Active suction cup actuated by ElectroHydroDynamics phenomenon

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

Electrohydrodynamic (EHD) pumps are a promising driving source for various fluid-driven systems owing to features such as simple structure and silent operation. The performance of EHD pumps depends on the properties of the working fluid, such as conductivity, viscosity, and permittivity. This implies that the tuning of these parameters in a working fluid can enhance the EHD performance. This study reports a method to modify the properties of a liquid for EHD pumps by mixing an additive. Specifically, dibutyl adipate (DBA) and polyvinyl chloride (PVC) are employed as the working fluid and the additive, respectively. The results show that when the concentration of PVC is 0.2%, the flow rate and pressure at applied voltage of 8 kV take highest value of 7.85 μL/s and 1.63 kPa, respectively. These values correspond to an improvement of 109% and 40% for the flow rate and pressure, respectively, compared to the pure DBA (PVC 0%). When the voltage is 10 kV, the flow rate of 10.95 μL/s and the pressure of 2.07 kPa are observed for DBA with PVC concentration of 0.2%. These values are more than five times higher than those observed for FC40 at the same voltage (2.02 μL/s and 0.32 kPa). The results also suggest that optimal conductivity and viscosity values exist for maximizing the EHD performance of a liquid. This demonstrates the validity of the proposed method for realizing high-performance EHD pumps by using additives in the working fluid.

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.

Vertebrate animals benefit from a combination of rigidity for structural support and softness for adaptation. Similarly, integrating rigidity and softness can enhance the versatility of soft robotics. However, the challenges associated with creating durable bonding interfaces between soft and rigid materials have limited the development of hybrid robots. Existing solutions require specialized machinery, such as polyjet 3D printers, which are not commonly available. In response to these challenges, we have developed a 3D printing technique that can be used with almost all commercially available FDM printers. This technique leverages the common issue of underextrusion to create a strong bond between soft and rigid materials. Underextrusion generates a porous structure, similar to fibrous connective tissues, that provides a robust interface with the rigid part through layer fusion, while the porosity enables interlocking with the soft material. Our experiments demonstrated that this method outperforms conventional adhesives commonly used in soft robotics, achieving nearly 200% of the bonding strength in both lap shear and peeling tests. Additionally, we investigated how different porosity levels affect bonding strength. We tested the technique under pressure scenarios critical to soft and hybrid robots and achieved three times more pressure than the current adhesion solution. Finally, we fabricated various hybrid robots using this technique to demonstrate the wide range of capabilities this approach and hybridity can bring to soft robotics.

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.

The suckers on the octopus arm play a pivotal role in the execution of tasks in unstructured environments by providing a means to grip objects as well as perceive the environment through (chemo‐)tactile receptors in the suckers. This work presents an octopus‐inspired suction cup with high‐resolution tactile sensing capabilities using a camera that captures the displacement of markers that are integrated in the suction cup. The orientation of the suction cup with respect to an object surface could be predicted with an average error of 1.97° for latitude and 9.41° for longitude. In a closed‐loop control experiment, the orientation of the suction cup with respect to the object surface is estimated by an initial touch and the suction cup is consequently reoriented to approach the object surface in a perpendicular manner. The passive compliance of the suction cup is sufficient to compensate for the prediction error and a seal could be created on all of the objects. In combination with the automated design and manufacturing process, this is a major step toward the deployment of sensory innervated suction cups for motion planning and control of soft continuum robot arms.

The research in this paper extends previous liquid film flow boiling studies by including the effect of an additional electrohydrodynamic (EHD) force, namely the dielectrophoretic (DEP) force. Rather than using only EHD conduction pumping of the liquid film to electro-wet the heater surface, a localized non-uniform electric field above the heater surface is also used to generate a dielectrophoretic force for improved vapor bubble extraction during the nucleate boiling regime. The effect of liquid film height and applied potential are studied as a function of heater superheat and heat flux. The study considers the sole and combined effect of DEP with EHD conduction pumping. A brief analytical study is also used to estimate the expected dielectrophoretic force magnitude and explain the results. All of the above studies are also used to quantify the enhancement in heat transfer that can be achieved when heat transport systems are driven or augmented by these electrohydrodynamic phenomena. The results show remarkable enhancement of up to 1217% in heat flux and boiling heat transfer coefficient for a given superheat when both mechanisms are used simultaneously. The experimental data are important for applications in thermal management in terrestrial and micro-gravity conditions.

