Excess Resin Research Articles

Three dimensionally printed template with an interproximal isolation design guide consecutive closure of multiple diastema with injectable resin composite.

This article describes a novel 3D-printed template armed with interproximal matrices to isolate interproximal contact areas and guide injectable resin composite for consecutive closure of multiple diastema. Among several treatment options proposed for diastema closure, direct resin composite is noninvasive and easy to repair. The "composite injection technique" has been introduced to improve time efficiency and reduce technique sensitivity for clinicians. However, in the case of multiple diastema, the overflow of excess resin materials onto the adjacent teeth during injection poses challenges for recontouring the interproximal anatomy. A 3D-printed template with special-designed gaps at interproximal areas was designed and fabricated based on a virtual diagnostic wax-up. Flowable resin composite was then consecutively injected through the template to close diastemata at multiple adjacent teeth. This technique using a 3D-printed template with interproximal isolation design contributed to an efficient and accurate operation for multiple anterior diastema closure. Efficient and accurate freehand buildups of composite restoration for multiple diastema are challenging in operative dentistry. The described noninvasive full digital workflow provides a predictable method to accurately recontour the multiple target restorations and reduce the chair-side time and technical sensitivity.

Effect of attachment flash on clear aligner force delivery: an in vitro study

BackgroundThe introduction of auxiliaries such as composite attachment has improved the force delivery of clear aligner (CA) therapy. However, the placement of the attachment may give rise to a flash, defined as excess resin around the attachment which may affect CA force delivery. This in vitro study aims to determine the differences in the force generated by the attachment in the presence or absence of flash in CA.Materials and methodsTristar Trubalance aligner sheets were used to fabricate the CAs. Thirty-four resin models were 3D printed and 17 each, were bonded with ellipsoidal or rectangular attachments on maxillary right central incisors. Fuji Prescale pressure film was used to measure the force generated by the attachment of CA. The images of colour density produced on the films were processed using a calibrated pressure mapping system utilising image processing techniques and topographical force mapping to quantify the force. The force measurement process was repeated after the flash was removed from the attachment using tungsten-carbide bur on a slow-speed handpiece.ResultsThe intraclass correlation coefficient showed excellent reliability (ICC = 0.96, 95% CI = 0.92–0.98). The average mean force exerted by ellipsoidal attachments with flash was 8.05 ± 0.16 N, while 8.11 ± 0.18 N was without flash. As for rectangular attachments, the average mean force with flash was 8.48 ± 0.27 N, while 8.53 ± 0.13 N was without flash. Paired t-test revealed no statistically significant difference in the mean force exerted by CA in the presence or absence of flash for both ellipsoidal (p = 0.07) and rectangular attachments (p = 0.41). Rectangular attachments generated statistically significantly (p < 0.001) higher mean force than ellipsoidal attachments for flash and without flash.ConclusionAlthough rectangular attachment generated a significantly higher force than ellipsoidal attachment, the force generated by both attachments in the presence or absence of flash is similar (p > 0.05).

Micro-computed tomographic evaluation of the shaping ability of three nickel-titanium rotary systems in the middle mesial canal of mandibular first molars: an ex vivo study based on 3D printed tooth replicas

