Polylactic Acid Polymer Research Articles

Production of compression and flexural test samples in 3D printer with PLA polymeric biomaterial and bone compression with appropriate properties

In this study, it is planned to design and develop a structure close to the real bone strength properties by using PLA (polylactic acid) material. 3D printers have started to take place in our daily lives with today's developing technology and are preferred because of their ease of production and low cost. It has been determined that the PLA biomaterial can be used as a bone substitute in the body. The samples produced have different filling ratios and different internal structures. In the study, the effects of changes in the internal structure on the mechanical properties were investigated. Bone geometry is considered as an important factor among the parameters affecting biomechanical properties. In order to determine the mechanical properties of PLA filament material, bending and compression samples were prepared as 3 pieces for each test. The aim of this study is to determine whether it can be used as bone in the body by measuring the mechanical properties of biocompatible PLA polymer material. In the current work, the quality of the 3d printer and the material used in production directly affects the mechanical properties. In bones in the human body, trabecular bone has 80% porosity and cortical bone 10% infill. In this study, it was tried to obtain structures with properties close to real bone strength by using test specimens with different infill rates. It has been determined from the obtained data that PLA polymer material can be developed and meet the mechanical values in bone.

Halloysite Nanotube doped poly lactic acid membrane preparation and seawater desalination

Halloysite nanotube (Hal) is a natural alumina silicate clay mineral. Hal is used in polymer composites for many reasons such as excellent physical and chemical properties, good miscibility, mechanical strength, antimicrobial properties, and cheapness. It is an important material used in water separation, especially due to its internal and external ionic structure hollow tubular structure. In this study, halloysite was used as a filler in polylactic acid polymer to produce a nanocomposite membrane for seawater purification. The morphological, physical, and chemical structures of the Hal filled, and unfilled membranes were investigated. The effect of HAL content (from 0% to 5% by weight), feed temperature (from 40 °C to 60 °C), NaCl concentration (from 2 wt% to 6 wt%), and the downstream pressure (from 10 mbar to 30 mbar) on the desalination performance were investigated as a function of flux and salt rejection. Hal improved the hydrophilicity, stability, mechanical strength, and the desalination performance of PLA membrane, significantly. The results showed that the highest desalination performance was achieved by 5 wt% of Hal-loaded membrane. The highest flux of 13.14 kg/m2.h was obtained accompanied by a rejection of 99.95%. The membrane was also used to purify seawater, and it was found that the permeate's ion concentrations met drinking water standards. The nanocomposite membrane was experimented over 100 h of testing, and no decrease in flux or salt rejection was seen.

Simultaneous Upcycling of Biodegradable Plastic and Sea Shell Wastes Through Thermocatalytic Monomer Recovery

Development of effective upcycling methods for biodegradable plastic waste (for example, straws made of polylactic acid (PLA)) has emerged. In this study, a catalyst derived from sea shell waste (SSC) was used for a thermocatalytic conversion of biodegradable straw (BDS) for the recovery of monomer (for example, lactic acid). In effect, a strategy for simultaneously upcycling of biodegradable plastic waste (for example, straws made of polylactic acid (PLA)) and marine waste (for example, sea shell waste) was proposed. The SSC mainly consisted of calcium carbonate; thus, it had basicity with no acidity. Notably, a temperature of 500 °C and an SSC/BDS mass ratio of 0.5 led to the highest lactic acid recovery from BDS in this study. In particular, the use of SSC under the above-mentioned temperature and SSC/BDS mass ratio resulted in a 130 times higher lactic acid recovery than noncatalytic BDS conversion, most likely because the base sites present on SSC catalyzed the thermal cracking of PLA polymer bond. However, coke deposition was the major deactivation pathway of SSC during the thermocatalytic BDS conversion. In essence, SSC has the potential to be a catalyst used to thermocatalytically recover high-value chemicals from biodegradable plastic waste. In addition, this study can offer insight into developing waste conversion processes for the simultaneous upcycling of biodegradable plastic and marine wastes.

