Incinerators are widely used to burn the municipal waste, biowaste, wood, straw, and biomedical waste. Combustion of these types of waste results in generation of chlorides of sodium and potassium ...which may attack the metallic part of the incinerator. In biofuel-fired boilers, similar type of highly corrosive environment is present. Attempt has been made to review the corrosion problems and their solutions as per the available literature.
Healing of bone fractures highly depends on the biocompatibility, stability in biological conditions, biodegradability, technical functionality, and shelf‐life of biomaterials. Metallic biomaterials ...offer excellent mechanical properties and biocompatibility. However, metallic bone implants result in stress shielding, release of toxic ions, excessive wear, and corrosion. Polymer materials are being explored for bone implants due to their light‐weight, biocompatibility, biodegradability, and absence of stress shielding. In the new era, additive manufacturing (AM) is being preferred due to its capability of fabricating customer specific implants with minimum material wastage. However, AM based polymer implants lack in mechanical strength and biological properties. Surface modification of polymeric substrates using coatings and incorporation of bioadditives have been regarded as alternatives for improvement of mechanical and biological properties. This review discusses about various coating techniques and gives an overview about coatings and bioadditives that can be used for enhancement of properties. From the review, it is evident that reinforcement of hydroxyapatite to polylactic acid resulted in prevention of crack growth during shape recovery cycles which can be used for self‐fitting implants. Coatings have been successful in enhancing hydrophilicity, mechanical properties, anti‐biofouling, antibacterial and anti‐coagulative properties, adhesion, proliferation, and differentiation of cells on the coated surface. This review also discusses the challenges that need to be overcome for progression in this field.
Surface modification of polymeric substrates using coatings and incorporation of bioadditives has been regarded as alternatives for improvement of mechanical and biological properties. This review discusses about various coating techniques and gives an overview about coatings and bioadditives that can be used for enhancement of properties. This review also discusses the challenges that need to be overcome for progression in this field.
Dopamine mainly consists of catechol and amine groups in high concentrations that are mainly responsible for interfacial adhesion of dopamine with the substrate and possesses the ability of oxidation ...through self‐polymerization that results in the formation of polydopamine. The weak mechanical properties of poly lactic acid (PLA) limit its applications in a variety of applications. Polydopamine is widely known for its deposition on a variety of organic and inorganic surfaces. The present study is aimed at studying the effect of the polydopamine coating on mechanical properties of PLA structures fabricated at varying infill density and coated at different concentrations of coating solution immersed for 4 and 7 h. The deposition of polydopamine coating on various PLA structures was confirmed with the help of scanning electron microscopy/energy dispersive spectroscopy analysis. Significant improvement in tensile and compression strengths was found, which was in agreement with the change in weight percentage analysis. The application of polydopamine coating led to improvement in hydrophilicity and degree of crystallinity with the increase in surface roughness of the polymer. The findings from this study will help in utilization of polydopamine‐coated PLA as an alternative over PLA with weak mechanical properties for biomedical applications involving high‐strength biomedical implants and bone tissue engineering.
Polydopamine Coating on additive manufactured PLA structures
Polymer based implants provide excellent biocompatibility due to porous structure and minimum chances of stress shielding. However, 3D Printed PLA structures possess insufficient mechanical strength, ...restricting their utility in biomedical domain. This challenge can be addressed by enhancing their mechanical properties through surface modification. The one-step oxidative polymerization process transforms dopamine hydrochloride into biocompatible polydopamine coating, that facilitates adhesion to both hydrophilic and hydrophobic surfaces. The mechanical performance of these structures is influenced significantly by the printing and coating parameters. Thus, this study undertakes the fabrication of bone plates at varying printing parameters followed by investigating the effects of polydopamine coating on their tensile and flexural behavior across varying coating conditions. In the study, SEM/EDS analysis has been performed for examining the morphological characteristics, interaction of coating with PLA and assessing the elemental distribution on the coated surface. The study further explores the impact of coating on substrate roughness and hydrophilicity through AFM and water contact angle measurement techniques. The deposition of polydopamine coating on PLA bone plates was confirmed using XRD and Raman spectroscopy. Upon application of coating, the findings suggested enhancement in tensile strength and flexural strength in the ranges of 47.18%–94.47% and 8.5%–33.78% respectively, across varying printing parameters. Similarly, varying coating parameters resulted in improvement ranging from 38.68% to 93.03% for tensile strength and 2.8%–30.57% for flexural strength. Furthermore, the deposition of coating substantially enhanced the hydrophilicity of the bone plates, making them suitable for tissue engineering applications. Thus, the successful deposition of polydopamine coating not only enhanced the mechanical behavior but also improved the hydrophilicity of bone plates, thereby advancing their suitability for biomedical applications.
