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The Role of Additive Manufacturing Technologies for Rehabilitation in Healthcare and Medical Applications

Vidyapati Kumar1, Ankita Mistri2* and Abhishek Mohata3

1Department of Mechanical Engineering, Indian Institute of Technology, Kharagpur, West Bengal, India

2Department of Mechanical Engineering, Indian Institute of Technology, Dhanbad, Jharkhand, India

3Department of Mechanical Engineering, Jalpaiguri Government Engineering College, West Bengal, India

Abstract

Additive manufacturing (AM) is a rapidly evolving technology that is being utilized to produce medical components across a wide range of sectors. Since each patient is unique in terms of health and dental care, AM has enormous potential for personalized and customized therapy. In addition to its bespoke design and reduced manufacturing time and cost, it also offers a broad and extended opportunity for the biological mimicry of desired complicated states of physiological devices. Scaffolds with a fitted outer shape and a porous internal structure may be created via additive manufacturing, which is critical for repairing vast segmental bone lesions. The scaffold-building process includes scaffold design, additive manufacturing, and post-treatments. This research attempts to provide a more systematic assessment of the use of various AM processes and their need in the current era with their classifications in the healthcare and medical field utilizing different biomaterials, as well as the scope of future research for advancing the medical field using various AM processes.

Keywords: Biomaterials, additive manufacturing, implants, scaffolds, prosthetics

1.1 Introduction

In this contemporary period of the Fourth Industrial Revolution, the marketplace must constantly improve itself via continual innovation and customization, in which the innovation and deployment of unconventional manufacturing processes play a vital role. Additive manufacturing (AM) has already been shown to play a significant part in the unconventional manufacturing process. Additive manufacturing, also known as 3D printing, rapid prototyping, or free-form fabrication, is an operation in which materials are joined by layer-by-layer deposition to produce a three-dimensional product from a computer-aided design (CAD) model thereby eliminating the need for various machining processes. AM technologies, which use metal powders to create intricate and sophisticated 3D geometry, are a burgeoning industry. AM technologies have been highlighted as a critical manufacturing priority and are considered one of the essential components of Industry 4.0, having the potential to amend the global manufacturing industry. Currently, it has been noted that the demand for AM surged fast after the start of COVID-19 in many industries where the economic downturn suffered as a consequence of the efforts implemented to limit the pandemic. Additive manufacturing is already enabling a design and industrial revolution in various industries, including aviation, power, automobile, healthcare, tooling, and consumer products.

The typical manufacturing procedure for printing tissues using the AM technique has been depicted in Figure 1.1. The first phase in this process is data collection, in which the data about the organ or portion of the body that needs to be printed are obtained using medical imaging methods such as X-ray and computed tomography (CT) scan. Once the data are obtained, a 3D model of the component is created using computer-assisted design (CAD) and computer-aided manufacturing (CAM) processes. The bioinks used for 3D bioprinting are then chosen, and the bioprinting settings and resolutions are calibrated. Once the material has been 3D bioprinted, its functionality is tested in an incubator or bioreactor to confirm stability, cell viability, tissue development, and so on. Following these procedures, the printed component is now ready for in vitro testing, disease modeling, and in vivo implantation in the human body, saving a significant amount of life in healthcare systems.

Figure 1.1 Typical process layout for the additive manufacturing process.

From this perspective, it is important to grasp the importance of additive manufacturing technologies like 3D bioprinting in healthcare and biological sciences. In the healthcare and medical fields, the general practice is to do preclinical research using animal-based models, notably rodents [1]. From a regulatory standpoint, it is critical and obligatory to conduct this experiment using animal-based models in order to bring forth the most current therapeutic breakthroughs from preclinical to clinical trials. These problems have not been highlighted for many decades, but a recent surge in opprobrium based on humanitarian and scientific considerations has shown that around 80% of putative treatments perish in clinical trials while having effectiveness and safety in preclinical investigations [2]. Potential underlying causes include inadequate characterization of relevant animal models [3, 4], a lack of acceptable experimental quality in in vivo investigations, and significant interspecies-related differences to humans in areas such as anatomy, (patho)physiology, and immunology. Many disorders that develop in humans are not ubiquitous in nature in animals; thus, an artificial disease induction is necessary to simulate the diseases, and even if the animals display identical diseases, the underpinning pathophysiology condition is entirely unknown. The mouse-based animal model for SARS coronavirus infection has recently shown severe encephalitis, which is not seen in human pathogenesis. Hence, as seen in Figure 1.2 [5], the translational utility of preclinical animal models has been called into doubt owing to a lack of concordance and reproducibility. Figure 1.2 displays the high expense of drug development as well as their relatively high failure rates in the clinical phase, raising concerns about the current applicability of research methodologies. To address the aforementioned limitations, additive manufacturing technologies play a critical role in which a 3D organ or human-based models may be generated in order to undertake fundamental and preclinical research. As a result, this AM technology has attracted conscientious scrutiny due to its usefulness in producing a human-based model as a replacement for animal models for scientific purposes.

Figure 1.2 Applicability of AM technologies for the production of 3D organ models [5].

1.2 Classification of the Additive Manufacturing Process

Several 3D printing technologies have been created to bioengineer three-dimensional tissue or organ frameworks for biomedical purposes, as demonstrated in Figure 1.3. The most extensively utilized forms of 3D bioprinting processes are extrusion-based bioprinting, laser-assisted bioprinting, and laser-based stereolithography. The effectiveness of each printing technique is heavily reliant on biomaterial choices and functions.

Figure 1.3 Types of 3D bioprinting.

1.2.1 Jetting-Based Bioprinting

Jetting-based bioprinting is the earliest printing method, in which bioinks are used to print. These bioinks may be either natural or manufactured substances that help in cell adherence, propagation, and replication. Bioink is pushed with force via a nozzle in this approach, resulting in a spray of droplets. These printers may have a single or several print heads. A chamber and a nozzle are both included in each print head. The surface tension of the fluid keeps the bioinks near the nozzle opening. In three ways, pressure pulses are injected into the print head chamber. As seen in Figure 1.4, it is provided via piezoelectric inkjet, thermal inkjet, or electrostatic bioprinting. The actuator in the piezoelectric inkjet generates pressure pulses to deposit the bioinks; however, certain print heads need back pressure to complement the pressure pulses to make droplets of bioinks. When a voltage pulse is supplied to a thermal inkjet printer's thermal actuator, it locally warms the bioink solution. Figure 1.4 [6] shows that local heating produces a vapor bubble. This bubble rapidly expands and shrinks, generating a force burst inside the fluid compartment and driving the bioink droplet to defy interfacial tension and accumulate on the scaffold. Thermal inkjet printers may discharge biological materials such as proteins and mammalian cells, among other things. Bioink droplets are created in electrostatic bioprinters by increasing the capacity of the fluid compartment with the aid of a bioink fluid attached to the plate. After that, the pressure plate deflects between the electrode and the plate once the voltage is applied. Finally, as the voltage drops, the bioink is evacuated as the pressure plate re-establishes its position, and printing happens.

Figure 1.4 Jetting-based 3D bioprinting [6].

1.2.2 Extrusion-Based Bioprinting

Extrusion-based bioprinting is based on the notion of applying extrusion pressure to the bioink, which is very beneficial for tissue regeneration and repair. The bioink contained in this process is largely deposited using pneumatic pressure, a mechanical pressure in the form of a screw or piston, and lastly, the substrate is extruded out, as illustrated in Figure 1.5 [6]. The robotic stage controller governs and controls the whole extrusion process of the bioprinter....