A Review on Barrier Properties of Nanocellulose and Polylactic acid Composites

Bio-based polymers, which are environmentally benign and contribute to a range of applications, are in great demand right now. The relevance of nanocellulose polylactic acid polymers, their benefits, production processes, and the wide variety of applications given by their barrier property are highlighted in this paper. Cellulose can be defined as the final product obtained as a result of biosynthesis of plants, animals, or bacteria, and nanocellulose refers to cellulosic take-outs or materials with definite nanoscale structural dimensions. Poly (lactic acid) or polylactide (PLA) is a thermoplastic polyester, which has the ability to replace petrochemical based polymers. Poly (lactic acid), often known as polylactide (PLA), is a thermoplastic polyester that can replace petrochemical-based polymers

Bioconversion of Corn Crop Residues: Lactic Acid Production through Simultaneous Saccharification and Fermentation

Lactic acid (LA) is a chemical building block with wide applications in the food, cosmetics, and chemical industries. Its polymer polylactic acid further increases this range of applications as a green and biocompatible alternative to petrol-based plastics. Corn is the fourth largest crop in the world, and its residues represent a potentially renewable feedstock for industrial lactic acid production through simultaneous saccharification and fermentation (SSF). The main goal of this work is to summarize and compare the pretreatment methods, enzymatic formulations and microbial strains that have been combined in a SSF setup for bioconversion of corn crop residues into LA. Additionally, the main concerns of scaling-up and the innovation readiness level towards commercial implementation of this technology are also discussed. The analysis on commercial implementation renders the current state of SSF technology unsustainable, mainly due to high wastewater generation and saccharification costs. Nonetheless, there are promising strategies that are being tested and are focused on addressing these issues. The present work proves that the study and optimization of SSF as a biorefinery framework represents a step towards the adoption of potentially sustainable waste management practices.

The sustainability debate on plastics: Cradle to grave Life Cycle Assessment and Techno-Economical Analysis of PP and PLA polymers with a “Polluter Pays Principle” perspective

We have studied the impacts of polypropylene (PP) and poly lactic acid (PLA) to quantify the differences between fossil-based and first generation biosourced plastics. Preliminary results on impact assessment from manufacturing stages suggested that the smaller the lot size and part weight of each injection molded plastic material, the higher the economic and environmental impacts. When lot size and part weight were equal, PLA performed better than PP. In three regional development scenarios, we have studied the impacts of end-of-life (EOL) options for smaller-sized and potentially landfilled single-use food packaging materials in town (population <10 k), city (population 30–250 k), and province (population >1 M) regional scales. The impacts of the change from PP to PLA as well as landfill (L) and open incineration (OI) to other EOL options, such as recycling (R), composting (CP), and incineration with energy recovery (IwE), were studied. Impacts of toxic damages are calculated as their impact on the healthcare sector. Thus, microplastics (MP) as a vector of bioaccumulation of toxins, such as dioxins, resulted in 16,5 $/kg MP on a province scale. In the Province scenario, where L PP (90%), a mix of R and OI PP was changed to a mix of R and CP PLA resulting in 63% economic gain and 39% lower global warming potential (GWP). In the City scenario, where L PP was changed to a mix of R PP (50%), IwE PP (25%), and IwE PLA (25%) resulting in 22% economic gain and 26% lower GWP. However, the higher the waste management activities such as sorting and waste processing, the higher the high-carcinogens (+137%), high non-carcinogens (+456%), and toxic release for total air (+9%) emissions. Future work should be done to study the impacts of other toxic compounds such as food contact chemicals to compare different food packaging materials to obtain more comprehensive results.

Optimal design and manufacturing of 3D printable prosthesis pylon

Abstract The aim of this study is to design a pylon with an engineering structure that gives it support and strength and manufacture a pylon characterized by low cost, lightweight, and bearing the patient's weight. This study designed two pylon models and fabricated by additive manufacturing techniques. The polylactic acid polymer is used as the filament for the 3D printing of pylons. A force plate and tensile test with finite element method simulation ANSYS software were applied to the pylons to evaluate their performance. The results showed that 3D printed pylon with Y-section has enough strength under stress and good safety factor, and the ability to bear a high patient load without buckling and exceed the requirements to become instead of the metallic prosthetic pylons.