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.

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.

Electrohydrodynamic (EHD) phenomena have been shown to enhance heat transfer in a variety of heat transport designs including capillary pumped loops for extraterrestrial nuclear applications. Previously, EHD enhancement has been shown to improve the heat transport of experimental CPLs. Further enhancement with the addition of EHD gas pumps to the vapour phase requires EHD gas pump phenomena and performance to be characterized with respect to gravity to determine the expected enhancement from this arrangement in zero and microgravity environments. In this paper an EHD gas pump is oriented with gravity (inverted), 90° to gravity (horizontal) and against gravity (vertical) to determine the effect gravitational and buoyancy forces have on the flow and heat transport of EHD gas pumps. The flow and temperature profiles of the pump at the outlet are presented to demonstrate the orientation effect gravity and buoyancy imposes on EHD gas pumps. The EHD number is calculated and presented. The paper determines that there is a noticeable orientation effect at lower applied voltages due to the heating effects causing recirculation in the flow being reduced with the aid of buoyancy forces. However, the effect is less noticeable at higher applied voltages due to the stronger EHD forces.

To improve the adaptability of soft robots to the environment and achieve reliable attachment on various surfaces such as smooth and rough, this study draws inspiration from the collaborative attachment strategy of insects, cats, and other biological claw hooks and foot pads, and designs an actuator with a bionic claw hook–suction cup hybrid structure. The rigid biomimetic pop-up claw hook linkage mechanism is combined with a flexible suction cup of a ‘foot pad’ to achieve a synergistic adhesion effect between claw hook locking and suction cup adhesion through the deformation control of a soft pneumatic actuator. A pop-up claw hook linkage mechanism based on the principle of cat claw movement was designed, and the attachment mechanism of the biological claw hooks and footpads was analysed. An artificial muscle-spring-reinforced flexible pneumatic actuator (SRFPA) was developed and a kinematic model of the SRFPA was established and analysed using Abaqus. Finally, a prototype of the hybrid actuator was fabricated. The kinematic and mechanical performances of the SRFPA and entire actuator were characterised, and the attachment performance of the hybrid actuator to smooth and rough surfaces was tested. The results indicate that the proposed biomimetic claw hook–suction cup hybrid structure actuator is effective for various types of surface adhesion, object grasping, and robot walking. This study provides new insights for the design of highly adaptable robots and biomimetic attachment devices.

