Promising Role of Polylactic Acid as an Ingenious Biomaterial in Scaffolds, Drug Delivery, Tissue Engineering, and Medical Implants: Research Developments, and Prospective Applications.

In the present scenario, the research is now being focused on the naturally occurring polymers that can gradually replace the existing synthetic polymers for the development of bio composites having applications in medical surgeries and human implants. With promising mechanical properties and bio compatibility with human tissues, poly lactic acid (PLA) is now being viewed as a future bio material. In order to examine the applicability of PLA in human implants, the current article sheds light on the synthesis of PLA and its various copolymers used to alter its physical and mechanical properties. In the latter half, various processes used for the fabrication of biomaterials are discussed in detail. Finally, biomaterials that are currently in use in the field of biomedical (Scaffolding, drug delivery, tissue engineering, medical implants, derma, cosmetics, medical surgeries, and human implants) are represented with respective advantages in the sphere of biomaterials.

Tissues and organ printing: An evolution of technology and materials.

Since its beginnings, three-dimensional printing (3DP) technology has been successful because of ongoing advances in operating principles, the range of materials and cost-saving measures. However, the 3DP technological progressions in the biomedical sector have majorly taken place in the last decade after the evolution of novel 3DP systems, generally categorised as bioprinters and biomaterials to provide a replacement, transplantation or regeneration of the damaged organs and tissue constructs of the human body. There is now substantial scientific literature accessible to support the benefits of digital healthcare procedures with the help of bioprinters. It is of the highest significance to know the fundamental principles of the available printers and the compatibility of biomaterials as their feedstock, notwithstanding the huge potential of bioprinting systems to manufacture organs and other human body components. This paper provides a precise and helpful reading of the different categories of bioprinters, suitable biomaterials, numerical simulations and modelling and examples of much acknowledged clinical practices. The paper will also cite the prominent issues that still have not received desired solutions. Overall, the article will be of great use for all the professionals, scholars and engineers concerned with the 3DP, bioprinting and biomaterials.

Nitinol: From historical milestones to functional properties and biomedical applications.

Isoatomic NiTi alloy (Nitinol) has become an important biomaterial due to its unique characteristics, including shape memory effect, superelasticity, and high damping. Nitinol has been widely used in the biomedical field, including orthopedics, vascular stents, orthodontics, and other medical devices. However, there have been convicting views about the biocompatibility of Nitinol. Some studies have shown that Nitinol has extremely low cytotoxicity, indicating Nitinol has good biocompatibility. However, some studies have shown that the in-vivo corrosion resistance of Nitinol significantly decreases. This comprehensive paper discusses the historical developments of Nitinol, its biomedical applications, and its specific functional property. These render the suitability of Nitinol for such biomedical applications and provide insights into its in vivo and in vitro biocompatibility in the physiological environment and the antimicrobial strategies that can be applied to enhance its biocompatibility. Although 3D metal printing is still immature and Nitinol medical materials are difficult to be processed, Nitinol biomaterials have excellent potential and commercial value for 3D printing. However, there are still significant problems in the processing of Nitinol and improving its biocompatibility. With the deepening of research and continuous progress in surface modification and coating technology, a series of medical devices made from Nitinol are expected to be released soon.

Effect of Ranque-Hilsch Vortex Tube Cooling to Enhance the Surface-Topography and Tool-Wear in Sustainable Turning of Al-5.6Zn-2.5Mg-1.6Cu-0.23Cr-T6 Aerospace Alloy.

