Polymer Patches Research Articles

Influence of reinforcement on vibration control in adhesively bonded single lap joints: a numerical and experimental validation

In this growing world, it is imperative to employ innovative techniques that effectively manage the structural response of materials without inducing adverse effects on the original structure. This can be achieved mainly by changing the material and geometrical features of the adhesive. In this work, an attempt has been made to control the eigenvalues of adhesively bonded single-lap joints (SLJs) by reinforcing them with polymer patches. Numerical techniques were utilized to adhere the polymer patches to the single-lap bonded joints using ABAQUS software. Subsequently, the eigenvalue responses of SLJs, both with and without patches, were experimentally well agreed with the numerical predictions. The validated numerical model was then used to investigate its structural response by modifying the parameters such as patch shape, patch position, and adhesive geometry. Additionally, it has been observed that a square-shaped polymer patch at the overlapping edge is more effective in reducing the eigenvalues compared to patches of different shapes and positions. The eigenvalue response follows a declining trend as the adhesive thickness increases, forming thicker bonds.

Surface-Templated Polymer Microparticle Synthesis Based on Droplet Microarrays.

Polymer microparticle synthesis based on the surface-templated method is a simple and environmentally friendly method to produce various microparticles. Unique particles with different compositions can be fabricated by simply annealing a polymer on a liquid-repellent surface. However, there are hurdles to producing particles of homogeneous sizes with large quantities and varying the shape of particles. Here, a new approach to synthesizing multiple polymer microparticles using micropatterns with wettability contrast is presented. Polymer microparticles are formed in two steps. First, a layer of poly(sodium-4-styrenesulfonate) is deposited on the hydrophilic regions by dipping and withdrawing this micropattern from a polymer solution, and an array of microdroplets is formed. A dewetting-inducing layer on the pattern is introduced, and then target polymer patches are sequentially generated on it. By annealing over Tg, the contact line of the target polymer patch is freely receded, creating a particle form. The size and shape of the microparticle can be controlled by varying the micropatterns. In addition, it is demonstrated that microparticles made of polymer blends or polymer/nanoparticle composite are easily produced. This versatile method offers the potential of surface-templated synthesis to tailor polymer microparticles with different sizes, shapes, and functionalities in various research and applications.

Evaluating the bonding effectiveness of CFRP patches in strengthening concrete structures

This study offers a thorough analysis of the efficiency of adhesively bonded Carbon Fiber-Reinforced Polymer (CFRP) patches in reinforcing concrete structures. In the dynamic field of civil engineering and infrastructure maintenance, utilizing modern materials and innovative techniques is crucial. Given the diverse stresses on concrete structures, sustainable reinforcement strategies like CFRP patching are vital. CFRP patches, with their high tensile strength and lightweight properties, reinforce concrete, enhancing its load-bearing capacity. The study reviews extensive literature on CFRP use, emphasizing its effectiveness in various environments. However, prevailing analyses often overlook shear-induced failures at the interface of bonded CFRP patches. To address this, the study introduces a novel fracture analytical technique, consolidating material parameters for assessing CFRP patch bonding efficiency. Experimental investigations compare epoxy, polyurethane, and silyl-modified polymers under mode-I loading conditions, revealing performance variations. The study underscores the importance of adhesive selection, advocating for a balance between strength and fracture energy absorption for optimal CFRP patch performance in concrete structures. It urges future design applications to consider these findings for enhanced selection and application of CFRP patches.