Background Negative pressure wound therapy (NPWT) includes closed vacuum drainage (VSD) technology and vacuum assisted closure (VAC) technology, which have been used as the new treatments to promote acute and chronic wound healing for nearly 20 years. Currently, the Medline database has collectively referred to these techniques as the negative pressure wound therapy (NPWT) . Among them, VAC is a medical foam material with pore spaces (commonly using hydrophobic polyurethane foam dressing) to cover the wound after debridement, and is sealed with a transparent film to form a confined space. Then it is connected with a dedicated negative pressure pump for continuous or discontinuous negative pressure suction, so as to fully drain wound exudate and infectious substances, reduce edema, increase local blood flow, reduce the number of bacteria on the wound, and accelerate the growth rate of granulation tissue, thereby effectively promoting of secondary or tertiary (delayed) wound healing. In recent years, VAC has been widely used in trauma orthopedics, mainly for acute and chronic wounds, soft tissue infections, ulcers (such as diabetic ulcers or pressure sores) , and wounds before and after flap transplantation. Due to the complexity of the VAC tubing connection, the lack of preventive measures against unplanned extubation during clinical care can result in wound exposure, increase the incidence of complications, and lead to adverse care events. Different methods of tubing fixation have various effects in preventing unplanned extubation. Therefore, the innovative fixation of the VAC tubing fixation method ensures safe and effective treatment while also reducing unplanned accidental extubation. Methods 1. General information: From July 2016 to June 2018, our department treated 77 patients with upper extremity trauma and infection, including 43 males and 34 females. Their ages ranged from 12 to 79 years. The reasons for VAC included 1 case of compartment syndrome, 28 cases of dog bite, 25 cases of open injury, 9 cases of soft tissue infection, 3 cases of postoperative wound nonunion, and 11 cases of postoperative wound infection. Forty-one patients received VAC tubing fixation with conventional methods, including 23 males and 18 females, and their ages ranged from 12 to 71 years (48.32±17.36) years; 36 patients received VAC tubing fixation with sandwich method, including 20 males and 16 females, and their ages ranged from 22 to79 years (55.19±14.27) years. 2. Intervention methods: (1) Conventional tube fixation group. The hydrophobic polyurethane foam dressing was cut during surgery to fit the wound size, including the fistula and ulcer; the sealing membrane was trimmed to completely cover the dressing and the area beyond the edge of the wound 3-5 cm. The operator used the index finger and thumb to pinch the sealing film, cut a small hole in the film to allow the wound to seep through (without opening the dressing) , opened the suction cup, and fixed the suction cup on the sealing film. Finally, the treatment host was connected, and the pressure was set by touching the screen of VAC negative pressure wound therapy device. (2) Sandwich method fixation group. On the basis of the last step of the conventional tubing fixation method, the film was covered on the fixed suction cup and the proximal end of the VAC tube, and the VAC tube was fixed on the corresponding limb with the high lift method. If the suction cup was fixed near the joint, it should be protected by a brace to prevent from falling off due to repeated movement of the joint. 3. Statistical methods: SPSS23.0 statistical software was used to analyze and process the data. The measurement data was expressed as±s; the count data was described by the number of cases and percentage, and the chi-square test was used. A value of P<0.05 was considered significant difference. Results There were no significant differences in gender and age between the two groups (P>0.05) . In the conventional tube fixation group, there were 8 cases of dissociations, 3 cases of sudden position change, 4 cases of postoperative delirium with postoperative sputum self-extraction, and 1 case of patient consciously uncomfortable to pull the tube accidentally. In the sandwich method group, 1 case of unplanned extubation occurred due to the reason of postoperative delirium and inability to corporate with care. There was a statistically significant difference in the unplanned extubation of the two tube fixation methods (P=0.032) . Conclusions The use of the sandwich method to fix the upper limb VAC vacuum suction tube can reduce the incidence of unplanned extubation to a certain extent, and help to reduce the incidence of negative clinical care events, which is worth promoting. Key words: Sandwich method; Vacuum assisted closure; Unplanned extubation; Care

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 the contemporary era, novel manufacturing technologies like additive manufacturing (AM) have revolutionized the different engineering sectors including biomedical, aerospace, electronics, etc. Four-dimensional (4D) printing aka AM of smart materials is gaining popularity among the scientific community, which has the excellent ability to make soft structures such as soft robots, actuators, and grippers. These soft structures are developed by applying various stimuli such as pH, temperature, magnetic field, and many combinations onto soft materials. Stimuli in 3D printing permit various shape-morphing behaviors such as bending, twisting, folding, swelling, rolling, shrinking, origami, or locomotion. A wide variety of soft magnetic structures can be fabricated through the incorporation of soft or hard magnetic particles into soft materials resulting in magneto-active soft materials (MASMs). With this integration, magneto-thermal coupling actuation allows diverse magneto-deformations, facilitating the development of personalized devices that are capable of enhanced deformation. In this review, guidelines are provided on the 3D printing for MASMs such as magneto-active polymers (MAPs), magneto-active composites, and magneto-active hydrogels (MAHs) on the booming development of various smart and flexible devices such as soft robots, wearable electronics, and biomimetic devices. Moreover, 3D-printed soft robotics have an outstanding capacity to adapt to complicated situations for many advanced actuating applications. Finally, some current challenges and emerging areas in this exciting technology have been proposed. Lastly, it is anticipated that technological advancements in developing smart and intelligent magneto-active structures will have a significant impact on the design of real-world applications.