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.

Revealing the compressive and flow properties of novel bone scaffold structure manufactured by selective laser sintering technique.

Additive manufacturing is revolutionizing the field of medical sciences through its key application in the development of bone scaffolds. During scaffold fabrication, achieving a good level of porosity for enhanced mechanical strength is very challenging. The bone scaffolds should hold both the porosity and load withstanding capacity. In this research, a novel structure was designed with the aim of the evaluation of flexible porosity. A CAD model was generated for the novel structure using specific input parameters, whereas the porosity was controlled by varying the input parameters. Poly Amide (PA 2200) material was used for the fabrication of bone scaffolds, which is a biocompatible material. To fabricate a novel structure for bone scaffolds, a Selective Laser Sintering machine (SLS) was used. The displacement under compression loads was observed using a Universal Testing Machine (UTM). In addition to this, numerical analysis of the components was also carried out. The compressive stiffness found through the analysis enables the verification of the load withstanding capacity of the specific bone scaffold model. The experimental porosity was compared with the theoretical porosity and showed almost 29% to 30% reductions when compared to the theoretical porosity. Structural analysis was carried out using ANSYS by changing the geometry. Computational Fluid Dynamics (CFD) analysis was carried out using ANSYS FLUENT to estimate the blood pressure and Wall Shear Stress (WSS). From the CFD analysis, maximum pressure of 1.799 Pa was observed. Though the porosity was less than 50%, there was not much variation of WSS. The achievement from this study endorses the great potential of the proposed models which can successfully be adapted for the required bone implant applications.

Microcontroller PIC 16F877A standard based on solar cooker using PV-evacuated tubes with an extension of heat integrated energy system.

The unavailability of sunlight during nighttime and cloudy weather condition has limited the usage of solar cookers throughout the day. This study will attempt to engineer a solar cooker with PV (photovoltaic panel), evacuated tubes with CPC reflectors, battery, and charge controller using the microcontroller PIC 16F877A. A mathematical model is developed to predict the electrical power (Ep) required during cloudy weather condition and nighttime as well as the temperatures occurring at different parts of the cooker. The proposed model is validated against experimental observations gathered for one of the typical working days of the system. The cooker is tested for various cooking loads to find the cooking time, and it is proven that the proposed cooker can be utilized over 24/7 without interruption.

Effect of Deep Cryogenic Treatment on Corrosion Behavior of AISI H13 Die Steel.

AISI H13 die steel specimens were subjected to heating at 1020 °C followed by oil quenching and double tempering at 520 °C. Subsequently, these specimens were subjected to deep cryogenic treatment at -185 °C in liquid nitrogen environment for 16 h and then subjected to soft tempering at 100 °C once the specimens attained room temperature. Thereafter, the specimens were subjected to scanning electron microscopy (SEM) analysis and electron backscatter diffraction (EBSD) analysis. The electrochemical corrosion activity was investigated in 3.5% NaCl at 23 ± 0.5 °C by evaluating the evolution of open circuit potential over time and potentiodynamic curves, and electrochemical impedance spectroscopy study was also carried out. The heat-treated specimens exhibited better resistance to corrosion through more electropositive values of open circuit potential. This could be attributed to lower grain boundary area in heat-treated specimens as compared to 16 h cryogenically treated specimen as higher grain boundary areas behave as an anode in an electrochemical cell, thereby enhancing the rate of corrosion. According to electrochemical tests, the cryogenically treated surface is more resistant to corrosion, followed by heated alloy. However, both surface modification treatments improved the corrosion behavior of the untreated alloy.

Development and Investigation of an Inexpensive Low Frequency Vibration Platform for Enhancing the Performance of Electrical Discharge Machining Process.

