Elastomeric Diaphragm Research Articles

The stiffness of elastomeric diaphragm in pneumatic springs

The stiffness of elastomeric diaphragm in pneumatic springs

Effect of applied pneumatic pressure on the polishing spot size and the total normal force in pneumatically configurable polishing

The present study pertains to a compliant polishing technique called Pneumatically Configurable Polishing (PCP) which uses the precise inflation of a thin elastomeric diaphragm or membrane using pneumatic pressure for generating nano level surface finish on substrate surfaces. The PC polishing tool which has a cup shape is made to contact the workpiece surface such that its flexible nature can adapt itself to the macro features on the workpiece. This inflated tool-work contact leads to the entrapment of the hard abrasives preplaced in the interface zone in the form of a slurry. The rotary motion of the tool along with the relative motion between the workpiece and tool, help to generate an improved surface finish in the interface area. The area of the finishing zone is an important outcome of the polishing regime because it defines the dimensions of the area which will be affected by the tool. It also helps to estimate the time needed for polishing a large area. Also, the force transmitted to the workpiece surface is an important measure to estimate the functional life of the tool. In the current study, the variation of the spot size and total normal force are modelled mathematically in terms of the physical and geometrical properties of the tool as well as the applied fluid pressure. The Hertz theory of contact is used to model the contact conditions in the polishing interface zone. The model studies the effect of pneumatic pressure on membrane inflation and its influence on the area of the polishing spot at varying working gaps. The effect of the applied fluid pressure is studied on the normal force experienced by the workpiece, and the results obtained from the model are validated with experimental verification under identical polishing conditions. The values obtained experimentally show a close agreement with the theoretical results obtained from the model.

Novel Pressure Vessel for Pressurizing Corrosive Liquids With Applications in Accelerated Life Testing of Composite Materials

Abstract A system was designed for high-pressure accelerated life testing (ALT) of composite materials exposed to saline water solutions or other potentially corrosive media. The system was comprised primarily of a large stainless steel pressure vessel with the capability to perform extended pressure holds of up to 41.3 MPa at temperatures up to 70 °C. Using a nylon fabric-reinforced Buna-N rubber diaphragm as a media isolator and an inert ceramic coating on all wetted surfaces of the vessel, 3.5% saline water solutions were successfully held at test pressures and temperatures for extended periods with no evidence of corrosion or other degradation even after several days of exposure. Pressurization was achieved through a hydraulic pump system, which contained pressure monitoring equipment and valves and was isolated from the saline water by the diaphragm. The temperature of the entire vessel and contents was maintained by complete immersion in a heated, filtered water bath. The efficacy of using an elastomeric diaphragm to transfer large pressures between two near-incompressible fluids without mixing was shown, provided adequate reinforcement in the form of an interwoven fabric was provided to prevent tearing and extrusion from the extreme through-thickness stresses, particularly at clamping locations. Discussion on the effects of temperature, material, thickness, reinforcement, and sealing methods on the effectiveness and repeatability of the system is provided, and a demonstration of an accelerated test on a carbon–fiber composite is also presented.

An organosynthetic soft robotic respiratory simulator.

In this work, we describe a benchtop model that recreates the motion and function of the diaphragm using a combination of advanced robotic and organic tissue. First, we build a high-fidelity anthropomorphic model of the diaphragm using thermoplastic and elastomeric material based on clinical imaging data. We then attach pneumatic artificial muscles to this elastomeric diaphragm, pre-programmed to move in a clinically relevant manner when pressurized. By inserting this diaphragm as the divider between two chambers in a benchtop model—one representing the thorax and the other the abdomen—and subsequently activating the diaphragm, we can recreate the pressure changes that cause lungs to inflate and deflate during regular breathing. Insertion of organic lungs in the thoracic cavity demonstrates this inflation and deflation in response to the pressures generated by our robotic diaphragm. By tailoring the input pressures and timing, we can represent different breathing motions and disease states. We instrument the model with multiple sensors to measure pressures, volumes, and flows and display these data in real-time, allowing the user to vary inputs such as the breathing rate and compliance of various components, and so they can observe and measure the downstream effect of changing these parameters. In this way, the model elucidates fundamental physiological concepts and can demonstrate pathology and the interplay of components of the respiratory system. This model will serve as an innovative and effective pedagogical tool for educating students on respiratory physiology and pathology in a user-controlled, interactive manner. It will also serve as an anatomically and physiologically accurate testbed for devices or pleural sealants that reside in the thoracic cavity, representing a vast improvement over existing models and ultimately reducing the requirement for testing these technologies in animal models. Finally, it will act as an impactful visualization tool for educating and engaging the broader community.

