Elastic Mold Research Articles

Fabrication of helix–fiber composites with mechanically coupled core-wrapping for programmable properties

Helix-fiber composites (HFCs), which involve wrapping a material around a flexible core, are of interest for intelligent stretchable functional materials or devices. Here, we reveal that mechanical coupling between the core and wrapping plays a critical role in controlling the structure and mechanical properties. Our results show that the mechanical properties of the HFC can be programmed by precisely tuning the mechanical coupling strength among them. Interestingly, the HFC also shows unique pseudo-elastic behavior under large strain due to the mechanical coupling effects. The HFC is demonstrated as an elastic metal conductor, programmable sensor, and finally as an elastic mold for structure transplantation by mechanically decoupling the elastomer core from the helix fiber. The results not only deepen the fundamental understanding of HFCs, but also may promote future structure-properties and fabrication studies on helix-structured functional composite and devices.

ОПРЕДЕЛЕНИЕ ДИНАМИЧЕСКОЙ ВЯЗКОСТИ НАПОЛНЕННЫХ КОМПОЗИЦИЙ НА ОСНОВЕ ТЕРМОРЕАКТИВНОГО ЛИТЬЕВОГО ПОЛИУРЕТАНА

The studies of the dynamic viscosity of compositions based on a two-component polyurethane compound with fillers in the form of shungite, talc and basalt fiber in an amount of 3% vol. and adding an organic solvent of dichloromethane in an amount of 10% wt. are described. According to the study results, it has been found out that the most rational compositions for molding into elastic molds are those that contain shungite and talc as fillers.

Evaluating shear bond strength efficacy of seventh and eighth generation bonding agents (an in vitro study).

Background and Objectives: The most important purpose of dental adhesives is to offer retention to composite fillings or composite cements. The most frequently applied laboratory parameter to evaluate the effectiveness of dentin bonding agents is shear bond strength. The aim of this study is to introduce the 8th generation of bonding to our country's dentists and investigating the manufacturer's claim in this research, and compare the shear bond strength of two types of systems. Material and Methods: Thirty freshly extracted maxillary premolars were collected. After preparation, the samples were randomly divided into two groups of fifteen and each group was treated with a different bonding agent. In group A, 15 specimens were treated by Gluma Bond Universal (Kulzer, Hanau, Germany). In group B, 15 specimens were treated by LuxaBond Universal (DMG, Hamburg, Germany). O‐Light Curing Light unit (Woodpecker, Guilin, China) used for polymerization of both bonding systems. Composite (Beautifil Injectable X, Shofu Inc, Kyoto, Japan) cylinders were afterwards placed on the bonded surfaces using an elastic mold and were light‐cured. To measure the shear bond strength of the specimens a universal material tester was used. Descriptive Statistics and One Sample test was conducted for statistical analysis. Results: The highest strength was seen in the 8th generation bonding agent (LuxaBond Universal (DMG, Hamburg, Germany). A highly significant difference (p < 0.000) was found between the seventh and eighth‐generation bonding groups. Conclusion: The eighth‐generation bonding agent showed higher mean bond strength than the seventh.

PREPARATION THE ROSE-LIKE HYDROPHOBIC SURFACE OF WOOD BASED MATERIALS BY SOFT LITHOGRAPHY

To prepare hydrophobic wood with rose-like hydrophobic surface and avoid moisture damage to wood. In this paper, With polyvinyl alcohol (PVA) as the elastic mold, the microstructure of the rose petals was replicated on the wood surfaces by soft lithography. The soft lithography technique was used to modify the wood sur-face, transferring over it a rose-like topography, based on a micro/nano hierarchical structure using fresh rose as the template. The surface of poplar coated with polystyrene was reconstructed twice using 1, 3, 5, 8 and 10% PVA as templates, respectively. The results show that the average contact angle of poplar surface coated with polystyrene is more than 130°, that of fresh rose surface is about 140°, and that of untreated wood is about 60°. Therefore, the wood surface with polystyrene has obtained a similar structure to that of rose surface and has a certain hydrophobicity. In addition, the microstructures observed by means of SEM, showing rough surface structures with micro-nanopapillate hills on wood surfaces. Water droplets could easily roll down on such wood surfaces, exhibiting super-hydrophobic and low adhesion properties. The successful fabrication of rose-like wood provided a new direction for researches on the super-hydrophobic of wood, which could effectively prevent the damage of moisture to wood.

