arXiv subjects

Youwen Liang

Publications and source records attributed to Youwen Liang.

3 recordsLinked to original sources

arXiv2025

Microscale selective laser sintering of Cu nanoparticles with a short-wavelength nanosecond laser

Microscale additive manufacturing of reflective copper is becoming increasingly important for microelectronics and microcomputers, due to its excellent electrical and thermal conductivity. Yet, it remains challenging for state-of-the-art commercial metal 3D printers to achieve sub-100-micron manufacturing. Two aspects are sub-optimal using commercial laser powder bed fusion systems with infrared (IR) lasers (wavelength of 1060-1070 nm): (1) IR laser has a low absorption rate for Cu, which is energy-inefficient for manufacturing; (2) short wavelength lasers can potentially offer higher resolution processing due to the diffraction-limited processing. On the other hand, laser sintering or melting typically uses continuous wave (CW) lasers, which may reduce the manufacturing resolution due to a large heat-affected zone. Based on these facts, this study investigates the UV (wavelength of 355 nm) nanosecond (ns) laser sintering of Cu nanoparticles. Different laser processing parameters, as well as different nanoparticle packing densities, are studied. Our results show that a short-wavelength laser can reduce the required energy for sintering with decent morphology, and a densified nanoparticle powder bed favors continuous melting. We further show that sub-20 micron printing can be readily achieved with a UV ns laser. These findings provide new insights into short-wavelength laser-metal nanoparticle interactions, which may pave the way to achieve high-resolution micro and nano-scale additive manufacturing.

physics.optics↗

arXiv2025

Additive Manufacturing of Lunar Regolith for Reconfigurable Building Blocks toward Lunar Habitation

Utilizing locally available materials is a crucial step towards sustainable planetary habitation. Lunar regolith has gained tremendous interest in additive manufacturing in the past decades. However, due to the constrained manufacturing facilities and materials on the moon, many existing additive manufacturing methods are not suitable for practical on-site manufacturing. Here, we envision that light-based direct sintering of lunar regolith can be a feasible approach. Instead of directly manufacturing large structures, we hypothesize that small-scale, reconfigurable building blocks can be an alternative to form large and complex structures. To verify the feasibility, we conducted laser sintering of lunar regolith simulants as a proof of concept, following a simple theoretical calculation for direct sintering using the light available in space. Different laser processing parameters are investigated to obtain controllable lunar regolith sintering. We further designed Lego-like interlocking bricks that are reconfigurable for different structure assemblies without additional material. Mechanical performance (compressive strength) of sintered cubic blocks is evaluated, showing a peak stress of ~1.5 MPa. We hope this work will inspire other in-space manufacturing techniques and enable low-cost space habitation.

astro-ph.IM↗

arXiv2025

Molecular dynamics simulation of silicon nanoparticle crystallization during laser-induced forward transfer printing

Laser-induced forward transfer (LIFT) printing is a versatile technique to realize micro/nano-scale additive manufacturing of functional materials, including metals and semiconductors. However, the crystallization phenomena during LIFT printing have not been well understood, which is critical to determine the resulting microstructure and properties. In this work, we systematically investigate silicon crystallization during LIFT printing using molecular dynamics (MD) simulations. Specifically, MD simulation with Stillinger-Weber (SW) potential is used to investigate the size effect and surface influence on the crystallization of Si nanoparticles during transportation in air. We found that with a decrease in nanoparticle size, crystallization becomes increasingly rare, even at low cooling rates. The nucleation location of different particles is also analyzed and almost always starts at a sub-surface location (below 5 {\AA}). The evolution of the atomic structure during solidification is also monitored to guide LIFT printing of Si. Our simulation results indicate that nano-confinement induced by the surface layer can lead to single-crystal structure formation, which may shed light on additive manufacturing of single-crystal structures and devices.

cond-mat.mtrl-sci↗