Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

Propulsion system development requires new, more affordable manufacturing techniques and technologies in a constrained budget environment, while future in-space applications will require in-space manufacturing and assembly of parts and systems. Marshall is advancing cuttingedge commercial capabilities in additive and digital manufacturing and applying them to aerospace challenges. The Center is developing the standards by which new manufacturing processes and parts will be tested and qualified. Rapidly evolving digital tools, such as additive manufacturing, are the leading edge of a revolution in the design and manufacture of space systems that enables rapid prototyping and reduces production times. Marshall has unique expertise in leveraging new digital tools, 3D printing, and other advanced manufacturing technologies and applying them to propulsion systems design and other aerospace materials to meet NASA mission and industry needs. Marshall is helping establish the standards and qualifications “from art to part” for the use of these advanced techniques and the parts produced using them in aerospace or elsewhere in the U.S. industrial base.

Additive manufacturing

Additive manufacturing technology for porous metal implant applications and triple minimal surface structures: A review.

2D Layered Materials: Synthesis, Nonlinear Optical Properties, and Device Applications

Environmental monitoring has become essential in order to deal with environmental resources efficiently and safely in the realm of green technology. Environmental monitoring sensors are required for detection of environmental changes in industrial facilities under harsh conditions, (e.g. underground or subsea pipelines) in both the temporal and spatial domains. The utilization of optical fiber sensors is a promising scheme for environmental monitoring of this kind, owing to advantages including resistance to electromagnetic interference, durability under extreme temperatures and pressures, high transmission rate, light weight, small size, and flexibility. In this paper, the optical fiber sensors employed in environmental monitoring are summarized for understanding of their sensing principles and fabrication processes. Numerous specific applications in petroleum engineering, civil engineering, and agricultural engineering are explored, followed by discussion on the potentials of OFS in manufacturing.

A review on optical fiber sensors for environmental monitoring

In recent years, additive manufacturing, also known as three-dimensional (3D) printing, has emerged as an environmentally friendly green manufacturing technology which brings great benefits, such as energy saving, less material consumption, and efficient production. These advantages are attributed to the successive material deposition at designated target areas by delivering the energy on it. In this regard, lasers are the most effective energy source in additive manufacturing since the laser beam can transfer a large amount of energy into micro-scale focal region instantaneously to solidify or cure materials in air, therefore enabling high-precision and high-throughput manufacturing for a wide range of materials. In this paper, we introduce laser-based additive manufacturing methods and review the types of lasers widely used in 3D printing machines. Important laser parameters relevant to additive manufacturing will be analyzed and general guidelines for selecting suitable lasers for additive manufacturing will be provided. Discussion on future prospects of laser technologies for additive manufacturing will be finally covered.

Lasers in additive manufacturing: A review

Stretchable energy storage devices are prerequisites for the realization of autonomous elastomeric electronics. Microsupercapacitors (MSCs) are promising candidates for this purpose due to their high power and energy densities, potential for miniaturization, and feasibility of embedding in circuits; however, efforts to realize stretchable MSCs have mostly relied on strain-accommodating materials and have suffered from limited stretchability, low conductivity, or complicated patterning processes. Here, we designed and fabricated a stretchable MSC based on reduced-graphene-oxide/Au heterostructures patterned by facile and versatile direct laser patterning. An interconnected and stable 3D network composed of vertically oriented heterostructures was realized by high-repetition-rate femtosecond laser pulses. Upon transferring to polydimethylsiloxane (PDMS), the 3D network achieved a high conductivity of ~105 S m−1, and the conductivity could be maintained at ~104 S m−1 even at 50% strain. A fully laser-patterned stretchable electronics system was integrated with embedded MSCs, which will find applications in soft robotics, wearable electronics, and the Internet of Things. By transforming flat graphene oxide films into vertically oriented sheets, researchers have constructed an energy storage device that may power wearable electronics. Graphene oxide’s ability to quickly store and release charge from its surface makes it attractive for supercapacitors, which recharge significantly faster than conventional batteries. Young-Jin Kim and Pooi See Lee from the Nanyang Technological University in Singapore and colleagues have now used ultrafast lasers to controllably heat graphene oxide into a spiky 3D network that accommodates large amounts of mechanical strain. Following deposition of a gold coating and subsequent transfer to an elastomeric substrate, the team’s supercapacitor retained its high energy output even after being rolled, bent, twisted, and crumpled hundreds of times. The laser-based fabrication enabled production of customized patterns, such as wavy electrode ‘fingers’ that can attach to curved surfaces. An intrinsically stretchable and highly conductive graphene electrode based on vertically oriented graphene/Au bilayer flakes are successfully fabricated by a direct-laser-patterning at a very high-repetition rate and fast scanning speed of laser with a femtosecond pulse, allowing micro-supercapacitors to be integrated with the complete soft electronics systems that can be standalone and be customized by user’s circuit designs.

