Polyether ether ketone (PEEK) and its 3D printed implants applications in medical field: An overview

Translational Aspects of 3D and 4D Printing and Bioprinting

Three-dimensional (3D) printed medical devices include orthopedic and craniofacial implants, surgical tools, and external prosthetics that have been directly used in patients. While the advances of additive manufacturing techniques in the production of medical devices have been on the rise, clinical translation of living cellular constructs face significant limitations in terms of regulatory affairs, process technology, and materials development. In this perspective, the current status-quo of 3D and four-dimensional (4D) (bio)printing is summarized, current advancements are discussed and the challenges that need to be addressed for improved industrial translation and clinical applications of bioprinting are highlighted. It is focused on a multidisciplinary approach in discussing the key translational considerations, from the perspective of industry, regulatory bodies, funding strategies, and future directions.

Vaso-Lock for sutureless anastomosis in a pig arteriovenous loop model

A vascular anastomosis is a critical surgical skill that involves connecting blood vessels. Traditional handsewn techniques can be challenging and resource intensive. To address these issues, we have developed a unique sutureless anastomotic device called Vaso-Lock. This intraluminal device connects free vascular ends using anchors to maintain traction and enable a rapid anastomosis. We tested the anastomotic capability of Vaso-Locks in a pig common carotid-internal jugular arteriovenous model. The use of Vaso-Lock allowed us to accomplish this procedure in less than 10 min, in contrast to the approximately 40 min required for a handsewn anastomosis. The Vaso-Lock effectively maintained patency for at least 6 weeks without causing significant tissue damage. Histological analysis revealed that the device was successfully incorporated into the arterial wall, promoting a natural healing process. Additionally, organ evaluations indicated no adverse effects from using the Vaso-Lock. Our findings support the safety and effectiveness of the Vaso-Lock for arteriovenous anastomosis in pigs, with potential applicability for translation to humans. Our novel sutureless device has the potential to advance surgical practice and improve patient outcomes.

A balance of biocompatibility and antibacterial capability of 3D printed PEEK implants with natural totarol coating

OBJECTIVE

Polyetheretherketone (PEEK), a biomaterial with appropriate bone-like mechanical properties and excellent biocompatibility, is widely applied in cranio-maxillofacial and dental applications. However, the lack of antibacterial effect is an essential drawback of PEEK material and might lead to infection and osseointegration issues. This study aims to apply a natural antibacterial agent, totarol coating onto the 3D printed PEEK surface and find an optimized concentration with balanced cytocompatibility, osteogenesis, and antibacterial capability.

METHODS

In this study, a natural antibacterial agent, totarol, was applied as a coating to fused filament fabrication (FFF) 3D printed PEEK surfaces at a series of increasing concentrations (1 mg/ml, 5 mg/ml, 10 mg/ml, 15 mg/ml, and 20 mg/ml). The samples were then evaluated for cytocompatibility with L929 fibroblast and SAOS-2 osteoblast using live/dead staining and CCK-8 assay. The antibacterial capability was assessed by crystal violet staining, live/dead staining, and scanning electron microscopy (SEM) utilizing the oral primary colonizer S. gordonii and isolates of mixed oral bacteria in a stirring system simulating the oral environment. The appropriate safe working concentration for totarol coating is selected based on the results of the cytocompatibility and antibacterial test. Subsequently, the influence on osteogenic differentiation was evaluated by alkaline phosphatase (ALP) and alizarin red staining (ARS) analysis of pre-osteoblasts.

RESULTS

Our results showed that the optimal concentration of totarol solution for promising antibacterial coating was approximately 10 mg/ml. Such surfaces could play an excellent antibacterial role by inducing a contact-killing effect with an inhibitory effect against biofilm development without affecting the healing of soft and hard tissues around FFF 3D printed PEEK implants or abutments.

SIGNIFICANCE

This study indicates that the totarol coated PEEK has an improved antibacterial effect with excellent biocompatibility providing great clinical potential as an orthopedic/dental implant/abutment material.

3D printing for spine pathologies: a state-of-the-art review

Three-Dimensional Printing has advanced throughout the years in the field of biomedical science with applications, especially in spine surgeries. 3D printing has the ability of fabricating highly complex structures with ease and high dimensional accuracy. The complexity of the spine's architecture and the inherent dangers of spinal surgery bring the evaluation of 3D printed models into consideration. This article summarizes the benefits of 3D printing based models for application in spine pathology. 3D printing technique is extensively used for fabrication of anatomical models, surgical guides and patient specific implants (PSI). The 3D printing based anatomical models assist in preoperative planning and training of students. Furthermore, 3D printed models can be used for improved communication and understanding of patients about the spinal disorders. The use of 3D printed surgical guides help in the stabilization of the spine during surgery, improving post procedural outcomes. Improved surgical results can be achieved by using PSIs that are tailored for patient specific needs. Finally, this review discusses the limitations and potential future scope of 3D printing in spine pathologies. 3D printing is still in its infancy, and further research would provide better understanding of the technology's true potential in spinal procedures.

