Mechanical meta-materials

The emerging concept of mechanical meta-materials has received increasing attention during the last few years partially due to the advances in additive manufacturing techniques that have enabled fabricating materials with arbitrarily complex micro/nano-architectures. The rationally designed micro/nano-architecture of mechanical meta-materials gives rise to unprecedented or rare mechanical properties that could be exploited to create advanced materials with novel functionalities. This paper presents an overview of the recent developments in the area of mechanical meta-materials. Extremal materials that are extremely stiff in certain modes of deformation, while extremely soft in other modes of deformation are discussed first. Penta-mode, dilational, and other auxetic meta-materials are all discussed within the context of extremal materials. Negative meta-materials are presented next with special focus on materials with negative compressibility and negative stiffness. Ultra-property meta-materials are the topic of the following section that covers ultra-light, ultra-stiff, and ultra-tough materials. Finally, the emerging areas of research in mechanical meta-materials including active, adaptive, programmable, and origami-based mechanical meta-materials are reviewed. This paper concludes with some suggestions for future research.Gold For Gold voucher Au-036289Biomaterials & Tissue Biomechanic

Design for additive bio-manufacturing: From patient-specific medical devices to rationally designed meta-biomaterials

Recent advances in additive manufacturing (AM) techniques in terms of accuracy, reliability, the range of processable materials, and commercial availability have made them promising candidates for production of functional parts including those used in the biomedical industry. The complexity-for-free feature offered by AM means that very complex designs become feasible to manufacture, while batch-size-indifference enables fabrication of fully patient-specific medical devices. Design for AM (DfAM) approaches aim to fully utilize those features for development of medical devices with substantially enhanced performance and biomaterials with unprecedented combinations of favorable properties that originate from complex geometrical designs at the micro-scale. This paper reviews the most important approaches in DfAM particularly those applicable to additive bio-manufacturing including image-based design pipelines, parametric and non-parametric designs, metamaterials, rational and computationally enabled design, topology optimization, and bio-inspired design. Areas with limited research have been identified and suggestions have been made for future research. The paper concludes with a brief discussion on the practical aspects of DfAM and the potential of combining AM with subtractive and formative manufacturing processes in so-called hybrid manufacturing processes.Biomaterials & Tissue Biomechanic

The evolution of biomaterials research

Amir A. Zadpoor discusses how the field of biomaterials has changed since the turn of the century.Biomechanical EngineeringMechanical, Maritime and Materials Engineerin

Additively manufactured porous biomaterials and implants

Biomaterials & Tissue Biomechanic

Current trends in metallic orthopedic biomaterials: From additive manufacturing to bio-functionalization, infection prevention, and beyond

There has been a growing interest in metallic biomaterials during the last five years, as recent developments in additive manufacturing (=3D printing), surface bio-functionalization techniques, infection prevention strategies, biodegradable metallic biomaterials, and composite biomaterials have provided many possibilities to develop biomaterials and medical devices with unprecedented combinations of favorable properties and advanced functionalities. Moreover, development of biomaterials is no longer separated from the other branches of biomedical engineering, particularly tissue biomechanics, musculoskeletal dynamics, and image processing aspects of skeletal radiology. In this editorial, I will discuss all the above-mentioned topics, as they constitute some of the most important trends of research on metallic biomaterials. This editorial will, therefore, serve as a foreword to the papers appearing in a special issue covering the current trends in metallic biomaterials.Biomaterials & Tissue Biomechanic

Biomaterials and tissue biomechanics: A match made in heaven?

Biomaterials and tissue biomechanics have been traditionally separate areas of research with relatively little overlap in terms of methodological approaches. Recent advances in both fields on the one hand and developments in fabrication techniques and design approaches on the other have prepared the ground for joint research efforts by both communities. Additive manufacturing and rational design are examples of the revolutionary fabrication techniques and design methodologies that could facilitate more intimate collaboration between biomaterial scientists and biomechanists. This editorial article highlights the various ways in which the research on tissue biomechanics and biomaterials are related to each other and could benefit from each other’s results and methodologies.Biomaterials & Tissue Biomechanic

Frontiers of additively manufactured metallic materials

Additive manufacturing (AM) (=3D printing) has emerged during the last few years as a powerful technological platform for fabrication of functional parts with unique complex geometries and superior functionalities that are next to impossible to achieve using conventional manufacturing techniques. Due to their importance in industrial applications and the maturity of the applicable AM techniques, metallic materials are at the forefront of the developments in AM. In this editorial, which has been written as a preamble to the special issue "Perspectives on Additively Manufactured Metallic Materials", I will highlight some of the frontiers of research on AM of metallic materials to help readers better understand the cutting edge of research in this area. Some of these topics are addressed in the articles appearing in this special issue, while others constitute worthy avenues for future research.Biomaterials & Tissue Biomechanic