The aerospace metal cutting industry's search for environmentally friendly practices that do not compromise machining performance is well known. One of the major objectives is the reduction in use of cutting fluids, which play a major role in containing the harsh effects of severe heat generated during machining. Machining performance and product quality can be improved by controlling heat during machining. The purpose of this study was to determine the effectiveness of various environmentally friendly metalworking fluid (MF) strategies for the sustainable turning of aerospace aluminum alloy (Al-5.6Zn-2.5Mg-1.6Cu-0.23Cr-T6) for automotive, marine, and aerospace industrial applications. The SEM images were analyzed for worn tool surfaces and machined surfaces. Under dry conditions, heat does not dissipate well, and will enter the workpiece due to the absence of coolant. This causes extreme damage beneath a turned workpiece. Thus, at 10 µm, a drop in microhardness of approximately 20% can be observed. A similar observation was made in a Ranque-Hilsch vortex tube (RHVT) and in compressed air; however, the drop in hardness was relatively low compared to dry conditions. This evaluation of microhardness indicated a heat-based attention in the turned workpiece, and thus, the heat-based effect was found to be lowest in RHVT and compressed air compared to dry conditions. Results showed that RHVT reduces temperature up to 10%, surface roughness 13%, and tool wear 20% compared to dry turning. Overall, RHVT was identified as more effective environmentally friendly cooling strategy than dry and compressed air for the turning of aluminum alloy 7075-T6.

Hand and Abrasive Flow Polished Tungsten Carbide Die: Optimization of Surface Roughness, Polishing Time and Comparative Analysis in Wire Drawing.

This research work highlights the benefits of abrasive flow polishing (AFP) applied to tungsten carbide dies compared with conventional hand polishing (HP). An indigenous experimental set-up for AFP was developed. The effect of prominent process parameters viz. extrusion pressure, number of cycles, and abrasive particle concentration on the final surface roughness, percentage improvement in surface roughness, and polishing time was investigated by Taguchi-designed experiments. The multi-objective optimization (MOO) was performed using the Taguchi-TOPSIS-Equal weight approach to find the respective optimized AFP parametric settings. A set of skilled operators performed the conventional HP of dies, and the best hand-polished (HPed) die was selected using the TOPSIS technique. The operational performance of the HPed dies and the abrasive flow polished (AFPed) dies were compared on the three-stage wire drawing operation. The results revealed that AFP's surface resulted in a better-quality surface than hand polishing with a 27.06% improvement in surface roughness. Furthermore, AFP can reduce the dependency on costly and tricky-to-locate skilled operators, with a reasonable amount of time saving (about 87.05%). Overall, the study's findings show that abrasive flow polishing of dies is fast and cost-effective.

Investigation of Functionally Graded Adherents on Failure of Socket Joint of FRP Composite Tubes.

Fiber-reinforced polymer (FRP) matrix materials are quickly being investigated for application in concrete construction repair, reinforcement, and refurbishment. The technology has progressed to the point that its future acceptance is mainly reliant on the availability of established design guidelines based on recognized performance criteria, as well as the cost competitiveness of these technologies in contrast to conventional rehabilitation methods. The goal of this study is to evaluate the different functional grades of adhesives throughout bond length for bonded socket joints of laminated FRP composite pipes. Damage development resistance is high with a functionally graded FRP composite socket joint, as shown. To extend the service life of the structure, the joint designer should use an FRP composite socket joint with a functionally graded adhesive (FGA).

Investigations on Melt Flow Rate and Tensile Behaviour of Single, Double and Triple-Sized Copper Reinforced Thermoplastic Composites.

Thermoplastic composite materials are emerging rapidly due to the flexibility of attaining customized mechanical and melt flow properties. Due to high ductility, toughness, recyclability, and thermal and electrical conductivity, there is ample scope of using copper particles in thermoplastics for 3d printing applications. In the present study, an attempt was made to investigate the Melt Flow Index (MFI), tensile strength, and electrical and thermal conductivity of nylon 6 and ABS (acrylonitrile butadiene styrene) thermoplastics reinforced with copper particles. Thus, the experiments were conducted by adding different-sized copper particles (100 mesh, 200 mesh, and 400 mesh) in variable compositions (0% to 10%) to ABS and nylon 6 matrix. The impact of single, double, and triple particle-sized copper particles on MFI was experimentally investigated followed by FTIR and SEM analysis. Also, the tensile, electrical, and thermal conductivity testing were done on filament made by different compositions. In general, higher fluidity and mechanical strength were obtained while using smaller particles even with higher concentrations (up to 8%) due to improved bonding strength and adhesion between the molecular chains. Moreover, thermal and electrical conductivity was improved with an increase in concentration of copper particles.

