Porous metal implants: processing, properties, and challenges

Abstract

Porous and functionally graded materials have seen extensive applications in modern biomedical devices – allowing for improved site-specific performance; their appreciable mechanical, corrosive, and biocompatible properties are highly sought after for lightweight and high-strength load-bearing orthopedic and dental implants. Examples of such porous materials are metals, ceramics, and polymers. Although easy to manufacture and lightweight, porous polymers do not inherently exhibit the necessary mechanical strength needed for hard tissue repair or replacement. Alternatively, porous ceramics are brittle and do not possess the required fatigue resistance. On the other hand, porous biocompatible metals have shown tailorable strength, fatigue resistance, and toughness. Thereby, a significant interest in investigating the manufacturing issues of porous metals has taken place in recent years. Research has shown that once the advantages of porous metallic structures in the orthopedic implant industry have been realized, their biological and biomechanical compatibility – with the host bone – has been followed up with extensive research. Various manufacturing methods for porous or functionally graded metals are discussed and compared in this review, specifically, how the manufacturing process influences microstructure, graded composition, porosity, biocompatibility, and mechanical properties. Most of the studies discussed in this review are related to porous structures for bone implant applications; however, the understanding of these investigations may also be extended to other devices beyond the biomedical field.

Additively Manufactured SiO2 and Cu-Added Ti Implants for Synergistic Enhancement of Bone Formation and Antibacterial Efficacy

“…12 Strategies to overcome Ti's bioinertness have focused on modifying Ti's surface porosities. 13,14 These surface porosities act as anchors for tissue attachment and growth from the host bone and promote nutrient exchange, enhancing tissue growth, vascularization, and adhesion to the implant surface. Whereas processing such porous surface implants via conventional methods is difficult, additive manufacturing (AM) has overcome this roadblock.…”

“…Early stage osseointegration essentially governs the implant’s longevity and stability, which is governed by the implant’s surface properties . Strategies to overcome Ti’s bioinertness have focused on modifying Ti’s surface porosities. , These surface porosities act as anchors for tissue attachment and growth from the host bone and promote nutrient exchange, enhancing tissue growth, vascularization, and adhesion to the implant surface. Whereas processing such porous surface implants via conventional methods is difficult, additive manufacturing (AM) has overcome this roadblock. , AM’s layer-wise processing nature enables fabricating implants with designed porosities with strong metallurgical bonding with the dense implant .…”

“…At the same time, AM aids in producing implants mimicking the patient’s bone shape and size, reducing potential post-surgical complications . Over a decade after realizing its potential, AM is heavily employed in metal implant manufacturing worldwide. ,− …”

Review on laser directed energy deposited aluminum alloys

“…With the demand to be lightweight, the proportion of Al alloy applied in aerospace structural parts and automotive fields is increasing continuously due to its excellent strength-ductility synergy, wear resistance, and thermodynamic stability [10][11][12]. In recent years, many high-strength Al alloys dedicated to AM have been developed and put into practical application [13][14][15]. For instance, Scalmalloy ® , developed by Airbus, has been employed to fabricate a bionic partition in the A320 aircraft cabin (figure 1(a)) [16].…”

A novel approach of jet polishing for interior surface of small-grooved components using three developed setups

“…The side-surface quality is controlled via contour laser power, scanning speed, and layer thickness. Under optimal process factors, the linear surface roughness (Ra) is typically in the range of 5-15 µm [10,11,[21][22][23]. To date, most studies have focused on the singletrack or regularly shaped samples.…”