BackgroundThe preparation of the middle mesial (MM) canal of mandibular molars represents a challenge because it is often curved, narrow, and close to the root concave. The purpose of this study was to evaluate the ex vivo shaping ability of 3 nickel-titanium (NiTi) rotary systems in the MM canal using 3D printed resin tooth replicas.MethodsA permanent mandibular first molar with a MM canal was acquired from a pool of extracted teeth and reproduced by a 3D printer. The resin tooth replicas (n = 18) were equally assigned to 3 groups for the evaluation of the shaping abilities of 3 NiTi rotary systems (OneShape [OS], Twisted Files [TF], and ProTaper Gold [PTG]) according to the manufacturer’s recommendations. The tooth replicas were scanned by micro-computed tomography (micro-CT) twice before and after instrumentation of the mesiobuccal (MB), mesiolingual (ML), and MM root canals. After 3D reconstruction, the canal straightening, change of root canal volume and surface area, the mesial and distal canal wall thickness and canal transportation at the levels of 1, 2, and 3 mm below furcation were assessed. One-way variance analysis and Turkey’s post hoc test were used for comparisons of the means among different groups, and paired-t test was used to compare the mesial and distal sides of the mesial roots.ResultsAs compared with OS and TF, the use of PTG in preparation of MM canals resulted in significantly more straightening of canal curvature (p < 0.05), greater post-instrumentation canal volume and surface area, and thinner mesial and distal remaining canal wall thickness at 1, 2 and 3 mm below furcation (all p < 0.05). Regarding the root canal transportation in the mesiodistal direction, there was no significant difference among the 3 instruments (all p > 0.05) after the preparation of the MB and ML canals. However, in the MM canal, more pronounced transportation was detected in the PTG group at 2 mm below furcation, and in the TF group at 3 mm below furcation as compared with the other 2 systems (both p < 0.05).Conclusions3D printed tooth replicas have the advantages of consistency and can be an ideal model to evaluate the shaping ability of different instruments in the MM canal. OS and TF files performed similarly and both are appropriate for shaping the MM canal, while PTG may cause excessive and uneven resin removal, especially near the furcation, and may lead to root fragility and procedural errors.

Evaluation of the ceramic laminate veneer-tooth interface after different resin cement excess removal techniques.

To compare, in vitro, resin cement excess removal techniques at the veneer-tooth interface. Anterior human teeth were restored with ceramic veneers and randomly divided according to the following techniques (n = 10): removal of excess resin cement with brush and dental floss, followed by light-curing with Valo (Group 1) or Elipar (Group 2) for 1min and 40s; tack-curing with Valo (Group 3) or Elipar (Group 4) for 1s; and tack-curing with Valo (Group 5) or Elipar (Group 6) for 5s. The tack-curing was followed by removal of excess with probe and dental floss and light-curing for 1min and 40s. The area of excess resin cement (mm2) was measured in micro-CT images using AutoCAD program. The failures at the cervical margin in the X, Y, and Z axes (µm) of greater value were measured using the DataViewer program. The specimens were submitted to microleakage with 2% basic fuchsin. According to the Kruskal-Wallis and multiple comparison test, the highest area of excess resin cement was found in Group 1 (5.06 mm2), which did not differ statistically from Groups 2 (3.70 mm2) and 5 (2.19 mm2). Groups 2, 3 (1.73 mm2), 4 (1.14 mm2), and 5 (2.18 mm2) did not differ statistically. Group 6 (0.77 mm2) obtained the lowest value, which did not differ statistically from Groups 3 and 4. According to the Kruskal-Wallis and Dunn test, there was no significant difference in failures in X (p = 0.981), Y (p = 0.860), and Z (p = 0.638) axes and no significant difference in microleakage (p = 0.203) among the groups. Tack-curing for 1s or 5s, followed by removal of excess resin cement using a probe and a dental floss, tended to result in a lower amount of excess material around the margin. The technique used for resin cement excess removal influences the amount of excess leaved at the veneer-tooth interface. Tack-curing for 1s or 5s is recommended to mitigate the excess resin cement.

A technique for easy removal of excess resin cement

In the context of cementing indirect dental restorations, the inadvertent bonding of excess cement to adjacent teeth poses a multifaceted challenge, affecting aesthetics, periodontal health and chair time. Using PTFE tape as the sole method for isolation can be time consuming, and occasionally presents challenges. The approach described in this Technique Tip involves manually holding a matrix holder to safeguard neighbouring teeth from sandblasting and etching contamination, providing a pragmatic resolution to these issues. It seamlessly integrates with the established practice of using PTFE tapes to prevent unwanted bonding and cement attachment to adjacent teeth. CPD/Clinical Relevance: Combining PTFE and matrix bands optimises bonding of indirect ceramic restorations for periodontal health and efficiency.

