Porous copper (Cu), with varying porosities, has been made using carbamide as a space holder through the powder metallurgy route. Two shapes of carbamide particles were used, (i) needlelike and (ii) spherical, in order to investigate the effect of the space holder shape on the pore structure and mechanical properties of porous Cu. The compressive deformation behavior of porous Cu was studied under a compression test. The pores\' structural characteristics and mechanical properties of the porous Cu varied significantly with the shape of the space holder. Although the effect of the space holder shape on the porosity was not regular, the effect on the mechanical properties was regular. The stress increased monotonically with the increase in the strain, and strain hardening occurred at the plastic yield stage. The elastic modulus and yield strength followed the power law, with the relative density irrespective of the space holder shape. The empirical constants associated with different empirically developed power law relations were different, according to the shape of space holder. A quantitative relationship between the elastic modulus and yield strength and the spacer content was obtained to control the mechanical properties of the present porous Cu or other porous metals and metal foams using the well-known space holder method.

BACKGROUND: Nonfusion technologies, such as motion-preservation devices, have begun a new era of treatment options in spine surgery. Motion-preservation approaches mainly include total disc replacement for anterior cervical discectomy and fusion. However, for multisegment fusion, such as anterior cervical corpectomy and fusion, the options are more limited. Therefore, we designed a novel 3D-printed motion-preservation artificial cervical corpectomy construct (ACCC) for multisegment fusion. The aim of this study was to explore the feasibility of ACCC in a goat model.
METHODS: Goats were treated with anterior C3 corpectomy and ACCC implantation and randomly divided into two groups evaluated at 3 or 6 months. Radiography, 3D CT reconstruction and MRI evaluations were performed. Biocompatibility was evaluated using micro-CT and histology.
RESULTS: Postoperatively, all goats were in good condition, with free neck movement. Implant positioning was optimal. The relationship between facet joints was stable. The range of motion of the C2-C4 segments during flexion-extension at 3 and 6 months postoperatively was 7.8° and 7.3°, respectively. The implants were wrapped by new bone tissue, which had grown into the porous structure. Cartilage tissue, ossification centres, new blood vessels, and bone mineralization were observed at the porous metal vertebrae-bone interface and in the metal pores.
CONCLUSIONS: The ACCC provided stabilization while preserving the motion of the functional spinal unit and promoting bone regeneration and vascularization. In this study, the ACCC was used for anterior cervical corpectomy and fusion (ACCF) in a goat model. We hope that this study will propel further research of motion-preservation devices.

Closed-cell aluminum foams have many excellent properties, such as low density, high specific strength, great energy absorption, good sound absorption, electromagnetic shielding, heat and flame insulation, etc. As a new kind of material, closed-cell aluminum foams have been used in lightweight structures, traffic collision protections, sound absorption walls, building decorations, and many other places. In this paper, the recent progress of closed-cell aluminum foams, on fabrication techniques, including the melt foaming method, gas injection foaming method, and powder metallurgy foaming method, and on processing techniques, including powder metallurgy foaming process, two-step foaming process, cast foaming process, gas injection foaming process, mold pressing process, and integral foaming process, are summarized. Properties and applications of closed-cell aluminum foams are discussed based on the mechanical properties and physical properties separately. Special focuses are made on the newly developed cast-forming process for complex 3D parts and the improvement of mechanical properties by the development of small pore size foam fabrication and modification of cell wall microstructures.

