate. These dissolved Ca2+ cations in the solution conduct to a partial coagulation making the delayed flocculation targeted initially with the addition of magnesium oxide less effective.

Tuning electrostatic repulsive and acid–base forces for efficient fouling mitigation in membrane filtration system

Membrane fouling caused by colloidal particles and microorganisms impose restrictions to further practical implementation of membrane separation technology. To advance the practical applications of this technology sustainably, this study explores an in-situ fouling control strategy utilizing an electrochemical membrane filtration (EMF) system. By applying varying electric potentials, the study evaluated the impact on dissolved organic matter (DOM) removal and elucidated the fouling mechanisms involved. The results indicate that increasing the potential significantly enhances the water flux of the conductive carbon membrane (CC/PVDF), with the flux at 3.0 V being 2.1 times greater than at 0 V. Moreover, this adjustment in potential significantly reduces the attachment of viable bacteria to the CC/PVDF membrane, with an applied potential greater than or equal to 2 V completely inactivating Escherichia coli (E. coli). The cohesive free energy (ΔGSWS) and extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theories suggest that imposing an external potential improved the acid–base and electrostatic repulsive forces between foulants and the membrane, as the applied potentials significantly increased the surface potential and wettability of the membrane. This EMF system not only mitigates fouling effectively but also delineates a path for enhancing membrane durability in practical applications.

Selective adsorption of anionic dyes by a macropore magnetic lignin-chitosan adsorbent

Dyes pollution is well known for their hazardous impacts on human health and the environment. The removal of dyes from wastewater has become an important issue. In this study, magnetic micrometer-sized particles AL-CTS@MNPs were synthesized from alkaline lignin (AL) and chitosan (CTS) by “one-pot method”. The adsorbent presented higher selectivity adsorption effect on anionic dyes than amphoteric and cationic dyes, and even no adsorption effect on cationic methylene blue (MB), which showed that the anionic dyes could be better separated from the other two types of dyes. The adsorption isotherms of the dyes were highly consistent with the Langmuir model, and the maximum adsorption capacity was 329.50 mg/g for methyl orange (MO) and 20.00 mg/g for rhodamine B (RhB). AL-CTS@MNPs showed good adsorption of anionic dyes (MO) in the pH range of 3–9. Meanwhile, the adsorbent AL-CTS@MNPs were also characterized, showing rough surface with specific surface areas of 37.38 m2/g, pore diameter of 95.8 nm and porosity of 17.62 %. The particle sizes were ranged from 800 μm to 1300 μm. The electrostatic attraction and π-π* electron donor-acceptor interactions were the main forces between the adsorbent and anionic dyes. While the electrostatic repulsive force between the adsorbent and the cationic dyes resulted in the non-absorption of MB by AL-CTS@MNPs. Subsequently, the adsorbent maintained a removal rate of >95 % after five adsorption-desorption cycles, demonstrating its excellent stability and recoverability. Ultimately, the prepared AL-CTS@MNPs illuminated good prospect on complex components dyes wastewater treatment.

A diffused double-layer model of bulk nanobubbles in aqueous NaCl solutions

Bulk nanobubbles, known for their extraordinary stability due to their electrically charged surface, still have an elusive mechanism. This research examines the surface electrical properties of oxygen nanobubbles in various NaCl solution concentrations, utilizing a diffused double-layer model. The process involves the creation of nanobubbles through the hydrodynamic cavitation technique, followed by an assessment of their size and zeta potential. To quantify their influence on nanobubble stability, the thickness of the double layer, the density of surface charge, electrostatic repulsion and attractive force, and interaction energy between bubbles are evaluated. The results show that adding NaCl to nanobubble solutions increases bubble size while decreasing their negative zeta potential, minimizing repulsive electrostatic interactions among the bubbles. These findings are consistent with the diffused double-layer theory. Specifically, higher NaCl concentrations in solutions lead to thinner double layers and decreased energy barriers. Observing nanobubble stability in a 10 mM NaCl solution over six months reveals a decrease in bubble size accompanied by an increase in zeta potential. This rise in negative zeta potential correlates with changes in Debye length and ionic strength, inversely proportional to the solution's conductivity, likely due to reduced NaCl concentration over time. Furthermore, the pressure differential at the bubble interface is insufficient to overcome the pressure caused by the liquid's surface tension, indicating potential limitations in applying the diffused double-layer model. This highlights the need for further investigation to establish a more comprehensive understanding of the mechanical stability of bulk nanobubbles.

