Flexible Resin Research Articles

Energy Harvesting Using Optimized ZnO Polymer Nanocomposite-Based 3D-Printed Lattice Structure.

A 3D-printable polymer can provide an effective solution for developing piezoelectric structures. However, their nanocomposite formulation and 3D printing processability must be optimized for fabricating complex geometries with high printability. In the present study, we optimized the 3D-printable piezoelectric composite formulation for developing complex geometries by an additive manufacturing approach. The zinc oxide (ZnO) nanomaterial was synthesized by the hydrothermal method. The ZnO loading in the 3D-printed flexible resin was optimized to exhibit good interfacial adhesion and enable 3D printing. The lattice structure was fabricated to improve the piezoelectric response compared with the solid structure. The lattice structure block printed with 10 wt% ZnO showed a good piezoelectric response, with a linear increase in the generated output voltage for an increase in force. The maximum power density of 0.065 μW/cm2 was obtained under 12 N force at 1 Hz. The fabricated structure generated a peak-peak voltage of ~3 V with a foot heel strike.

Strain rate sensitivity of rotating-square auxetic metamaterials

This study provides an in-depth analysis of the mechanical behavior of rotating-square auxetic structures under various strain rates. The structures are fabricated using stereolithography additive manufacturing with a flexible resin. Mechanical tests performed on structures include quasi-static, intermediate, and high strain rate compression tests, supplemented by high-speed optical imaging and two-dimensional digital image correlation analyses. In quasi-static conditions (5 × 10–3 s-1), multiscale measurements reveal the correlation between local and global strains. It is shown that cell hinges play a significant role in structural deformation and load-bearing capacity. In drop tower impact conditions (intermediate strain rate of ca. 200 s-1), the auxetic structures display significant strain rate hardening compared to loading at quasi-static rates. The thin-hinge structures maintain a Poisson's ratio of approximately -0.8, showing higher auxeticity than slow-rate compression tests. High strain rate conditions (ca. 2000s-1) activate additional deformation mechanisms, including a delayed state of equilibrium exemplified by a heterogeneous distribution of lateral strains, possibly due to stress wave interactions and inertial stresses. The study further reveals nonlinear correlations between Poisson's ratio, strain, and strain rate, indicating reduced auxeticity at higher strain rates. These observations are discussed in terms of complex wave interactions and the strain rate hardening characteristics of the base polymer.

Cosmetic Makeover of Periodontally Compromised Patients using Flexible Gingival Mask and Porcelain Laminate Veneers: Report of Two Cases

Chronic periodontal disease can lead to advanced gingival tissue loss that can result in problems with esthetics, phonetics, food impaction and tooth sensitivity. One of the most difficult problem encountered in the management of periodontal disease is loss of interdental papillae which leaves unsightly “black triangles” between the teeth. The first step in the management of these problems is surgical correction of the defect. In cases where mucogingival surgery is unpredictable due to generalized recession and loss of large volume of gingival tissue, removable gingival prosthesis is an excellent alternative to correct the deformities remaining after the control of destructive periodontal disease specially in the maxillary anterior region. Gingival prostheses may be fixed or removable. It can be made from a range of materials like acrylic, silicones, porcelain- based materials and flexible resin denture material. This report describes two clinical situations in which combined periodontal/prosthodontic rehabilitation was done for patients with advanced periodontal disease. Accurately fitting flexible gingival prostheses and porcelain laminate veneers were fabricated to restore advanced gingival tissue loss in esthetic area following periodontal flap surgery. The flexible gingival masks not only help to achieve excellent cosmetic results but also reinstate the functional and psychological wellbeing of the patient.

Wafer-Scale Growth and Transfer of High-Quality MoS2 Array by Interface Design for High-Stability Flexible Photosensitive Device.