Effect of Different Lubricating Environment on the Tribological Performance of CNT Filled Glass Reinforced Polymer Composite.

In recent years, the engineering implications of carbon nanotubes (CNTs) have progressed enormously due to their versatile characteristics. In particular, the role of CNTs in improving the tribological performances of various engineering materials is well documented in the literature. In this work, an investigation has been conducted to study the tribological behaviour of CNTs filled with glass-reinforced polymer (GFRP) composites in dry sliding, oil-lubricated, and gaseous (argon) environments in comparison to unfilled GFRP composites. The tribological study has been conducted on hardened steel surfaces at different loading conditions. Further, the worn surfaces have been examined for a particular rate of wear. Field-emission scanning electron (FESEM) microscopy was used to observe wear behaviours. The results of this study explicitly demonstrate that adding CNTs to GFRP composites increases wear resistance while lowering friction coefficient in all sliding environments. This has also been due to the beneficial strengthening and self-lubrication properties caused by CNTs on GFRP composites, according to FESEM research.

A collection of the novel coronavirus (COVID-19) detection assays, issues, and challenges.

The global pandemic of COVID-19 has rapidly increased the number of infected cases as well as asymptomatic individuals in many, if not all the societies around the world. This issue increases the demand for accurate and rapid detection of SARS-CoV-2. While accurate and rapid detection is critical for diagnosing SARS-CoV-2, the appropriate course of treatment must be chosen to help patients and prevent its further spread. Testing platform accuracy with high sensitivity and specificity for SARS-CoV-2 is equally important for clinical, regional, and global arenas to mitigate secondary transmission rounds. The objective of this article is to compare the current detection technology and introduce the most accurate and rapid ones that are suitable for pandemic circumstances. Hence, the importance of rapid detection in societies is discussed initially. Following this, the current technology for rapid detection of SARS-CoV-2 is explained and classified into three different categories: nucleic acid-based, protein-based, and point of care (PoC) detection testing. Then, the current issues for diagnostic procedures in laboratories are discussed. Finally, the role of new technologies in countering COVID-19 is also introduced to assist researchers in the development of accurate and timely detection of coronaviruses. As coronavirus continues to affect human lives in a detrimental manner, the development of rapid and accurate virus detection methods could promote COVID-19 diagnosis accessible to both individuals and the mass population at patient care. In this regard, rRT-PCR and multiplex RT-PCR detection techniques hold promise.

Multiple-Criteria Decision-Making and Sensitivity Analysis for Selection of Materials for Knee Implant Femoral Component.

Total knee replacement (TKR) is a remarkable achievement in biomedical science that enhances human life. However, human beings still suffer from knee-joint-related problems such as aseptic loosening caused by excessive wear between articular surfaces, stress-shielding of the bone by prosthesis, and soft tissue development in the interface of bone and implant due to inappropriate selection of TKR material. The choice of most suitable materials for the femoral component of TKR is a critical decision; therefore, in this research paper, a hybrid multiple-criteria decision-making (MCDM) tactic is applied using the degree of membership (DoM) technique with a varied system, using the weighted sum method (WSM), the weighted product method (WPM), the weighted aggregated sum product assessment method (WASPAS), an evaluation based on distance from average solution (EDAS), and a technique for order of preference by similarity to ideal solution (TOPSIS). The weights of importance are assigned to different criteria by the equal weights method (EWM). Furthermore, sensitivity analysis is conducted to check the solidity of the projected tactic. The weights of importance are varied using the entropy weights technique (EWT) and the standard deviation method (SDM). The projected hybrid MCDM methodology is simple, reliable and valuable for a conflicting decision-making environment.

Vibration Exposure and Transmissibility on Dentist's Anatomy: A Study of Micro Motors and Air-Turbines.

