Perforated Pores Research Articles

Numerical Simulation on the Structural Design of a Multi-Pore Water Diffuser during the External Ice Melting Process of an Ice Storage System

A water diffuser is a critical auxiliary equipment for an ice storage system during the external ice melting process. This paper proposes a linear multi-pore water diffuser for an ice storage system with 500 t of refrigeration capacity to enhance the performance of external ice melting. By establishing a three-dimensional two-phase volume of fluid (VOF) model, different structural designs of water diffusers for the ice storage device are numerically examined regarding the degree of turbulence, flow velocity, and pressure drop. The results show that the optimal water diffuser with five rows of trunk pipe and six perforated pores arranged in per row of branch pipe with a 4 mm diameter of perforated pores exhibiting a relatively lower degree of turbulence with a lower pressure drop compared with the other designs in this study. Meanwhile, the influence of the flow velocity on the ice melting process is also investigated by a numerical model of ice melting. It is found that the fed flow velocity from the main pipe inlet exhibits a great impact on the external ice melting process. Compared with the external ice melting process without the water diffuser, the external ice melting process with optimal water diffuser design under flow velocity of 1.0 m s−1 could shorten the overall ice-melting time by 16 h. Additionally, through adjusting the water flow velocity, different output cooling can be realized to provide a fast response speed to the cooling variations in demand of the terminal users with a reduced cost.

Theoretical and Experimental Studies on the Ability of Intracrystalline Pores of β-La2(SO4)3 To Accommodate Various Gas Species with a Special Focus on Ammonia Insertion Behaviors.

β-La2(SO4)3 is a microporous inorganic crystal with one-dimensional perforated pores where H2O molecules can be inserted. To evaluate the nature of the pores and extend the application range, we investigate the ability to accommodate various hydrogen compound molecules XHn (CH4, NH3, HF, H2S, HCl, and HI) by insertion. The stable structures of the XHn molecules in the pores of β-La2(SO4)3 and the change in the Gibbs energy for XHn insertion ΔinsertG (T) are estimated by first-principles calculations. The guest XHn molecules are stabilized by forming H-O and X-La bonds with the β-La2(SO4)3 host structure. Based on the values of ΔinsertG (T), NH3, H2O, and HF are energetically stable in the crystal even above 0 °C. Correspondingly, thermogravimetry (TG) of β-La2(SO4)3 in NH3, CH4, and CO2 gases revealed that NH3 can be inserted into β-La2(SO4)3 below 360 °C, but CH4 and CO2 cannot. Unlike the case of H2O insertion, NH3 insertion proceeds via two steps. The first step is a single-solid-phase reaction of β-La2(SO4)3·yNH3, where NH3 molecules are inserted into the host structure with a continuously changing nonstoichiometric y value between 0 and 0.1. The second step is a two-solid-phase reaction between β-La2(SO4)3·0.1NH3 and β'-La2(SO4)3·0.3NH3, which is a phase formed after further NH3 insertion into β-La2(SO4)3·0.1NH3 with a minor change in the host structure. The fact that both NH3 and H2O can be inserted confirms that the pores of β-La2(SO4)3 allow for the insertion of molecules with a strong polarity. This nature is similar to zeolites and metal-organic frameworks (MOFs) with polar surfaces in the pores.

Homogenization of the Equations of Filtration of a Viscous Fluid in Two Porous Media

A homogenized model of filtration of a viscous fluid in two domains with common boundary is deduced on the basis of the method of two-scale convergence. The domains represent an elastic medium with perforated pores. The fluid, filling the pores, is the same in both domains, and the properties of the solid skeleton are distinct.

Fabrication of polymeric dual-scale nanoimprint molds using a polymer stencil membrane

We report on a simple and effective process that allows fabricating polymeric dual-scale nanoimprinting molds. The key for the process is the use of a thin flexible SU-8 stencil membrane, which was fabricated by either photolithography or thermal nanoimprint lithography (NIL). The stencil membrane with microscale pores was assembled into a nanopatterned substrate, producing a dual-scale structure. The assembled structure was used as a template to produce polymeric imprinting molds via UV-NIL. With this method, we demonstrated dual-scale nanoimprint molds having nano-pillars of 251 nm diameter and 146 nm high on top of microscale square protrusions of 5 μm wide and 3.6 μm high. The resin mold with the dual-scale structure was successfully used to produce a freestanding membrane with dual-scale perforated pores via UV-NIL. After metal coating and integrated into microfluidic devices, this freestanding membrane can potentially be used as a substrate for surface plasmon resonance sensors.