A new strategy for the preparation of wood-epoxy resin composites reinforced with controllable osmotic interfaces

As a multifunctional material, wood is widely used in interior decoration and construction engineering. The full-cell process of impregnating monomers into wood pores cavity in situ is one of the most common wood modification methods. However, this approach is time-consuming, material-wasting, and not environmentally friendly. In this study, we proposed a simple strategy to directly convert wood into high-performance composites by controlling wood surface penetration through resin pre-curing. A slight amount of resin used was sufficient to penetrate the wood surfaces, and the weight percent gain (WPG) of 11.45 %. High energy efficiency was achieved by simple temperature control (60 °C/120 °C). In addition, this method can rapidly produce wood composites with ultra-low density (0.51 g/cm3) and ultra-high specific bending strength (284 MPa·cm3g−1) in a very short time (4 h and 30 min). The results showed that the problem of excessive resin penetration was effectively solved by the pre-curing process, which enriched the gradient distribution of resin from the surface to the bottom of the wood and significantly improved the material properties. This efficient and environmentally friendly preparation strategy makes natural wood a low-cost, low-density, high-strength engineering material, which broadens the application of wood composites in construction engineering and interior decoration.

Porous Electrode Optimization for PEMFCs Using 3D Printing Technology

Proton Exchange Membrane Fuel Cells (PEMFCs) represent a class of fuel cells that transform the chemical energy of fuels, ideally hydrogen and oxygen, into electrical power. Utilized in diverse applications, PEMFCs power vehicles and supply backup energy to buildings. The core of a PEMFC is the membrane electrode assembly (MEA), composed of a polymer electrolyte membrane, an anode, and a cathode. Oxygen, protons, and electrons merge at the cathode, forming water. One challenge PEMFCs face is water-induced cathode flooding at low temperatures, a consequence of the electrochemical reaction's water accumulation. This reduces the oxygen supply, potentially leading to decreased cell performance or even failure. This issue can have substantial undesired consequences, as PEMFCs depend on oxygen availability at the cathode to generate electricity.Gas Diffusion Layers (GDLs) serve as critical PEMFC components, providing porous structures that facilitate reactant access to the catalyst layer and enabling electron flow through the external circuit. GDLs also offer structural support and promote reactant distribution across the membrane surface. Water accumulation in the cathode may cause pore clogging within the GDL, restricting reactant flow, and reducing cell performance. Additionally, water build-up increases pressure drop across the GDL, hindering reactant access to the catalyst layer and diminishing fuel cell efficiency.Three-dimensional (3D) printing has emerged as a potential technique for fabricating GDLs in PEMFCs. 3D printing enables the creation of GDLs with ordered pore size structures, offering a more uniform surface than traditional GDLs with randomly oriented fibres. This uniformity enhances reactant distribution across the membrane surface and mitigates water accumulation risks. In addition, to prevent cathode flooding, 3D printed GDLs are immersed in PTFE solution to increase hydrophobicity.This talk delves into the creation and evaluation of 3D printed carbonized GDLs for PEMFC implementation. A desktop 3D printer constructed a polymer framework, which was subsequently carbonized in a high-temperature tube furnace. Isothermal thermogravimetric analysis (TGA) tests were performed to identify weight change across a temperature range of 30-900 °C under an N2 atmosphere, optimizing the carbonization step to reduce structural distortion and increase electrical conductivity.The 3D printed GDLs displayed pore size diameters spanning 80 to 120 μm and fibre radii of 20-30 μm. The 3D printing technique produced GDLs characterized by a consistent, planar structure without blocked pores that are normally caused by excess resin residue. Electrical conductivity assessments were conducted on the carbonized specimens, and tensile and compression tests measured their mechanical properties.GDLs possessing minimal pore sizes and thicknesses were integrated into membrane electrode assemblies (MEAs) and examined in low-temperature PEMFCs. Diverse spraying methodologies were investigated, involving either the catalyst being sprayed onto the 3D printed GDL or the membrane receiving a catalyst coating. Commercial MEAs, comprising Nafion membranes and platinum electrodes, acted as benchmarks for MEAs featuring 3D printed GDLs. Furthermore, the current challenges facing 3D printed GDLs, including material selection, production consistency, compatibility with other PEMFC components, costs, and scaling up are highlighted in the talk.These findings underscore the promise of 3D printed carbonized GDLs in boosting PEMFC performance, showing their potential as a cost-effective and proficient substitute for conventional carbon paper based GDLs. Figure 1

Effects of different removal methods of excess resin adhesive on the microleakage of alumina all-ceramic crowns