Chitosan-Based Biomaterials for Bone Tissue Engineering Applications: A Short Review

Natural bone tissue is composed of calcium-deficient carbonated hydroxyapatite as the inorganic phase and collagen type I as the main organic phase. The biomimetic approach of scaffold development for bone tissue engineering application is focused on mimicking complex bone characteristics. Calcium phosphates are used in numerous studies as bioactive phases to mimic natural bone mineral. In order to mimic the organic phase, synthetic (e.g., poly(ε-caprolactone), polylactic acid, poly(lactide-co-glycolide acid)) and natural (e.g., alginate, chitosan, collagen, gelatin, silk) biodegradable polymers are used. However, as materials obtained from natural sources are accepted better by the human organism, natural polymers have attracted increasing attention. Over the last three decades, chitosan was extensively studied as a natural polymer suitable for biomimetic scaffold development for bone tissue engineering applications. Different types of chitosan-based biomaterials (e.g., molded macroporous, fiber-based, hydrogel, microspheres and 3D-printed) with specific properties for different regenerative applications were developed due to chitosan’s unique properties. This review summarizes the state-of-the-art of biomaterials for bone regeneration and relevant studies on chitosan-based materials and composites.

In vitro Evaluation of a 20% Bioglass-Containing 3D printable PLA Composite for Bone Tissue Engineering.

Three-dimensional (3D) printing is considered a key technology in the production of customized scaffolds for bone tissue engineering. In a previous work, we developed a 3D printable, osteoconductive, hierarchical organized scaffold system. The scaffold material should be osteoinductive. Polylactic acid (PLA) (polymer)/Bioglass (BG) (mineral/ion source) composite materials are promising. Previous studies of PLA/BG composites never exceed BG fractions of 10%, as increase of bioactive BG component negatively affects the printability of the composite material. Here, we test a novel, 3D printable PLA/BG composite with BG fractions up to 20% for its biological activity in vitro. PLA/BG filaments suitable for microstructure 3D printing were spun and the effect of different BG contents (5%, 10%, and 20%) in this material on mesenchymal stem cell (MSC) activity was tested in vitro. Our results showed that all tested composites are biocompatible. MSC cell adherence and metabolic activity increase with increasing BG content. The presence of BG component in scaffold has only slight effect on osteogenic gene expression, but it has significant suppressive effect on the expression of inflammatory genes in MSC. In addition, the material did not provoke any significant inflammatory response in whole-blood stimulation assay. The results show that by increasing the BG content, the bioactivity can be further enhanced.

Effect of sodium hydroxide and acetone pretreatments on the adhesion of three-dimensional printed polylactic acid filaments on linen and polyester fabrics

Three-dimensional (3D) printing on textile substrates is regarded as one of the most efficient methods to bond rigid polymers and soft fabrics to impart novel physical properties and extend the functionality of 3D printed objects. Although the feasibility and potential of such applications have been demonstrated, problems arise during the printing process due to the poor adhesion between the interface of the two materials. This means that usually some sort of pretreatment and/or post treatment needs to be done on the fabric, which is the focus of this paper. This study examines the effects of using sodium hydroxide (NaOH) and acetone (C3H6O) as pretreatments to enhance the adhesion between printed polylactic acid (PLA) polymer and woven linen/polyester fabric samples. The results indicate that both NaOH and C3H6O can significantly enhance the adhesive force by 49.7% and 10.2% for the linen substrate and by 95% and 17.1% for the polyester substrate, respectively. As such, this paper reports on an effective approach to enhance the adhesion of 3D printed PLA on woven linen and polyester fabrics as well as providing more options for designing on fabric surfaces.

Polylactic acid and lanolin based nanofibrous structures for wound management application

Polylactic acid (PLA) polymer and wool oil (lanolin) have been used to develop nanostructures for wound dressing management. Lanolin has been extracted from raw wool surfaces and used as a by-product in wide range of pharmaceutical areas. Different solutions with varying concentration of the PLA/lanolin and sodium alginate/lanolin solutions have been prepared and then nanostructures are developed using electrospinning method. The developed structures are aimed to use as smart wound dressings. During the production stage, the parameters of the electrospinning process have been changed to develop the optimum structures. The effect of solution concentrations on the applied voltage and the distance between the pipette tip and the collector is highlighted. The spinnability of lanolin is the main objectives of this study and the PLA/lanolin nanostructures are designed and manufactured successfully. The essential test methods have been performed to measure the usability of the produced materials as wound dressings. These are liquid absorption capacity, horizontal/vertical wicking, SEM, degradation, pH, antibacterial assay, and tensile properties. From the tested parameters, it is obviously found that the use of PLA/lanolin as wound dressing is suitable according to initial in vitro test results.