Experimental and numerical analysis of the behavior of rehabilitated aluminum structures using chopped strand mat GFRP composite patches

PurposeThis paper comprehensively addresses the influence of chopped strand mat glass fiber-reinforced polymer (GFRP) patch configurations such as geometry, dimensions, position and the number of layers of patches, whether a single or double patch is used and how well debonding the area under the patch improves the strength of the cracked aluminum plates with different crack lengths.Design/methodology/approachSingle-edge cracked aluminum specimens of 150 mm in length and 50 mm in width were tested using the tensile test. The cracked aluminum specimens were then repaired using GFRP patches with various configurations. A three-dimensional (3D) finite element method (FEM) was adopted to simulate the repaired cracked aluminum plates using composite patches to obtain the stress intensity factor (SIF). The numerical modeling and validation of ABAQUS software and the contour integral method for SIF calculations provide a valuable tool for further investigation and design optimization.FindingsThe width of the GFRP patches affected the efficiency of the rehabilitated cracked aluminum plate. Increasing patch width WP from 5 mm to 15 mm increases the peak load by 9.7 and 17.5%, respectively, if compared with the specimen without the patch. The efficiency of the GFRP patch in reducing the SIF increased as the number of layers increased, i.e. the maximum load was enhanced by 5%.Originality/valueThis study assessed repairing metallic structures using the chopped strand mat GFRP. Furthermore, it demonstrated the superiority of rectangular patches over semicircular ones, along with the benefit of using double patches for out-of-plane bending prevention and it emphasizes the detrimental effect of defects in the bonding area between the patch and the cracked component. This underlines the importance of proper surface preparation and bonding techniques for successful repair.Graphical abstract

Profile of a Multivariate Observation under Destructive Sampling-A Monte Carlo Approach to a Case of Spina Bifida.

A biodegradable hybrid polymer patch was invented at the University of Cincinnati to cover gaps on the skin over the spinal column of a growing fetus, characterized by the medical condition spina bifida. The inserted patch faces amniotic fluid (AF) on one side and cerebrospinal fluid on the other side. The goal is to provide a profile of the roughness of a patch over time at 0, 4, 8, 12, and 16 weeks with a 95% confidence band. The patch is soaked in a test tube filled with either amniotic fluid (AF) or phosphate-buffered saline (PBS) in the lab. If roughness is measured at any time point for a patch, the patch is destroyed. Thus, it is impossible to measure roughness at all weeks of interest for any patch. It is important to assess the roughness of a patch because the rougher the patch is, the faster the skin grows under the patch. We use a model-based approach with Monte Carlo simulations to estimate the profile over time with a 95% confidence band. The roughness profiles are similar with both liquids. The profile can be used as a template for future experiments on the composition of patches.

Sustained release of human placental extract from chitosan patch incorporated with GO/Zn(Cu)O nanocomposite for enhanced healing of diabetic wounds

Chronic wounds are caused due to microbial infections at wound site. Especially, diabetic wounds are a major challenge worldwide. Infection is the major concern in diabetic wound healing. In severe cases, it leads to amputation and death. Human placental extract (HPE) acts as therapeutic agent which possesses anti-inflammatory and angiogenesis property. In this work, HPE was incorporated along with GO/Zn(Cu)O nanocomposite in the wound dressing chitosan patch. It has antibacterial activity and enhances the cell proliferation. The HPE and nanocomposite incorporated polymeric patches are fabricated using gel casting technique. The patch was tested for its antibacterial activity against E. coli, P. aeruginosa, S. typhi, S. flexneri, S. aureus and E. faecium. The PVA/Cs/GO/Zn(Cu)O/HPE patch has swelling percentage of 70 ± 3.5% on 7th day. The water vapour transmission rate (WVTR) for PVA/Cs/GO/Zn(Cu)O/HPE patch is 2249 ± 2.94 g/m2 day−1. The PVA/Cs/GO/Zn(Cu)O/HPE patch shows a porosity of 77 ± 3.8%. In scratch assay the rate of wound closure for PVA/Cs/GO/Zn(Cu)O/HPE patch is 99.4 ± 4.9%. The sustained release of HPE was observed to be 78% at day 14. So far up to our knowledge, sustained release of HPE was not established for diabetic treatment. The biocompatibility and hemocompatability analysis were performed using NIH 3T3 fibroblast cells. In in vivo study the patch shows healing efficiency of 98%. The patch does not cause any toxic effects.