BackgroundMicroleakage is a common problem that affects the quality and longevity of all-ceramic crowns. It is influenced by factors such as the resin cement, crown margin design and curing technique. However, few studies focus on the effect of different methods of removing excess resin adhesive on the microleakage of all-ceramic crowns. This study aimed to compare two methods of removing excess resin adhesive (the small brush and sickle methods) on the microleakage of all-ceramic crowns with different marginal clearances.MethodsForty extracted third molars were prepared with a 90° shoulder margin and randomly divided into four groups according to their marginal lift (30, 60, 90 or 0 μm). Procera alumina crowns were fabricated using computer-aided design/computer-aided modelling and cemented onto the teeth with 3 M RelyX Unicem (3 M Company, United States) resin cement. Excess resin cement was removed by either the small brush or the sickle scalpel method. The marginal adaptation was observed with a digital microscope. After thermal cycling of the teeth, microleakage was assessed using the dye penetration test under a stereomicroscope. The Mann–Whitney U test and Kruskal–Wallis H test were used to compare the microleakage scores among different groups.ResultsThe small-brush group showed significantly better marginal adaptation and lower microleakage scores than the sickle group (p < 0.05). There was no significant difference in the microleakage score (grade 0) among different marginal clearances within each group (p > 0.05).ConclusionThe small-brush method was more effective than the sickle scalpel method in reducing the microleakage of all-ceramic crowns with different marginal clearances. This method can improve the marginal adaptation and sealability of all-ceramic crowns, thus preventing secondary caries and other complications.

Optimizing Sample Preparation Process for Transmission Electron Microscopy of Neuromuscular Junctions in Drosophila Larvae.

The Drosophila neuromuscular junction (NMJ) has emerged as a valuable model system in the field of neuroscience. The application of confocal microscopy at the Drosophila NMJ enables researchers to acquire synaptic information, encompassing both quantitative data on synapse abundance and detailed insights into their morphology. However, the diffuse distribution and limited visual range of the TEM present challenges for the ultrastructural analysis. This study introduces an innovative and efficient sample preparation method that surpasses the conventional approach. The procedure begins by placing a metal mesh at the base of a flat-bottomed bottle or test tube, followed by positioning fixed larvae samples onto the mesh. An additional mesh is placed over the samples, ensuring that they are positioned between the two meshes. The fixed samples are thoroughly dehydrated and infiltrated before proceeding with the embedding procedure. Then embedding of the samples in epoxy resin is performed in a flat sheet manner, which allows for the preparation of muscles for positioning and sectioning. Benefiting from these steps, all the muscles of Drosophila larvae can be visualized under light microscopy, therey facilitating subsequent positioning and sectioning. Excess resin is removed after locating the 6th and 7th muscles of body segments A2 and A3. Serial ultra-thin sectioning of the 6th or 7th muscle is performed.

A technique to remove polymerized excess resin cement from interproximal regions following bonding of porcelain laminate veneers

A technique to remove polymerized excess resin cement from interproximal regions following bonding of porcelain laminate veneers

Quality assurance of stereolithography based biocompatible materials for dental applications

Additive Manufacturing (AM) is increasingly being used in healthcare sectors for its potential to fabricate patient-specific customized implants, and specifically in dentistry, AM finds its applications in maxillofacial implants, dentures, and other prosthetic aids. However, in most applications, AM is largely being used for prototyping purposes. The full-scale realization of AM can only be achieved if the downsides of AM are addressed and resolved. Hence this paper focuses on providing a detailed analysis of surface quality, dimensional accuracy, and mechanical properties of the biocompatible material produced, using the Stereolithography (SLA) method for a dental application. For quality analysis, test artefacts were produced, and the quality was assessed before and after the sterilization process. The results suggest that micro-surface roughness essential for cell growth is similar for all build inclinations and well within the control limit required for effective bone regeneration. Multi-scale surface characterization revealed that the sterilization process involving heat can potentially alter the micro-roughness features of resin-based materials. The results from the dimensional analysis show that the SLA parts produced had negligible dimensional deviations from the CAD model to the printed parts and were unaffected by the sterilization process. The tensile test results suggest that the part orientation does not affect the tensile strength and that the sterilization process seems to have an insignificant effect on the tensile properties of the SLA parts. Furthermore, the results were validated by producing a membrane barrier for Guided Bone Regeneration (GBR). The validation results showed that excess resin entrapment was due to the geometrical design of the membrane barrier. In conclusion, this paper provides an overview of quality variations that can help in optimizing the AM and sterilization process to suit dental needs.

