Polyvinyl chloride-added dibutyl adipate for high-performance electrohydrodynamic pumps

In recent years, functional fluidic and gas electrohydrodynamic (EHD) pumps have received considerable attention due to their remarkable features, such as simple structure, quiet operation, and energy-efficient utilization. EHD pumps can be applied in various industrial applications, including flow transfer, thermal management, and actuator drive. In this paper, the authors reviewed the literature surrounding functional fluidic and gas EHD pumps regarding the following aspects: the initial observation of the EHD effect, mathematical modeling, and the choice of pump structure, electrode configuration, and working medium. Based on the review, we present a summary of the development and latest research on EHD pumps. This paper provides a critical analysis of the current limitations of EHD pumps and identifies potential areas for future research. Additionally, the potential application of artificial intelligence in the field of EHD pumps is discussed in the context of its cross-disciplinary nature. Many reviews on EHD pumps focus on rigid pumps, and the contribution of this review is to summarize and analyze soft EHD pumps that have received less attention, thus reducing the knowledge gap.

EHD gas pump as a cooling device for electronic components in a horizontal channel

Developing soft actuators has emerged as one of the most promising areas in robotics, with a growing demand for tunable lenses driven by the rapid advancements in intelligent mobile devices and cameras. Traditional mechanical lens systems are characterized by their heaviness, complexity, and rigidity. To address these limitations, this research introduces a novel approach: a dual‐chamber liquid lens actuated by an electrohydrodynamic (EHD) pump. The study involves the fabrication of a planar EHD pump, with an experimental investigation into the impact of electrode gap, electrode width, and electrode‐pair gap on the pump's pressure. Following the optimization of the EHD pump, a dual‐chamber lens is constructed, comprising two chambers, a rigid transparent plate, and two prestretched elastic membranes, which are connected to the EHD pump via tubes. Additionally, a mathematical model is developed to predict the focal length of the lens. Both experimental and theoretical analyses are conducted to explore the effects of the prestretch ratio of the elastic membranes and the radius ratio of the two chambers on focal length variation. The theoretical predictions of the focal length–voltage curves align closely with the experimental findings, providing validation for the proposed theoretical model.

So far, electrohydrodynamic (EHD) pumps based on the injection or the field-enhanced dissociation (the Wien effect) at the surface of metal electrodes have been studied. This paper proposes and studies both numerically and experimentally a fundamentally new pump scheme, namely, the EHD pump operating due to the Wien effect in a conical hole located in the solid insulation barrier. An experimental setup of the pump has been created, and performance (pressure vs flow rate) characteristics have been measured that satisfactorily agree with the results of computer simulation. With the size of the hole being a fraction of a millimeter, the proposed system performance is comparable to that of the previously studied EHD pumps.

The effect of electrode orientation in an electrohydrodynamic (EHD) gas pump inside a square channel is experimentally examined for its effective use in thermal management. The two-stage gas pump with electrodes flush mounted on two parallel walls in each stage is powered by DC voltages ranging from 24 to 28 kV. In addition to the volume flow rate produced, the performance of the pump is evaluated using an energy efficiency factor, which is defined as the volume flow rate delivered by a unit power input. It is found that this parameter has a larger value for the EHD pump with aligned electrodes. However, the EHD pump with offset electrodes can produce more mixing of flow inside the channel, which may be more favorable for the application in thermal management. Most importantly, EHD gas pumps with either electrode configuration have a greater energy efficiency than conventional fans, and thus have a greater advantage for applications in the thermal management. This advantage is even more prominent when pumps are operated with uneven applied voltages.

Flow control and heat transfer enhancement represent critical research in the aerospace field, facing challenges such as complex environments, long-term thermal management requirements, low energy consumption, and high integration. As an emerging fluid-driven and thermal management technology, the electrohydrodynamic (EHD) pump is independent of gravity, and it demonstrates significant application potential. This study presents a modular EHD pump and systematically tests its flow control, heat transfer enhancement, and dynamic response characteristics. Experimental results indicate that as the applied voltage increases, the flow rate of the EHD pump increases significantly. At a heat flux of 10 000 W/m2, the enhancement efficiency of the pump reaches 107.59%. By constructing an energy consumption characteristic curve, the energy consumption of the EHD pump is evaluated, showing a maximum of 0.046 W at 10 kV. Dynamic response tests reveal that the startup and shutdown processes of the pump can be divided into four stages: initiation, progression, stabilization, and decay. Owing to its compact, gravity-independent, and modular design, the pump shows potential for use in spacecraft thermal management and compact electronic cooling systems.