Naringin and graphene oxide incorporated Moringa oleifera gum/poly(vinyl) alcohol patch for enhanced wound healing

Patients and healthcare systems stand to gain much from the use of substances that can accelerate wound healing. In this research work, a polymeric patch was fabricated using polymers like poly (vinyl alcohol) (PVA) and Moringa oleifera gum (MO) incorporated with graphene oxide (GO) and naringin (Nar) (drug). This study determined the impact of using PVA/MO/GO/Nar polymeric patch on wound healing via in vitro and in vivo investigations. Graphene oxide was synthesized by modified Hummer's method. The synthesized sample was characterized using XRD, FT-IR, RAMAN Spectroscopy, FESEM and HRTEM. Antibacterial analysis of the GO on four different bacteria was studied through well diffusion, colony count, growth curve and biofilm assay. Biocompatibility was analysed by haemolysis assay. The morphology, antibacterial activity, haemolysis assay, swelling, degradation, porosity, water vapour transmission rate, drug release, blood pump model, in-vitro scratch assay and MTT assay were analysed for the fabricated polymeric patches under in-vitro condition. The PVA/MO/GO/Nar patch has shown enhanced wound healing in in-vivo wound healing experiments on albino Wistar rats.

Direct Imaging of "Patch-Clasping" and Relaxation in Robust and Flexible Nanoparticle Assemblies.

Polymer patching on inorganic nanoparticles (NPs) enables multifunctionality and directed self-assembly into nonclosely packed optical and mechanical metamaterials. However, experimental demonstration of such assemblies has been scant due to challenges in leveraging patch-induced NP-NP attractions and understanding NP self-assembly dynamics. Here we use low-dose liquid-phase transmission electron microscopy to visualize the dynamic behaviors of tip-patched triangular nanoprisms upon patch-clasping, where polymer patches interpenetrate to form cohesive bonds that connect NPs. Notably, these bonds are longitudinally robust but rotationally flexible. Patch-clasping is found to allow highly selective tip-tip assembly, interconversion between dimeric bowtie and sawtooth configurations, and collective structural relaxation of NP networks. The integration of single particle tracking, polymer physics theory, and molecular dynamics simulation reveals the macromolecular origin of patch-clasping-induced NP dynamics. Our experiment-computation integration can aid the design of stimuli-responsive nanomaterials, such as topological metamaterials for chiral sensors, waveguides, and nanoantennas.

Activation of Ostwald ripening and electrical conductivity in polyHIPEs through the addition of ascorbic acid to graphene-stabilized emulsions

Ascorbic acid was employed to increase the sphere-to-sphere contact of polyHIPEs. Adding a radical inhibitor to the aqueous phase of a graphene-stabilized water-in-oil emulsion was hypothesized to delay the formation of a polymer skin around the dispersed droplet, leading to intimate contact between the surfactant-stabilized drops. Optical microscopy analysis of samples made with varying ascorbic acid concentrations showed decreased sphere size and increased size dispersity at increasing inhibitor concentrations. Electrical conductivity measurements showed an increase at low concentrations of ascorbic acid but a decrease in conductivity at higher concentrations. Our results suggest that the presence of an inhibitor does delay the formation of the polymer skin and allows more intimate contact between spheres, but at higher concentrations, it leads to Ostwald ripening. Scanning electron microscopy of polystyrene/graphene composites revealed that the inhibitor also stopped the polymerization of aqueous-dispersed monomer, leading to polymer patches on the interior of the spheres.

Inducible nonhuman primate models of retinal degeneration for testing end-stage therapies.