Preparation of polyaniline conductive membranes through immersion of dopant solution for dye/salt separation

The preparation of conductive loose nanofiltration (NF) membranes for effective separation of dye/salt wastewater mixtures remains a great challenge. In the current study, a novel method of immersing the polyaniline (PANI) membrane in some organic salt solutions to dope PANI membrane was employed to prepare conductive PANI loose NF membranes. Three dopants with different molecular weight, poly (sodium 4-styrene sulfonate) (PSS), sodium dodecyl sulfate (SDS), and sodium dodecylbenzene sulfonate (SDBS), were chosen to prepare the doping solutions under neutral and acidic (pH = 0.5 in HCl) conditions. The neutrally doped PANI membranes all had lower pore size distribution, lower Zeta potential, and higher conductivity compared with the undoped PANI membrane; and these properties were further enhanced for the membranes doped under acidic condition. The PANI membrane doped by acidic PSS solution (PANI-PSS-HCl membrane) had a pore size of 1.7 nm and a pure water flux of 44.7 L·m−2·h−1, and exhibited a rejection of over 99.9 % for eriochrome black T, acid fuchsin, congo red, and sunset yellow in the dye solutions, whereas less than 5 % for NaCl solution, which was suitable for dye/salt separation due to the large molecular size of PSS. When PANI-PSS-HCl membrane was used as the cathode, the membrane exhibited excellent anti-fouling performance with increased external voltage due to enhancement of electrostatic repulsion force between the anionic dyes and the surface of the conductive membrane. This work provides a simple and reliable method to prepare conductive loose NF membranes for effective separation of dye/salt wastewater with excellent anti-fouling performance under external voltage.

Hollow anion-Janus-modified poly(vinylidene fluoride) (PVDF) fiber membranes for nanosized virus removal

In this study, a hollow polyvinylidene fluoride (PVDF) fiber was developed and modified into a Janus membrane (Janus-VM) and an entirely hydrophobic membrane (Hydrophobic-VM) for removing 20-nm-scale viruses during biopharmaceutical processing. The Janus-VM has anionic properties on the outer and feed hydrophilic surfaces, and the inner pore surface (I.P.S) maintains the anionic-hydrophobic properties of the PVDF. Theoretically, an electrostatic repulsion force might be formed between the surface of the strong anionic membrane and anionic bacteriophages, preventing bacteriophages from adsorbing to the membrane surface. As a result, water flux can be increased through the reduction of membrane fouling. The PVDF membrane was modified through UV-irradiation, which causes –OH radicals to form on the membrane surface, and chemical grafting with anionic-hydrophobic/anionic-hydrophilic modifiers, which enhances the membrane’s anion characteristics (−27, −48 mV). Additionally, the average pore size was reduced from 34 nm to less than 20 nm through chemical surface modification, after which the Janus membrane showed an excellent initial water flux, with the protein recovery ratio (PRR) approaching 98.9 %. UV absorbance analysis revealed 100 % removal efficiency for 20- and 40-nm gold particles on the membranes. Furthermore, the initial log reduction value (LRV) was observed through flux performance using MS2 and PP7 bacterial phages, for which the Janus membrane showed an excellent virus removal performance (LRV > 6.8 and 6.5).

Bile-induced biofilm formation in Bacteroides thetaiotaomicron requires magnesium efflux by an RND pump.

Bacteroides thetaiotaomicron is a prominent member of the human gut microbiota contributing to nutrient exchange, gut function, and maturation of the host's immune system. This obligate anaerobe symbiont can adopt a biofilm lifestyle, and it was recently shown that B. thetaiotaomicron biofilm formation is promoted by the presence of bile. This process also requires a B. thetaiotaomicron extracellular DNase, which is not, however, regulated by bile. Here, we showed that bile induces the expression of several Resistance-Nodulation-Division (RND) efflux pumps and that inhibiting their activity with a global competitive efflux inhibitor impaired bile-dependent biofilm formation. We then showed that, among the bile-induced RND-efflux pumps, only the tripartite BT3337-BT3338-BT3339 pump, re-named BipABC [for Bile Induced Pump A (BT3337), B (BT3338), and C (BT3339)], is required for biofilm formation. We demonstrated that BipABC is involved in the efflux of magnesium to the biofilm extracellular matrix, which leads to a decrease of extracellular DNA concentration. The release of magnesium in the biofilm matrix also impacts biofilm structure, potentially by modifying the electrostatic repulsion forces within the matrix, reducing interbacterial distance and allowing bacteria to interact more closely and form denser biofilms. Our study therefore, identified a new molecular determinant of B. thetaiotaomicron biofilm formation in response to bile salts and provides a better understanding on how an intestinal chemical cue regulates biofilm formation in a major gut symbiont.IMPORTANCEBacteroides thetaiotaomicron is a prominent member of the human gut microbiota able to degrade dietary and host polysaccharides, altogether contributing to nutrient exchange, gut function, and maturation of the host's immune system. This obligate anaerobe symbiont can adopt a biofilm community lifestyle, providing protection against environmental factors that might, in turn, protect the host from dysbiosis and dysbiosis-related diseases. It was recently shown that B. thetaiotaomicron exposure to intestinal bile promotes biofilm formation. Here, we reveal that a specific B. thetaiotaomicron membrane efflux pump is induced in response to bile, leading to the release of magnesium ions, potentially reducing electrostatic repulsion forces between components of the biofilm matrix. This leads to a reduction of interbacterial distance and strengthens the biofilm structure. Our study, therefore, provides a better understanding of how bile promotes biofilm formation in a major gut symbiont, potentially promoting microbiota resilience to stress and dysbiosis events.