Mechanical behaviour of reconstructed defected skull with custom PEEK implant and Titanium fixture plates under dynamic loading conditions using FEM

Skull reconstruction using cranial implants is often required for repairing skull defects caused due to trauma, diseases, or malignancy to protect intracranial structures. For relieving Intracranial Pressure (ICP) surgeons restore cranial defects either using natural bones or fabricated custom cranial implants. With the increase in Traumatic Brain Injuries (TBI) and challenges faced by TBI patients to regain normalcy, it is imperative to analyse the mechanical behaviour of skull-implant assemblies under some Head Injury Criteria (HIC). Medical grade materials including Titanium Alloys (Ti-6Al-4V) and Polyether-ether-ketone (PEEK) are used by fabricating Patient-Specific Implants (PSI) manufactured using 3D imaging, modelling and printing techniques. 3D technologies are preferred over conventional manufacturing methods, as they enable fabrication of custom shapes, sizes and properties for these PSI. For an effective attachment of PSI with a defective skull, a stable joint and plate arrangement as fixture plates is necessary at their interface. These fixtures can have variable numbers, design shapes, materials and location arrangements. This paper presents the Finite Element Method/Analysis (FEM/FEA) study of PSI attached to a defected skull for reconstruction, with linear shaped fixture configuration, when subjected to an external dynamic loading at 5 m/s, strain rate of 10s-1 to 243s-1 and ICP of 15mm Hg from three sides of the skull faces. Three different materials as Neoprene (soft), Concrete (medium rigid) and E-Glass (highly rigid) have been used, in the form of a rectangular thin cuboidal wall structure, at an angle of 45° with the skull face. Four linear shaped fixture plates which were simplest to design, were used to attach the PSI-skull assembly, to ensure that weight of the PSI-fixation assembly on the patient remains minimal, overall assembly has symmetrical fixations and efforts required by a surgeon for fitment of these plates remain minimal. Placement of these fixture plates has been optimized to encompass the complete PSI-skull interface section, due to which the stresses within all the assembly components (PSI, fixture plate and skull) reduced by nearly 2.5 times than the initial design and remained within yielding limits, thereby, averting any failure under heavy external dynamic loading.

Antimicrobial Peptide Conjugated on Graphene Oxide-Containing Sulfonated Polyetheretherketone Substrate for Effective Antibacterial Activities against Staphylococcus aureus

In the present study, the antimicrobial peptide nisin was successfully conjugated onto the surface of sulfonated polyetheretherketone (SPEEK), which was decorated with graphene oxide (GO) to investigate its biofilm resistance and antibacterial properties. The PEEK was activated with sulfuric acid, resulting in a porous structure. The GO deposition fully covered the porous SPEEK specimen. The nisin conjugation was accomplished using the crosslinker 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) through a dip-coating method. The surface micrographs of the SPEEK-GO-nisin sample indicated that nisin formed discrete islets on the flat GO surface, allowing both the GO and nisin to perform a bactericidal effect. The developed materials were tested for bactericidal efficacy against Staphylococcus aureus (S. aureus). The SPEEK-GO-nisin sample had the highest antibacterial activity with an inhibition zone diameter of 27 mm, which was larger than those of the SPEEK-nisin (19 mm) and SPEEK-GO (10 mm) samples. Conversely, no inhibitory zone was observed for the PEEK and SPEEK samples. The surface micrographs of the bacteria-loaded SPEEK-GO-nisin sample demonstrated no bacterial adhesion and no biofilm formation. The SPEEK-nisin and SPEEK-GO samples showed some bacterial attachment, whereas the pure PEEK and SPEEK samples had abundant bacterial colonies and thick biofilm formation. These results confirmed the good biofilm resistance and antibacterial efficacy of the SPEEK-GO-nisin sample, which is promising for implantable orthopedic applications.

Evaluation of polyetheretherketone composites modified by calcium silicate and carbon nanotubes for bone regeneration: mechanical properties, biomineralization and induction of osteoblasts

Desired orthopedic implant materials must have a good biological activity and possess appropriate mechanical property that correspond to those of human bone. Although polyetheretherketone (PEEK) has displayed a promising application prospect in musculoskeletal and dentistry reconstruction thanks to its non-biodegradability and good biocompatibility in the body, the poor osseointegration and insufficient mechanical strength have significantly limited its application in the repair of load-bearing bones and surgical operations. In this study, carbon nanotubes (CNT)/calcium silicate (CS)/polyetheretherketone ternary composites were fabricated for the first time. The addition of CS was mainly aimed at improving biological activities and surface hydrophilicity, but it inevitably compromised the mechanical strength of PEEK. CNT can reinforce the composites even when brittle CS was introduced and further upgraded the biocompatibility of PEEK. The CNT/CS/PEEK composites exhibited higher mechanical strengths in tensile and bending tests, 64% and 90% higher than those of brittle CS/PEEK binary composites. Besides, after incorporation of CNT and CS into PEEK, the hydrophilicity, surface roughness and ability to induce apatite-layer deposition were significantly enhanced. More importantly, the adhesion, proliferation, and osteogenic differentiation of mouse embryo osteoblasts were effectively promoted on CNT/CS/PEEK composites. In contrast to PEEK, these composites exhibited a more satisfactory biocompatibility and osteoinductive activity. Overall, these results demonstrate that ternary CNT/CS/PEEK composites have the potential to serve as a feasible substitute to conventional metal alloys in musculoskeletal regeneration and orthopedic implantation.