On strain rate and temperature dependent mechanical properties and constitutive models for additively manufactured polylactic acid (PLA) materials

Fused deposition modeling (FDM) has demonstrated its effectiveness in the additive manufacturing (AM) field thanks to its numerous merits, such as low cost and ease of implementation. Polymeric polylactic acid (PLA) has been widely used in FDM attributed to its recyclable, renewable, degradable and biocompatible characteristics. However, the material properties of polymeric materials can be largely affected by temperature and strain rate; and the mechanical behavior of polymer printed by FDM are fairly different from those manufactured by traditional technology. In this study, uniaxial tensile tests of the PLA specimens printed by FDM are performed under different strain rates and temperatures. For the first time, the digital image correlation (DIC) technique is employed to capture the surface strain of the AM specimens under loading, allowing us to quantify thermal stress concentration in the FDM printed polymer. Significant strain localization induced by the embrittlement of PLA is identified by the DIC system. The scanning electron microscope (SEM) technique is used to characterize the failure modes and failure mechanisms of the printed PLA samples. With increasing strain rate or decreasing temperature, the ductile to brittle failure modes can be observed by SEM. The modified Zener model is developed here to predict the stress–strain responses accounting for the combined effects of strain rate and temperature with proper modeling accuracy. The Cowper–Symonds material model is also employed to describe the effect of the strain rate on yield strength with a maximum 3.2% relative error between the experimental results and the theoretical model. Further, the yield strength, failure strain and Young’s modulus show a strong linear correlation with temperature. This study is anticipated to provide an effective and precise material model for the mechanical analysis of composite structural components made by the additive manufacturing process.

Characterization of 3D Printed Metal-PLA Composite Scaffolds for Biomedical Applications

Three-dimensional printing is revolutionizing the development of scaffolds due to their rapid-prototyping characteristics. One of the most used techniques is fused filament fabrication (FFF), which is fast and compatible with a wide range of polymers, such as PolyLactic Acid (PLA). Mechanical properties of the 3D printed polymeric scaffolds are often weak for certain applications. A potential solution is the development of composite materials. In the present work, metal-PLA composites have been tested as a material for 3D printing scaffolds. Three different materials were tested: copper-filled PLA, bronze-filled PLA, and steel-filled PLA. Disk-shaped samples were printed with linear infill patterns and line spacing of 0.6, 0.7, and 0.8 mm, respectively. The porosity of the samples was measured from cross-sectional images. Biocompatibility was assessed by culturing Human Bone Marrow-Derived Mesenchymal Stromal on the surface of the printed scaffolds. The results showed that, for identical line spacing value, the highest porosity corresponded to bronze-filled material and the lowest one to steel-filled material. Steel-filled PLA polymers showed good cytocompatibility without the need to coat the material with biomolecules. Moreover, human bone marrow-derived mesenchymal stromal cells differentiated towards osteoblasts when cultured on top of the developed scaffolds. Therefore, it can be concluded that steel-filled PLA bioprinted parts are valid scaffolds for bone tissue engineering.

Eklemeli İmalat Yöntemiyle Tekne İnşaatında Dolgu Yoğunluğu ve Örüntüsünün Mukavemet Üzerindeki Bileşik Etkisi