The anatomical differences between the retinas of humans and most animal models pose a challenge for testing novel therapies. Nonhuman primate (NHP) retina is anatomically closest to the human retina. However, there is a lack of relevant NHP models of retinal degeneration (RD) suitable for preclinical studies. To address this unmet need, we generated three distinct inducible cynomolgus macaque models of RD. We developed two genetically targeted strategies using optogenetics and CRISPR-Cas9 to ablate rods and mimic rod-cone dystrophy. In addition, we created an acute model by physical separation of the photoreceptors and retinal pigment epithelium using a polymer patch. Among the three models, the CRISPR-Cas9-based approach was the most advantageous model in view of recapitulating disease-specific features and its ease of implementation. The acute model, however, resulted in the fastest degeneration, making it the most relevant model for testing end-stage vision restoration therapies such as stem cell transplantation.

Polymeric Patches Based on Chitosan/Green Clay Composites and Hazelnut Shell Extract as Bio-Sustainable Medication for Wounds.

Hazelnut shells, the main waste deriving from hazelnut processing, represent an interesting source of active molecules useful in pharmaceutics, although they have not yet been examined in depth. A hydrosoluble extract (hazelnut shell extract, HSE) was prepared by the maceration method using a hydroalcoholic solution and used as the active ingredient of patches (prepared by casting method) consisting of composites of highly deacetylated chitosan and green clay. In vitro studies showed that the formulation containing HSE is able to stimulate keratinocyte growth, which is useful for healing purposes, and to inhibit the growth of S. aureus (Log CFU/mL 0.95 vs. 8.85 of the control after 48 h); this bacterium is often responsible for wound infections and is difficult to treat by conventional antibiotics due to its antibiotic resistance. The produced patches showed suitable tensile properties that are necessary to withstand mechanical stress during both the removal from the packaging and application. The obtained results suggest that the developed patch could be a suitable product to treat wounds.

Flexible Topical Hydrogel Patch Loaded with Antimicrobial Drug for Accelerated Wound Healing.

A hydrogel topical patch of neomycin was developed by using sodium alginate (SA) and hydroxyethylcellulose (HEC) as polymers. Free radical polymerization in an aqueous medium was initiated by using acrylic acid (AA) and N,N'-methylenebisacrylamide (MBA). Prepared hydrogels were characterized for pH sensitivity and sol-gel analysis. In addition, the effect of reactant contents on the developed formulation was evaluated by swelling behavior. SEM assay showed the rough structure of the hydrogel-based polymeric matrix, which directly enhances the ability to uptake fluid. FTIR spectra revealed the formation of a new polymeric network between reactant contents. TGA and DSC verified that fabricated polymeric patches were more thermodynamically stable than pure components. Gel fractions increased with increases in polymer, monomer, and cross-linker contents. The swelling study showed the pH-dependent swelling behavior of patches at pH 5.5, 6.5, and 7.4. The release pattern of the drug followed zero-order kinetics, with diffusion-controlled drug release patterns according to the Korsmeyer-Peppas (KP) model. Ex vivo studies across excised rabbit skin verified the drug retention in the skin layers. The hydrogel patch effectively healed the wounds produced on the rabbit skin, whereas the formulation showed no sign of irritation on intact skin. Therefore, neomycin hydrogel patches can be a potential candidate for controlled delivery for efficient wound healing.

Fabrication of a Chitosan-Based Wound Dressing Patch for Enhanced Antimicrobial, Hemostatic, and Wound Healing Application.

Wounds are a serious life threat that occurs in daily life. The complex cascade of synchronized cellular and molecular phases in wound healing is impaired by different means, involving infection, neuropathic complexes, abnormal blood circulation, and cell proliferation at the wound region. Thus, to overcome these problems, a multifunctional wound dressing material is fabricated. In the current research work, we have fabricated a wound dressing polymeric patch, with poly(vinyl alcohol) (PVA) and chitosan (Cs) incorporated with a photocatalytic graphene nanocomposite (GO/TiO2(V-N)) and curcumin by a gel casting method, that focuses on multiple stages of the healing process. The morphology, swelling, degradation, moisture vapor transmission rate (MVTR), porosity, light-induced antibacterial activity, hemolysis, blood clotting, blood abortion, light-induced biocompatibility, migration assay, and drug release were analyzed for the polymeric patches under in vitro conditions. PVA/Cs/GO/TiO2(V-N)/Cur patches have shown enhanced wound healing in in vivo wound healing experiments on Wister rats. They show higher collagen deposition, thicker granulation tissue, and higher fibroblast density than conventional dressing. A histological study shows excellent re-epithelialization ability and dense collagen deposition. In vitro and in vivo analysis confirmed that PVA/Cs/GO/TiO2(V-N) and PVA/Cs/GO/TiO2(V-N)/Cur patches enhance the wound healing process.