One of the most promising applications of electrohydrodynamic (EHD) pumps occurs at the microscopic scale. However, microscopic dimensions do not always imply microscopic characteristics, and stringent requirements are sometimes imposed on the values of certain variables—for instance, a flow rate of the order of 10 ml/s and a pumping pressure of 100 kPa. This study proposes an EHD pump system based on a holed metal-clad insulation barrier pair that generates high-performance characteristics. A feature of the system is the focusing of electric field lines inside the holes, which increases the electric field strength and activates charge formation processes. Dodecane with 10% Span 85 was used as the working dielectric liquid with a conductivity of 8 × 10−9 S/m. The Onsager effect is believed to be the dominant charge formation mechanism in the pump with some injection contribution. We measured the characteristics of the electric current (curves of current–voltage and current–time) as well as the performance-related characteristics of the pump in experiments (curves of pressure–voltage and flow rate–pressure at different voltages). The scalability of the flow rate of the proposed EHD pump was investigated by comparing single-hole and nine-hole configurations. As a result, a non-linear growth of the pump performance on the number of holes was obtained, with the distance between the holes comparable to the inter-electrode gap. The estimated flow rate and pressure for the proposed modulus EHD pump with dimensions of 1 cm3 can reach values of 82 ml/s and 620 kPa, respectively.

The electrohydrodynamics (EHD) technique has shown promising results in enhancing heat transfer and mass transport. It has endless potential in industrial applications such as drying technology, design of evaporators, condensers, electrostatic precipitator, plasma actuator, and micropumps in microfluidic, chip-integrated cooling, and drug delivery systems. In recent years, a significant amount of research has been directed to design EHD micropumps as researchers realize their attractive features (e.g., no moving part, simple fabrication process) are most suitable in the aforementioned microelectro-mechanical systems (MEMS). This paper evaluates the performance of an EHD pump in a vertical square (4 × 4 inch) channel with a non-intrusive wire-electrode configuration. The voltage and current characteristics of the EHD pump are measured such that numerical simulations can be carried out. Measurements were taken from the corona threshold voltage to the occurrence of sparkover with a 1 kV increment. Due to the corona wind generated, the average volume flow rate in the channel was as high as 10 liter per second subjected to a voltage difference of 25 kV.

Steady-state 2-D electrohydrodynamic pumping through bipolar hetero-charge conduction phenomenon has been investigated numerically. In order to validate the presented numerical algorithm, the pump geometry was chosen to be identical to the device whose experimental data is available in the literature. The concentrations of the positive and negative ions and the electric field distribution of the pump were calculated. The resulting static pressure generation of the pump was predicted for the refrigerant R-123 at different applied voltages ranging between 2 to 20kV DC. The comparison between the predicted static pressure generation and the previous experimental results in the absence of fluid flow shows a good agreement with a maximum deviation of 12.5% at 20 kV applied voltage. In the present work, the electrical conductivity of R-123 was assumed to be the most recent proposed value of σ=7×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-11</sup> S/m. Assuming this value of electrical conductivity, the numerical model predicts the hetrocharge layer thicknesses in the order of gap spacing even at low applied voltage and weak field regime. By increasing the applied voltage, above ~15kV, the heterocharge layers of the opposite electrodes extend to the entire gap spacing and create an overlapping region. Assuming three orders of magnitude higher value of electrical conductivity for R-123 in the previous numerical studies, the thickness of the hetrocharge layer and pressure generation was underestimated by almost two orders of magnitude. Through extensive numerical experiments, the electrical conductivity of the working fluid was found to be an important parameter to determine the heterocharge layer thickness, electric body force, and predicted static pressure. The issues related to the scaling of the conduction pump when the heterocharge layers create an overlapping region in the reduced gap spacing are discussed.

Designing and manufacturing actuators using soft materials are among the most important subjects for future robotics. In nature, animals made by soft tissues such as the octopus have attracted the attention of the robotics community in the last years. Suckers (or suction cups) are one of the most important and peculiar organs of the octopus body, giving it the ability to apply high forces on the external environment. The integration of suction cups in soft robots can enhance their ability to manipulate objects and interact with the environment similarly to what the octopus does. However, artificial suction cups are currently actuated using fluid pressure so most of them require external compressors, which will greatly increase the size of the soft robot. In this work, we proposed the use of the ElectroHydroDynamics (EHD) principle to actuate a suction cup. EHD is a fluidic phenomenon coupled with electrochemical reaction that can induce pressure through the application of a high-intensity electric field. We succeeded in developing a suction cup driven by EHD keeping the whole structure extremely simple, fabricated by using a 3D printer and a cutting plotter. We can control the adhesion of the suction cup by controlling the direction of the fluidic flow in our EHD pump. Thanks to a symmetrical arrangement of the electrodes, composed by plates parallel to the direction of the channel, we can change the direction of the flow by changing the sign of the applied voltage. We obtained the pressure of 643 Pa in one unit of EHD pump and pressure of 1428 Pa in five units of EHD pump applying 6 kV. The suction cup actuator was able to hold and release a 2.86 g piece of paper. We propose the soft actuator driven by the EHD pump, and expand the possibility to miniaturize the size of soft robots.