Prototip ve ürün üretim hızı, tasarımcılara sağladığı form geliştirme özgürlüğü, görece düşük kapasitedeki üretim ihtiyaçları için rekabetçi maliyeti, iyi kaliteye hızlı ulaşım olanaklarıyla, bilgisayar destekli tasarım ve üç boyutlu yazıcı teknolojisi temelindeki eklemeli imalat yöntemi, denizcilik endüstrisini de kapsayacak şekilde yaygın bir ilgi görmektedir. Bu ilginin temel kanıtı, eklemeli imalat yöntemine ilişkin araştırma, geliştirme etkinlikleri ve bilimsel yayın sayılarındaki ciddi artıştır. Esnek tasarımların sıklıkla güncellenmesiyle rekabetçiliği sürdürülebilir kılınabilecek küçük tekne endüstrisinin anılan avantajları nedeniyle eklemeli imalat yöntemine yönelmesi kaçınılmazdır. Eklemeli imalat yöntemi, teknelerin tasarım ve üretim sürecini verimli kılmakla birlikte, bu yöntemden iyi sonuç alabilmek onun bileşenleri üzerinde uygulamayla elde edilmiş deneyimlere dayanan verileri gereksinir. Bu çalışma kapsamında eklemeli imalat yönteminin önemli bileşenlerinden dolgu yoğunluğu ve örüntüsünün nihai ürünün temel mekanik özelliklerinden çekme mukavemeti üzerindeki etkisi deneysel olarak incelenmiştir. Üç boyutlu yazım teknolojileri temelinde yaygın olarak kullanılan polimerlerden polilaktik asitin (PLA) 13 farklı basım örüntüsü ve %10, 25, 50, 75 ve 100 olmak üzere beş farklı dolgu yoğunluğundan oluşan deney matrisi uyarınca çekme deneyleri Dokuz Eylül Üniversitesi (DEÜ) Kompozit Laboratuvarı’nda yapılmıştır. Sonuçlar, mekanik niteliklerin üzerinde durulan parametrelere çok duyarlı olduğu, “kübik” örüntünün incelenen yoğunluklarda genel olarak en iyi mekanik niteliklere ulaşmakta etkin olduğunu göstermiştir. Bu örüntü ve %25 yoğunluktan yararlanılarak 1/5 ölçeğinde bir yelkenli tekne gövdesi PLA polimer kullanılarak eklemeli imalat yöntemiyle DEÜ Deniz Bilimleri ve Teknolojileri Eklemeli imalat Laboratuvarı’nda üretilmiştir.

Investigation into impact properties of adhesively bonded 3D printed polymers

Nowadays, 3D printing is used to produce various engineering parts thanks to improved mechanical properties and surface roughness. Despite its many superior features, the limitation of 3D printing is the size of the parts that can be produced. The use of 3D printing to fabricate smaller sub-parts and then adhesively bond them to each other is a potential solution to this problem. This method is used in many industries to bond various metal and plastic materials. In this study, ASTM D 950-3 standard test specimens were additively manufactured using polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) polymers subsequently bonded with cyanoacrylate/epoxy mixture hybrid adhesive (133 g/m2). The layer thickness (0.1 mm–0.5 mm) and printing direction (edgewise, flatwise) effect of on the impact strength (kJ/m2) of the resulting joints was investigated by Izod impact tests (maximum potential energy of 15 J). As a result of the tests, it was found that the impact strength of the connections of the ABS parts was higher than that of the joints of the PLA parts. It has been concluded that ABS parts with 0.3 mm layer thickness have the highest impact strength. These results may help achieve higher impact strength when adhesively bonding parts fabricated by 3D printing for engineering applications.

Nodal beam stack vibration isolators

This paper introduces additively manufactured beam networks that isolate vibration with multiple broad bandgaps. The isolators consist of symmetric stacks of beams with tip masses connected in series via compliant hinges near nodal points. An analytical model is derived to predict the vibration behavior of a beam stack. An isolator with four beams is designed to provide a band gap of 32 Hz with a center frequency at 72 Hz. A Polylactic acid polymer prototype is 3D printed and the frequency response of input force to transmitted force is experimentally measured showing a large 41 Hz band gap with a center frequency also around 72 Hz. The experimentally validated model is used to design a 10 beam isolator with a low frequency band gap from 10 to 86 Hz, and a high frequency band gap from 202 to 543 Hz.

A review of current advancements for wound healing: Biomaterial applications and medical devices.

Wound healing is a complex process that is critical in restoring the skin's barrier function. This process can be interrupted by numerous diseases resulting in chronic wounds that represent a major medical burden. Such wounds fail to follow the stages of healing and are often complicated by a pro‐inflammatory milieu attributed to increased proteinases, hypoxia, and bacterial accumulation. The comprehensive treatment of chronic wounds is still regarded as a significant unmet medical need due to the complex symptoms caused by the metabolic disorder of the wound microenvironment. As a result, several advanced medical devices, such as wound dressings, wearable wound monitors, negative pressure wound therapy devices, and surgical sutures, have been developed to correct the chronic wound environment and achieve skin tissue regeneration. Most medical devices encompass a wide range of products containing natural (e.g., chitosan, keratin, casein, collagen, hyaluronic acid, alginate, and silk fibroin) and synthetic (e.g., polyvinyl alcohol, polyethylene glycol, poly[lactic‐co‐glycolic acid], polycaprolactone, polylactic acid) polymers, as well as bioactive molecules (e.g., chemical drugs, silver, growth factors, stem cells, and plant compounds). This review addresses these medical devices with a focus on biomaterials and applications, aiming to deliver a critical theoretical reference for further research on chronic wound healing.