Transition metal disulfide compounds (TMDCs) emerges as the promising candidate for new-generation flexible (opto-)electronic device fabrication. However, the harsh growth condition of TMDCs results in the necessity of using hard dielectric substrates, and thus the additional transfer process is essential but still challenging. Here, an efficient strategy for preparation and easy separation-transfer of high-uniform and quality-enhanced MoS2 via the precursor pre-annealing on the designed graphene inserting layer is demonstrated. Based on the novel strategy, it achieves the intact separation and transfer of a 2-inch MoS2 array onto the flexible resin. It reveals that the graphene inserting layer not only enhances MoS2 quality but also decreases interfacial adhesion for easy separation-transfer, which achieves a high yield of ≈99.83%. The theoretical calculations show that the chemical bonding formation at the growth interface has been eliminated by graphene. The separable graphene serves as a photocarrier transportation channel, making a largely enhanced responsivity up to 6.86mAW-1, and the photodetector array also qualifies for imaging featured with high contrast. The flexible device exhibits high bending stability, which preserves almost 100% of initial performance after 5000 cycles. The proposed novel TMDCs growth and separation-transfer strategy lightens their significance for advances in curved and wearable (opto-)electronic applications.

Research on FBG Tactile Sensing Shape Recognition Based on Convolutional Neural Network.

Shape recognition plays a significant role in the field of robot perception. In view of the low efficiency and few types of shape recognition of the fiber tactile sensor applied to flexible skin, a convolutional-neural-network-based FBG tactile sensing array shape recognition method was proposed. Firstly, a sensing array was fabricated using flexible resin and 3D printing technology. Secondly, a shape recognition system based on the tactile sensing array was constructed to collect shape data. Finally, shape classification recognition was performed using convolutional neural network, random forest, support vector machine, and k-nearest neighbor. The results indicate that the tactile sensing array exhibits good sensitivity and perception capability. The shape recognition accuracy of convolutional neural network is 96.58%, which is 6.11%, 9.44%, and 12.01% higher than that of random forest, k-nearest neighbor, and support vector machine. Its F1 is 96.95%, which is 6.3%, 8.73%, and 11.94% higher than random forest, k-nearest neighbor, and support vector machine. The research of FBG shape sensing array based on convolutional neural network provides an experimental basis for shape perception of flexible tactile sensing.

Engineering digital light processing ceramic composites for wide-range flexible sensing arrays

Flexible ceramic composites are promising candidates in capacitive pressure sensing applications. However, the fabrication of complex composite structures typically involves costly and time-consuming processes such as lithography or mold utilization. Digital light processing (DLP)-based 3D printing offers a layer-by-layer approach via photopolymerization, facilitating rapid prototyping of various ceramic composite structures in a single-step synthesis process. This study presents the successful implementation of a flexible ceramic composite based on the highly dielectric ceramic BaTiO3 and conductive MWCNT fillers by employing DLP 3D printing to create an hourglass-shaped stress concentration structure, aiming at enhancing flexible capacitive sensing capabilities. Blending commercial flexible resin with 4-acryloyl morpholine monomers yields a photocurable resin formulation with appropriate mechanical flexibility, photocurability, and optimal suspension viscosity suitable for DLP 3D printing. Furthermore, the proposed 3D-printed sensor arrays comprising hourglass-shaped unit cells demonstrate improved linear sensitivity across a broad pressure range owing to efficient stress concentration effects in a symmetric geometry, as corroborated by both finite element methods and experiments. DLP 3D printing, combined with tailored resin formulations and optimized ceramic and conductive filler contents, enables the rapid prototyping of diverse sensor structures with significantly enhanced sensitivity, highlighting the versatility of this approach for a wide range of applications.

Synergistic improvement of mechanical and piezoelectric properties of the flexible piezoelectric ceramic composite and its high-precision preparation

Flexible piezoelectric ceramic composites (FPCCs) hold promising applications in fields such as flexible sensing and energy harvesting. However, the previous methods are difficult to achieve high-precision preparation of the FPCCs with complex structures, as well as the synergistic enhancement of piezoelectric performance and flexibility. In this study, by configuring a flexible resin matrix and employing a surface functionalization treatment on the piezoelectric ceramic particles, the flexibility and piezoelectric performance of the FPCCs are synergistically improved. Moreover, the addition of a light absorber, TiO2, significantly improves the 3D printing precision. The mechanical properties, piezoelectric performance, and printing precision of the FPCCs are analyzed. It is found that the printing error is less than 2 μm, the tensile fracture strength is 4.07 MPa, the elongation at break is 350 %, and the piezoelectric constant d33 can reach 7.7 pC/N. In addition, the cyclic loading tests show that FPCCs with high-precision 3D complex microstructure have good recovery performance. This study not only enriches the formulation of FPCCs slurry for 3D printing, but also provides a research foundation for the multifunctional applications.