Facile fabrication of reinforced homoporous MF membranes by in situ breath figure and thermal adhesion method on substrates

Homoporous membranes are promising for size-sieving filtration, but their prospect is restricted by the lack in mechanical strength. A facile and low-cost route based on in situ breath figure and thermal adhesion method is proposed to fabricate the reinforced homoporous MF membranes in this research. The substrates specific to this route are fabricated by PVDF coating and then ice sealing on nonwoven fabrics. On the tailor-made substrates, the porous film is formed as usual by the breath figure method, and then immobilized on the substrate conveniently by PVDF melting. Acetone is introduced into the casting solution with intent to accelerate solution spreading on ice surface and facilitate micron-scale water droplets floating down to the solution film, so that the resistance layer could be formed thinner and abundant in perforated pores to attain high water permeation flux. Four usually used homoporous membrane materials, i.e., PSF, PES, PPO and PEI, have succeeded in membrane fabrication. FE-SEM images reveal that membrane pores are perforated and homogeneous with controllable size, again the homoporous layer is tightly adhered on substrate. Water permeation, particle sieving and regeneration tests indicate that the reinforced homoporous membranes made by this novel method are practicable for high-resolution separation under moderate pressure and long-time service.

Small perforations in corrugated sandwich panel significantly enhance low frequency sound absorption and transmission loss

Numerical and experimental investigations are performed to evaluate the low frequency sound absorption coefficient (SAC) and sound transmission loss (STL) of corrugated sandwich panels with different perforation configurations, including perforations in one of the face plates, in the corrugated core, and in both the face plate and the corrugated core. Finite element (FE) models are constructed with considerations of acoustic-structure interactions and viscous and thermal energy dissipations inside the perforations. The validity of FE calculations is checked against experimental measurements with the tested samples provided by additive manufacturing. Compared with the classical corrugated sandwich without perforation, the corrugated sandwich with perforated pores in one of its face plate not only exhibits a higher SAC at low frequencies but also a better STL as a consequence of the enlarged SAC. The influences of perforation diameter and perforation ratio on the vibroacoustic performance of the sandwich are also explored. For a corrugated sandwich with uniform perforations, the acoustical resonance frequencies and bandwidth in its SAC and STL curves decrease with increasing pore diameter and decreasing perforation ratio. Non-uniform perforation diameters and perforation ratios result in larger bandwidth and lower acoustical resonance frequencies relative to the case of uniform perforations. The proposed perforated sandwich panels with corrugated cores are attractive ultralightweight structures for multifunctional applications such as simultaneous load-bearing, energy absorption, sound proofing and sound absorption.

Liquid-crystal self-assembly of lipid membranes on solutions: A dissipative particle dynamic simulation study

The self-assembly of the amphiphilic lipid molecules in aqueous solution is investigated via dissipative particle dynamic simulation. Lipid bilayer and perforated bilayer membranes, together with the micelles and vesicles, which couple the spatial inhomogeneity and orientation ordering, are observed in equilibrium states and dynamics processes. For the equilibrium states, the phase diagrams are arranged by the lengths of head and tail chains in various lipid-water mixtures, where the influence of chain length and water composition on formation of bilayer and perforated bilayer membranes is carefully analyzed. In the dynamic processes, we investigate the bilayer membranes by analyzing the energies of systems, which indicates that the formations of bilayers and perforated bilayers strongly depended on the initial chain distributions and lipid types. Moreover, we also investigate the dependence of elastic modulus on the chain lengths for the bilayer membranes and the tension for the perforated pores in the perforated bilayer membranes. The observations on these liquid-crystalline self-assembly provided a promising approach that could be used to design and understand the biomembrane based on the lipid molecules.

Dual‐Scaled Porous Nitrocellulose Membranes with Underwater Superoleophobicity for Highly Efficient Oil/Water Separation

Large-area dual-scaled porous nitrocellulose (p-NC) membranes are fabricated by a facile, inexpensive and scalable perforating approach. These p-NC membranes show stable superhydrophilicity in air and underwater superoleophobicity. The p-NC membranes with intrinsic nanopores and array of microscale perforated pores could selectively and efficiently separate water from various oil/water mixtures with high efficiency (>99%) rapidly.

A solvent-shrinkage method for producing polymeric microsieves with sub-micron size pores

This paper presents a thorough investigation of a simple method to decrease the dimensions of polymeric microsieves. Pore sizes of microsieves are usually in the micrometer scale, but need to be reduced to below 1µm to make the microsieves attractive for aqueous filtration applications. In this work polyethersulfone/polyvinylpyrrolidone microsieves were prepared with pores with diameters in the range of 2–8µm (perforated pores) and a very open internal structure containing many voids. Subsequently, size reduction in terms of pore size and periodicity of the perforated pores was performed by immersing microsieves in mixtures of acetone and N-methylpyrrolidone. Microsieves shrunk because of swelling and weakening of the polymers, and subsequently collapse of the open internal structure. Shrinking typically occurred in two stages: first, a stage where both the perforated pores and periodicity shrink, and second, a stage where the perforated pores continue to shrink while the periodicity remains constant. Microsieves with initial pore diameters of 2.6µm were reduced down to only 0.2µm. The maximum isotropic shrinkage was ~35%, which was determined by the amount of voids in the polymer matrix. We propose that to come to higher (nearly) isotropic shrinkage, the amount of voids should be further increased.