Fully laser-patterned stretchable microsupercapacitors integrated with soft electronic circuit components

In the paper, a passively mode-locked erbium-doped fiber ring laser in the long-wavelength band (L-band) is presented by using a single-wall nanotube saturable absorber (SWNT-SA). The optical properties of the SWNT-SA are compared with those in the C-band in view of the absorbance spectrum and the power-dependent transmittance of the SWNT-SA film. The effects of the net cavity dispersion and the length of the erbium-doped fiber (EDF) on L-band stretched pulse generation are discussed. The designed stretched-pulse L-band laser has a net dispersion of 0.017-ps2 and generates ultrashort (110 fs), broad-spectrum (41 nm) pulses with a signal-to-noise ratio over 70 dB.

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Ultrashort stretched-pulse L-band laser using carbon-nanotube saturable absorber

In this research, additively manufacturing a functionally graded material (FGM) with a compositional range of Ni-based Inconel superalloy (Inconel 718) and Fe-based stainless steel (SS 316L) via directed energy deposition (DED) was examined. The microstructural transformation, defect behavior, and Vickers hardness of the material were each determined as a function of the discrete chemical composition of the FGM varied in steps of 10 wt% of the two materials across its length. In particular, for the specific compositions of 30 wt% Inconel 718/70 wt% SS 316L and 20 wt% Inconel 718/80 wt% SS 316L, critical pores and cracks (defects) initiated by ceramic oxides occurred due to the presence of intermetallic and carbide compounds. In addition, the results of electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) analyses of the FGM demonstrate that the thermal and residual stresses due to constitutional supercooling and columnar-to-equiaxial transition (CET) became concentrated at the grain boundaries, thereby further contributing to the formation of the defects. The measured Vickers hardness was inevitably found to be minimal near the defective compositional range regardless of laser parameter optimization due to the reduced generation of segregants in the inter-dendritic regions and the increased formation of precipitates at the grain boundaries. The results of microstructural and mechanical analyses indicate that deliberate and strategic removal of the defective compositional range helped obtain a robust FGM composed of Inconel 718 and SS 316L without noticeable defects.

Selective compositional range exclusion via directed energy deposition to produce a defect-free Inconel 718/SS 316L functionally graded material

The precise shape of a shift block support for the turbine blade of a hovercraft was additively manufactured using 17–4 precipitation-hardened stainless steel (STS 630) powder through laser powder ...

Hyub Lee

Papers

Lasers in additive manufacturing: A review

Fully laser-patterned stretchable microsupercapacitors integrated with soft electronic circuit components

Ultrashort stretched-pulse L-band laser using carbon-nanotube saturable absorber

Selective compositional range exclusion via directed energy deposition to produce a defect-free Inconel 718/SS 316L functionally graded material

Additive manufacturing of a shift block via laser powder bed fusion: the simultaneous utilisation of optimised topology and a lattice structure