Preparation and Mechanical Properties of Flexible Prepreg Resin with High Strength and Low Creep.

In this study, aiming at the problem of low strength and high creep caused by medium-low modulus flexible resin based on the formulation design idea of high-molecular-weight epoxy resin (E12)-reinforced flexible epoxy-terminated urethane resin (EUR), a flexible epoxy prepreg resin with high strength and low bending creep was prepared to be suitable for hot melt processing technology. Flexible EUR was synthesized by grafting flexible polyurethane segments onto the epoxy side chain by urethane bonding. By adjusting the ratio of E12 and EUR, the effects of different ratios of the two components on the mechanical properties and viscoelasticity of the resin were systematically studied with dicyandiamide as the latent curing system. Research has found that when the E12 content is between 20%wt and 40%wt, the resin system has the best coating viscosity at 65 °C to 85 °C. The molecular weight and the content of aromatic heterocyclic groups of the resin determine the strength and creep behavior of the resin. When the content of E12 in the system is less than 50%wt, modulus and strength increase linearly, but after more than 50%wt E12 content, the modulus is almost unchanged and the strength begins to decrease. By increasing the content of E12 in the resin, the creep behavior of the resin is greatly reduced. When the content of E12 increases to 50%wt, the bending creep is the lowest.

Evaluation of Color Stability for Two Types of Denture Base Materials: Heat Cured Acrylic and Flexible Resin.

Commonly consumed beverages used by human being daily (Tea & Cola) caused external staining. This study is done to evaluate the color stability for two different types of denture base materials against this external staining caused by (Tea & Cola). Sixty (60) samples were prepared, divided into two groups, 30 samples of heat cure acrylic material & 30 samples of flexible resin material (Valplast). Each group divided into three subgroups 10 samples in each, according to the type of staining solution that immersed in it, (synthetic saliva & tea), (synthetic saliva & Cola), and (synthetic saliva alone as a control). Tea & Cola were mixed with synthetic saliva in order to create intraoral environment to certain extent. Color measurement was made at Baghdad University, Collage of Engineering, using reflected spectrophotometer before immersion (at baseline) & after immersion, at intervals of (24 hours) & (1 week) respectively. The result was a highly significant difference between, heat cure acrylic & flexible resin a t baseline & the (flexible samples) were the higher value in discol oration than (heat cure acrylic samples) regardless the type of s taining solution. Maximum discoloration was seen in (synthetic sal iva & tea) solution for both denture base materials. Followed by (synthetic saliva & Cola) & (synthetic saliva alone) respectively . Both denture base mater ials had a color changes after immersion in staining solution (tea , Cola & synthetic saliva). The color changes, for two materi als, were increased with the increase of immersion time.

Impact of Sorts Disinfection and Cleansing Material on Hardness of Different Types of Denture Base Material

Dentist, dental technician and assistants are faced a several kinds of microorganisms during wor like bacteria, fungi and viruses .So, we can prevent cross contamination by using either chemica or mechanical disinfection. The aim of the research was to measure the effect of different types of chemical disinfection on the hardness of two types of denture base resin, heat activated acry and nylon (flexible). A total number of 80 denture resin specimens (40 specimens from hea activated acrylic and 40 specimens from flexible resin) were prepared. Each type of specim was subdivided into 4 groups. Three groups were divided according to the type of dentur disinfectants (1%sodium hypochlorite, 1% povidine/iodine, Kin solution) and the fourth whi considered as control group was immersed in distilled water. All specimens were immersed testing solution for 90 minutes at 370C. The hardness of the specimens before and af immersion was tested using Shore D machine. Our study showed that the mean value hardness test for poly methyl methacrylate higher than polyamide and there need aid non significant Contrast in the resistance of the surface to scratches and indentation between diver sorts of thermoplastic resin after using chemical disinfectant and denture cleansers w i comparison with control group for each type of denture base resin. The resistance to indentati of different types of denture base would not affected by short time immersion in chemica disinfectant.

Fabrication of Soft Transparent Patient-Specific Vascular Models with Stereolithographic 3D printing and Thiol-Based Photopolymerizable Coatings.