Difficulty in debris removal and the transport of fresh dielectric into discharge gap hinders the process performance of electrical discharge machining (EDM) process. Therefore, in this work, an economical low frequency vibration platform was developed to improve the performance of EDM through vibration assistance. The developed vibratory platform functions on an eccentric weight principle and generates a low frequency vibration in the range of 0-100 Hz. The performance of EDM was evaluated in terms of the average surface roughness (Ra), material removal rate (MRR), and tool wear rate (TWR) whilst varying the input machining parameters viz. the pulse-on-time (Ton), peak current (Ip), vibration frequency (VF), and tool rotational speed (TRS). The peak current was found to be the most significant parameter and contributed by 78.16%, 65.86%, and 59.52% to the Ra, MRR, and TWR, respectively. The low frequency work piece vibration contributed to an enhanced surface finish owing to an improved flushing at the discharge gap and debris removal. However, VF range below 100 Hz was not found to be suitable for the satisfactory improvement of the MRR and reduction of the TWR in an electrical discharge drilling operation at selected machining conditions.

Progressing towards Sustainable Machining of Steels: A Detailed Review.

Machining operations are very common for the production of auto parts, i.e., connecting rods, crankshafts, etc. In machining, the use of cutting oil is very necessary, but it leads to higher machining costs and environmental problems. About 17% of the cost of any product is associated with cutting fluid, and about 80% of skin diseases are due to mist and fumes generated by cutting oils. Environmental legislation and operators' safety demand the minimal use of cutting fluid and proper disposal of used cutting oil. The disposal cost is huge, about two times higher than the machining cost. To improve occupational health and safety and the reduction of product costs, companies are moving towards sustainable manufacturing. Therefore, this review article emphasizes the sustainable machining aspects of steel by employing techniques that require the minimal use of cutting oils, i.e., minimum quantity lubrication, and other efficient techniques like cryogenic cooling, dry cutting, solid lubricants, air/vapor/gas cooling, and cryogenic treatment. Cryogenic treatment on tools and the use of vegetable oils or biodegradable oils instead of mineral oils are used as primary techniques to enhance the overall part quality, which leads to longer tool life with no negative impacts on the environment. To further help the manufacturing community in progressing towards industry 4.0 and obtaining net-zero emissions, in this paper, we present a comprehensive review of the recent, state of the art sustainable techniques used for machining steel materials/components by which the industry can massively improve their product quality and production.

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.

Deep Learning Approach for Discovery of In Silico Drugs for Combating COVID-19.

Early diagnosis of pandemic diseases such as COVID-19 can prove beneficial in dealing with difficult situations and helping radiologists and other experts manage staffing more effectively. The application of deep learning techniques for genetics, microscopy, and drug discovery has created a global impact. It can enhance and speed up the process of medical research and development of vaccines, which is required for pandemics such as COVID-19. However, current drugs such as remdesivir and clinical trials of other chemical compounds have not shown many impressive results. Therefore, it can take more time to provide effective treatment or drugs. In this paper, a deep learning approach based on logistic regression, SVM, Random Forest, and QSAR modeling is suggested. QSAR modeling is done to find the drug targets with protein interaction along with the calculation of binding affinities. Then deep learning models were used for training the molecular descriptor dataset for the robust discovery of drugs and feature extraction for combating COVID-19. Results have shown more significant binding affinities (greater than -18) for many molecules that can be used to block the multiplication of SARS-CoV-2, responsible for COVID-19.

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.

Improvement of the Machining Performance of the TW-ECDM Process Using Magnetohydrodynamics (MHD) on Quartz Material.

Many microslits are typically manufactured on quartz substrates and are used to improve their industrial performance. The fabrication of microslits on quartz is difficult and expensive to achieve using recent traditional machining processes due to its hardness, electrically insulating nature, and brittleness. The key objective of the current study was to demonstrate the fabrication of microslits on quartz material through a magnetohydrodynamics (MHD)-assisted traveling wire-electrochemical discharge micromachining process. Hydrogen gas bubbles were concentrated around the entire wire surface during electrolysis. This led to a less active dynamic region of the wire electrode, which decreased the adequacy of the electrolysis process and the machining effectiveness. The test results affirmed that the MHD convection approach evacuated the gas bubbles more rapidly and improved the void fraction in the gas bubble scattering layer. Furthermore, the improvements in the material removal rate and length of the cut were 85.28% and 48.86%, respectively, and the surface roughness was reduced by 30.39% using the MHD approach. A crossover methodology with a Taguchi design and ANOVA was utilized to study the machining performance. This exploratory investigation gives an unused strategy that shows a few advantages over the traditional TW-ECDM process.