Electrohydrodynamic (EHD) pumping of two-phase media has potential applications related to both pure pumping as well as heat transfer enhancement. Utilization as pumping mechanism is attractive for terrestrial and outer space systems. Augmentation of mass flow rate in two-phase heat transfer applications, such as boiling and condensation, leads to enhanced heat transfer coefficients, thus making EHD pumping an attractive candidate for these situations. A theoretical model is presented for EHD induction pumping of a stratified liquid/vapor medium accounting for electric shear stresses due to interfacial and bulk charges. Bulk charges are a result of temperature gradient in the liquid phase of the fluid. Conditions are established under which the bulk effect plays a significant role in the pumping process.

In this study, fluid flow induced by a two stage electrohydrodynamic (EHD) gas pump in a square channel has been evaluated by experimental measurement and numerical simulations. This study is implemented for a two stage EHD gas pump with three emitting electrode configurations: 8, 24, and 56 respectively to seek the relation between the number of stages and emitting electrodes. The EHD pump is evaluated for a wide range of operating voltages starting from 20 kV up to 28 kV for further improvement in its performance over a single stage. To achieve the maximum enhancement, the emitting electrodes of the EHD gas pump are flush mounted on the channel walls so that the corona wind produced directly disturbs the boundary layer thickness and improves the heat transfer. This is leading to a higher velocity near the channel walls and resulting in an inverted parabolic velocity profile at the center of the channel, which is opposite to the fully developed velocity profile of a forced flow. Velocities are measured at three cross-sections along the tube length and then integrated to obtain the volume flow rate. The results show that EHD technique has a great potential for many engineering applications.

An induction electrohydrodynamic (EHD) pump in an axisymmetric configuration was designed and built to examine the heat transfer enhancement which accompanies fluid pumping under laminar flow conditions. The apparatus was operated at several tilt angles between 0 (horizontal) and 90/spl deg/ while the augmentation of heat transfer was measured and compared to typical forced pumping and natural circulation. The increase in the overall conductance value for EHD pumping compared to typical forced pumping and natural circulation was as high as 105 and 122%, respectively. This corresponded, to a much higher increase in the inside convection coefficient, which was the only resistance to heat transfer being affected by induction pumping. The operating frequency had an effect on the peak overall conductance value. >

Rolling motions have been observed in many animals and insects. In the previous fluidic rolling system, a deformed chamber and long cables were imperative to drive the soft rolling actuators, which required high pressure and a sophisticated controlling strategy. In this study, we propose a soft fluidic roller using a simple structure composed of a bendable and twistable electrohydrodynamic (EHD) pump and a layer of natural latex. To realize the rolling motion, we first optimized the electrode and channel height of the EHD pumps using different patterns and designs. We also examined the output power, efficiency, pressure loss, bending, and twisting performance. Subsequently, the optimized electrodes and channel height were selected to design the power source of the EHD roller. This roller was lightweight (0.7 g) with an amount of liquid (0.6 g). This EHD robot can roll as the EHD liquid oscillates under a duty-controlled voltage realized using a high-voltage circuit. Next,we investigated the influence of frictional forces on rolling performance. Finally, the rolling motion in the liquid was demonstrated. This study extends the EHD pumps to independent soft actuators integrated with a soft power source.

The performance of a two-stage electrohydro-dynamic (EHD) gas pump in a circular tube has been investigated for operating conditions in which each stage is charged at a different voltage. The main objective of the study is to examine the characteristics of resulting flow as well as the efficient use of energy in sustaining and improving the volume flow rate produced by a single-stage pump over a greater distance. To this end, two different sizes of tube are employed (61.8 mm and 127.8 mm in diameter). Each stage uses eight emitting electrodes flush mounted on the tube wall. In addition, two electrode configurations, aligned and offset, with fixed electrode spacing have been considered. The electrodes at both stages are charged at voltages in positive polarity from 18 kV to 22 kV. The velocity profile and volume flow rate delivered are compared with those produced by the same pump operating at even voltages to provide additional insight to the problem. The results thus obtained have important implications for practical use of EHD gas pump.