Solvent-induced assembly of mono- and divalent silica nanoparticles.

Particles with attractive patches are appealing candidates to be used as building units to fabricate novel colloidal architectures by self-assembly. Here, we report the synthesis of one-patch silica nanoparticles, which consist of silica half-spheres whose concave face carries in its center a polymeric patch made of grafted polystyrene chains. The multistage synthesis allows for a fine control of the patch-to-particle size ratio from 0.23 to 0.57. The assembly of the patchy nanoparticles can be triggered by reducing the solvent quality for the polystyrene chains. Dimers or trimers can be obtained by tuning the patch-to-particle size ratio. When mixed with two-patch nanoparticles, one-patch nanoparticles control the length of the resulting chains by behaving as colloidal chain stoppers. The present strategy allows for future elaboration of novel colloidal structures by controlled assembly of nanoparticles.

Smart Adhesive Patches of Antibacterial Performance Based on Polydopamine-Modified Ga Liquid Metal Nanodroplets

Patches have been widely used in medical and healthcare, motion detection, and other fields. Patches are required to possess strong adhesive forces to keep them effectively adhered to the skin during use and to be removed from the skin with relative ease after usage. Moreover, a large number of bacteria will proliferate at the interface between the patch and the skin, when the patch is used for lengthy durations, which is harmful to human health. Hence, there is an increasing demand for patches with combined switchable adhesions and excellent antibacterial performances. Inspired by the natural adhesive performance of snail slime in wet (liquid) and dry (solid) states, smart Ga liquid metal nanodroplet-based polymer patch (GxPP, x = 10, 30, 50) with switchable adhesion properties were prepared by incorporating polydimethylsiloxane (PDMS) into polydopamine (PDA)-modified Ga nanodroplets (PDA-Ga). Since the melting point of Ga is 29.8 °C, solid Ga melts to the liquid state at temperatures above 29.8 °C, and this significantly decreases the modulus of GxPP, resulting in significantly decreased adhesive strength of GxPP. The adhesion of G30PP decreased from 40.4 to 22.1 kPa. In addition to this obvious change in the adhesion properties of GxPP, the unique antibacterial performances of Ga imparted GxPP with excellent antibacterial effects. Compared with the PDMS, the antibacterial rates of G30PP against Escherichia coli and Staphylococcus aureus were 98 and 99%, respectively. The excellent antibacterial performance and smart switchable adhesion properties of GxPP revealed its high application prospects in the field of wearable flexible skin electronics.

Ligancy effects on nucleation kinetics.

Nucleation of particles into crystalline structures can be observed in a wide range of systems from metallic and metal-organic compounds to colloidal and polymeric patch particles. Here, we perform kinetic Monte Carlo simulations to study the nucleation kinetics of particles with different ligancies z at constant supersaturation s. This approach allows one to determine several physico-chemical quantities as a function of s, including the growth probability P(n), the critical nucleus size n*, and the stationary nucleation rate Js. Our numerical results are rationalized in terms of a self-consistent nucleation theory where both n* and Js present a non-trivial dependence on s, but which can be determined from the values of effective z-dependent parameters.

Patches as Polymeric Systems for Improved Delivery of Topical Corticosteroids: Advances and Future Perspectives.