Enhanced flowability and film properties of ultrafine powder coatings modulated by modified flow additive

Ultrafine powder coatings have superior film performance but poor flowability due to the high interaction between particles, which can be improved by the addition of inorganic flow additives. However, the improvement is limited and more importantly, the film performance deteriorates because of their incompatibility with the organic coating resin. In this study, a resin encapsulation approach was proposed to modify the commercial inorganic flow additives for the improvement of powder flowability and maintaining film quality. The effects of resin content and additive dosage on the flowability characterized by angle of repose (AOR) and avalanche angle (AVA), and film performance characterized by gloss, seed density and surface roughness were systematically investigated in two powder coating systems. It was found that the encapsulation of additives with the same resin of the host powder coating can enhance both flowability and film properties, compared to commercial nano-silica. With the increase of resin content, both the AOR and AVA first decrease to a minimal value at resin content of 5 % to 10 % and then increase when applying excessive resin encapsulation. Similar to the effect of resin content, there is also an optimal additive dosage at 0.3 to 0.5 wt% for the best flowability, while excessive additives lead to “bridge effect”. The negative effect raised by the additives on film quality can be mitigated by resin encapsulation. Higher gloss and lower roughness are obtained at larger resin content, while the smallest seed density is at resin content of 10 %. The study provides an effective and facile way to ameliorate the function of the flow additive and enhance the properties of powder coating films.

SINGLE IMPLANT-RETAINED MANDIBULAR OVERDENTURE: A CASE REPORT

Edentulism is a public health problem, impacting the quality of life of many people worldwide. Factors related to the mandibular ridge minimal support may hinder the common use of complete dentures. The use of overdentures supported by a minimum of one implant can be considered as reliable approach in this situation. Aim: To present a case report of a single implant-supported overdenture in the mandibular symphysis fot public health policies. Case report: A 65-year-old edentulous patient complaining of discomfort in a mandibular denture was referred to the Universidade Federal Fluminense. On clinical examination, residual mandibular ridge resorption and soft tissue trauma were observed, which was in line with the reported discomfort. A mandibular overdenture retained by a single implant in the symphysis region was planned. A hex-type 4.0 mm in diameter and 11.0 mm in length implant was placed and a new set of complete dentures were made till the date of complete osseointegration. After four months, a second surgery exposed the implant platform to fit a ball attachment with a 32 N.cm torque. The denture was relieved on its tissue surface for the placement of a metal attachment matrix with a rubber O-ring inside, using a fast-curing resin, and the patient was locked into maximum intercuspidation during the acrylic polymerization process. Excessive resin was removed and the region was polished for daily use after the process. The patient reported an improvement in chewing condition and restorative esthetics. Conclusions: A minimum requirements protocol has achieved relevant results and may be feasible in public health policies. Maintenance visits are recommended to maintain retention quality and to decrease the risk of failures.

Resin cement around tissue and bone level dental implants after two cementation techniques (an in vitro study)

Purpose: To detect the retained excess resin cement around tissue and bone level dental implants following two different cementation techniques. Methods: Fourteen tissue level and fourteen bone level implants (OCO Biomedical, U.S.A.) were embedded in models (Salvin Dental Specialties, U.S.A.) having rubber surface simulating the gingiva. Twenty-eight metal copings were fabricated and cemented to the implant’s abutments by RelyX U200 resin cement (3M, U.S.A.). Each group was subdivided according to the cementation technique into two subgroups: A1 and B1: Tack cure of the excess cement for three seconds, the partially set resin cement was carefully removed before complete cure. A2 and B2: 1mm vent was performed on the occlusal surfaces. Excess cement was carefully removed followed by a final cure. Rubber coverage was removed, retained cement net weight was determined. All specimens were visually examined under 30x magnification using Stereomicroscope (SZ-11, Japan). Results: Tissue level implants following the tack cure protocol had less retained excess cement percentage than the occlusal vent protocol. Statistical comparison showed a significant difference in the excess cement percentage within the tissue level subgroups (p=0.018), No significant difference observed within the bone level subgroups (p=0.096).

