Abstract:Selective laser sintering of nanoparticles has received much attention recently as it enables rapid fabrication of functional layers including metal conductors and metal-oxide electrodes on heat-sensitive polymer substrate in ambient conditions. Photothermal reactions induced by lasers rapidly increase the local temperature of the target nanoparticle in a highly selective manner, and subsequent sintering steps including melting and coalescence between nanoparticles occur to fabricate interconnected sintered fi… Show more
“…Different AM technologies use lasers as a source to process materials and fabricate complex 3D printed components. Such processes include SLS [22,67,68], SLM [22,69], direct metal deposition (DMD) [22], direct writing (DW) [70] and stereolithography (SLA) [69,70]. All of these, except for the SLA process, are executable with metallic materials [25].…”
Section: Lasers In Metal Additive Manufacturingmentioning
The ever-growing interest in additive manufacturing (AM) is evidenced by its extensive utilisation to manufacture a broad spectrum of products across a range of industries such as defence, medical, aerospace, automotive, and electronics. Today, most laser-based AM is carried out by employing continuous-wave (CW) and long-pulsed lasers. The CW and long-pulsed lasers have the downside in that the thermal energy imparted by the laser diffuses around the irradiated spot and often leads to the creation of heat-affected zones (HAZs). Heat-affected zones may degrade the material strength by producing micro-cracks, porous structures and residual stresses. To address these issues, currently, attempts are being made to employ ultrafast laser sources, such as femtosecond (fs) lasers, in AM processes. Femtosecond lasers with pulse durations in the order of 10−15 s limit the destructive laser–material interaction and, thus, minimise the probability of the HAZs. This review summarises the current advancements in the field of femtosecond laser-based AM of metals and alloys. It also reports on the comparison of CW laser, nanosecond (ns)/picosecond (ps) lasers with fs laser-based AM in the context of heat-affected zones, substrate damage, microstructural changes and thermomechanical properties. To shed light on the principal mechanisms ruling the manufacturing processes, numerical predictions are discussed and compared with the experimental results. To the best of the authors’ knowledge, this review is the first of its kind to encompass the current status, challenges and opportunities of employing fs lasers in additive manufacturing.
“…Different AM technologies use lasers as a source to process materials and fabricate complex 3D printed components. Such processes include SLS [22,67,68], SLM [22,69], direct metal deposition (DMD) [22], direct writing (DW) [70] and stereolithography (SLA) [69,70]. All of these, except for the SLA process, are executable with metallic materials [25].…”
Section: Lasers In Metal Additive Manufacturingmentioning
The ever-growing interest in additive manufacturing (AM) is evidenced by its extensive utilisation to manufacture a broad spectrum of products across a range of industries such as defence, medical, aerospace, automotive, and electronics. Today, most laser-based AM is carried out by employing continuous-wave (CW) and long-pulsed lasers. The CW and long-pulsed lasers have the downside in that the thermal energy imparted by the laser diffuses around the irradiated spot and often leads to the creation of heat-affected zones (HAZs). Heat-affected zones may degrade the material strength by producing micro-cracks, porous structures and residual stresses. To address these issues, currently, attempts are being made to employ ultrafast laser sources, such as femtosecond (fs) lasers, in AM processes. Femtosecond lasers with pulse durations in the order of 10−15 s limit the destructive laser–material interaction and, thus, minimise the probability of the HAZs. This review summarises the current advancements in the field of femtosecond laser-based AM of metals and alloys. It also reports on the comparison of CW laser, nanosecond (ns)/picosecond (ps) lasers with fs laser-based AM in the context of heat-affected zones, substrate damage, microstructural changes and thermomechanical properties. To shed light on the principal mechanisms ruling the manufacturing processes, numerical predictions are discussed and compared with the experimental results. To the best of the authors’ knowledge, this review is the first of its kind to encompass the current status, challenges and opportunities of employing fs lasers in additive manufacturing.
“…SLS is a commonly used technique in AM to sinter/melt powdered materials using high power lasers to create 3D objects [42][43][44]. However, in this work, SLS was used to create conductive patterns on Ag-BST insulating films.…”
Section: Sls Of Ag-bst Blended Inkmentioning
confidence: 99%
“…Although investigations of the dielectric properties of Ag-BST are not within the scope of this work, we anticipate that the tunable, low-loss dielectric properties of BST will be used to fabricate selective laser-sintered RF devices. This Ag-BST composite material is converted from an insulating phase to a conductive phase by the selective laser sintering (SLS) of silver nanoparticles [42][43][44][45][46]. Moreover, this Ag-BST composite nanoparticle ink can be used as a conventional resistive ink for AM and the ink was tested for dispensing printers.…”
Here, we report a previously un-reported printed electronics/additive manufacturing (AM) approach to fabricate conductive/resistive features on novel insulating silver–barium strontium titanate (Ag–BST) printed composite films. Ag–BST composite functional ink was formulated by blending a conductive Ag nanoparticle ink and an insulating BST nanoparticle ink. The blending ratio of Ag and BST inks was optimized to obtain the insulating phase after the initial curing and the conductive/resistive phase following selective laser sintering under ambient conditions. Selective laser sintered Ag–BST resistors showed an ohmic behavior and the resistivity could be adjusted by varying the laser sintering parameters, such as the wavelength, power and the rastering speed/pitch of the laser. This insulator to conductor/resistor transitioning Ag–BST ink paves a new path for direct write printed electronics/AM applications. Proofs of concept for potential applications utilizing this functional ink are demonstrated. Also, this Ag–BST ink can be used as a conventional resistive ink for dispensing printers. Thermally sintered Ag–BST resistors showed less than 8% variation in resistance between −50 °C and 150 °C.
“…The state-of-the-art techniques to control the NP size involve thermal annealing, which is not always desirable because it is limited to static, rigid surfaces and is not suitable for applications where non-planar, conformal, and flexible polymer substrates are required. Selective laser sintering of NPs can be used for processing polymer substrates; however, it is challenging to control the laser beam [15]. Plasma-assisted synthesis of NPs has emerged as an important research area of material science and nanotechnology [16].…”
The use of plasma processes in nanomaterial synthesis is limited by a lack of understanding of the effects of plasma treatment on the morphology and other properties. Here, we studied the effects of atmospheric plasma treatment on the morphology and optical properties of Ag nanoparticles. The Ag nanoparticles were deposited on substrates by injecting an aerosol into flowing argon gas and then treated with a low-temperature atmospheric plasma jet. After plasma treatment, the mean Ag nanoparticle diameter reduced to an average of 5 nm, which was accompanied by a blue shift of ∼70 nm in the peak of the surface plasmon resonance; these results are similar to those obtained by thermal treatment at elevated temperatures. The reduction in nanoparticle size is explained by the redox reaction that occurs on the nanoparticle surface, which is evident from the presence of AgO and Ag 2 O Raman peaks in the treated sample. The surface charge changed as a result of plasma treatment, as indicated by a large change in the zeta potential from +25.1 ± 4 mV for the untreated sample to −25.9 ± 6 mV after 15 min of plasma treatment. Surface-enhanced Raman spectroscopy of the plasma-treated films was carried out with the fluorescent dye Rhodamine 6 G, which showed a ∼120-fold enhancement in the signal intensity relative to the untreated substrates. We, therefore, conclude that cold-plasma treatment modified the surface morphology of the Ag nanoparticles, thereby enhancing their optical properties. This technique could be applied to a wide range of nanoparticle systems used in biosensing applications.
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