3D-Printed PEEK/Silicon Nitride Scaffolds with a Triply Periodic Minimal Surface Structure for Spinal Fusion Implants

The issue of spine-related disorders is a global healthcare concern that requires effective solutions to restore normal spine functioning. Spinal fusion implants have become a standard approach for this purpose, making it crucial to develop biomaterials and structures that possess high osteogenic capacities and exhibit mechanical properties and dynamic responses similar to those of the host bone. This study focused on the fabrication of 3D-printed polyether ether ketone/silicon nitride (PEEK/SiN) scaffolds with a triply periodic minimal surface (TPMS) structure, which offers several advantages, such as a large surface area and uniform stress distribution under load. The mechanical properties and dynamic response of PEEK/SiN scaffolds with varying porosities were evaluated through mechanical testing and finite element analysis. The scaffold with 30% porosity exhibited a compressive strength (34.56 ± 1.91 MPa) and elastic modulus (734 ± 64 MPa) similar to those of trabecular bone. In addition, the scaffold demonstrated favorable damping properties. The biological data revealed that incorporating silicon nitride into the PEEK scaffold stimulated osteogenic differentiation. In light of these findings, it can be inferred that PEEK/SiN TPMS scaffolds exhibit significant potential for use in bone tissue engineering and represent a promising option as candidates for spinal fusion implants.

Thermo-Mechanical Characterization of 4D-Printed Biodegradable Shape-Memory Scaffolds Using Four-Axis 3D-Printing System

This study was conducted on different models of biodegradable SMP (shape-memory polymer) scaffolds. A comparison was conducted utilizing a basic FDM (fused deposition modeling)/MEX (material extrusion) printer with a standard printing technique and a novel, modified, four-axis printing method with a PLA (poly lactic acid) polymer as the printing material. This way of making the 4D-printed BVS (biodegradable vascular stent) made it possible to achieve high-quality surfaces due to the difference in printing directions and improved mechanical properties-tensile testing showed a doubling in the elongation at break when using the four-axis-printed specimen compared to the regular printing, of 8.15 mm and 3.92 mm, respectfully. Furthermore, the supports created using this method exhibited a significant level of shape recovery following thermomechanical programming. In order to test the shape-memory effect, after the thermomechanical programming, two approaches were applied: one approach was to heat up the specimen after unloading it inside temperature chamber, and the other was to heat it in a warm bath. Both approaches led to an average recovery of the original height of 99.7%, while the in-chamber recovery time was longer (120 s) than the warm-bath recovery (~3 s) due to the more direct specimen heating in the latter case. This shows that 4D printing using the newly proposed four-axis printing is an effective, promising technique that can be used in the future to make biodegradable structures from SMP.

Feasibility of 3D-Printed Locking Compression Plates with Polyether Ether Ketone (PEEK) in Tibial Comminuted Diaphyseal Fractures

The applicability of a polyether ether ketone locking compression plate (PEEK LCP) fabricated using FDM (fused deposition modeling)-based 3D printing to treat actual patients was studied. Three different tests-bending, axial compression, and axial torsion-were conducted on tibial non-osteoporotic comminuted diaphyseal fracture samples fixed with the commercial titanium alloy LCP and 3D-printed PEEK LCP. Comparing the outcomes of these tests revealed that the commercial titanium alloy LCP underwent plastic deformation in the bending and axial torsion tests, though the LCP did not fail even when an external force greater than the maximum allowable load of the tibia fixture of the LCP was applied. Elastic deformation occurred in the 3D-printed PEEK LCP in the bending and axial torsion tests. However, deformation occurred even under a small external force, and its stiffness was 10% compared to commercial titanium alloy LCP. Thus, 3D-printed PEEK LCP can be applied to the fracture conditions in non-weight-bearing regions. The experimental results reveal detailed insights into the treatment of actual patients by considering the stiffness and high toughness of 3D-printed PEEK LCP.

Analysis of the approach angle to medial orbitotomy that avoids accidental neurotrauma in the mesaticephalic dog skull utilizing 3D computer models and virtual surgical planning

This study was conducted to determine an approach angle to medial orbitotomy that avoids accidental neurotrauma in mesaticephalic dogs. Medical records of dogs with mesaticephalic skulls that were presented to the veterinary medical teaching hospital for head computed tomography (CT) between September 2021 and February 2022 were reviewed. Descriptive data were queried, and CT findings were analyzed. Dogs greater than 20 kg and possessing a disease-free orbitozygomaticomaxillary complex (OZMC) on at least one side of the skull were included in this study. Digital imaging and communications in medicine (DICOM) files of head CT studies were imported into medical modeling software, and the safe approach angle for medial orbitotomy was determined using three-dimensional (3D) computer models and virtual surgical planning (VSP) principles. Angles were measured along the ventral orbital crest (VOC) from the rostral cranial fossa (RCF) to the rostral alar foramen (RAF). The safe approach angle at four points from rostral to caudal along the VOC was measured. The results at each location were reported as mean, median, 95% CI, interquartile ranges, and distribution. The results were statistically different at each location and generally increased from rostral to caudal. The variances between subjects and the differences between locations were large enough to suggest a standard safe approach angle in mesaticephalic dogs cannot be determined and should be measured for each patient. A standardized approach angle to medial orbitotomy is not possible in the mesaticephalic dog. Computer modeling and VSP principles should be implemented as part of the surgical planning process to accurately measure the safe approach angle along the VOC.

Classification, processing, and applications of bioink and 3D bioprinting: A detailed review

With the advancement in 3D bioprinting technology, cell culture methods can design 3D environments which are both, complex and physiologically relevant. The main component in 3D bioprinting, bioink, can be split into various categories depending on the criterion of categorization. Although the choice of bioink and bioprinting process will vary greatly depending on the application, general features such as material properties, biological interaction, gelation, and viscosity are always important to consider. The foundation of 3D bioprinting is the exact layer-by-layer implantation of biological elements, biochemicals, and living cells with the spatial control of the implantation of functional elements onto the biofabricated 3D structure. Three basic strategies underlie the 3D bioprinting process: autonomous self-assembly, micro tissue building blocks, and biomimicry or biomimetics. Tissue engineering can benefit from 3D bioprinting in many ways, but there are still numerous obstacles to overcome before functional tissues can be produced and used in clinical settings. A better comprehension of the physiological characteristics of bioink materials and a higher level of ability to reproduce the intricate biologically mimicked and physiologically relevant 3D structures would be a significant improvement for 3D bioprinting to overcome the limitations.