Titanium, being the ultimate choice of metallic material for implant applications, its bio-inertness causes delayed bone-tissue integration at the implant site and prevents expedited healing for the patient. This can cause a severe issue for patients with immunocompromised bone health. Infections at the implant site are another concern; titanium does not offer inherent antimicrobial properties. Current strategies addressing the issues above include using cemented implants as a coating on Ti6Al4V bulk material for orthopedic applications. Roadblock arises with coating failure due to weak interfacial bond at the Ti-cement interface, resulting in revision surgeries. We have added osteogenic MgO and antibacterial Cu to CpTi and processed them using metal additive manufacturing (AM) to address these issues. Mg, an essential trace element in the body, has been proven to enhance osseointegration in vivo. Cu has been popular for its bactericidal capabilities. With 1 wt.% of MgO addition in the CpTi matrix, we have observed a four-fold increase in the mineralized bone formation at the bone-implant interface in vivo. The presence of 3 wt.% of Cu showed no cytotoxicity markers, and adding Cu to CpTi-MgO chemical makeup showed similar in vivo performance to CpTi-MgO. In vitro bacterial studies with gram-positive Staphylococcus aureus bacteria showed 81% bacterial efficiency displayed by CpTi-MgO-Cu at the end of 72 h of culture. Our findings highlight the synergistic benefits of CpTi-MgO-Cu, which exhibit superior early-stage osseointegration and antimicrobial capabilities.

During the last 20 years, tantalum has known ever wider applications for the production of endosseous implantable devices in the orthopedic and dental fields. Its excellent performances are due to its capacity to stimulate new bone formation, thus improving implant integration and stable fixation. Tantalum\'s mechanical features can be mainly adjusted by controlling its porosity thanks to a number of versatile fabrication techniques, which allow obtaining an elastic modulus similar to that of bone tissue, thus limiting the stress-shielding effect. The present paper aims at reviewing the characteristics of tantalum as a solid and porous (trabecular) metal, with specific regard to biocompatibility and bioactivity. Principal fabrication methods and major applications are described. Moreover, the osteogenic features of porous tantalum are presented to testify its regenerative potential. It can be concluded that tantalum, especially as a porous metal, clearly possesses many advantageous characteristics for endosseous applications but it presently lacks the consolidated clinical experience of other metals such as titanium.

The preparation of the wavelength-scale micropores on metallic surfaces is limited by the high opacity of metal. At present, most micropores reported in the literature are more than 20 µm in diameter, which is not only large in size, but renders them inefficient for processing so that it is difficult to meet the needs of some special fields, such as aerospace, biotechnology, and so on. In this paper, the rapid laser fabrications of the wavelength-scale micropores on various metallic surfaces are achieved through femtosecond MHz burst Bessel beam ablation. Taking advantage of the long-depth focal field of the Bessel beam, high-density micropores with a diameter of 1.3 µm and a depth of 10.5 µm are prepared on metal by MHz burst accumulation; in addition, the rapid fabrication of 2000 micropores can be achieved in 1 s. The guidelines and experimental results illustrate that the formations of the wavelength-scale porous structures are the result of the co-action of the laser-induced periodic surface structure (LIPSS) effect and Bessel beam interference. Porous metal can be used to store lubricant and form a lubricating layer on the metallic surface, thus endowing the metal resistance to various liquids\' adhesion. The microporous formation process on metal provides a new physical insight for the rapid preparation of wavelength-scale metallic micropores, and promotes the application of porous metal in the fields of catalysis, gas adsorption, structural templates, and bio-transportation fields.

Two-to 6-year results of reconstruction of severe bone defects in revision total knee arthroplasty (TKA) with highly porous tantalum cones have been encouraging, but 10-year follow-up is lacking. The purpose of this study was to determine the minimum 10-year results of tantalum cones in revision TKA.
From 2005 to 2010, 30 consecutive patients (30 knees) underwent revision TKA with the use of cones. All patients were followed clinically and radiographically for a minimum of 10 years. A total of 42 cones (25 tibial and 17 femoral) were used to reconstruct massive bone defects classified as Anderson Orthopaedic Research Institute Types 2A (10), 2B (12), and 3 (19). The mean age of the patients was 73 years (range, 55 to 84) at the time of revision. The indication for the revision included aseptic loosening (15 patients) and second-stage reimplantation for deep infection (15 patients). Six patients were lost to follow-up.
In total, 6 cones had to be revised. Minimum 10-year cone survivorship for any reason was 81% (25 of 31 cones). With cone revision for aseptic loosening as the end point, survivorship was 96% (30 of 31). No evidence of loosening or migration of any implant was noted on the most recent radiographs.
Metaphyseal fixation with tantalum cones in revision TKA demonstrated excellent survivorship and fixation at a minimum follow-up of 10 years. This type of metaphyseal reconstruction can be a durable option for revision TKA in patients who have massive bone defects.