The use of dental hand pieces endanger dentists to vibration exposure as they are subjected to very high amplitude and vibration frequency. This paper has envisaged a comparative analysis of vibration amplitudes and transmissibility during idling and drilling with micro motor (MM) and air-turbine (AT) hand pieces. The study aims to identify the mean difference in vibration amplitudes during idling, explore different grasp forces while drilling with irrigant injection by the dentist, and various vibration transmission of these hand pieces. The study utilized 22 separate frequency resonances on two new and eight used MMs and two new and eight used ATs of different brands by observing the investigator at 16 different dentist clinics. The study adopted a descriptive research design with non-probability sampling techniques for selecting dentists and hand pieces. Statistical methods like Levene Test of Homogeneity, Welch ANOVA, independent t-test, and Games-Howell test were utilized with SPSS version 22 and MS-Excel. The results reveal that vibration amplitudes and vibration transmissibility when measured at position 2 are higher than in another position 1. Vibrations during idling for used MMs are more than AT hand pieces, and the used MM (MUD) and used AT (AUA) hand pieces differ due to their obsolescence and over-usage. Vibration amplitudes increase every time with the tightening of grasping of the hand piece. Vibration amplitudes for each grasping style of MM hand piece differ from all other grasping styles of AT hand pieces. Routine exposure to consistent vibrations has ill physical, mental, and psychological effects on dentists. The used hand pieces more hazardous as compared to newer ones. The study suggests that these hand pieces must be replaced periodically, sufficient to break between two operations, especially after every hand piece usage. Hence, the present research work can be further extended by creating some control groups among dentists and then studying the vibration amplitude exposure of various dental hand pieces and subsequent transmissibility to their body parts.

Investigating the Efficacy of Adhesive Tape for Drilling Carbon Fibre Reinforced Polymers.

In the present research work, an effort has been made to explore the potential of using the adhesive tapes while drilling CFRPs. The input parameters, such as drill bit diameter, point angle, Scotch tape layers, spindle speed, and feed rate have been studied in response to thrust force, torque, circularity, diameter error, surface roughness, and delamination occurring during drilling. It has been found that the increase in point angle increased the delamination, while increase in Scotch tape layers reduced delamination. The surface roughness decreased with the increase in drill diameter and point angle, while it increased with the speed, feed rate, and tape layer. The best low roughness was obtained at 6 mm diameter, 130° point angle, 0.11 mm/rev feed rate, and 2250 rpm speed at three layers of Scotch tape. The circularity error initially increased with drill bit diameter and point angle, but then decreased sharply with further increase in the drill bit diameter. Further, the circularity error has non-linear behavior with the speed, feed rate, and tape layer. Low circularity error has been obtained at 4 mm diameter, 118° point angle, 0.1 mm/rev feed rate, and 2500 RPM speed at three layers of Scotch tape. The low diameter error has been obtained at 6 mm diameter, 130° point angle, 0.12 mm/rev feed rate, and 2500 rpm speed at three layer Scotch tape. From the optical micro-graphs of drilled holes, it has been found that the point angle is one of the most effective process parameters that significantly affects the delamination mechanism, followed by Scotch tape layers as compared to other parameters such as drill bit diameter, spindle speed, and feed rate.

Revealing the WEDM Process Parameters for the Machining of Pure and Heat-Treated Titanium (Ti-6Al-4V) Alloy.

Ti-6Al-4V is an alloy that has a high strength-to-weight ratio. It is known as an alpha-beta titanium alloy with excellent corrosion resistance. This alloy has a wide range of applications, e.g., in the aerospace and biomedical industries. Examples of alpha stabilizers are aluminum, oxygen, nitrogen, and carbon, which are added to titanium. Examples of beta stabilizers are titanium-iron, titanium-chromium, and titanium-manganese. Despite the exceptional properties, the processing of this titanium alloy is challenging when using conventional methods as it is quite a hard and tough material. Nonconventional methods are required to create intricate and complex geometries, which are difficult with the traditional methods. The present study focused on machining Ti-6Al-4V using wire electrical discharge machining (WEDM) and conducting numerous experiments to establish the machining parameters. The optimal setting of the machining parameters was predicted using a multiresponse optimization technique. Experiments were planned using the response surface methodology (RSM) technique and analysis of variance (ANOVA) was used to determine the significance and contribution of the input parameters to changes in the output characteristics (cutting speed and surface roughness). The cutting speed obtained during the processing of the annealed titanium alloy using WEDM was quite large as compared to the cutting speed obtained in the case of processing the pure, quenched, and hardened titanium alloys using WEDM. The maximum cutting speed obtained while processing the annealed titanium alloy was 1.75 mm/min.