Experimental and Numerical Buckling Analysis of Carbon Fiber Composite Lattice Conical Structure before and after Lateral Impact

In this research, the numerical and experimental analysis of the carbon fiber composite lattice conical structure has been performed to assess the buckling stability of the structure before and after the lateral impact. In the experimental analysis, the carbon fiber composite lattice conical structure was constructed with the winding method and using elastic molds and metal mandrel. In order to investigate the buckling stability of the structures before each lateral impact, they are subjected to be compressive-axial loading. The rest of the structures first subjected under the axial-compressive loading, then in the next step, a compressive loading is applied to determine the effect of the impact on the compressive strength of the damaged structures. In the numerical analysis, the Abaqus software is used to modeling and performing the mentioned analysis. Finally, the comparison of the results shows that the effect of the lateral impact causes how many reductions will be occurred in the buckling strength. So, it should be considered during the design of the applied structures. On the other hand, the low difference between the numerical and experimental simulations shows that the experimental and numerical methods can be used to analyze the structures with different geometric characteristics and material.

Facile Fabrication of Thin-Bottom Round-Well Plates Using the Deformation of PDMS Molds and Their Application for Single-Cell PCR.

Recently, microdevices made of resins have been strongly supporting cell analysis in a range of fields, from fundamental life science research to medical applications. Many microdevices are fabricated by molding resin to a mold made precisely from rigid materials. However, because dimensional errors in the mold are also accurately printed to the products, the accuracy of the product is limited to less than the accuracy of the rigid mold. Therefore, we hypothesized that if dimensional errors could be self-corrected by elastic molds, microdevices could be facilely fabricated with precision beyond that of molds. In this paper, we report a novel processing strategy in which an elastic mold made of polymethylsiloxane (PDMS) deforms to compensate for the dimensional error on the products. By heat-press molding a polycarbonate plate using a mold that has 384 PDMS convexes with a large dimensional error of height of ± 15.6 µm in standard deviation, a 384-round-well plate with a bottom thickness 13.3 ± 2.3 µm (n = 384) was easily fabricated. Finally, single-cell observation and polymerase chain reactions (PCRs) demonstrated the application of the products made by elastic PDMS molds. Therefore, this processing method is a promising strategy for facile, low-cost, and higher precision microfabrication.

Experimental study on elastic modulus of concrete mortar under high temperature

In order to study the change of elastic modulus of mortar concrete under high temperature, the mortar cube was tested at high temperature.The results show that the elastic modulus of the mortar cube is not linear with the change of temperature. The elastic modulus of the mortar decreases with the increase of temperature. When the temperature rises to 150 °C, the mortar elastic mold will have a The situation of slowing down and then falling again.

The Elastic Mold Deformation During the Filling and Packing Stage of the Injection Molding Process

The accurate numerical prediction of the mold filling process of long and thin walled parts is dependent on numerous factors. This paper investigates the effect of various influencing variables on the filling pattern by means of simulation and experimental validation. It was found that mold temperature, process settings and venting conditions have little effect on the predicted filling pattern. However, in the actual case study, the filling behavior observed during the experiments was significantly different compared to the numerical prediction. A structural finite element analysis of the moving mold half showed an unacceptable large deformation of the mold plates under injection pressure. A very good correlation between simulation and experiment was attained after improving the stiffness of the mold. Therefore it can be concluded, that the elasticity of the mold may have a significant influence on the filling pattern when long and thin walled products are considered. Furthermore, it was shown, that even an apparently stiff mold can exhibit a distinct deformation during filling and packing stage.

