Applied Air Pressure Research Articles

Modelling and FEM simulation of a rotating hyperelastic spherical balloon actuator

ABSTRACT This paper presents static modelling and simulation of a spherically-shaped hyperelastic balloon actuator subjected to an angular rotation with an internally applied air pressure. These actuators are extensively used in soft robotics because its safe and flexible nature. The balloon actuator is a pneumatic-type actuator made of a polymeric material. A continuum mechanics-based analytical modelling and Finite element method-based simulation are performed to predict the response of the actuator for a given angular rotation with internally applied air pressure. The proposed modelling framework is subsequently utilised to perform the parametric studies for varying pressure, thickness, and rotational speed of the actuator. Various elastic instability curves are also obtained to examine the critical inflation of the rubber balloon actuator. The analytical findings agree well with the FEM simulations.

A green extrusion-based 3D printing of hierarchically porous aluminum

Additive manufacturing (AM) of porous Al via laser-assisted techniques is limited by the intrinsic high reflectivity of the laser and high oxidation propensity of Al. Herein, a green extrusion-based three-dimensional (3D) printing method was proposed for the fabrication of Al structures, whereby, hierarchical porosity is generated via solvent evaporation, starch removal, and parameter optimization. The process comprises slurry preparation, 3D printing and thermal post-treatment. The feasibility of the procedure and the effect of starch addition on the porous Al microstructure were investigated. An ethyl alcohol-based slurry exhibiting appropriate shear thinning behavior with sufficient yield stress was utilized for the extrusion-based 3D printing, and slurry filaments could be extruded smoothly and unyieldingly deposited by adjusting the nozzle diameter, applied air pressure, and printing speed. Furthermore, hierarchically porous Al structures were obtained following sintering, demonstrating that the proposed extrusion-based 3D printing method is suitable for direct AM of Al structures.

A Pneumatic-Based Mechanism for Inserting a Flexible Microprobe Into the Brain

Abstract Insertion of flexible microprobes into the brain requires withstanding the compressive penetration force by the microprobes. To aid the insertion of the microprobes, most of the existing approaches use pushing mechanisms to provide temporary stiffness increase for the microprobes to prevent buckling during insertion into the brain. However, increasing the microprobe stiffness may result in acute neural tissue damage during insertion. Moreover, any late or premature removal of the temporary stiffness after insertion may lead to further tissue damage due to brain micromotion or inaccuracy in the microprobe positioning. In this study, a novel pneumatic-based insertion mechanism is proposed which simultaneously pulls and pushes a flexible microprobe toward the brain. As part of the brain penetration force in the proposed mechanism is supplied by the tensile force, the applied compressive force, which the microprobe must withstand during insertion, is lower compared with the existing approaches. Therefore, the microprobes with a critical buckling force less than the brain penetration force can be inserted into the brain without buckling. Since there is no need for temporary stiffness increment, neural tissue damage during the microprobe insertion will be much lower compared with the existing insertion approaches. The pneumatic-based insertion mechanism is modeled analytically to investigate the effects of the microprobe configuration and the applied air pressure on the applied tensile and compressive forces to the microprobe. Next, finite element modeling is conducted, and its analysis results not only validate the analytical results but also confirm the efficiency of the mechanism.

Advanced Pneumatic Mechanical System for Water Treatment Application: Dosing Rate Assessment for Lime Dosage

This paper presents a new developed pneumatic mechanism for lime dosing system in water treatment application. Technically, a choke formation due to scaling problem in such existing water treatment system utilising pump as the transferring medium has caused the high cost of operation due to scheduling maintenance and replacement of pump tubing. In that sense, the pneumatic system will be a new advancement in replacing the transferring medium. In this work, the air regulator is used to control air pressure at several levels. At the same time, there is one valve that is installed to control the airflow the regulator (air compressor) to the pneumatic cylinder cartridge. The assessment is conducted for water with 10% of lime concentration on water sample 25 PPM as the standard lime concentration for water treatment plant as the domestic usage in Malaysia. The trend of dosing rate for the present novel lime dosage utilising a pneumatic system shows consistency of increment with the increment of applied air pressure during the dosing process.