A Comparative Analysis of Laser Additive Manufacturing of High Layer Thickness Pure Ti and Inconel 718 Alloy Materials Using Finite Element Method.

Investigation of the selective laser melting (SLM) process, using finite element method, to understand the influences of laser power and scanning speed on the heat flow and melt-pool dimensions is a challenging task. Most of the existing studies are focused on the study of thin layer thickness and comparative study of same materials under different manufacturing conditions. The present work is focused on comparative analysis of thermal cycles and complex melt-pool behavior of a high layer thickness multi-layer laser additive manufacturing (LAM) of pure Titanium (Ti) and Inconel 718. A transient 3D finite-element model is developed to perform a quantitative comparative study on two materials to examine the temperature distribution and disparities in melt-pool behaviours under similar processing conditions. It is observed that the layers are properly melted and sintered for the considered process parameters. The temperature and melt-pool increases as laser power move in the same layer and when new layers are added. The same is observed when the laser power increases, and opposite is observed for increasing scanning speed while keeping other parameters constant. It is also found that Inconel 718 alloy has a higher maximum temperature than Ti material for the same process parameter and hence higher melt-pool dimensions.

Magneto-Rheological Fluid Assisted Abrasive Nanofinishing of ß-Phase Ti-Nb-Ta-Zr Alloy: Parametric Appraisal and Corrosion Analysis.

The present work explores the potential of magneto-rheological fluid assisted abrasive finishing (MRF-AF) for obtaining precise surface topography of an in-house developed ß-phase Ti-Nb-Ta-Zr (TNTZ) alloy for orthopedic applications. Investigations have been made to study the influence of the concentration of carbonyl iron particles (CIP), rotational speed (Nt), and working gap (Gp) in response to material removal (MR) and surface roughness (Ra) of the finished sample using a design of experimental technique. Further, the corrosion performance of the finished samples has also been analyzed through simulated body fluid (SBF) testing. It has been found that the selected input process parameters significantly influenced the observed MR and Ra values at 95% confidence level. Apart from this, it has been found that Gp and Nt exhibited the maximum contribution in the optimized values of the MR and Ra, respectively. Further, the corrosion analysis of the finished samples specified that the resistance against corrosion is a direct function of the surface finish. The morphological analysis of the corroded morphologies indicated that the rough sites of the implant surface have provided the nuclei for corrosion mechanics that ultimately resulted in the shredding of the appetite layer. Overall results highlighted that the MRF-AF is a potential technique for obtaining nano-scale finishing of the high-strength ß-phase Ti-Nb-Ta-Zr alloy.

Three-dimensional printing in the fight against novel virus COVID-19: Technology helping society during an infectious disease pandemic.

Indeed, the scientific milestones set by the ever-emerging three-dimensional printing (3DP) technologies are tremendous. Till now, the innovative 3DP technologies have benefitted the aerospace, automobile, textile, pharmaceutical, and biomedical sectors by developing pre-requisite designed and customized performance standards of the end-user products. As the scientific world, at this moment, is expediting efforts to fight against the highly damaging novel coronavirus (COVID-19) pandemic, the 3DP technologies are facilitating creative solutions in terms of personal protective equipment (PPE), medical equipment (such as ventilators and other respiratory devices), and other health and welfare tools to aid the personal hygiene as well as safe environment for humans by restricting the communication of risks. Various sources (including journal articles, news articles, white papers of the government and other non-profit organizations, commercial enterprises, as well as academic institutions have been reviewed for the collection of the information relevant to COVID-19 and 3DP. This communication presents the recent applications of the 3DP technologies aiding in developing innovative products designed to save the lives of millions of people around the world. Moreover, the potential of 3DP technologies in developing test swabs and controlled medicines has been highlighted. The literature reviewed in the present study indicated that the fused filament fabrication (FFF) is one of the most preferred technologies and contribute about 62% in the overall production of the protective gears developed through overall class of 3DP.