Visco-Hyperelastic Characterization of the Equine Immature Zona Pellucida.

This article presents a very detailed study on the mechanical characterization of a highly nonlinear material, the immature equine zona pellucida (ZP) membrane. The ZP is modeled as a visco-hyperelastic soft matter. The Arruda-Boyce constitutive equation and the two-term Prony series are identified as the most suitable models for describing the hyperelastic and viscous components, respectively, of the ZP's mechanical response. Material properties are identified via inverse analysis based on nonlinear optimization which fits nanoindentation curves recorded at different rates. The suitability of the proposed approach is fully demonstrated by the very good agreement between AFM data and numerically reconstructed force-indentation curves. A critical comparison of mechanical behavior of two immature ZP membranes (i.e., equine and porcine ZPs) is also carried out considering the information on the structure of these materials available from electron microscopy investigations documented in the literature.

Bézier Curves-Based Optimal Trajectory Design for Multirotor UAVs with Any-Angle Pathfinding Algorithms.

Multirotor Unmanned Aerial Vehicles (UAVs) play an imperative role in many real-world applications in a variety of scenarios characterized by a high density of obstacles with different heights. Due to the complicated operation areas of UAVs and complex constraints associated with the assigned mission, there should be a suitable path to fly. Therefore, the most relevant challenge is how to plan a flyable path for a UAV without collisions with obstacles. This paper demonstrates how a flyable and continuous trajectory was constructed by using any-angle pathfinding algorithms, which are Basic Theta*, Lazy Theta*, and Phi* algorithms for a multirotor UAV in a cluttered environment. The three algorithms were modified by adopting a modified cost function during their implementation that considers the elevation of nodes. First, suitable paths are generated by using a modified version of the three algorithms. After that, four Bézier curves-based approaches are proposed to smooth the generated paths to be converted to flyable paths (trajectories). To determine the most suitable approach, particularly when searching for an optimal and collision-free trajectory design, an innovative evaluation process is proposed and applied in a variety of different size environments. The evaluation process results show high success rates of the four approaches; however, the approach with the highest success rate is adopted. Finally, based on the results of the evaluation process, a novel algorithm is proposed to increase the efficiency of the selected approach to the optimality in the construction process of the trajectory.

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.

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.

The effects of hot forging on the preform additive manufactured 316 stainless steel parts.

Additive Manufacture (AM) offers great potential for creating metallic parts for high end products used in critical application i.e. aerospace and biomedical engineering. General acceptance of AM within these fields has been held back by a lack of confidence in the consistency of the mechanical properties of AMed parts associated by the occurrence of porosity, large columnar grains and texture. In this research, to counters this problem we have combined hot forging and subsequent heat treatment. Although, perhaps not best suited to components featuring fine detail, this technique should be well suited to the manufacture of forged components such as fan blades. Here, AM is able to create a near net-shape blank which is then hot forged to size, eliminating intermediate production stages and generating good mechanical properties in the final component. The material used in the current study is AM 316 L Stainless Steel. By altering the printing parameters of the AM machine, two batches of samples were built, each displaying a different porosity content. This allowed the influence of initial build quality to be illustrated. By comparing the two sample batches, it was possible to gain an insight into the possibilities of controlling porosity and material microstructure. The success of the proposed hot forging and heat treatment technique was validated by mechanical testing (i.e. tensile and hardness experiments) and microstructure evolution characterization (i.e. optical microscopy observation and electron backscatter diffraction (EBSD) techniques). The results revealed that the post processing strategy reduced material porosity and enabled the creation of a more robust microstructure, resulting in improved mechanical properties of the AM material.

A COVID-19 Supply Chain Management Strategy Based on Variable Production under Uncertain Environment Conditions.