Comparison of mechanical properties of 3D-printed and compression-molded wood-polylactic acid (PLA) composites

Mechanical properties of materials obtained by compression-molding were compared with three-dimensional (3D) printed materials. Firstly, wood flour was added at different levels (0, 5, 10, and 20%) to polylactic acid (PLA) polymer to produce filaments. Then, mechanical test samples were printed from the produced filaments with a 3D printer. The produced filaments were made into pellets, and sheets were obtained by compression molding. According to the mechanical test results, it was observed that the tensile strength of the 3D-printed and compression-molded materials were close to each other, and the elasticity modulus of the compression-molded samples was higher than the 3D-printed samples. In the hardness comparison, the compression-molded specimens exhibited higher hardness values than the 3D-printed specimens. When the morphological properties of the materials were examined, it was seen that the cross-sections of the compression-molded materials were smooth and had less void than the 3D printed ones. The glass transition, crystallization, and melting temperatures of the materials did not change much with the processing methods. Only the 3D-printing process increased the crystallinity percentages.

Poly(Lactic Acid) (PLA)-Based Nanocomposites: Impact of Vermiculite, Silver, and Graphene Oxide on Thermal Stability, Isothermal Crystallization, and Local Mechanical Behavior

The structural, thermal, and mechanical properties of unreinforced and reinforced polylactic acid (PLA) were investigated. The PLA was a biopolymer that was reinforced with four fillers (i.e., graphene oxide (GO) and silver (Ag); vermiculite (VMT) and silver (Ag); and two organically modified vermiculites). The processing technique for the production of the composite materials were carefully planned. The PLA nanocomposites were investigated by examining their morphological aspects, changes in PLA phases and transitions and, most importantly, the effect on certain final properties. X-ray diffraction and differential scanning calorimetry (DSC) analysis indicated that the sample was completely amorphous. Thermogravimetric analysis (TGA) results indicated that the presence of reinforcing particles in the PLA matrix did not affect the thermal degradation of these composites. Furthermore, the local mechanical properties were investigated using the microindentation method to evaluate the effect of different nanofillers. Scanning electron microscopy (SEM) and a VHX-500 optical digital microscope (Keyence International, Mechelen, Belgium) were also used to examine the surface morphology of the PLA polymer composites. These results can help to select suitable fillers to enhance the PLA performance of biopolymers.

Characterization of PLA nanofiber structures containing herbal extracts

The use of renewable, sustainable, and biocompatible products without chemical side effects is increasing day by day in antibacterial applications instead of materials that harm nature and humans. In biomedicine, antibacterial nanofiber composite surfaces with generally produced from materials with antibacterial properties such as chitosan, hyaluronic acid, collagen, and silver nanoparticles. In this study, olive leaf, terebinth, and fumitory plants and biocompatible, biodegradable, and environmentally friendly polylactic acid (PLA) polymer were used to obtain nanofiber structures with 100% plant extracts. Viscosity and conductivity of solutions prepared with optimum properties were analysed, the nanofiber material was produced in solution with electrospinning method, and the morphological evaluation and mechanical measurement of the nanofiber material were performed. Finally, bacterial exchange analyses were performed before and after incubation in the UV-VIS spectrophotometer. As a result of the study, the thinnest and the most uniform fiber materials were found in CFO (consist of PLA (C1) and fumitory (FO)) coded nanofiber material, the best strength values were found in COE (consist of PLA (C1) and olive leaf (OE)) coded nanofiber structure, and the highest bacterial exchange was observed in CFO coded nanofiber material. Based on these results, it has been suggested that the CFO coded nanofiber structure can be used in biomedicine. It has been observed that olive leaf, terebinth, and fumitory plant extracts, which can be grown easily in every region in Turkey, have a significant level of bacterial resistance. In conclusion, fumitory and terebinth plants can be used in antibacterial agent applications since they allow obtaining smooth and uniform nanofiber structures, and thanks to their high bacteria nullification properties.