Influence of Processing Parameters on the Mechanical Properties of Peek Plates by Hot Compression Molding

Thermoplastic components are gaining more and more attention due to their advantages which include high specific strength, high toughness, and low manufacturing costs. Despite the fast development of such materials in engineering applications, the major challenge for the wider use of thermoplastic components is the diverse mechanical properties that are caused by uncertain factors during the molding process. In this paper, the effects of processing parameters on the mechanical properties of PEEK plates by hot compression molding are systematically investigated, including the temperature, pressure, and compression time. It was found that both temperature and time can sensitively change the mechanical properties; however, a pressure larger than 1.5 MPa showed a limited impact on the mechanical behaviors of PEEK plates. The optimal process parameters include a hot compression temperature of 400 °C, a compression time of 30 min, and a pressure of 2.5 MPa.

Green Manufacturing-Oriented Polyetheretherketone Additive Manufacturing and Dry Milling Post-Processing Process Research

The application of polyetheretherketone (PEEK) in additive manufacturing (AM) can effectively reduce material and energy waste in the manufacturing process and help achieve lightweight parts. As a result, AM PEEK is considered an emerging technology in line with green manufacturing concepts. However, 3D-printed PEEK parts often suffer from low mechanical strength and poor surface quality due to the immaturity of the manufacturing process. Therefore, this research investigates the feasibility of improving the surface quality of 3D-printed parts by dry milling post-processing. Meanwhile, the mechanical strength of the parts is improved by optimizing the printing process parameters, and the effects of mechanical strength on milling quality are investigated. The novelty of this research is to design experiments based on the anisotropy of 3D-printed parts. For the first time, the delamination of the milling post-processing surface of 3D-printed PEEK parts is investigated. The results show that the milled surfaces of 3D-printed PEEK parts are prone to delamination problems. The printing direction has a significant effect on the quality of milling post-processing, whereas the milling directions have little effect on milling post-processing quality. The delamination problem can be significantly improved by a side milling process where the specimen is printed at 90° and then milled. Milling surface delamination is caused by the poor mechanical strength (internal bonding) of 3D-printed PEEK parts. By improving the mechanical strength of 3D-printed PEEK parts, the delamination of its milled surfaces can be significantly improved.

The application of 3D bioprinting in urological diseases

Urologic diseases are commonly diagnosed health problems affecting people around the world. More than 26 million people suffer from urologic diseases and the annual expenditure was more than 11 billion US dollars. The urologic cancers, like bladder cancer, prostate cancer and kidney cancer are always the leading causes of death worldwide, which account for approximately 22% and 10% of the new cancer cases and death, respectively. Organ transplantation is one of the major clinical treatments for urological diseases like end-stage renal disease and urethral stricture, albeit strongly limited by the availability of matching donor organs. Tissue engineering has been recognized as a highly promising strategy to solve the problems of organ donor shortage by the fabrication of artificial organs/tissue. This includes the prospective technology of three-dimensional (3D) bioprinting, which has been adapted to various cell types and biomaterials to replicate the heterogeneity of urological organs for the investigation of organ transplantation and disease progression. This review discusses various types of 3D bioprinting methodologies and commonly used biomaterials for urological diseases. The literature shows that advances in this field toward the development of functional urological organs or disease models have progressively increased. Although numerous challenges still need to be tackled, like the technical difficulties of replicating the heterogeneity of urologic organs and the limited biomaterial choices to recapitulate the complicated extracellular matrix components, it has been proved by numerous studies that 3D bioprinting has the potential to fabricate functional urological organs for clinical transplantation and in vitro disease models.

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Outline the advantages and characteristics of 3D printing compared with traditional methods for urological diseases.

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Guide the selection of 3D bioprinting technology and material in urological tissue engineering.

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Discuss the challenges and future perspectives of 3D bioprinting in urological diseases and clinical translation.

Polyetheretherketone subperiosteal implant retaining a maxillary fixed prosthesis: A case series

STATEMENT OF PROBLEM

Patients needing dental rehabilitation of a complete atrophic maxilla would benefit from simplified treatment plans.

PURPOSE

The purpose of this case series was to demonstrate the prosthetic management of 4 edentulous patients with severe maxillary ridge resorption who declined multiple stage surgery and sought a fixed prosthesis in single-stage surgery.

MATERIAL AND METHODS

The patients were provided with completely digital computer-aided designed and computer-aided manufactured (CAD-CAM) polyetheretherketone (PEEK) maxillary subperiosteal frameworks, which were surgically placed in a 1-step procedure. The patients were followed up for 12 months and evaluated for signs of implant rejection, infection, prosthetic fracture or mobility, or implant exposure.

RESULTS

At the 12-month follow-up, all the implants were functionally stable with healthy soft tissue and showed no sign of prosthetic fracture, infection, or pus discharge.

CONCLUSIONS

PEEK subperiosteal implants for maxillary atrophied ridges can be considered a promising treatment option within the limitations of this clinical study with low patient numbers and a short observational time.

The Use of the Three-Dimensional Printed Polyether Ether Ketone Implant in Secondary Craniosynostosis Revision

BACKGROUND

Skull deformities may be seen in patients years after craniosynostosis correction. These deformities cause psychosocial distress in affected patients. In this series, the authors describe the use of patient specific polyether ether ketone (PEEK) implants for correction of skull deformities after cranial vault remodeling for craniosynostosis.