Mucoadhesive polymer patches are a promising alternative for prolonged and controlled delivery of topical corticosteroids (CS) to improve their biopharmaceutical properties (mainly increasing local bioavailability and reducing systemic toxicity). The main biopharmaceutical advantages of patches compared to traditional oral dosage forms are their excellent bioadhesive properties and their increased drug residence time, modified and unidirectional drug release, improved local bioavailability and safety profile, additional pain receptor protection, and patient friendliness. This review describes the main approaches that can be used for the pharmaceutical R&D of oromucosal patches with improved physicochemical, mechanical, and pharmacological properties. The review mainly focuses on ways to increase the bioadhesion of oromucosal patches and to modify drug release, as well as ways to improve local bioavailability and safety by developing unidirectional -release poly-layer patches. Various techniques for obtaining patches and their influence on the structure and properties of the resulting dosage forms are also presented.

Gate‐to‐Gate Study for Collaborative Robot‐Assisted Composite Parts Manufacturing Using a Work Effort Unit Approach

AbstractThis work presents one example from a set of technologies that aim at improving the efficiency of manufacturing processes of aircraft components in one of Airbus Defence and Space plants in regards to environmental aspects. Among the proposed technologies, one relates to the automation of two key manufacturing steps of the reference technology in the composite manufacturing of omega stringers: 1) lamination of main omega stringer structure through an Automated Fiber Placement robotic process; and 2) cobotic pick‐and‐place process for Carbon Fiber Reinforced Polymer patches. To evaluate potential environmental benefits, Fraunhofer performs a gate‐to‐gate study using as main parameter the “Work effort unit,” in this case representing the average energy consumption per productive hour in a typical assembly factory. When comparing the results for the composite part manufacturing by hand lay‐up with the use of collaborative robots, the key technical parameter is the reduction in lead time. While production using robots consume additional electricity when compared to human workers, automation significantly shortens lead times (‐74%), resulting in lower energy consumption per manufactured unit. The results indicate that this new technology from Airbus Defence and Space can potentially improve the overall environmental performance of composite parts during their manufacture.

Fatigue performance of edge cracked aluminium alloy repaired with asymmetrical CFRP patches

The numerical study was conducted on the repair of edge cracked aluminium (Al) alloy (6061-T6) panels with the help of an asymmetrical carbon fibre, reinforced polymer (CFRP) patches. The numerical models were designed for different patched specimens. Numerical simulations were performed for the different patch configurations of varying lengths. It was observed that as the patch length was increased fatigue performance was also improved. As the length of a patch was increased, the induced bending moment in the asymmetrical patch was reduced and fatigue performance was enhanced. Damage tolerance for each configuration was calculated and it was found that damage tolerance was increased for specimen with the highest patch length. Overall; using bonded composite patches fatigue performance of the specimen was enhanced, which increased the fatigue performance of the repaired specimen.

Combinatorial Approach of Polymeric Patches and Solid Microneedles for Improved Transdermal Delivery of Valsartan: A Proof-of-Concept Study

Valsartan (VALS) is a first-line therapy for hypertension that belong to the Angiotensin II Receptor Blockers class. VALS is currently administered orally, but it is associated with its low bioavailability. The transdermal route can be an alternative to overcome this problem. However, this route has low permeation caused by the presence of stratum corneum on the skin. The use of permeation enhancers is needed. This study aims to determine the effect of PEG 400 concentration on physical characteristics and release of VALS from transdermal patch preparations and determine the effect of solid microneedles on VALS permeation. The transdermal patch formula was made using HPMC as a base and PEG 400 as a permeation enhancer with various concentrations. The patches were evaluated for their physical appearance, weight uniformity, thickness, moisture content, folding endurance, drug content, in vitro drug release, in vitro drug permeation, and ex vivo permeation test. The results showed that all formulations showed good characteristics for transdermal administration, and the use of PEG 400 could increase the permeation of VALS. Importantly, when combined with solid microneedles, the permeation of VALS was significantly improved. To conclude, the combination of VALS patch transdermal and MNs can increase the amount of VALS permeated.