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•Printing and coating parameters play an important role in affecting the mechanical properties of 3D printed structures.•Polydopamine improves the mechanical behavior of 3D printed PLA based bone plates by covalent interactions.•Polydopamine improved the maximum tensile and flexural strengths of the bone plates.•The coating led to reduction in water contact angle with increase in surface roughness.
Distal ulna locking bone plates (DLBPs) are commonly employed in the treatment of distal ulna fractures. However, commercially available metallic bone plates experience stress shielding and lack ...corrosion resistance. Poly lactic acid (PLA) is highly favored biopolymer due to its biocompatible and bioabsorbable nature with human tissues. The use of additive layer manufacturing (ALM) is gaining attention for creating customized implants with intricate structures tailored to patient autonomy. ALM-based PLA bone plates must provide high resistance against impact and torsional forces, necessitating the adjustment of printing process parameters. This study focuses on examining the influence of key printing parameters, on the impact strength and torque-withstanding capability of DLBPs. Experimental results, along with microscopic images, reveal that an increase in infill density (IF) and wall thickness imparts strong resistance to layers against crack propagation under impact and torsional loads. On the contrary, an increase in layer height and printing speed leads to delamination and early fracture of layers during impact and torsional testing. IF significantly contributes to improving the impact strength and torque-withstanding capability of DLBPs by 70.53% and 80.65%, respectively. The study highlights the potential of the ALM technique in developing DLBPs with sufficient mechanical strength for biomedical applications.
Abstract
Polylactic acid (PLA)‐based implants fabricated by 3D Printing process are biocompatible, porous in nature and light in weight. These biomimetic implants can be used as an alternative to ...metallic implants. However, such PLA‐based implants lack mechanical strength, limiting their application in biomedical field. In the present study, direct immersion coating technique has been used for application of polydopamine coating followed by studying the effect of input process parameters such as infill density, immersion time, speed of incubator shaker and concentration of coating solution using response surface methodology (RSM)‐based approach. Analysis of variance (ANOVA) has been applied for prediction of statistical models with respect to ultimate tensile and flexural strengths. The effect of individual process parameters has been discussed using main effect plots and the interactions occurring between significant parameters has been discussed using response surface and contour plots. From the findings, it was evident that infill density was highly significant parameter followed by immersion time, speed of incubator shaker and concentration of coating solution. Also, the mechanical properties improved with increase in infill density and immersion time. However, they initially increased and then decreased with increase in speed of incubator shaker and concentration of coating solution.
Distal fractures are the most commonly experienced type of fractures that require fixation of bone plates for healing of fractured bones. Poly Lactic Acid (PLA)‐based bone plates are porous and light ...in weight. However, they lack mechanical properties that limit their application in biomedical field. Polydopamine coating has been witnessed to undergo covalent interactions, enhancing the mechanical properties of the substrate. The present study is based on the fabrication of PLA‐based bone plates using Fused Filament Fabrication with varying infill patterns. The infill patterns in the study include octet, cubic, grid, concentric, lines, and gyroid. Thereafter, polydopamine coating was deposited on these bone plates using direct immersion coating method. In the study, the effect of infill pattern on coating deposition and modification of mechanical properties has been studied. The microscopic images of fractured bone plates were captured. It was concluded that polydopamine coating was successful in improving mechanical properties for all infill patterns. The findings suggested that a concentric pattern should be used for applications that require both high mechanical strength and maximum elongation at break because elongation at break is higher for concentric patterns than gyroid patterns. Also, for applications requiring only high mechanical strength, a gyroid pattern should be used.
PLA based distal ulna small locking bone plates have been fabricated using FFF with varying infill patterns. The infill patterns in the study include octet, cubic, grid, concentric, lines and gyroid. The polydopamine coating was deposited on bone plates using direct immersion method. In the study, the effect of infill pattern on coating deposition and mechanical properties have been studied.