Modeling and analysis of an electro-magneto-elastic rotating cylindrical tube actuator

This paper presents the static modeling and analysis of a novel cylindrical tube actuator subjected to a rotation about longitudinal axis with an internally applied air pressure under an electromagnetic field. The current tube actuator belongs to a smart actuator category and is made of an electro-magneto-active polymer filled with a particular volume fraction of suitable fillers. A continuum mechanics-based electro-magneto-mechanical model is developed to predict the response of the actuator for a combined pressure and electromagnetic field loading. To validate the same, the model is compared with the outputs of an existing spring roll actuator. Parametric studies are subsequently performed for varying input pressure, electric field, magnetic field, fillers content, and actuator’s rotational speed. The output sensitivity in terms of strain intensity at inner and outer surfaces of the actuator is also checked at different controlling inputs. In addition, various electro-magneto-mechanical instability curves are drawn to examine the critical inflation of the tube actuator. In general, the developed model provides initial steps toward the modern actuator designs for applications where a precise control with high load-carrying capability of the actuator plays a significant role.

Real-time measurement of droplet size and its distribution of an air-induced air-assisted electrostatic nozzle

In this paper, a critical assessment has been carried out to understand the droplet size and its distribution with the variation of various parameters such as applied high voltage, applied air pressure, liquid flow rate, position and orientation of the nozzle. The mean droplet size for an electrostatic nozzle is 15.54 μm which is minimum amongst all four nozzle droplet sizes 24.17, 138.25 and 259.43 μm for a pressure swirl nozzle, a motorized and a handheld agricultural nozzle respectively. Statistical analysis shows that an electrostatic nozzle has the mean of 15.53 μm, standard deviation of 0.1538 and variance of 0.02368.

Dehulling effectiveness of high-oleic and linoleic sunflower oilseeds using air-jet impact dehuller: a comparative study

Sunflower seeds and kernels are very common in the preparation of protein meals. Dehulling sunflower seeds for meal preparation and direct consumption is a very important operation. High-oleic sunflower contains the most oleic fatty acids in the oil which significantly improves the oxidative stability of the meal with this sunflower compared to meals with standard linoleic sunflower seed. In this work, a air-jet impact dehuller was used to determine, optimize and compare the effectiveness of dehulling of two types of sunflower: high-oleic (HOSS) and linoleic sunflower seed (LSS). A two-factorial experimental design (32) was used to estimate the effect of seed moisture and applied air pressure on the efficiency (E criterion) and quality of dehulling (K1 and K2 criteria). Samples with a moisture content of 6, 8 and 10% were dehulled at an air pressure of 400, 600 and 800 kPa. The most efficient dehulling of HOSS, was achieved at a dehulling pressure in the range of 600-800 kPa and moisture content of 6.0%. As for the LSS sample, the highest efficiency of LSS and the highest K2 criterion were obtained at the dehulling pressure of 800 kPa, and moisture content of 7.3%.

The benefit of tympanometry for certain ear diseases

Tympanometry is an objective test measure the mobility (compliance) of the tympanic membrane as a function of applied air pressure in external canal, It is particularly useful in assessing the secretory otitis media during childhood. This is a prospective study performed at ENT department of the Basrah Teaching Hospital for the period from November / 2013 to February / 2014. The study is to assess the advantage of tympanometry as a diagnostic tool and to audit the uses of tympanometry in the ear diseases in ENT department of Basrah Teaching Hospital. The statistical calculations were carried out using chi-square test. The p value >0.05 was considered statistically insignificant. Fifty patients aged (4—84years) who were referred by otolaryngologist to our audiological unit for audiological assessment were included in the study. Out of these 50 patients (55 ears had otitis media with effusion, 12 ears had Eustachian tube dysfunction, 4 ears had barotraumas, 7 ears had acute otitis media, 4 ears had chronic suppurative otitis media, 2 ears had otosclerosis and 15 ears were normal on clinical examination). The clinical diagnoses was compared with tympanometric findings and the coincidence between two, was as follow; 80% in otitis media with effusion, 75% in barotraumas , 100% in acute otitis media. In conclusion; tympanometry is an important tool in the diagnosis of some of the ear diseases. It is not necessary to performed in every case as the clinical examination could clarify the diagnosis in most cases . Keywords: benefit , tympanometry