METHODS

A chart review was conducted for 3 revision procedures performed by 1 plastic surgeon in collaboration with 1 neurosurgeon, both affiliated with Northwell Health. Preoperative computed tomography scans were used to design three-dimensional (3D) printed PEEK implants manufactured by KLS Martin. Implants were used to correct frontal and orbital asymmetry and skull deformities in each patient. Outcomes were assessed at 1 week, 1 month, and 3 months post-operation.

RESULTS

Two males and 1 female, ages 13, 17, and 19, underwent revision cranioplasty or orbital rim reconstruction using a custom, single piece 3D printed PEEK implant. All 3 patients underwent cranial vault remodeling in infancy; 1 was treated for coronal craniosynostosis and 2 were treated for metopic craniosynostosis. Revision cranioplasty operative times were 90, 105, and 147 minutes, with estimated blood loss of 45 mL, 75 mL, and 150 mL, respectively. One patient went home on post op day 1 and 2 patients went home on post op day 2. All patients had an immediate improvement in structural integrity and cranial contour, and all patients were pleased with their aesthetic results.

CONCLUSIONS

Custom 3D printed PEEK implants offer a single piece solution in revision cranioplasty surgery to correct skull deformities after cranial vault remodeling for craniosynostosis.

Laser Sintering Approaches for Bone Tissue Engineering

The adoption of additive manufacturing (AM) techniques into the medical space has revolutionised tissue engineering. Depending upon the tissue type, specific AM approaches are capable of closely matching the physical and biological tissue attributes, to guide tissue regeneration. For hard tissue such as bone, powder bed fusion (PBF) techniques have significant potential, as they are capable of fabricating materials that can match the mechanical requirements necessary to maintain bone functionality and support regeneration. This review focuses on the PBF techniques that utilize laser sintering for creating scaffolds for bone tissue engineering (BTE) applications. Optimal scaffold requirements are explained, ranging from material biocompatibility and bioactivity, to generating specific architectures to recapitulate the porosity, interconnectivity, and mechanical properties of native human bone. The main objective of the review is to outline the most common materials processed using PBF in the context of BTE; initially outlining the most common polymers, including polyamide, polycaprolactone, polyethylene, and polyetheretherketone. Subsequent sections investigate the use of metals and ceramics in similar systems for BTE applications. The last section explores how composite materials can be used. Within each material section, the benefits and shortcomings are outlined, including their mechanical and biological performance, as well as associated printing parameters. The framework provided can be applied to the development of new, novel materials or laser-based approaches to ultimately generate bone tissue analogues or for guiding bone regeneration.

The Field Guide to 3D Printing in Optical Microscopy for Life Sciences

The maker movement has reached the optics labs, empowering researchers to create and modify microscope designs and imaging accessories. 3D printing has a disruptive impact on the field, improving accessibility to fabrication technologies in additive manufacturing. This approach is particularly useful for rapid, low-cost prototyping, allowing unprecedented levels of productivity and accessibility. From inexpensive microscopes for education such as the FlyPi to the highly complex robotic microscope OpenFlexure, 3D printing is paving the way for the democratization of technology, promoting collaborative environments between researchers, as 3D designs are easily shared. This holds the unique possibility of extending the open-access concept from knowledge to technology, allowing researchers everywhere to use and extend model structures. Here, it is presented a review of additive manufacturing applications in optical microscopy for life sciences, guiding the user through this new and exciting technology and providing a starting point to anyone willing to employ this versatile and powerful new tool.

Mechanical and wear behaviour of PEEK, PTFE and PU: review and experimental study

Soft polymers such as polyether ether ketone (PEEK), polyurethane (PU) and polytetrafluoroethylene (PTFE) have gained significant research interest in the last few decades owing to their excellent material properties which can be harnessed to meet the demands of various applications such as biomedical implants and accessories, insulation panels to cooking utensils, inner coating material for non-stick cookware etc. In the present study, we provide a comprehensive review on the mechanical and tribological behaviour of PEEK, PU and PTFE polymers. Samples of these materials were also fabricated and the experimentally obtained tensile strength, flexural strength, wear rate and coefficient of frictions were ascertained with values reported in literature. It is highlighted that coefficient of friction of polymers were highly dependent on the surface texture of the polymer’s surface; where an uneven surface exhibited higher coefficient of friction. Perspectives for future progress are also highlighted in this paper.

Success Factors of Additive Manufactured Root Analogue Implants

Dental implantation is an effective method for the treatment of loose teeth, but the threaded dental implants used in the clinic cannot match with the tooth extraction socket. A root analogue implant (RAI) has the congruence shape, which reduces the damage to bone and soft tissue. Additive manufacturing (AM) technologies have the advantages of high precision, flexibility, and easy operation, becoming the main manufacturing method of RAI in basic research. The purpose of this systematic review is to summarize AM technologies used for RAI manufacturing as well as the factors affecting successful implantation. First, it introduces the AM technologies according to different operating principles and summarizes the advantages and disadvantages of each method. Then the influences of materials, structure design, surface characteristics, implant site, and positioning are discussed, providing reference for designers and dentists. Finally, it addresses the gap between basic research and clinical application for additive manufactured RAIs and discusses the current challenges and future research directions for this field.