Investigation of modal properties and layout of elastomer diaphragm tanks in telecommunication satellite

Elastomer diaphragm tanks have been adopted in many spacecraft applications, such as upper stages, space platforms, commercial and civil spacecraft as a propellant tank in which liquid propellant is covered with a diaphragm and compressed into a combustion chamber by gas pressure. Investigating the dynamic response and the influence of various parameters on the modal properties is a significant issue in the modeling of the space diaphragm tanks. In this work, the numerical study is presented to investigate the modal properties of a spherical fuel tank in both uncovered and covered cases with a flexible diaphragm as fluid–structure interacting situations. The filling volume ratio of fluid ranges is from 25 to 50%. Numeric dynamic simulations created by ANSYS software are verified by the experimental results of test tank and then, the validation of the numeric model is used to determine the natural frequencies and mode shapes of really elastomer diaphragm tank as the second case study for two conditions: fluid filling volume ratio of 80% that the tank is in full load condition and liquid filling volume ratio of 14% when the diaphragm completely inverted. After that, the best layout of diaphragm tanks in two-story satellite is detected by calculating deviations from center of gravity and cross moments of inertia objective functions in multi objective optimization software. Then the natural frequencies of satellite include diaphragm tanks computed and compared with natural frequencies and static loads of launch vehicle requirements. The achieved results of this study showed that the numeric simulations are able to renovate the experimental vibration characteristics of the diaphragm tank with a good precision. In addition numeric model can detect the best layout of diaphragm tank components.

Highly Sensitive Tactile Shear Sensor Using Spatially Digitized Contact Electrodes.

In this article, we report on a highly sensitive tactile shear sensor that was able to detect minute levels of shear and surface slip. The sensor consists of a suspended elastomer diaphragm with a top ridge structure, a graphene layer underneath, and a bottom substrate with multiple spatially digitized contact electrodes. When shear is applied to the top ridge structure, it creates torque and deflects the elastomer downwards. Then, the graphene electrode makes contact with the bottom spatially digitized electrodes completing a circuit producing output currents depending on the number of electrodes making contact. The tactile shear sensor was able to detect shear forces as small as 6 μN, detect shear direction, and also distinguish surface friction and roughness differences of shearing objects. We also succeeded in detecting the contact slip motion of a single thread demonstrating possible applications in future robotic fingers and remote surgical tools.

An Analytical Model for a Pneumatic Vibration Isolator with the Stiffness Effect of the Elastomeric Diaphragm

The elastomeric diaphragm is widely used in pneumatic vibration isolators, and the relevant model is often ignored due to its complexity. Considering that the ignored model of the elastomeric diaphragm in pneumatic vibration isolators plays an important role in the discrepancy between the predicted and practical behavior, this paper develops an analytical model for the elastomeric diaphragm using the Mooney‐Rivlin modeling method and elastomeric theory. Specifically, the elastomeric diaphragm consists of several segments in the axial section. After considering the structural restriction, each segment can be simplified as uniaxial stretching, and the force‐strain equation can be established for each segment. By combining the equations of all segments, an analytical model of the elastomeric diaphragm can be built and solved via numerical methods. The developed model is added to the standard model of pneumatic cylinders to supply a complete analytical model for pneumatic vibration isolators. The experimental results demonstrate that the analytically predicted behavior is similar to the practical behavior. The proposed analytical model can be used as a guide for the parameter design of pneumatic isolators in practice.