스퀴징 공정변수에 따른 형광체막 성형 거동에 관한 연구

It was confirmed that when phosphor slurry is formed in the cavity of an elastic mold, the pressure distribution of the phosphor slurry varies as a function of the major squeegee parameters (squeegee angle, squeegee velocity, and the viscosity of the phosphor slurry). The higher the slurry viscosity, the faster the squeegee velocity, and the smaller the squeegee angle, the higher the filling completeness of the phosphor slurry. The optimum conditions for complete filling of the phosphor slurry were found when the squeegee angle was between 30 to 45 degrees, squeegee velocity at 40 to 70mm/sec, and the viscosity of the phosphor slurry composite was at 6,556 cps (i.e. phosphor content around 50 wt. %).

Deformation grating fabrication technique based on the solvent-assisted microcontact molding.

A deformation grating fabrication technique based on solvent-assisted microcontact molding (SAMIM) is reported in this paper. The fabrication process can be divided into three steps: imprinting a grating on a medium polymer substrate (MPS) by SAMIM, coating a thin metal film on the MPS, and transferring the film to the measured surface. In order to increase the stiffness of the elastic mold without decreasing its conformal contact formation ability, a re-useable, glass-embedded polydimethylsiloxane (PDMS) mold is used. In addition, a characterization method based on the Fourier transform and phase analysis is proposed to check the quality of the fabricated grating. Verified by experiment, the proposed fabrication technique can fabricate a high-frequency large-area grating on different specimens, which can be a qualified deformation sensor for the moiré method.

The Elastic Mold Deformation During the Filling and Packing Stage of the Injection Molding Process

The accurate numerical prediction of the mold filling process of long and thin walled parts is dependent on numerous factors. This paper investigates the effect of various influencing variables on the filling pattern by means of simulation and experimental validation. It was found that mold temperature, process settings and venting conditions have little effect on the predicted filling pattern. However, in the actual case study, the filling behavior observed during the experiments was significantly different compared to the numerical prediction. A structural finite element analysis of the moving mold half showed an unacceptable large deformation of the mold plates under injection pressure. A very good correlation between simulation and experiment was attained after improving the stiffness of the mold. Therefore it can be concluded, that the elasticity of the mold may have a significant influence on the filling pattern when long and thin walled products are considered. Furthermore, it was shown, that even an apparently stiff mold can exhibit a distinct deformation during filling and packing stage.

Thermal imprint techniques for preparation of superhydrophobic polymer coatings

The self-cleaning property of superhydrophobic surfaces has raised considerable interest among scientists. Many preparation methods require complex and expensive fabrication techniques that cannot be used to directly modify substrates. We designed an imprint process using a micro/nano-structured mold to emboss several polymer coatings in order to introduce superhydrophobicity and still maintain their transparent/translucent properties. Polydimethylsiloxane (PDMS) elastic molds with various micro and nano features were fabricated using different grades of sandpaper as master molds, increasing the water contact angles (WCAs) on the PDMS surfaces from 120° (plain) to more than 170°. The PDMS molds were then applied to replicate some commercial polymer coatings at an elevated temperature of about 140°C to transfer the mold pattern to the coatings. The hydrophobic property of those polymer coatings was then enhanced to a WCA of greater than 150°. After fluoroalkylsilane deposition on the surfaces, the surfaces displayed an improved lipophobic property (hexadecane contact angle (HCA) went from 90° to 110°). The arbitrarily-rough surfaces displayed ‘sticky superhydrophobicity’ due to the water drops being adsorbed and not rolling off from the surfaces. Atomic force microscopy (AFM) was employed to measure the morphologies of imprinted coatings and also estimate the roughness, occupying polymer ratios, and critical CA to evaluate the wetting of sample surfaces. From the evaluation of surface properties, all the samples using sandpaper as templates exhibited stable Cassie or metastable wetting. The rougher surfaces provided some large protrusions to contact with and be immersed into water droplets, leading to high water penetration depth and thus stickiness. Additionally, the rougher the mold was, the greater the WCA was, but the transparency of the coating was reduced. However, the imprinted polymer surfaces could still maintain sufficient transparency for use in applications requiring preservation of the appearance of the underlying surface.