An ideal vascular phantom should be anatomically accurate, have mechanical properties as close as possible to the tissue, and be sufficiently transparent for ease of visualization. However, materials that enable the convergence of these characteristics have remained elusive. The fabrication of patient-specific vascular phantoms with high anatomical fidelity, optical transparency, and mechanical properties close to those of vascular tissue is reported. These final properties are achieved by 3D printing patient-specific vascular models with commercial elastomeric acrylic-based resins before coating them with thiol-based photopolymerizable resins. Ternary thiol-ene-acrylate chemistry is found optimal. A PETMP/allyl glycerol ether (AGE)/polyethylene glycol diacrylate (PEGDA) coating with a 30/70% AGE/PEGDA ratio applied on a flexible resin yielded elastic modulus, UTS, and elongation of 3.41MPa, 1.76 MPa, and 63.2%, respectively, in range with the human aortic wall. The PETMP/AGE/PEGDA coating doubled the optical transmission from 40% to 80%, approaching 88% of the benchmark silicone-based elastomer. Higher transparency correlates with a decrease in surface roughness from 2000 to 90nm after coating. Coated 3D-printed anatomical replicas are showcased for pre-procedural planning and medical training with good radio-opacity and echogenicity. Thiol-click chemistry coatings, as a surface treatment for elastomeric stereolithographic 3D-printed objects, address inherent limitations of photopolymer-based additive manufacturing.

Effect of CTBN and Nano-SiO2 modified epoxy resin powder on the mechanical properties of cement-based composites

The high brittleness of oil well cement seriously affects the cementing quality. In order to maintain the safe and effective production of oil and gas wells, it is crucial to employ solid flexible fillers to reduce the brittleness of cement. In this study, a new type of flexible resin material (C-ER) was prepared by modifying epoxy resin with liquid nitrile butadiene rubber (CTBN) and nano-SiO2. The chemical composition, hydrophilicity, dispersibility, microstructure, and mechanical properties of C-ER were studied by FT-IR, XPS, contact angle, UV spectroscopy, SEM, DMA, and uniaxial compression. The results show that CTBN reacted with the epoxy group successfully. Due to the presence of SiO2, C-ER has good hydrophilicity and dispersion properties. The introduction of flexible segments makes C-ER have a lower modulus and crosslinking density, and its compressive elastic modulus is reduced by 47.4 % compared with pure resin. In addition, the effect of C-ER on the performance of oil well cement was tested. The results show that the addition of C-ER does not affect the fluidity of cement slurry and can improve the strain capacity of cement stone under load. Compared with blank cement and unmodified resin cement, the flexural strength of cement sample containing 4 % C-ER particles increased by 9.0 % and 25.1 %, respectively, and the elastic modulus of cement stone decreased by 31.2 % and 25.0 %, respectively. SEM images show that C-ER maintains good dispersion and bonding properties in cement matrix. C-ER can reduce the brittleness of cement effectively through its own elastic deformation and debonding to the cement matrix.

Effect of Thermal Aging and Chemical Disinfection on the Microhardness and Flexural Strength of Flexible Resins

This article examines the effects of thermal aging and chemical disinfection on the microhardness and flexural strength of flexible resins. The influence of the resin type on the mechanical properties was also investigated. Two flexible resins, Deflex Classic SR and Deflex Supra SF, produced by the injection method, and a thermopolymerizable acrylic resin—ProBase Hot, produced by the flasking method, were subjected to 1000 cycles of thermal aging and three chemical disinfection protocols (n = 8), with daily immersion and during a recommended time, in Corega Whitening, Corega Oxygen Bio-Active, 2.5% sodium hypochlorite, and distilled water (control). Knoop microhardness and three-point flexural strength were evaluated. Data were analyzed using Wilcoxon, Mann–Whitney and Kruskal Wallis tests (α = 0.05). The results varied between 14.5 KHN and 80.1 MPa for ProBase Hot and 7.3 KHN for Deflex Classic SR and 52.5 MPa for Deflex Supra SF. Thermal aging reduced the microhardness of the flexible resins, but not their flexural strength. The microhardness of Deflex Classic SR was influenced by chemical disinfection with Corega Bio-active (p < 0.001). The flexural strength of Deflex Supra SF was influenced by chemical disinfection with Corega Whitening (p < 0.05). It can be concluded that chemical disinfection led to changes in the flexible resins and should be used with caution to maintain the mechanical properties of the resins. Flexible resins showed reduced resistance to physical and chemical environmental influences, which can affect their longevity.