Alkali metals (i.e., Li, Na, and K) are promising anode materials for next-generation high-energy-density batteries due to their superior theoretical specific capacities and low electrochemical potentials. However, the uneven current and ion distribution on the anode surface probably induces undesirable dendrite growth, which leads to significant safety hazards and severely hinders the commercialization of alkali metal anodes. A smart and versatile strategy that can accommodate alkali metals into porous metal current collectors (PMCCs) has been well established to resolve the issues as well as to promote the practical applications of alkali metal anodes. Moreover, the proposal of PMCCs can meet the requirement of the dendrite-free battery fabrication industry, while the electrode material loading exactly needs the metal current collector component as well. Here, a systematic survey on advanced PMCCs for Li, Na, and K alkali metal anodes is presented, including their development timeline, categories, fabrication methods, and working mechanism. On this basis, some significant methodology advances to control pore structure, surface area, surface wettability, and mechanical properties are systematically summarized. Further, the existing issues and the development prospects of PMCCs to improve anode performance in alkali metal batteries are discussed.

Photovoltaic (PV) panels are one of the most important solar energy sources used to convert the sun\'s radiation falling on them into electrical power directly. Many factors affect the functioning of photovoltaic panels, including external factors and internal factors. External factors such as wind speed, incident radiation rate, ambient temperature, and dust accumulation on the PV cannot be controlled. The internal factors can be controlled, such as PV surface temperature. Some of the radiation falling on the surface of the PV cell turns into electricity, while the remainder of incident radiation is absorbed inside the PV cell. This, in turn, elevates its surface temperature. Undesirably, the higher panel temperature, the lower conversion performance, and lesser reliability over the long term occur. Hence, many cooling systems have been designed and investigated, aiming to effectively avoid the excessive temperature rise and enhance their efficiency. Many cooling methods are used to cool solar cells, such as passive cooling, active cooling, cooling with phase change materials (PCMs), and cooling with PCM with other additives such as nanoparticles or porous metal. In this work, the common methods utilized for cooling PV panels are reviewed and analyzed, focusing on the last methods, and summarizing all the researches that dealt with cooling PV solar cells with PCM and porous structures.

Future electronic packaging technology requires semiconductor chips having a larger size and higher power for advanced applications, e.g., new energy conversion systems, electric vehicles, and data center servers, yet traditional thermal interface materials (TIMs) with a high thermal conductivity are generally stiff materials with weak joints, which cause the accumulated thermal stress to concentrate at the chip corners, leading to cracking and popcorn problems. To address such a critical challenge, herein for the first time we report a low-cost and high-performance porous copper (Cu)-indium (In) laminar structure as TIM, which can provide a superior thermal conductivity (50 W m-1 K-1) comparable to indium, yet the Young\'s modulus (1.0 GPa) is an order of magnitude lower than indium, which is a state-of-the-art value. Additionally, the In-based intermetallic compound (IMC) joints enable more robust mechanical interconnection above the melting point of pure indium, providing better high-temperature performance. The discontinuous IMCs spread the global interfacial thermal stress into numerous isolated local areas, ensuring a reliable joint to resist thermal-mechanical fatigue. In the silicon-TIM-copper package testing vehicles with a large die size (1 × 1 square inch), this structure shows excellent thermal management ability and superior reliability, compared with classical indium and classic commercial silver pastes.