Thermoplastic Extrusion Additive Manufacturing of High-Performance Carbon Fiber PEEK Lattices

Polyetheretherketone (PEEK) has been the focus of substantial additive manufacturing research for two principal reasons: (a) the mechanical performance approaches that of aluminum at relatively high temperatures for thermoplastics and (b) the potential for qualification in both the aerospace and biomedical industries. Although PEEK provides outstanding strength and thermal stability, printing can be difficult due to the high melting point. Recently, high-temperature soluble support has enabled the printing of lattices and stochastic foams with overhanging features in these high-performance carbon fiber thermoplastics, in which density can be optimized to strike a balance between weight and strength to enhance performance in applications such as custom implants or aerospace structures. Although polymer powder bed fusion has long been capable of the combination of these geometries and materials, material extrusion with high-temperature sacrificial support is dramatically less expensive. This research provides a comprehensive mechanical analysis and CT-scan-based dimensional study of carbon fiber PEEK lattice structures enabled with high-temperature support and including model validation.

Applications of 3D-Printed PEEK via Fused Filament Fabrication: A Systematic Review

Polyether ether ketone (PEEK) is an organic polymer that has excellent mechanical, chemical properties and can be additively manufactured (3D-printed) with ease. The use of 3D-printed PEEK has been growing in many fields. This article systematically reviews the current status of 3D-printed PEEK that has been used in various areas, including medical, chemical, aerospace, and electronics. A search of the use of 3D-printed PEEK articles published until September 2021 in various fields was performed using various databases. After reviewing the articles, and those which matched the inclusion criteria set for this systematic review, we found that the printing of PEEK is mainly performed by fused filament fabrication (FFF) or fused deposition modeling (FDM) printers. Based on the results of this systematic review, it was concluded that PEEK is a versatile material, and 3D-printed PEEK is finding applications in numerous industries. However, most of the applications are still in the research phase. Still, given how the research on PEEK is progressing and its additive manufacturing, it will soon be commercialized for many applications in numerous industries.

Near-field electrospinning polycaprolactone microfibers to mimic arteriole-capillary-venule structure

The ability to create three-dimensional (3D) cell-incorporated constructs for tissue engineering has progressed tremendously. One of the major challenges that limit the clinical applications of tissue engineering is the inability to form sufficient vascularization of capillary vessels in the 3D constructs. The lack of a functional capillary network for supplying nutrients and oxygen leads to poor cell viability. This paper presents the near-field electrospinning (ES) technique to fabricate a branched microfiber structure that mimics the morphology of capillaries. Polycaprolactone solution was electrospun onto a sloped collector that resulted in morphological and geometric variation of the fibers. With proper control over the solution viscosity and the electrospinning voltage, a single fiber was scattered into a branched fiber network and then converged back to a single fiber on the collector. The obtained fibers have a diameter of less than 100 microns at the two ends with coiled and branched fibers of less than 10 microns that mimics the arteriole-capillary-venule structure. The formation of such a structure in the near-field ES strongly depends on the solution viscosity. Low viscosity solutions form beads and discontinuous lines thus cannot be used to achieve the desired structure. The branching of PCL fiber occurs due to an electrohydrodynamic instability. The transition from the straight large fiber to smaller coiled/branched fibers is not instantaneous and stretches over a horizontal region of 1.5 cm. The current work shows the feasibility of electrospinning the stem-branch-stem fibrous structure by adopting a valley-shaped collector with potentials for tissue engineering applications.

Progress of 3D Bioprinting in Organ Manufacturing

Three-dimensional (3D) bioprinting is a family of rapid prototyping technologies, which assemble biomaterials, including cells and bioactive agents, under the control of a computer-aided design model in a layer-by-layer fashion. It has great potential in organ manufacturing areas with the combination of biology, polymers, chemistry, engineering, medicine, and mechanics. At present, 3D bioprinting technologies can be used to successfully print living tissues and organs, including blood vessels, skin, bones, cartilage, kidney, heart, and liver. The unique advantages of 3D bioprinting technologies for organ manufacturing have improved the traditional medical level significantly. In this article, we summarize the latest research progress of polymers in bioartificial organ 3D printing areas. The important characteristics of the printable polymers and the typical 3D bioprinting technologies for several complex bioartificial organs, such as the heart, liver, nerve, and skin, are introduced.

The Surface Characterisation of Fused Filament Fabricated (FFF) 3D Printed PEEK/Hydroxyapatite Composites

Polyetheretherketone (PEEK) is a high-performance thermoplastic polymer which has found increasing application in orthopaedics and has shown a lot of promise for 'made-to-measure' implants via additive manufacturing approaches. However, PEEK is bioinert and needs to undergo surface modification to make it at least osteoconductive to ensure a more rapid, improved, and stable fixation that will last longer in vivo. One approach to solving this issue is to modify PEEK with bioactive agents such as hydroxyapatite (HA). The work reported in this study demonstrates the direct 3D printing of PEEK/HA composites of up to 30 weight percent (wt%) HA using a Fused Filament Fabrication (FFF) approach. The surface characteristics and in vitro properties of the composite materials were investigated. X-ray diffraction revealed the samples to be semi-crystalline in nature, with X-ray Photoelectron Spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry revealing HA materials were available in the uppermost surface of all the 3D printed samples. In vitro testing of the samples at 7 days demonstrated that the PEEK/HA composite surfaces supported the adherence and growth of viable U-2 OS osteoblast like cells. These results demonstrate that FFF can deliver bioactive HA on the surface of PEEK bio-composites in a one-step 3D printing process.