Research on seedling sowing method based on high voltage electrostatic characteristics

In response to the difficult problem of high leakage rate and low seed pick-up rate of traditional air-suction seed dischargers. This study proposes a new high-voltage electrostatic vegetable seedling sowing method and system based on phase sucking of opposite charges and repulsive seeding of same charges. This method does away with small orifices and long conductance suction holes. It can solve the technical bottleneck of the traditional air-suction seed rower at the source, which causes a decrease in seed rowing accuracy due to clogging of the suction holes when facing irregular small vegetable seeds that are not pelleted. Combining high voltage electrostatic polarisation for seed vigour with precision seeding technology. Improving seed vigour and crop yield while precision sowing. Modelling the mechanics of adsorption seeding and repulsive seeding systems. Identify the main factors affecting electrostatic adsorption and phase repulsion forces and their interrelationships; Analysis of the decay mechanism of the electrostatic adsorption force upon repeated action. Proposing measures for the rapid restoration of the original equilibrium state of the dielectric insulation by reverse electric field polarization; Analysis of the migration pattern of electric particles during polarisation. Solving the equations for seed dynamics during sowing; At positive input voltages of 16 kV and negative input voltages of 0, 4, 8, 12, 16 and 20 kV. Separate dielectric insulation layer adsorption seeding tests. The test results show that: The reverse electric field polarisation of the dielectric insulating layer is effective in containing the electrostatic adsorption decay. The best containment was achieved at a positive input voltage of 16 kV and a negative input voltage of 16 kV; Seeding performance verification tests at a positive input voltage of 16 kV and a negative input voltage of 16 kV. The test results show that: The sowing conformity index was 90.25 %, the reseeding index 3.40 % and the missed sowing index 6.35 %. In the evaluation of applied research, the multi-objective optimization design with the objective function of maximum seed discharge qualification index, minimum leakage index and replanting index, the optimal parameter combinations of the test factors can be obtained as follows: the size of the type hole is 5.977 mm, and the output voltage of the positive high-voltage electrostatic generator is 16.423 kV, and at this time, the seeding machine's seed discharge qualification index is 90.78 %, the replanting index is 3.05 %, and the leakage index is 6.17 %. To verify the reliability of the optimal design of structural parameters, the seeding performance verification test is carried out, which can be obtained: the qualified index of row seeding is 90.54 %, the index of reseeding is 2.86 %, and the index of leakage is 6.60 %, which meets the technical requirements of precision seeding. The research not only provides a reference for the development of precision sowing machinery and equipment for irregular small-grain vegetable seeds. It also provides an academic reference for the research of quantitative adsorption and rapid separation methods and theories for irregular small particle materials.

3D Multimodal, omnidirectional router of aqueous microdroplets based on the synergy of photovoltaic and triboelectric effects

In this paper, we present a 3D multimodal router for aqueous microdroplets, addressing the ongoing challenge of 3D transportation of microdroplets in free space. Our strategy combines the photovoltaic effect of a LiNbO3:Fe substrate with the triboelectric effect of a superhydrophobic coating. We demonstrate that by positively charging the aqueous microdroplets through the contact-electrification process while they roll or elongate on the superhydrophobic surface, we can achieve their controlled and electrostatically ballistic ejection for free-space transportation. Leveraging the superfast and repetitive laser-scanning capabilities of a laser marking system, we develop various 2D/3D routing modes that utilize repulsive or attractive electrostatic forces to deflect or trap the microdroplets in parallel or cascading configurations. We propose a 3D routing mode suitable for photosensitive microdroplets, employing asynchronous illumination with an appropriate ON/OFF duty ratio. We also enable the 3D omnidirectional routing of initially motionless and traveling microdroplets using toroidal and linear laser-scanning, respectively, thus facilitating the transportation of sequential microdroplets in overpass configurations. Our proposed technique opens up new possibilities for free-space microfluidics, enabling the complex delivery of biochemical substance.