A robust dual-membrane dielectric elastomer actuator for large volume fluid pumping via snap-through

A pressurized dielectric elastomer (DE) diaphragm under electrical actuation can experience snap-through large deformation due to electromechanical instability, which was shown to be a promising mechanism for large volume fluid pumping. However, snap-through actuation in a DE fluid pump will not occur when the inlet pressure to the pump is small and cannot be robustly utilized for different applications. To solve this problem, in this study, we proposed a dual-membrane DE pump design featuring an active DE membrane interacting with a passive elastic membrane. This design enabled snap-through of the DE membrane over a wide range of inlet pressures, making it feasible for large volume fluid pumping even at low pressures. Merits of this dual-membrane DE actuator design were experimentally verified; for example, the pumping volume of the dual-membrane DE pump could be as large as 3944% of the pumping volume of the conventional single-membrane DE pump. We further proposed an analytical framework to describe the mechanism of the dual-membrane DE fluid pump, involving the superimposition of the pressure-volume curves of the active and passive membranes. The theoretically predicted equilibrium states agreed well with experimental observations. Findings in this study will broaden the applications of the DE actuator in scenarios where a large pumping volume is needed over a wide range of pressures.

Chemical ageing effects on the mechanical behaviour of ethylene-propylene diene monomer

Ethylene-propylene diene monomer (EPDM) elastomer diaphragm failures due to material degradation pose a major risk in the biopharmaceutical industry, as they can result in long periods of production downtime. It is suspected that a key cause of this EPDM degradation is due to the chemical solutions used in equipment cleaning processes. However this has never been empirically investigated in the public domain. Twenty four virgin samples were utilised for testing, twelve of which were subject to common chemical cleaning solutions used in the biopharmaceutical sector. The chemical solutions under investigation were aqueous solutions of NaOH, NaClO, H3PO4, and the interaction between 100 °C H2O and NaClO. The characterisation of the degradation process was conducted by mechanical testing. The results show that degradation of the polymer bulk proceeds predominantly via crosslinking for all exposure types. NaOH and H3PO4 exposure results in an accelerated rate of crosslinking compared to NaClO in the early stages of exposure.

Making a hydrophoretic focuser tunable using a diaphragm.

Microfluidic diagnostic devices often require handling particles or cells with different sizes. In this investigation, a tunable hydrophoretic device was developed which consists of a polydimethylsiloxane (PDMS) slab with hydrophoretic channel, a PDMS diaphragm with pressure channel, and a glass slide. The height of the hydrophoretic channel can be tuned simply and reliably by deforming the elastomeric diaphragm with pressure applied on the pressure channel. This operation allows the device to have a large operating range where different particles and complex biological samples can be processed. The focusing performance of this device was tested using blood cells that varied in shape and size. The hydrophoretic channel had a large cross section which enabled a throughput capability for cell focusing of ∼15 000 cells s(-1), which was more than the conventional hydrophoretic focusing and dielectrophoresis (DEP)-active hydrophoretic methods. This tunable hydrophoretic focuser can potentially be integrated into advanced lab-on-a-chip bioanalysis devices.

Spatially digitized tactile pressure sensors with tunable sensitivity and sensing range

When developing an electronic skin with touch sensation, an array of tactile pressure sensors with various ranges of pressure detection need to be integrated. This requires low noise, highly reliable sensors with tunable sensing characteristics. We demonstrate the operation of tactile pressure sensors that utilize the spatial distribution of contact electrodes to detect various ranges of tactile pressures. The device consists of a suspended elastomer diaphragm, with a carbon nanotube thin-film on the bottom, which makes contact with the electrodes on the substrate with applied pressure. The electrodes separated by set distances become connected in sequence with tactile pressure, enabling consecutive electrodes to produce a signal. Thus, the pressure is detected not by how much of a signal is produced but by which of the electrodes is registering an output. By modulating the diaphragm diameter, and suspension height, it was possible to tune the pressure sensitivity and sensing range. Also, adding a fingerprint ridge structure enabled the sensor to detect the periodicity of sub-millimeter grating patterns on a silicon wafer.

Thermal analysis of the girth weld of an elastomeric diaphragm tank

The finite-element thermal analysis of the welding process of a titanium-alloy tank with an elastomeric diaphragm is described. The analysis takes into account the latent heat due to phase changes, the dependence of the material properties with temperature and the effects of the convection in the weld pool. The model is calibrated and validated by comparing its predictions with experimental results from the welding of AISI 304 specimens. The comparison between the model and the experimental results is made in terms of the temperature fields and the dimensions of the weld molten pool. The time evolution of the temperature in the experiments is monitored using thermocouples and a thermographic camera. The molten pool dimensions are measured via macro etching. The girth weld of the tank is analyzed for various hypotheses for the efficiency of the contact heat conduction between the hemispheres and the diaphragm-retaining ring. The results show the convenience to include a heat sink to the welding setup in order to guarantee the thermal integrity of the elastomeric diaphragm.