Surface Characteristics of Machined Polystyrene with 3D Printed Thermoplastic Tool.

An effort is made in this work to appraise the surface characteristics of machined expandable polystyrene (EPS) with a novel 3D printed thermoplastic acrylonitrile-butadiene-styrene (ABS) tool. Linear grooves on EPS were made on a vertical milling machine that was modified to conduct experiments in the laboratory. The tests were designed as per the Taguchi L9 based factorial design of experimentation while varying process parameters such as depth of cut, spindle speed, and feed rate. The machining responses dimensional accuracy and surface roughness of the machined grooves were studied. Furthermore, the surface topography of the machined specimens was considered to investigate the mechanism of material removal in response to the processing conditions. Moreover, mathematical models developed for the prediction of the output responses showed a significant correlation with the experimental results. The results of the statistical study indicate that the surface roughness is influenced by the spindle speed and dimensional accuracy by the depth-of-cut. Overall, the findings of the experimental work advocated the feasibility of 3D printed thermoplastic tools for machining soft polymeric materials. It can become a useful alternative for mass and batch production.

3D printed biodegradable functional temperature-stimuli shape memory polymer for customized scaffoldings.

Shape memory polymers (SMPs) and their composites have become the prominent choice of the various industries owing to the unique inherent characteristics which can be stimulated through the exposure of external stimuli. The use of SMPs in the three-dimensional (3D) technologies has produced enormous advantages. However, the potential of SMPs in 3D printing has limitedly explored. In the present study, an investigation was performed to study the shape memory effect (SME) of the fused filament fabricated (FFF) chitosan (CS) reinforced poly-lactic-acid (PLA) based porous scaffolds. Firstly, the composite filaments, with 1, 1.5, and 2% wt. of CS, were fabricated by using the twin-screw extrusion process, which was later used to print the test specimens at different infill density. The printed samples were selectively pre-elongated to 2.5 mm and then processed through direct heating, at 60-70 °C, for enabling the SME. It has been observed that the CS particles acted as rigid phases and interrupted the re-ordering of PLA chain. However, the scaffoldings showed 18.8% shape recovery at optimized process parametric settings. In addition, wettability and biocompatibility analyses of developed scaffoldings have also been performed to investigate the biological aspects of the developed scaffoldings. The stimulated samples found to be possessed with good wettability and cell proliferation. Overall, the 3D printed PLA/CS porous scaffoldings have shown significant shape recovery characteristics and are biologically active to be used as self-healing implants for acute bone deficiencies.

On the characterization of functionally graded biomaterial primed through a novel plaster mold casting process.

The current work presents a novel plaster mold casting (PMC) process for fabricating functionally graded biodegradable materials (FGBMs) for orthopedics applications. According to the proposed route, the plaster molds were first prepared by using a hybrid and variable mixture of Plaster of Paris (PoP) and hydroxyapatite (HAP). Upon drying, molten magnesium (Mg) alloy was poured in the mold cavity and allowed to solidify. Various experiments have been conducted as per Taguchi based design of experimentation to study the effect of PoPX/HAP proportion, mixing time, and baking times on mechanical, corrosion, and cytocompatibility performances of the resulting FGBM. It has been revealed by the scanning electron microscopy (SEM) that uniform layers of HAP particles were developed on the prepared specimens, revealed the novelty of the route. The mechanical properties, in case of surface hardness and impact strength, the optimum results were obtained with PoP(x = 90% by wt.) and HAP(y = 10% by wt.). Further, the corrosion investigations highlighted that the sample prepared with PoP(x = 70% by wt.) and HAP(y = 30% by wt.) proportion possessed excellent corrosion resistance. Moreover, the cytocompatibility analysis revealed that all the developed FGBM are substantially bioactive and promoted cell adhesion, proliferation, differentiation, and various other cytoplasmic activities. However, in this case, FGBM with PoP(x = 70% by wt.) and HAP(y = 30% by wt.) proportion was found superior. The overall results of the present work supported the developed FGBM components and involved the PMC route as a potential candidate for various orthopedics fabrications.