Femtosecond laser-induced periodic grooves and nanopore clusters make a synergistic effect on osteogenic differentiation

Polyether-ether-ketone (PEEK) materials have good biocompatibility, excellent corrosion resistance, chemical stability and an elastic modulus close to that of natural bone. However, due to its biological inertness, PEEK may affect osteogenic differentiation and leads to osseointegration failure, though PEEK is expected to improve osseointegration. In this work, by changing the power of femtosecond laser, micro-grooves are made on the PEEK surface. As observed by scanning electron microscopy, the trench has a periodic structure, the micro shape is neat, and the trench is also covered with nanometer-level pore clusters. In the in vitro culture experiments, through the proliferation experiment of mouse bone marrow mesenchymalstem cells (mBMSCs), cell viability analysis and alkaline phosphatase activity analysis, it is proven that after femtosecond laser treatment of the PEEK surface, the micro-grooves on the surface and the nanopore clusters due to laser energy ablation can produce a synergistic effect, enhancing the osteogenic differentiation ability of cells, and improving the bone integration ability of PEEK materials.

Fabrication of Mg Coating on PEEK and Antibacterial Evaluation for Bone Application

Polyetheretherketone (PEEK) is an alternative biomedical polymer material to traditional metal and ceramic biomaterials. However, as a bioinert material, its wide application in the medical field is seriously restricted due to its lack of bioactivity. In this research, pure Mg was successfully deposited on a PEEK substrate by vapor deposition to improve the antibacterial properties of PEEK implants. The morphology and elemental composition of the coating were characterized by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The higher the deposition temperature, the larger the Mg particle size. The Mg coating possesses a hydrophilic surface and a higher surface free energy that create its good biocompatibility. The Mg coating on a PEEK substrate withstands up to 56 days’ immersion. The antibacterial test showed that the antibacterial rate of coated PEEK is 99%. Mg-coated PEEK demonstrates promising antibacterial properties.

3D Printing of Micro- and Nanoscale Bone Substitutes: A Review on Technical and Translational Perspectives

Recent developments in three-dimensional (3D) printing technology offer immense potential in fabricating scaffolds and implants for various biomedical applications, especially for bone repair and regeneration. As the availability of autologous bone sources and commercial products is limited and surgical methods do not help in complete regeneration, it is necessary to develop alternative approaches for repairing large segmental bone defects. The 3D printing technology can effectively integrate different types of living cells within a 3D construct made up of conventional micro- or nanoscale biomaterials to create an artificial bone graft capable of regenerating the damaged tissues. This article reviews the developments and applications of 3D printing in bone tissue engineering and highlights the numerous conventional biomaterials and nanomaterials that have been used in the production of 3D-printed scaffolds. A comprehensive overview of the 3D printing methods such as stereolithography (SLA), selective laser sintering (SLS), fused deposition modeling (FDM), and ink-jet 3D printing, and their technical and clinical applications in bone repair and regeneration has been provided. The review is expected to be useful for readers to gain an insight into the state-of-the-art of 3D printing of bone substitutes and their translational perspectives.

Thermo-Mechanical Behavior of Poly(ether ether ketone): Experiments and Modeling

Observations are reported on poly(ether ether ketone) (PEEK) in uniaxial tensile tests, relaxation tests and creep tests with various stresses in a wide interval of temperatures ranging from room temperature to 180 °C. Constitutive equations are developed for the thermo-mechanical behavior of PEEK under uniaxial deformation. Adjustable parameters in the governing equations are found by matching the experimental data. Good agreement is demonstrated between the observations and results of numerical simulation. It is shown that the activation energies for the elastoplastic, viscoelastic and viscoelastoplastic responses adopt similar values at temperatures above the glass transition point.

Mechanical, Chemical, and Processing Properties of Specimens Manufactured from Poly-Ether-Ether-Ketone (PEEK) Using 3D Printing

As part of the experiments herein, the mechanical properties of specimens made of poly-ether-ether-ketone (PEEK) material using 3D printing technology were determined. Two populations of specimens were investigated, the first of which contained an amorphous structure, while the other held a crystal structure. The studies also investigated the influence of the print directionality on the mechanical properties obtained. Static tensile, three-point bending, and impact tests were carried out. The results for the effect of the structure type on the tensile properties showed that the modulus of elasticity was approximately 20% higher for the crystal than for the amorphous PEEK form. The Poisson’s ratios were similar, but the ratio was slightly higher for the amorphous samples than the crystalline ones. Furthermore, the studies included a chemical PEEK modification to increase the hydrophilicity. For this purpose, nitrite and hydroxyl groups were introduced into the chain by chemical reactions. The results demonstrate that the modified PEEK specimens had worse thermoplastic properties than the unmodified specimens.