Special Issue on Tribology of Additive Manufacturing

Special Issue on Tribology of Additive Manufacturing

Pressure Effects on Structured Optical Fibre Drawing by Modified Single-Capillary Modelling

The impact of drawing pressure on the structure of solid-core structured optical fibres (SOFs) is investigated. A modified single-capillary model to cater for multi-capillary structural constraint in the radial axis within a larger single capillary draw, whilst retaining analytical simplicity, is proposed and shown to give improved fits with experimental data. For the cases we have experimented, an effective pressure is found approximately one-fifth less than that of the applied air pressure, based on the model and contributed from the interplay of applied pressure and the surface tension associated with the structure. In addition, the proposed model indicates that when birefringent SOFs with asymmetric holes having thinner walls were examined, the reduction in effective pressure is found to be about one-quarter of the pressure applied – it is larger than the uniform case and supports the explanation. Thus the model offers a simple and useful relation between the structure and draw pressure in fabricating structured optical fibre.

Fully 3D-Printed Hydrogel Actuator for Jellyfish Soft Robots

Recently, interest to develop soft robots that mimic flora and fauna in the natural environment has been growing in order to meet the demand for shortage in labor, working in hazardous environments, disaster management, health care and oceanography. Actuators that are made from soft materials, such as elastomers and hydrogels, are integral components of soft robots. Although, 3D printing is a versatile technique to fabricate prototypes, it is a well-known fact that 3D printing for soft materials is challenging. In this work, we present the fabrication and characterization of 3D-printed hydrogel soft actuator that mimics a jellyfish. The developed actuators consist of three parts; (1) Connector: which is the joint part between the main body of actuator and the inlet tube for air pressure, (2) Box: which is balloon-like inflation part and; (3) Base: which is connected to the Box. The results indicate that the normalized contraction ratio of the 3D-printed actuator is close value to that of moon jellyfish and is applicable to a jellyfish-mimic robot. Furthermore, it is observed that, the relationship between applied air pressure and injected volume is linear without balloon defects.

An on-chip wound healing assay fabricated by xurography for evaluation of dermal fibroblast cell migration and wound closure

Dermal fibroblast cell migration is a key process in a physiological wound healing. Therefore, the analysis of cell migration is crucial for wound healing research. In this study, lab-on-a-chip technology was used to investigate the effects of basic fibroblast growth factor (bFGF), mitomycin C (MMC), MEK1/2 inhibitor (U0126) and fetal calf serum (FCS) on human dermal fibroblast cell migration. The microdevice was fabricated consisting of microchannels, pneumatic lines and pneumatically-activated actuators by xurographic rapid prototyping. In contrast to current approaches in in vitro wound healing such as scratch assays and silicone inserts in wellplate format, which show high variability and poor reproducibility, the current system aims to automate the wounding procedure at high precision and reproducibility using lab-on-a-chip. Traumatic wounding was simulated on-chip on fibroblast cell monolayers by applying air pressure on the flexible circular membrane actuator. Wound closure was monitored using light microscopy and cell migration was evaluated using image analysis. The pneumatically controlled system generates highly reproducible wound sizes compared to the conventional wound healing assay. As proof-of-principle study wound healing was investigated in the presence of several stimulatory and inhibitory substances and culture including bFGF, MMC, U0126 MEK1/2 inhibitor as well as serum starvation to demonstrate the broad applicability of the proposed miniaturized culture microsystem.

Recent Developments on Modeling for a 3-DOF Micro-Hand Based on AI Methods.

Recently, soft actuators have been expected to have many applications in various fields. Most of the actuators are composed of flexible materials and driven by air pressure. The 3-DOF micro-hand, which is a kind of soft actuator, can realize a three degrees of freedom motion by changing the applied air pressure pattern. However, the input–output relation is nonlinear and complicated. In previous research, a model of the micro-hand was proposed, but an error between the model and the experimental results was large. In this paper, modeling for the micro-hand is proposed by using multi-output support vector regression (MSVR) and ant colony optimization (ACO), which is one of the artificial intelligence (AI) methods. MSVR estimates the input–output relation of the micro-hand. ACO optimizes the parameters of the MSVR model.