Variable-focus Liquid Lens Based on a Laterally-integrated Thermopneumatic Actuator

We report a focal-length tunable liquid lens based on thermopneumatically driven fluidic pressure. The fluidic pressure is generated by deformation of an elastomeric diaphragm induced by thermopneumaticity from a laterally integrated microheater sealed within an air chamber. The pressure is transmitted by a confined liquid to a lens diaphragm through an internal fluid channel. The liquid filling under the lens diaphragm functions as a liquid lens for dynamic focusing with properties depending on the curvature of the deformed diaphragm. The diaphragm area of the air chamber is designed five times larger than that of the lens cavity to yield high focal-length tunability by amplified deflection of the lens diaphragm. With our method, we achieved excellent focal-length tunability from infinity (without an input current) to 4 mm (with an input current of 12 mA) with a lens aperture diameter of 2 mm.

Mechanical characterization of a dielectric elastomer microactuator with ion-implanted electrodes

We report on the mechanical characterization and modeling of a non-prestretched dielectric elastomer diaphragm microactuator with ion-implanted electrodes under the influence of a distributed load (pressure). Thin polydimethysiloxane (PDMS) membranes (30 μ m thick, 2–3 mm diameter) were implanted on both side with gold ions by Filtered Cathodic Vacuum Arc (FCVA) and bonded on silicon chips with through-holes. A voltage applied between the implanted electrodes creates a compressive stress in the dielectric and causes the membrane to buckle and form a bump whose height depends on the mechanical properties of the electroactive compound, the voltage and the force applied on the membrane. Maximum unloaded displacements up to 7% of the membrane’s lateral dimensions were achieved, which was reduced to 3% when a distributed force of 1 kPa was applied on the membrane. The maximum mechanical work obtained by the actuators is in the range of 0.3 μ J. An analytical model was developed to calculate the displacement of the Dielectric Elastomer Actuators (DEAs) based on their mechanical and geometrical properties, voltage and applied force. The model shows very good agreement with the measurements and allows accurate performance prediction and dimensioning of such actuators.

Kinematically Stabilized Microbubble Actuator Arrays

In this paper, the concept, fabrication, and characterization of a kinematically stabilized polymeric microbubble actuator (endoskeletal microbubble actuator) for a pneumatic tactile display application are presented. The kinematic stabilization is achieved by the combination of two polymeric layers with complementary functions: a microcorrugated parylene diaphragm layer as a ldquoskeletonrdquo to provide a directional deflection in a desired axial direction while suppressing undesired lateral deflections and an overcoated elastomer diaphragm layer as a ldquoskinrdquo to help the extended membrane recoil to its original shape, ensuring diaphragm stability. Arrays of microcorrugated diaphragms are implemented in a mass producible fashion using inclined rotational UV lithography, micromolding, and pattern transfer techniques. Both the number of corrugations and the corrugation profile of the endoskeletal actuator are determined through numerical analysis, taking into account the constraints of the microfabrication processes utilized. A prototype of a single endoskeletal bubble actuator with a diameter of 2.6 mm has been fabricated and characterized. For comparison purposes, elastomer microcorrugated diaphragm (skin only) actuators and parylene microcorrugated diaphragm (skeleton only) actuators of the same materials and dimensions have also been fabricated and tested. While the skin-only diaphragm actuators demonstrated undesired omnidirectional inflation and the skeleton-only diaphragm actuators have shown unstable and irreversible deformation during extension, the proposed endoskeletal microbubble actuators have shown stable reversible axial extensions with a deflection of approximately 0.9 mm. A 6 6 array of endoskeletal polymer microbubble actuators integrated with a microfluidic manifold has been successfully fabricated, demonstrating its mass manufacturability.

Selection guide – considerations for elastomer diaphragms

What factors do you consider when ordering an elastomer diaphragm? In many cases this critical component is seen perhaps as a commodity item, something that is to be sourced as cheaply as possible. If you were aware of the potential differences between components from different sources, more care would be taken in their selection. Peter Warren, head of materials engineering at James Walker & Co, and Pete Smith, business development manager at James Walker Keaflex, present some guidelines to make the selection process easier.