Microfluidic channels fabricated on mesoporous electrospun fiber mats: A facile route to microfluidic chips

We report a facile way of preparing microfluidic channels filled with electrospun functional fibers. Patterned elastic molds were in tight contact with electrospun fiber mats without any leak of the analyte solution. As an example of the simple devices, we demonstrated a microfluidic protein chip selectively purifying histidine-tagged proteins. Highly mesoporous nitrilotriacetic acid-functionalized polystyrene (PS-NTA) fibers were produced by taking advantage of interpenetrating phase separation between PS and PEO during electrospinning. The specific interaction of Ni-complexed PS-NTA fibers with histidine enabled us to immobilize only target proteins from highly heterogeneous protein mixtures. The easy process to fabricate functionalized microchannels combined with the high production throughput from electrospinning may greatly contribute to chip-based chromatographic and bioanalytical devices. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011

High-Efficiency Stepwise Contraction and Adsorption Nanolithography

A new miniaturization protocol is demonstrated using stretching and relaxation of an elastomer substrate. A designed microstructure is formed on the stretched substrate and subsequently becomes miniaturized when the substrate relaxes. More importantly, the miniaturized structures can be transferred onto a new substrate for further miniaturization or can be utilized as stamps for nanolithography of designated materials. As an example of this approach, an elastic mold was first cast from a Si mold containing periodic line arrays of 1.5-microm line width. Upon relaxation, line width is reduced to 240 nm. The new elastomer may be used as stamps for micro- and nanofabrication of materials such as proteins. The polymer surface roughness or wrinkling behavior at nanoscale is found to follow classic stability model in solid mechanics. This observation provides means to design and control the surface roughness to meet specific requirements.

Resin Jig to Prevent Aspiration or Ingestion of Restorations

Purpose: The aim of this study is to present a new procedure in dental practice to prevent aspiration or ingestion of restorations; this procedure is economical and applicable to many kinds of indirect restoration materials.Methods: The jig comprises three rings in a line and bends at a right angle at the central ring. It is made of autopolymerizing acrylic resin that is molded with a self-made elastic mold. A 30-cm length of dental floss is tied to the ring at one side. The ring at the other side is glued with cyanoacrylate onto the non-occlusal surface of the restoration. If the ring does not properly fit the surface, a small amount of autopolymerizing resin may be brushed on it before gluing.Results: After ensuring that the jig is fixed firm enough, the operators can try-in, adjust, and retrieve the restoration without concerns regarding aspiration/ingestion. After cementation, the jig can easily be removed from the restoration by using scalers.Conclusion: This procedure allows us to decrease the risk of aspiration and ingestion of restorations in daily dental practice.

Patterned growth of ZnO nanorods by micromolding of sol-gel-derived seed layer

An effective method for fabricating micropatterned ZnO nanorods without a catalyst via hydrothermal synthesis using a micromolding technique is presented. Micromolding of a sol-gel-derived seed layer was flawlessly accomplished by conformal contact of elastic mold with microscale pattern. The patterned growth of the nanorods over a large area of the preconfined seed layer was observed with a pattern feasibility attaining 1μm. The orientation of the resulting crystalline nanorods was observed to be normal to the seed layer while characteristic sizes of the nanorods did not show any dependences on the diameter of the seed particles. The presented synthetic process can provide a simpler and more inexpensive way for the fabrication of an array of one-dimensional nanostructures using a wet-chemical method.

TRANSIENT THERMAL STRESSES IN A CHEMICALLY HARDENING MATERIAL CAST WITHIN AN ELASTIC CYLINDRICAL MOLD

Abstract A method is formulated for determining the transient thermal stresses that evolve during the molding process within a material hardening as the result of an exothermic chemical reaction. The formulation is applied to the restricted case in which the shear-to-bulk-modulus ratio for the fully hardened material is small, and where the material is cast in the form of an infinitely long solid cylinder in a thermally thin elastic mold. The heat-generation rate and temperature variation are derived from a first-order chemical reaction. The solidification of the material is described by a transformation from an initial liquidlike state to an elastic solid, with thermoelastic constitutive rate equations during the hardening process based upon a two-component mixture model whose composition is related to the degree of reaction. Graphs for transient stresses and residual stress distributions are shown in terms of dimensionless variables, with hardening rate related to thermochemical constants, and with the ...