Fabrication of Non‐Uniform Nanolattices with Spatially Varying Geometry and Material Composition

Abstract

Polymer nanostructures can also be employed as the sacrificial template for thin-film deposition to fabricate hollow-core nanolattices. These periodic architectures with thin-shell elements can have even lower density, demonstrating interesting properties such as lower thermal conductivity, [27] refractive index closer to air, [21] higher mechanical stiffness, and resilience at high strain. [1] These recent progress in the fabrication of 3D nanostructure have provided new opportunity in nanoscience and nanoengineering.Beyond uniform nanolattices, 3D nanostructures with spatially varying geometry and/or material composition can further enable the control of the material properties. For example, aerogel with gradient porosity was used to capture and spatially separate high-speed particles of different sizes from comets during the NASA Stardust mission. [28,29] Nanostructures with changing lattice geometry can also be used to create complex profiles for nanophotonic and acoustic devices. [1,[30][31][32] Analogous to the recent interest in metasurfaces with spatially varying properties, [33,34] the ability to create nonuniform nanolattices can enable material behavior to be tailored within the full 3D volume.Fabrication of 3D nanostructures or nanolattices with spatially varying parameters is extremely challenging, and most existing processes are limited to uniform nanostructures. Methods to stack layers of nanostructures [35][36][37] have been explored, but are restricted in simple geometry such as 1D or 2D grating layers that are strong enough to survive the mechanical transferring process. Direct-write approaches such as twophoton polymerization and focused-ion beam lithography have the capability for arbitrary 3D patterning. [1,7,27,31,32,38] Varying the material composition is possible in these techniques, [39] however the voxel-by-voxel writing methods are serial in nature and can be prohibitively expensive to scale for large-area patterning. There are two key challenges to fabricate non-uniform nanolattices. The first challenge is creating nanostructures with various lattice geometry and periodicity in a scalable manner. This is difficult for existing lithography and self-assembly that are parallel, which are limited to making structures with a single periodicity. The second challenge is altering the material composition as a function of position. The existing deposition methods coat uniformly on the structure surface and it is difficult to selectively deposit in isolated regions. To further The fabrication of periodic 3D nanostructures with uniform material properties has been widely investigated and is important for applications in photonics, mechanics, and energy storage. However, creating nanostructures with spatially varying lattice geometry and material composition is still largely an unexplored challenge in nanofabrication. This work presents the fabrication of non-uniform nanolattices by patterning multiple layers of 3D nanostructures using phase shift lithography and atomic layer deposition. By contro...

Microchannel Liquid-Cooled Heat Exchanger Based on a Nonuniform Lattice: Study on Structure Calculation, Formation Process, and Boiling Heat Transfer Performance

“…This nonuniform lattice design, however, is unhelpful under uneven external heat conduction and nonuniform heat flow. By designing nonuniform lattices according to the optimised theoretical results [ 26 , 27 ], the adaptability of lattice structures to the requirements of two-phase boiling heat transfer can be improved while enhancing heat transfer and dissipation efficiencies. This is the first study to systematically investigate the applications of SLM-formed nonuniform lattices in boiling heat transfer and explore structure calculations and formation through the combination of SLM formation with the requirements of the two-phase microchannel liquid-cooled heat transfer structure.…”