Electro-elastomers: Large deformation analysis of silicone membranes

Electro-elastomers are large strain smart materials capable of both sensing and actuation. Typical electro-elastomer setups consist of either a silicone or acrylic membrane sandwiched between two compliant grease electrodes. Silicone electro-elastomers have maximum elastic strains between 200% and 350%. Acrylic electro-elastomers are more widely employed due to larger actuation strains but are softer than silicone and have a lower force output [Goulbourne, N.C., Frecker, M., Mockensturm, E.M., Snyder, A.J., 2003. Modeling of a dielectric elastomer diaphragm for a prosthetic blood pump. In: Proceedings of SPIE, Smart Structures and Materials: EAPAD, San Diego; Goulbourne, N.C., Mockensturm, E.M., Frecker, M., 2005b. Quasi-static and dynamic inflation of a dielectric elastomer membrane. In: Proceedings of SPIE, Smart Structures and Materials: EAPAD, San Diego]. A numerical formulation for the large deformation response of electro-elastomer membranes subject to electromechanical loading is derived in this paper. The approach is based on modifying the elastic membrane theory of Green, Adkins, and Rivlin [Adkins, J.E., Rivlin, R.S., 1952. Large elastic deformations of isotropic materials IX. The deformation of thin shells. Philosophical Transactions of the Royal Society of London. Series A Mathematical and Physical Sciences 244, 505–531; Green, A.E., Adkins, J.E., 1970. Large Elastic Deformations. Oxford University Press, London]. The electro-elastic stress state is defined as the combination of the electrical Maxwell stress and the mechanical stress for hyperelastic materials [Goulbourne, N.C., Mockensturm, E.M., Frecker, M., 2005a. A nonlinear model for dielectric elastomer membranes. ASME Journal of Applied Mechanics 72, (6) 899–906]. This paper augments our previous work by presenting a mathematical solution procedure for simulating the field responsive behavior of silicone electro-elastomers configured for both in-plane and out-of-plane deformation. Thin axisymmetric membranes subject to electromechanical loads are the focus of this investigation. The numerical analysis shows that there is a delicate balance between the electrical and the mechanical portions of the stress, which must be maintained for the overall stress to remain tensile and by extension the electro-elastomer to remain stable. It is shown that at very high voltages the stress can become negative ultimately leading to transducer failure. For sensing applications, the varying capacitive behavior of electro-elastomers is used to extract information about the membrane’s deformed state.

Strain analysis of flexing blood pump diaphragms.

Blood pumps usually use elastomer diaphragms that undergo repeated small-strain flexing (deformation). The stresses and strains that develop in the mechanically actuated diaphragms dictate the useful life and fluid-solid interactions of the diaphragm. A knowledge of these stresses and strains is essential for proper design of the pump's elastomer diaphragm. A nonlinear axisymmetric finite-element stress-strain analysis has been carried out on a Hexsyn rubber diaphragm used in a blood pump to illustrate a finite-element modeling technique. A situation involving the application of an axial deformation load on the diaphragm has been considered. In particular, the strains developed in a blood pump diaphragm during pumping have been quantified to illustrate the analysis technique.

High-pressure filtration—a chance for the downstream processing of biological dispersions

High-pressure filtration is a common practice in solid-liquid separation. A pressure up to 150 bar is used first for short-time drainage and then to press the filter cake with the help of an elastomer diaphragm. After the principal investigation of this concept and measurements to separate biological dispersions, its use in several processes is proposed. For suspensions of cells a filter cake with a high proportion of dry residue can be obtained within a very short time. The optimal regulation of this process on an industrial scale can be obtained by evaluation of laboratory experiments. For separation procedures with biomass and fermentation liquid the high pressure can be used to shorten the filtration time. Bacterial dispersions may be separated effectively with a cross-flow filtration apparatus which is to be developed for work at high pressure. The filtration experiments were performed on bakers' yeast (leaven) and Escherichia coli (E. coli) bacteria as model substances with a laboratory filter press apparatus. The filtration velocity and the specific filtration resistance are reported. Furthermore, the processing costs in relation to the proportion of dry residue were calculated as a function of pressure. The minimum cost corresponds to the economical operation range. Though this process is unjustifiably considered as relatively expensive, it is possible that, worked at its best, it will be able to compete with other mechanical separation processes.

Hydraulic-elastomeric mount

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