Resin cement around tissue and bone level dental implants after two cementation techniques (An In Vitro Study)

Purpose: To detect the retained excess resin cement around tissue and bone level dental implants following two different cementation techniques. Methods: Fourteen tissue level and fourteen bone level implants (OCO Biomedical, U.S.A.) were embedded in models (Salvin Dental Specialties, U.S.A.) having rubber surface simulating the gingiva. Twenty-eight metal copings were fabricated and cemented to the implant’s abutments by RelyX U200 resin cement (3M, U.S.A.). Each group was subdivided according to the cementation technique into two subgroups: A1 and B1: Tack cure of the excess cement for three seconds, the partially set resin cement was carefully removed before complete cure. A2 and B2: 1mm vent was performed on the occlusal surfaces. Excess cement was carefully removed followed by a final cure. Rubber coverage was removed, retained cement net weight was determined. All specimens were visually examined under 30x magnification using Stereomicroscope (SZ-11, Japan). Results: Tissue level implants following the tack cure protocol had less retained excess cement percentage than the occlusal vent protocol. Statistical comparison showed a significant difference in the excess cement percentage within the tissue level subgroups (p=0.018), No significant difference observed within the bone level subgroups (p=0.096). &#x0D;

Design of Microstructured Flat Optical Fiber for Multiaxial Strain Monitoring in Composite Materials

An innovative microstructured flat optical fiber is designed to obtain a multiaxial strain sensor for composite material monitoring. The sensing regions are constituted by the two eyelets where Bragg gratings are written. To achieve multiaxial sensing, a suitable microstructure is designed close to only one of the eyelets. The effect of the strain field, evaluated via a 3D finite element method approach, is considered to obtain the change of the refractive index distribution. The electromagnetic modal analysis and the coupled mode theory are exploited to evaluate the Bragg wavelength shift for the slow and fast axis fundamental modes, guided in the two eyelets and affecting the sensor response. The designed microstructured flat optical fiber is technologically feasible and promises sensing performance higher than that obtainable with the conventional optical fibers. In addition, flat optical fiber can be embedded in composite materials reducing the drawbacks related to both orientation and excess resin.

A multiphase flow approach to gas permeability of composite facesheets during Co-cure of honeycomb core sandwich structures

Co-curing composites facesheets to produce sandwich structures involves heating a prepreg-core assembly in a vacuum bag and compacting it by an external pressure until the prepreg cures and bonds to the core. During this process, vacuum pressure can cause atmospheric air in the honeycomb core to bubble through uncured prepreg facesheets and impact material quality, such as excess resin bleed and void growth in either the facesheet or the bondline. In this paper, we propose a multiphase flow model to predict core gas pressure throughout the process. Fully impregnated prepreg facesheets only become permeable to gas as liquid resin desaturates pores in the fabric weave. To solve for the core gas pressure, resin and gas transport equations are solved simultaneously. The permeability of each phase is a function of saturation–defined by the Brooks-Corey model to be a power law function of the capillary pressure. Deviating from a single phase (gas only) model, using dimensionless analysis we identify four material properties which control the outcome: (i) an intrinsic permeability, K i, which only depends on the fabric architecture and is invariant to all process variables (time, temperature, pressure), (ii) the ratio of fluid viscosities, μ w/ μ g, where resin viscosity varies strongly with temperature and degree of cure, (iii) a bubbling (capillary) pressure, P b, which defines the minimum pressure needed to penetrate the largest pore, and (iv) a pore size distribution parameter, λ, which defines the percentage of pores which may desaturate given the evolving capillary pressure. Changes in observed gas permeability due to time and temperature are explained by the evolving desaturation of facesheet resin and the known relationship to resin viscosity. By applying this model, a reduced set to material characterization is required and complex process cycles can quickly be interrogated. With our experiments we demonstrate that one single value for K i and one single value for λ can be used to predict the gas pressure decay (time dependent) at different temperatures, confirming that the intrinsic permeability is constant for the fiber network and changes in the relative permeability to air are due to the decrease in viscosity only. The limitations of this model are presented and discussed.