Shape memory polymer (SMP) scaffolds with improved self-fitting properties

"Self-fitting" shape memory polymer (SMP) scaffolds prepared as semi-interpenetrating networks (semi-IPNs) with crosslinked linear-poly(ε-caprolactone)-diacrylate (PCL-DA, M_n∼10 kg mol^-1) and linear-poly(l-lactic acid) (PLLA, M_n∼15 kg mol^-1) [75/25 wt%] exhibited robust mechanical properties and accelerated degradation rates versus a PCL-DA scaffold control. However, their potential to treat irregular craniomaxillofacial (CMF) bone defects is limited by their relatively high fitting temperature (T_fit∼55 °C; related to the T_m of PCL) required for shape recovery (i.e. expansion) and subsequent shape fixation during press fitting of the scaffold, which can be harmful to surrounding tissue. Additionally, the viscosity of the solvent-based precursor solutions, cast over a fused salt template during fabrication, can limit scaffold size. Thus, in this work, analogous semi-IPN SMP scaffolds were formed with a 4-arm star-PCL-tetracryalate (star-PCL-TA) (M_n∼10 kg mol^-1) and star-PLLA (M_n∼15 kg mol^-1). To assess the impact of a star-polymer architecture, four semi-IPN compositions were prepared: linear-PCL-DA/linear-PLLA (L/L), linear-PCL-DA/star-PLLA (L/S), star-PCL-TA/linear-PLLA (S/L) and star-PCL-TA/star-PLLA (S/S). Two PCL controls were also prepared: LPCL (i.e. 100% linear-PCL-DA) and SPCL (i.e. 100% star-PCL-TA). The S/S semi-IPN scaffold exhibited particularly desirable properties. In addition to achieving a lower, tissue-safe T_fit (∼45 °C), it exhibited the fastest rate of degradation which is anticipated to more favourably permit neotissue infiltration. The radial expansion pressure exerted by the S/S semi-IPN scaffold at T_fit was greater than that of LPCL, which is expected to enhance osseointegration and mechanical stability. The intrinsic viscosity of the S/S semi-IPN macromer solution was also reduced such that larger scaffold specimens could be prepared.

Mechanical Properties and Gamma-Ray Shielding Performance of 3D-Printed Poly-Ether-Ether-Ketone/Tungsten Composites

Nuclear energy provides enduring power to space vehicles, but special attention should be paid to radiation shielding during the development and use of nuclear energy systems. In this paper, novel composite materials containing poly-ether-ether-ketone (PEEK) as a substrate and different tungsten contents as a reinforcing agent were developed and tested as shielding for gamma-ray radiation. Shielding test bodies were quickly processed by fused deposition modeling (FDM) 3D printing, and their mechanical, shielding properties of composite materials were evaluated. The results revealed shielding materials with excellent mechanical properties which can further be improved by heat treatment. Under 0.45 MPa load, the heat deflection temperature of PEEK/tungsten (metal) composites was significantly lower than that of PEEK/boron carbide (non-metal) composites. The new shielding materials also demonstrated better shielding of low-energy ¹³⁷Cs than high-energy ⁶⁰Co. The gamma-ray shielding rates of test pieces shielding materials made of the same thickness changed exponentially with the tungsten content present in the composite materials. More tungsten led to a better shielding effect. At the same tungsten content, the gamma-ray shielding effect showed a proportional relationship with the thickness of the shielding test bodies, in which thicker test bodies induced better shielding effects. In sum, the integration of 3D printing in the mechanical design and manufacturing of shielding bodies is an effective and promising way for quick processing when considering diverse rays and complex environments. Lighter shielding bodies, at lower costs, can be achieved by structural design in limited space to maximize the material utilization rate and reduce waste.

FDM-Based 3D Printing of Polymer and Associated Composite: A Review on Mechanical Properties, Defects and Treatments

Fused deposition modelling (FDM) is one of the fastest-growing additive manufacturing methods used in printing fibre-reinforced composites (FRC). The performances of the resulting printed parts are limited compared to those by other manufacturing methods due to their inherent defects. Hence, the effort to develop treatment methods to overcome these drawbacks has accelerated during the past few years. The main focus of this study is to review the impact of those defects on the mechanical performance of FRC and therefore to discuss the available treatment methods to eliminate or minimize them in order to enhance the functional properties of the printed parts. As FRC is a combination of polymer matrix material and continuous or short reinforcing fibres, this review will thoroughly discuss both thermoplastic polymers and FRCs printed via FDM technology, including the effect of printing parameters such as layer thickness, infill pattern, raster angle and fibre orientation. The most common defects on printed parts, in particular, the void formation, surface roughness and poor bonding between fibre and matrix, are explored. An inclusive discussion on the effectiveness of chemical, laser, heat and ultrasound treatments to minimize these drawbacks is provided by this review.

Redesign of Car Body by Reverse Engineering Technique using Steinbichler 3D Scanner and Projet 3D Printer

Product designing requires concept development tool like TRIZ to obtain innovative solutions. In this paper, we have applied available concept development and design tool to develop a relationship between the problem definitions, identified as per customer needs, and the design of the products physical parameters complying with the required specifications. Product development techniques like Reverse Engineering, Surface Modeling, and Rapid Prototyping technologies are employed to improve the existing design of a specific problem. These technologies are used for customization of product and are helpful for research and development purpose. In this paper, the outer body of an existing car is redesigned, and we have further created a prototype with improved aerodynamics and futuristic aesthetics. In this Additive Manufacturing (AM) process, Steinbichler 3D Scanner, Projet 3D printer and associated Scanning and printing software are used, by which redesign and associated development process of a car become easy in lesser time and cost.

A Comparative Analysis of Different Rapid Prototyping Techniques for Making Intricately Shaped Structure

Rapid Prototyping (RP) encompasses a group of technologies being used to produce a scaled model of a physical object using a three-dimensional (3D) computer-aided design (CAD) data. The objective of this paper is to see how the manufacturing productivity of intricately shaped jewelry designs is possible using different RP techniques. In this research, we have used RP techniques for the efficient development and production of an intricately shaped jewelry structure, which otherwise is difficult to produce with existing technologies. The primary purpose of this research is to find the economical and efficient method for three-dimensional printing of artificial jewelry structures. Stereolithography (SLA), fused deposition modeling (FDM) and Projet 3D printing technologies are used for the production of some intricate jewelry. By using RP, artificial jewelry makers can produce 3D printed parts quickly, and customize limited-edition jewelry as it enables the production of beautiful and colorful pieces that previously required large-scale, complex and expensive machinery.