Influence of Coca-cola on Surface Roughness and Microhardness of Flexible Denture Base Material

Two potential problems commonly associated with flexible denture base material are surface roughness and the reduction of microhardness due to many reasons, rough surface can cause bacterial collection and the patient feels discomfort, and the possibility of the denture scratched when the surface hardness is reduced. The aim of this study was to evaluate the influence of Coca-cola on the surface quality of the flexible denture base material represented by the surface roughness and microhardness. A total of (10) samples were prepared for this study with the dimension of ( 40mm, 10mm, 3mm) length, width, and height respectively from thermo-plastic flexible resin (X-flexible capsules, color; K2 , size; L\China) by the conventional methods following the manufacturer instructions. The samples were immersed in Coca-cola drink for 12 days at room temperature. This period represents the average of one year of the beverage consumption, the drink has been changing daily.The samples were marked randomly and kept in special containers, and each sample has two rectangular surfaces used for the tests. One side is used for microhardness test and the other side used for the surface roughness test. The first tests were done before immersing the samples in coca-cola as control group. And after immersing the second tests were done as experimental group. In this study the data was analyzed using Independent samples (T- test). And results showed that there is no statistically significant difference in the surface roughness of the samples before and after immersing in Coca-cola (P-value > 0,05), while the microhardness test showed statistically a significant difference (P-value < 0,05) before and after immersing in Coca-cola. The surface roughness of flexible thermoplastic resin is not affected by coca-cola drink. While the levels of mirohardness showed decreasing after immersion in coca-cola drink. Therefore, the flexible thermoplastic material could be damaged if it is subjected to extra consumption of Coca-cola drink by the patient and this leads to lessen the amount of hardness by the time that could affect the efficiency of the prostheses, also could affect the mechanical bonding between artificial teeth and flexible denture base.

Structural Performance of Additively Manufactured Composite Lattice Structures: Strain Rate, Cell Geometry, and Weight Ratio Effects

The proliferation of ordered cellular structures in industrial and technological applications is justified by their superior mechanical performance, including tunable energy absorption strategies and potential multifunctionality. This research evaluates the mechanical response of composite lattice structures fabricated using vat photopolymerization additive manufacturing process and printable particulate composite materials. Several generations of modified printable resins are prepared by hybridizing flexible resin with varying glass microballoons reinforcement weight percentages. Multifaceted characterization regiments highlight the process–property–performance interrelationship by submitting printed composite structures to quasi‐static and impact‐loading scenarios combined with digital stills and high‐speed photography, respectively. Image analyses of optical and scanning electron micrographs quantify the dimensional accuracy of the composite lattice structures with cylindrical and hexagonal cellular geometries. The mechanical characterization uncovers the effect of cell geometry and reinforcement on the global structural behavior, eliciting differences in load‐bearing capacity, local strain developments, and structural densification. Exploratory digital image correlation supports the global structural deformations, revealing their relationship with the developed local strain state within the unit cells. The outcomes of this research elucidate the effect of strain rate, unit cell geometry, and reinforcing ratios on the structural performance of composite lattice structures at the macro‐ and microstructure levels.

A novel digital workflow for fabricating artificial periodontal ligament using three-dimensional printing flexible resin: A dental technique

The fabrication of periodontal ligament (PDL) models for in vitro dental studies has seen a wide range of techniques and materials being utilized. This paper introduces a novel dental technique that employs a digital workflow for the fabrication of artificial PDL using three-dimensional printing of flexible resin. This innovative approach offers several advantages, including enhanced accuracy and realism in simulating PDL. The digital workflow facilitates a streamlined fabrication process, ensuring efficiency and precision. By presenting this novel technique, this digital approach contributes to the advancement of in vitro dental research, providing researchers with a reliable and realistic model for studying various dental phenomena.