An additional hole to compensate for mechanical property of thermoset composite and aluminum alloy joint during resistance welding

A hole in the center of the aluminum (Al) alloy was processed to compensate for the mechanical properties of resistance welded joints of the carbon fiber reinforced epoxy resin matrix (CF/Epoxy) laminate and Al alloy for solving the problem of poor bonding quality in the center of the joint due to uneven temperature distribution in the resistance welding process. The resistance welded lap configuration of the upper Al and the lower laminate was employed, and through holes with a different diameter (d h) were prefabricated on the upper Al alloy plates. The molten polyetherimide (PEI) resin was bonded to the surfaces of the samples on both sides under the action of Joule heat, and the excess PEI resin filled the prefabricated through-hole of the Al alloy plate under pressure and realized the jointing of the 6063Al alloy plate and the CF/Epoxy laminate. The micro-morphology of the welded interface was characterized by scanning electron microscopy (SEM), and the heat distribution of the sample was simulated using COMSOL. The tensile shear force of the joint was tested, which rises with an increase of d h. The failure interface was analyzed in detail, which showed a strong correlation with d h.

Suppressing the Step Effect of 3D Printing for Constructing Contact Lenses.

3D printing has been considered as a sustainable method to construct complicated 3D structures. However, the step effect induced by the traditional point-by-point or layer-by-layer additive manufacturing mode inevitably occurs and remains an obstacle to realizing the smoothness and uniformity of 3D samples. Here, a continuous liquid film confined 3D printing strategy is proposed to fabricate high-precision 3D structures based on the Digital Light Processing (DLP) technology. With the control of the confinement of the liquid-solid interface and the continuous printing mode, liquid film adhering to the cured structure is sucked into the cured layer structures with excess resin adhering to the cured structure scraping off, where the step effect is eliminated and post-washing is avoided. The morphology and dimension of the confined liquid film can be well regulated by ink properties and printing parameters to optimize the surface smoothness and printing fidelity. In addition, heat accumulation and thermal diffusion are also suppressed, ensuring the long-term printing stability. A centimeter-scale contact lens structure with central thickness of ≈135µm comparable to commercial ones can be printed, which possesses extreme smoothness (sub 1.3nm), homogeneous mechanical characteristic, biocompatibility, and high optical properties with imaging resolution of up to 228.1 lp mm-1 .

Experimental study on the key influencing factors of phase inversion and stability of heavy oil emulsion: Asphaltene, resin and petroleum acid

This study investigates the effects of asphaltene, resin and petroleum acid on the phase inversion, stability and oil–water interface characteristics of emulsions. First, different ratios of asphaltene, resin, petroleum acid and formation water were emulsified and the emulsion viscosity was measured to obtain the phase inversion point. Through comparative analysis of phase inversion point data under different conditions, we showed that the synergy of asphaltene and resin was the key to the emulsion phase inversion and the best asphaltene to resin ratio was 1:3. Moreover, the addition of petroleum acid would accelerate the phase inversion. Then, the dynamic interfacial tension of oil and water was measured using the rotating drop method. The synergistic effect of asphaltene and resin would decrease the interfacial tension. However, excessive resin would compete with asphaltene for adsorption, which would increase the interfacial tension. The lowest interfacial value was observed when the mass concentration ratio of asphaltene to resin was. Thus, the addition of petroleum acid significantly reduced the interfacial tension of oil and water. Next, the hanging drop method was employed to measure the interfacial tension of oil and water and the expansion modulus was obtained using the oscillatory drop method. Experimental studies have shown that asphaltene influences the expansion modulus more than resin and the synergistic effect of asphaltene and resin increases the expansion modulus. However, the addition of petroleum acid would decrease the expansion modulus towing to the small molecular weight of petroleum acid. Finally, the emulsion stability was determined using the bottle test method. Experiments showed that the synergistic effect of asphaltene and resin would enhance the emulsion stability. However, the addition of asphaltene played a pivotal role in enhancing the emulsion stability. Further, the addition of petroleum acid would severely destroy the emulsion stability.