Alveolar mimics with periodic strain and its effect on the cell layer formation.

We report on the development of a new model of alveolar air-tissue interface on a chip. The model consists of an array of suspended hexagonal monolayers of gelatin nanofibers supported by microframes and a microfluidic device for the patch integration. The suspended monolayers are deformed to a central displacement of 40-80 µm at the air-liquid interface by application of air pressure in the range of 200-1,000 Pa. With respect to the diameter of the monolayers, that is, 500 µm, this displacement corresponds to a linear strain of 2-10% in agreement with the physiological strain range in the lung alveoli. The culture of A549 cells on the monolayers for an incubation time of 1-3 days showed viability in the model. We exerted a periodic strain of 5% at a frequency of 0.2 Hz for 1 hr to the cells. We found that the cells were strongly coupled to the nanofibers, but the strain reduced the coupling and induced remodeling of the actin cytoskeleton, which led to a better tissue formation. Our model can serve as a versatile tool in lung investigations such as in inhalation toxicology and therapy.

Modeling and System Integration for a Thin Pneumatic Rubber 3-DOF Actuator

Recently, soft actuators have been getting increased attention within various fields. The actuators are composed of flexible materials and driven by pneumatic pressure. A thin pneumatic rubber actuator generating 3 degrees of freedom motion, called 3-DOF micro-hand, has small diameter McKibben artificial muscles which generate a contraction force in the axial direction. By this structure, the micro-hand contracts in the longitudinal direction and bends in any direction by changing the applied air pressure pattern to the artificial muscles. The input–output relation of the micro-hand, however, is complicated and has not been modeled. In this paper, modeling for 3-DOF micro-hand is proposed. Moreover, the experimental system is built for the micro-hand and the proposed model is evaluated by using the experimental results.

Removal of Algae from Surface Water by Deep Flotation

When algae are present in surface water it becomes an important issue in the production of drinking water, causing problems such as the interruption of coagulation and sedimentation processes and blockage of the filter. In this research, an evaluation is carried out on the effectiveness of deep flotation as an alternative method for algae removal from water. Different pressures of air and different depths of diffusers were applied. Results indicated that using deep floatation increases percentage removal of algae from 32 % (without any air) to 65% (at 6 bar pressure). Also the percentage removal of algae from raw water increases from 18 to 65 % when the applied air pressure increases from 1 bar to 6 bar, also percentage removal of algae increases from 53 to 65 % when the depth of diffuser increased from 5 to 10 m.

Screwed micro fluidic connections fabricated by ultrasonic hot embossing and welding

Recent connection methods to micro fluidic chips, such as gluing tubes and hoses into orifices or pressing a gasket on them have been studied to improve the common problem to establish a connection of the macroscopic world to a fluidic micro system. In this study, micro fluidic chips from polycarbonate plates with screwed connections have been fabricated by ultrasonic hot embossing and welding, both as in plain and out of plain arrangements. To fabricate threads in the polymer plates, an M3 screw was ultrasonically welded into a hole in the chip and the screw was turned out after the process. The tightness of micro channels and fittings was proven by pumping ink and yeast cells through the micro channels and by applying air pressure of up to 700 kPa, respectively. The process introduced here is especially advantageous because sealing micro channels and welding in micro fluidic screwed connections is done in a single fabrication step.

Analysis of pre-test failures and bond-strengths of seven adhesive systems to bovine dentine: A nine-year novice/beginner operator study