Meta-biomaterials

Meta-biomaterials are designer biomaterials with unusual and even unprecedented properties that primarily originate from their geometrical designs at different (usually smaller) length scales. This concept has been primarily used in the context of orthopedic biomaterials with the ultimate aim of improving the bone tissue regeneration performance of implants and decreasing the risk of implant-associated infections. In this paper, we review the ways though which geometrical design at the macro-, micro-, and nanoscales combined with advanced additive manufacturing techniques (3D printing) could be used to create the unusual properties of meta-biomaterials. Due to their intended applications in orthopedics, metallic and hard polymeric biomaterials have received the most attention in the literature. However, the reviewed concepts are, at least in principle, applicable to a wide range of biomaterials including ceramics and soft polymers. At the macroscale, we discuss the concepts of patient-specific implants, deployable meta-implants, and shape-morphing implants. At the microscale, we introduce the concept of multi-physics meta-biomaterials while also covering the applications of auxetic meta-biomaterials for improving the longevity of orthopedic implants. At the nanoscale, the different aspects of the geometrical design of surface nanopatterns that simultaneously stimulate the osteogenic differentiation of stem cells and kill bacteria are presented. The concept of origami-based meta-biomaterials and the applications of self-folding mechanisms in the fabrication of meta-biomaterials are addressed next. We conclude with a discussion on the available evidence regarding the superior performance of meta-biomaterials and suggest some possible avenues for future research.Biomaterials & Tissue Biomechanic

Etiology of Femoroacetabular Impingement in Athletes: A Review of Recent Findings

The relationship between hip deformities and osteoarthritis has recently received a lot of attention. In particular, it has been shown that both osteoarthritis and its precursors, such as the hip deformities that lead to femoroacetabular impingement (FAI), are more prevalent in elite athletes compared with the general population. However, the etiology of the above-mentioned types of hip deformity is not currently well understood. Many recent studies have attempted to shed light on the etiology of this disease. In this article, the main clinical, radiological, mechanobiological, and biomechanical findings of relevance to understanding the etiology of hip deformities leading to FAI are reviewed. Based on these findings, a consistent biomechanical theory explaining the development of hip deformities in athletes is then presented. According to the presented theory, the repetitive, impact-like musculoskeletal loads that athletes experience, particularly when they undertake extreme ranges of hip motion, cause the development of hip deformities. According to this theory, these musculoskeletal loads trigger abnormal growth patterns during the years of skeletal development and cause the formation of hip deformities. A number of hypotheses based on the proposed theory are then formulated that could be tested in future studies to ascertain whether the proposed theory could sufficiently describe the development of hip deformities in athletes.Biomechanical EngineeringMechanical, Maritime and Materials Engineerin

Additively manufactured porous metallic biomaterials

Additively manufactured (AM, =3D printed) porous metallic biomaterials with topologically ordered unit cells have created a lot of excitement and are currently receiving a lot of attention given their great potential for improving bone tissue regeneration and preventing implant-associated infections. This paper presents an overview of the various aspects of design, manufacturing, and bio-functionalization of these materials from a "designer material" viewpoint and discusses how rational design principles could be used to topologically design the underlying lattice structures in such a way that the desired properties including mechanical properties, fatigue behavior, mass transport properties (e.g., permeability, diffusivity), surface area, and geometrical features affecting the rate of tissue regeneration (e.g., surface curvature) are simultaneously optimized. We discuss the different types of topological design including those based on beam-based unit cells, sheet-based unit cells (e.g., triply periodic minimal surfaces), and functional gradients. We also highlight the use of topology optimization algorithms for the rational design of AM porous biomaterials. The topology-property relationships for all of the above-mentioned types of properties are presented as well followed by a discussion of the applicable AM techniques and the pros and cons of different types of base materials (i.e., bioinert and biodegradable metals). Finally, we discuss how the huge (internal) surfaces of AM porous biomaterials and their pore space could be used respectively for surface bio-functionalization and accommodation of drug delivery vehicles so as to enhance their bone tissue regeneration performance and minimize the risk of implant-associated infections. We conclude with a general discussion and by suggesting some possible areas for future research.Biomaterials & Tissue Biomechanic