•Application of ultrasonic assisted polydopamine coating on polymeric bone plates.•Effect of ultrasonic based coating parameters on three-point bending strength.•Ultrasonic vibrations provided forced ...striking of coating particles against surface.•Precipitation of coating particles at bottom was restricted with ultrasonic vibrations.•Ultrasonic based coating improved three-point bending strength than normal coating.
3D printed Poly Lactic Acid (PLA) bone plates exhibit limited three-point bending strength, restricting their viability in biomedical applications. The application of polydopamine (PDM) enhances the three-point bending strength by undergoing covalent interactions with PLA molecular structure. However, the heavy nature of PDM particles leads to settling at the container base at higher coating solution concentrations. This study investigates the impact of ultrasonic-assisted coating parameters on the three-point bending strength. Utilizing Response Surface Methodology (RSM) for statistical modeling, the study examines the influence of ultrasonic vibration power (UP), coating solution concentration (CC), and submersion time (TIME). RSM optimization recommended 100 % UP, 6 mg/ml CC, and 150 min TIME, resulting in maximum three-point bending strength of 83.295 MPa. Microscopic images from the comparative analysis revealed non-uniform coating deposition with mean thickness of 6.153 µm under normal coating. In contrast, ultrasonic-assisted coating promoted uniform deposition with mean thickness of 18.05 µm. The results demonstrate that ultrasonic-assisted coating induces PDM particle collision, preventing settling at the container base, and enhances three-point bending strength by 7.27 % to 23.24 % compared to the normal coating condition. This study emphasizes on the potential of ultrasonic-assisted coating to overcome the limitations of direct immersion coating technique.
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Purpose
The implications of metallic biomaterials involve stress shielding, bone osteoporosis, release of toxic ions, poor wear and corrosion resistance and patient discomfort due to the need of ...second operation. This study aims to use additive manufacturing (AM) process for fabrication of biodegradable orthopedic small locking bone plates to overcome complications related to metallic biomaterials.
Design/methodology/approach
Fused deposition modeling technique has been used for fabrication of bone plates. The effect of varying printing parameters such as infill density, layer height, wall thickness and print speed has been studied on tensile and flexural properties of bone plates using response surface methodology-based design of experiments.
Findings
The maximum tensile and flexural strengths are mainly dependent on printing parameters used during the fabrication of bone plates. Tensile and flexural strengths increase with increase in infill density and wall thickness and decrease with increase in layer height and wall thickness.
Research limitations/implications
The present work is focused on bone plates. In addition, different AM techniques can be used for fabrication of other biomedical implants.
Originality/value
Studies on application of AM techniques on distal ulna small locking bone plates have been hardly reported. This work involves optimization of printing parameters for development of distal ulna-based bone plate with high mechanical strength. Characterization of microscopic fractures has also been performed for understanding the fracture behavior of bone plates.
Poly Lactic Acid (PLA) based bone plates fabricated using Fused Deposition Modeling have poor mechanical strength which can be improved by biocompatible polydopamine (PDM) coating. However, PDM ...particles, being heavy in nature, settle at the container bottom with increase in coating solution concentration at the time of bone plate coating using dip coating technique. Thus, the present work aims to witness the effect of ultrasonic assisted coating parameters on tensile strength of coated bone plates. The coating parameters involving power of ultrasonic vibrations, coating solution concentration and immersion time were varied. The standard Response Surface Methodology (RSM) was applied and experimental trials were performed for obtaining tensile strength of bone plates under varied coating parameters. The objective of the present study was to compare the values of tensile strength predicted using RSM and machine learning (ML) models. Based on the obtained experimental values, gradient boosting regression (GBReg), linear regression (LReg) and random forest regression (RFReg) were trained and tested for predicting tensile strength of bone plates. The accuracy and prediction errors corresponding to RSM and ML based models were compared with respect to R2, Mean Squared Error (MSE), Mean Absolute Error (MAE) and Root Mean Squared Error (RMSE). The findings revealed that GBReg exhibited R2, MSE, RMSE and MAE values as 0.9312, 1.7142, 1.2877 and 1.0861 respectively, while RSM showed R2, MSE, RMSE and MAE values as 0.882, 2.13, 1.4595 and 1.258 respectively. RSM model has shown minimum accuracy with high prediction errors amongst the four models. GBReg has outperformed other ML models in terms of their accuracy and error metrics. The present study therefore suggests the application of GBReg based ML model for predicting tensile strength of PDM coated bone plates in response to its accurate and robust prediction performance.
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