Creep Properties of a Viscoelastic 3D Printed Sierpinski Carpet-Based Fractal

In this paper, the phenomenon of creep compliance and the creep Poisson’s ratio of a 3D-printed Sierpinski carpet-based fractal and its bulk material (flexible resin Resione F69) was experimentally investigated, as well as the quantification of the change in the viscoelastic parameters of the material due to the fractal structure. The samples were manufactured via a vat photopolymerization method. The fractal structure of the samples was based on the Sierpinski carpet at the fourth iteration. In order to evaluate the response of both the fractal and the bulk material under the creep phenomenon, 1 h-duration tensile creep tests at three constant temperatures (20, 30 and 40 °C) and three constant stresses (0.1, 0.2 and 0.3 MPa) were conducted. A digital image correlation (DIC) technique was implemented for strain measurement in axial and transverse directions. From the results obtained, the linear viscoelastic behavior regime of the fractal and the bulk material was identified. The linear viscoelastic parameters of both fractal and bulk materials were then estimated by fitting the creep Burgers model to the experimental data to determine the effect of the fractal geometry on the viscoelastic properties of the samples. Overall, it was found that the reduction in stiffness induced by the fractal porosity caused a more viscous behavior of the material and a reduction in its creep Poisson’s ratio, which means an increase in the compliance of the material.

Research on Anti-ballistic Mechanism and Numerical Simulation of Biomimetic Composite

The multilayer toughening conch-nacre structure biomimetic composite consisted of alternant thin-hard layer ceramic and flexible resin matrix composite was prepared and designed, and its ballistic mechanism was studied. The testing results showed the damage effects of biomimetic composite were mitigated evidently while shielded the impact effectively in contrast with the smash of the common armour ceramic when encountered ballistic impact. The ballistic performances of the resin matrix composite and biomimetic composite were simulated by using ANSYS/LS-DYNA, material models of the resin matrix composite and biomimetic composite were expatiated. The calculation results were in accorded with testing result very well. This research methods and conclusions were valuable for engineering applications.

Design of crosslinked networks with hydroxyurethane linkages via bio‐based alkyl methacrylates and diamines

AbstractA hybrid methodology is used to combine the favorable properties of non‐isocyanate polyurethanes (NIPUs) in the side chains with poly(methacrylates) as the backbone into thermoset hybrid resins with hydroxyurethane linkages (HNIPU)s. Using NIPUs linkages avoids the use of toxic isocyanates in the poly(urethane) segments. The backbone is synthesized from cyclic carbonated copolymer templates derived from atom transfer radical polymerization (ATRP) of an alkyl methacrylate (C13MA with average side‐chain length of 13)/glycidyl methacrylate (GMA) mixtures (initial GMA mol fraction = 0.1–0.4). The resulting flexible resins with pendent epoxy functional groups were subsequently carbonated and then reacted with 1,10‐diaminodecane (90°C, 24 h) to form rigid side chains via hydroxyurethane linkages. Manipulating template functionality (2–11 urethane linkages out of 35 backbone units) yielded crosslinked networks with Young's moduli from 0.1 to 71.9 MPa while decreasing tensile elongation at break from 105% to 10%. Swelling ratios (SR) of the networks in tetrahydrofuran (THF) decrease as urethane linkage concentration increases, indicating tighter networks, consistent with the rheologically obtained molecular weight between crosslinks. Gel content indicated less than 15% of the networks are soluble in THF. The HNIPU networks derived show their ready tunability by simply changing the precursor functionality.

Investigation of the impact of additive manufacturing techniques on the acoustic performance of a coiled-up resonator

Acoustic metamaterials (AMMs) offer innovative solutions for physics and engineering problems, allowing lighter, multiphysics, and sustainable systems. They are usually studied analytically or numerically and then tested on prototypes. For this reason, additive manufacturing (AM) techniques are a popular way of quickly realising AMMs' innovative geometrical designs. However, AM parameters are often standardised without considering the specific issues of each AMM geometrical shape, leading to a possible mismatch between the analytical (or numerical) and experimental results. In this study, a simple AMM-a coiled-up resonator-has been produced with different AM technologies [fused deposition modeling (FDM), stereolithography (SLA), and selective laser melting and materials (polylactic acid, polyethylene terephthalate glycol, resin, flexible resin, and stainless steel). The sound absorption performance of these samples has been measured in two research labs in Italy and compared with the analytical and numerical calculations. This permitted the identification of the best combinations of AM technologies, their setup, and materials matching the expected results. The SLA/resin combination performed better overall; however, cheaper and more easily manageable samples made with FDM and polyethylene terephthalate glycol can achieve the same acoustic performance through the optimal AM printing setup. It is expected that this methodology could also be replicated for other AMMs.