Fabrication of Perforated Micro/Nanopore Membranes via a Combination of Nanoimprint Lithography and Pressed Self-Perfection Process for Size Reduction

Artificial membranes with perforated nanopores in defined locations provide an important biomimicking platform for sensing and analysis of biomolecules. This study presents a simple and flexible method to fabricate a freestanding polymer membrane with perforated micro- and nanopores using a combination of nanoimprint lithography (NIL) and pressed self-perfection (PSP) process. NIL was used to define initial pores of a few micrometers in diameter in the SU-8 membrane layer, which was followed by the PSP process where the patterned SU-8 membrane is pressed with a blank silicon wafer at an elevated temperature. This PSP process results in a lateral flow of the SU-8 resist and consequently reduces the pore size in the membrane. With this method, we have demonstrated fabrication of a SU-8 membrane with perforated pores down to approximately 300 nm in diameter. The results indicate that by employing a pore reduction process nanopore membranes can be manufactured without requirements of having a stamp with nanoscale structures and high aspect ratio imprinting with the stamp.

Numerical studies of interfacial phenomena in liquid water transport in polymer electrolyte membrane fuel cells using the lattice Boltzmann method

Water management is an important issue in the polymer electrolyte membrane (PEM) fuel cell, which is considered as a promising alternative power source for future automotive applications. In this article, lattice Boltzmann simulations are conducted to examine the interfacial phenomena in liquid water transport in porous materials of a PEM fuel cell. Numerical results clearly indicate that large perforated pores through the porous diffusion layers can serve as a convenient liquid water transport pathway and thus assist in liquid water removal. An interconnected horizontal and vertical pore combination is especially beneficial to liquid water transport through the porous layers in flooding conditions. Therefore, liquid water transport in a PEM fuel cell may be effectively managed through well engineered interfacial structures in porous materials.

The Utilization of Perforated Bioinert Chambers to Generate an In Vivo Isolated Space for Tissue Engineering Involving Chondrocytes, Mesenchymal Stem Cells, and Fibroblasts

Vascular invasion and admixture of the nude mouse cells with seeded cells make it difficult to reapply the regenerated tissues to the restoration of host tissue defects. Therefore, a device that is capable of allowing for autologous or allogenic tissue growth while preventing host tissue invasion will be a valuable tool for in vivo tissue engineering. We have previously fabricated a novel silicon-perforated chamber. The aim of this study was to evaluate whether this chamber, after being implanted subcutaneously in experimental animals, would hinder host tissue ingrowth while providing an environment inside its cavity for in vivo growth of either autologous or allogenic implant cells. We found that the chamber did not induce severe foreign body reaction, and the chambers with perforated pores of 1-3 mm in diameter effectively inhibited the host granulation tissue or vascular invasion for as long as 3 months. In addition, the exudates rich in vascular endothelial growth factor, basic fibroblast growth factor, transforming growth factor-β, insulin-like growth factor-1, and platelet-derived growth factor-BB were steadily generated and collected in the chambers. In vitro cell culture studies revealed that the exudates were able to support the viability and proliferation of rabbit chondrocytes, rat mesenchymal stem cells, and human fibroblasts. The results indicate that this novel chamber could potentially provide an environment favorable for in vivo tissue engineering while effectively preventing host tissue or vascular invasion.

Fibrinolytic system in the process of wound healing in rat

We investigated the involvement of fibrinolytic system in the process of wound healing as well as angiogenesis in rats using a model system, in which polystyrene capsules with 100 perforated pores filled without (empty capsule) or with fibrin gel (fibrin capsule) were subcutaneously implanted into the dorsal of rats. The intracapsular tissue was accompanied by neovascularization and the tissue weight in the fibrin capsule was three times that of the empty capsule on day 5 after implantation. Both plasminogen activation and amidolytic activities of urokinase-type plasminogen activator (u-PA) in the tissue extracts and intracapsular fluid obtained from the fibrin capsule were higher than those in the empty capsule on day 5 after implantation. Both u-PA and its specific receptor (u-PAR) mRNAs were detected in the intracapsular tissues formed in both capsules. On day 5 after implantation, though the levels of u-PA mRNA in the tissue of the empty capsule and those of the fibrin capsule were not significantly different, more u-PAR mRNA was expressed in the tissue of the fibrin capsule than in the empty capsule. Furthermore, when the cultured endothelial cells were incubated with intracapsular fluids, the proliferation of the cells was significantly enhanced. These results indicate that fibrinolytic activities increase in the presence of fibrin gel, possibly by up-regulation of the u-PA/u-PAR system in the early stage of rat wound healing.