Laser Sintering Of Metal Nanoparticles Research Articles

Effect of pulse overlapping on temperature field and physical characteristics in pulsed laser sintering of inkjet-printed silver nanoparticles

Pulsed laser sintering of metal nanoparticles (NPs) has been studied owing to its minimal impact on heat-sensitive zones. The characteristic effects of pulse overlapping during pulsed laser sintering of metal NPs on metal NP surface morphology and electrical properties have not been reported to date. We therefore investigated millisecond pulsed laser sintering of inkjet-printed silver (Ag) NP lines at 30, 50, 70, 80, and 90% pulse overlaps (POs). We then assessed the thermal, electrical, and surface-morphological characteristics for each PO case. The temperature history was investigated via numerical analysis using a designed algorithm for treating thermal conductivity. The 70% PO produced the lowest Ag NP line resistivity with the highest degree of consistency as a result of the uniform temperature distribution and relatively continuous surface morphology with minimal porosity. The results of this study can guide the understanding of the thermal response, electrical performance, and surface morphology of Ag NPs corresponding to pulse overlapping during a pulsed laser sintering operation.

Femtosecond laser sintering of silver nanoparticles for conductive thin-film fabrication

Femtosecond laser sintering of metal nanoparticles for fabricating thin metal films/patterns has drawn substantial attention owing to its potential in fabrication of thin-film electrodes in various applications. In such applications, the electrical conductivity and the adhesion strength of the sintered film need to be optimized by forming desired microstructures. However, the physical mechanisms of sintering by ultrashort laser pulses without the effect of inter-pulse heat accumulation, especially microstructure formation, have not yet been clarified. Also, the relation between the microstructure of various sintered films and their properties are largely unknown. In this work, the microstructures and the properties (electrical conductivity and adhesion strength) of sintered film are analyzed by varying the process conditions for Ti:sapphire femtosecond laser sintering of silver nanoparticles. Sintering occurred mainly by surface necking at low laser fluences while by melting of the particles at high laser fluences. When laser fluence was further increased, the balling phenomenon occurred by capillary instability of the molten pool. These sintering phenomena were largely similar to those observed in typical thermal sintering. Both the electrical conductivity and the adhesion strength increased with the laser fluence to reach maximum when melting of the particles began before triggering the balling phenomenon. The maximum electrical resistivity ~ 8.7 μΩ cm obtained in this work was similar to that obtained by other thermal-sintering processes.

Uncertainty quantification and management in additive manufacturing: current status, needs, and opportunities

One of the major barriers that hinder the realization of significant potential of metal-based additive manufacturing (AM) techniques is the variation in the quality of the manufactured parts. Uncertainty quantification (UQ) and uncertainty management (UM) can resolve this challenge based on the modeling and simulation of the AM process. This paper reviews the research state of the art and discusses needs and opportunities in the UQ/UM of the AM processes, with a focus on laser powder bed fusion AM. The major methods and models of laser powder bed fusion AM process are summarized first. The current research work in UQ of AM processes is then reviewed. Based on the review of AM process models and current UQ approaches for the AM process, this paper presents insights into how the current state of the art UQ and UM techniques can be applied to AM to improve the product quality. Future research needs in UQ and UM of AM are also discussed. Laser sintering of metal nanoparticles, which is part of the micro-AM process, is used as an example to illustrate the application of UQ and UM in the AM.

Transparent Conductive Films by Laser Sintering of Metal Nanoparticles

Transparent Conductive Films by Laser Sintering of Metal Nanoparticles

Effect of laser-induced temperature field on the characteristics of laser-sintered silver nanoparticle ink

Laser sintering of metal nanoparticles is a key technology for high-performance printed electronics fabricated on heat-sensitive substrates such as glass or plastic. Although laser-sintered electronic devices have been successfully fabricated, the role of the induced temperature field in the laser sintering process has not been reported thus far. In this work, the effect of temperature on the laser sintering process is described for the first time using a two-dimensional transient heat conduction equation for inkjet-printed silver nanoparticle ink. The in situ electrical resistance was measured to estimate the transient thermal conductivity and hence the temperature of the sintered ink during the laser sintering process. To verify the estimated laser sintering temperature, the morphology of furnace-sintered silver nanoparticle ink was compared with that of laser-sintered ink. The electrical characteristics and surface morphology of laser-sintered ink are found to be related to the process temperature.

Fabrication of submicron-sized metal patterns on a flexible polymer substrate by femtosecond laser sintering of metal nanoparticles

The femtosecond laser sintering of metal nanoparticles was studied in order to fabricate submicron-sized metal patterns on flexible polymer substrates for various applications in the electronic and photonic industries. In this process, a mode-locked Ti:sapphire laser beam was tightly focused on silver nanoparticles. To achieve a homogeneous dispersion of the silver nanoparticles, the nanoparticles were prepared using a two-phase reduction method wherein the silver nanoparticles were encapsulated by functional surfactants. The key advantage of the femtosecond laser sintering process is that it reduces the heat-affected zone during sintering, as the femtosecond (10–15 s) laser pulse is shorter than the heat diffusion time (picosecond: 10–12 s). Therefore, sintering of metal nanoparticles is limited to the laser focal spot and the thermal diffusion effect is suppressed, enabling the realisation of submicron-sized metal patterns on flexible polymer substrates. Through this process, metal conductors with submicron-sized features and high conductivity were successfully fabricated. As demonstrated by the obtained results, the femtosecond laser sintering of metal nanoparticles is a process that offers direct, low-temperature, ultra-high-resolution results, and which will have numerous further applications in flexible electronics.

All-inkjet-printed flexible electronics fabrication on a polymer substrate by low-temperaturehigh-resolution selective laser sintering of metal nanoparticles

All-printed electronics is the key technology to ultra-low-cost, large-area electronics. As acritical step in this direction, we demonstrate that laser sintering of inkjet-printed metalnanoparticles enables low-temperature metal deposition as well as high-resolutionpatterning to overcome the resolution limitation of the current inkjet direct writingprocesses. To demonstrate this process combined with the implementation of air-stablecarboxylate-functionalized polythiophenes, high-resolution organic transistorswere fabricated in ambient pressure and room temperature without utilizing anyphotolithographic steps or requiring a vacuum deposition process. Local thermal control ofthe laser sintering process could minimize the heat-affected zone and the thermal damageto the substrate and further enhance the resolution of the process. This local nanoparticledeposition and energy coupling enable an environmentally friendly and cost-effectiveprocess as well as a low-temperature manufacturing sequence to realize large-area, flexibleelectronics on polymer substrates.