The management of a controllable production in the manufacturing system is essential to achieve viable advantages, particularly during emergency conditions. Disasters, either man-made or natural, affect production and supply chains negatively with perilous effects. On the other hand, flexibility and resilience to manage the perpetuated risks in a manufacturing system are vital for achieving a controllable production rate. Still, these performances are strongly dependent on the multi-criteria decision making in the working environment with the policies launched during the crisis. Undoubtedly, health stability in a society generates ripple effects in the supply chain due to high demand fluctuation, likewise due to the Coronavirus disease-2019 (COVID-19) pandemic. Incorporation of dependent demand factors to manage the risk from uncertainty during this pandemic has been a challenge to achieve a viable profit for the supply chain partners. A non-linear supply chain management model is developed with a controllable production rate to provide an economic benefit to the manufacturing firm in terms of the optimized total cost of production and to deal with the different situations under variable demand. The costs in the model are set as fuzzy to cope up with the uncertain conditions created by lasting pandemic. A numerical experiment is performed by utilizing the data set of the multi-stage manufacturing firm. The optimal results provide support for the industrial managers based on the proactive plan by the optimal utilization of the resources and controllable production rate to cope with the emergencies in a pandemic.

Characterization of Zinc Oxide-Urea Formaldehyde Nano Resin and Its Impact on the Physical Performance of Medium-Density Fiberboard.

The main purpose of this research work is to characterize zinc oxide-urea formaldehyde nano resin and identify the physical performance of medium-density fiberboard (MDF). Considering the dry weight of natural fibers, the ZnO nanoparticles were added to urea formaldehyde (UF) glue at four levels-0.0%, 1.0%, 2.0% and 3.0%-and their effects were investigated in terms of the physical properties of MDF. The surface morphology and crystalline structure of ZnO, UF and UF-ZnO nanofillers were characterized using Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) analysis and significant improvements were achieved as a result of the addition of nanoparticles. Thermal properties were analyzed by means of differential scanning calorimetry (DSC) and thermogravemetric analysis (TGA) and it was observed that increasing the concentration of ZnO nanoparticles ultimately enhanced the curing of UF-ZnO nanofillers. Finally, density, thickness swelling and water absorption properties were investigated and it was observed that thickness swelling and water absorption properties were improved by 38% and 12%, respectively, when compared to control MDF.

Influence of ß-phase stability in elemental blended Ti-Mo and Ti-Mo-Zr alloys.

This paper investigated the improvement of mechanical properties for one of the most used biomaterials, titanium-based alloy. To improve its mechanical properties, molybdenum was chosen to be added to Ti and Ti-Zr alloys through a mechanical blending process. After homogenization of Ti (12, 15) Mo and Ti (12, 15) Mo-6 Zr, the compaction pressure and sintering temperature were varied to create pellets. Characterization has been done using scanning electron microscopy (SEM), X-ray diffraction (XRD), Vickers's hardness, Archimedes test and ultrasonic method, and 3-point bending test. Micrograph of each pellet revealed the influence of Mo content that plays a prominent role in the variation of microstructure in the alloys Ti-Mo and Ti-Zr-Mo. The porosity and density were also influenced by changing the ß-phase. EBSD analysis shows the increase in ß-phase with the addition of Zr. The overall results indicated that the percentage of ß-phase greatly affects the mechanical properties for the specimens.

A novel Ag/carrageenan-gelatin hybrid hydrogel nanocomposite and its biological applications: Preparation and characterization.

A novel biohybrid hydrogel nanocomposite made of natural polymer carrageenan and gelatin protein were developed. The silver nanoparticles were prepared using the carrageenan polymer as reduction and capping agent. Here, the Ag/Carrageenan was combined with gelatin hydrogel using glutaraldehyde having a cross-link role in order to create the biohybrid hydrogel nanocomposite. The manufactured composite performances were anaylised by UV-visible spectroscopy, Fourier Transform infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Energy dispersive X-ray (EDX) spectroscopy and Transmission Electron Microscopy (TEM) methods. The swelling behaviour of the Ag/Carrageenan-gelatin hybrid hydrogel nanocomposite was also analyzed. The antibacterial activity was tested against human pathogens viz. S.agalactiae 1661, S. pyogenes 1210 and E. coli. The bacterial cell wall damage of S.agalactiae 1661 was analyzed by scanning electron microscopy. The cytotoxic assay was performed against the A549 lung cancer cells.