ObjectiveThe aims were to evaluate, via multi-year student cohorts: (i) the incidence of pre-test failures and (ii) shear bond strengths of single- and multi-step adhesives to bovine dentin. MethodsThe experiments were performed by cohorts of dental students (2008–2016). Each year the bond strengths of three dental adhesives to bovine dentin were tested. Four self-etching adhesives (Optibond-All-in-One, [OBAIO]; Optibond XTR [OBXTR]); Xeno V [XV]; Xeno V+ [XV+]; a three-step etch-and-rinse-system (Optibond FL, [OBFL]), a self-etch universal adhesive (Scotchbond Universal [SBU]) and a self-etch/etch-and-rinse adhesive (Xeno Select, [XS]) were included in the study. Composite-cylinders were bonded perpendicularly to prepared bovine dentin surfaces. Shear-tests were performed with a universal-testing-machine. ResultsBoth overall, and within years, XV and XV+ showed significantly (p<0.01) higher percentages of pre-test failures versus other adhesive systems tested in the period 2008–2014 (OAIO, OBFL, OBXTR). Fewest pre-test failures were observed for OBFL, OBXTR and SBU. Trends in mean bond strengths and Weibull distributions were noted, per adhesive, with trends in the incidence of pre-test failures. Pre-test-failures and bond strengths depended on the air-drying technique. The adhesive systems showed variable technique sensitivity.Multistep bonding systems (Optibond FL and Optibond XTR) showed minimal pre-test failures and high bond strength applied by relatively inexperienced operators and irrespective of the applied air-drying technique. However, two single-step adhesives (OAIO and SBU) showed comparable results to the multi-step systems. SignificanceThe clinical need for rapid application dentine adhesives can result in varied outcomes with relatively inexperienced operators. These outcomes include both the incidence of pre-test failures as well as the distributions of shear bond strengths achieved, although these measures appear to be related. However, both outcomes are dependent upon the adhesive products utilised and especially upon the applied air pressure (flow rate). Some rapid application systems appear to perform comparably with well-established multi-step adhesives.

Property Investigation of Replaceable PDMS Membrane as an Actuator in Microfluidic Device

This paper investigates the basic deflection properties of polydimethylsiloxane (PDMS) membrane as an actuator component in a microfluidic device. Polydimethylsiloxane membrane is a widely used structure in various applications in microfluidics. Most of the applications using PDMS membrane as actuators are pumps, valves, microlenses, and cell stimulators. In these applications, PDMS membranes are deflected to function by applied pressure. However, based on our literature survey, correlations between thickness, applied air pressure, and the deflection properties of replaceable PDMS membrane have not been theoretically and experimentally investigated yet. In this paper, we first conducted a simulation to analyze the relationship between deflection of the replaceable PDMS membrane and applied pressure. Then we verified the deflection of the PDMS membrane in different experimental conditions. Finally, we demonstrated that the PDMS membrane functioned as a valve actuator in a cell-capturing device as one application. We expect this study would work as an important reference for research investigations that use PDMS membrane as an actuator.

Modelling water trap seal boundary conditions in building drainage systems: Computational fluid dynamics analysis of unsteady friction to improve accuracy

The safe removal of disease-carrying human waste is the objective of all sanitation systems and the limiting of air pressure transients within the system remains a significant part of current codes and regulations. The water trap seal offers fundamental protection and is the system’s sole barrier between the public sewer network and habitable space inside a building. Modelling water trap seal responses to air pressure fluctuations offers an opportunity to analyse whole system performance, but the quality of the data depends on the accuracy of the modelling technique and that of the defining inputs. AIRNET, a 1D Method of Characteristics based model, enables rapid whole system testing; however, the present boundary condition for the water trap seal within the model is based solely on steady state conditions, ignoring system dynamics. Computational fluid dynamics offers an opportunity to numerically evaluate the flow patterns within the trap seal in response to applied air pressure transients. This research confirms the importance of the rate of rise, and hence frequency of air pressure transients incident on water trap seals and relates this to potential vulnerabilities of different device geometries, particularly the ratio between inner and outer wall length. The research led to the development of a dynamic velocity decrement model encapsulating unsteady friction and separation losses linked to device geometry for the first time. The development of a frequency-dependent internal energy term Δ v, suitable for inclusion in AIRNET provides the capability to predict more realistic water trap response to air pressure transients over a range of air pressure transient frequencies likely to cause problems: 1 Hz to 8 Hz.Practical application: Whole system modelling can greatly improve the ability of design engineers to fully simulate the operation of a building drainage system in a realistic way. The work described in this paper improves the accuracy of whole system models by evaluating water dynamic responses to air pressure transients using a range of techniques including computational fluid dynamics and more traditional 1D finite difference method of characteristics models. The work also paves the way for more robust evaluation of building drainage products through in-depth investigation of the fluid mechanics associated with their operation.