ABSTRACT
Capillary-driven heat pipes are an effective thermal solution for compacting electronic cooling systems. We advance such a heat pipe thermal solution with ultralightweighting for mobile applications. In our advancement, the envelope that encapsulates the phase-change process of a working fluid is fabricated via electroless plating being â¼40 µm thick. Furthermore, the wick structure that transports condensate to a heat source via capillarity is also electroless-plated onto the envelope's inner surfaces, creating a 100-µm-thick, microporous layer. This wick structure is sequentially superhydrophilized by blackening that forms a nanotexture on the microporous wick layer. An effective density of our prototype ultralight heat pipes (uHPs), as a measure of lightweighting, indicates, on average, a remarkable 73% weight reduction of commercial counterparts with sintered copper powder wick in similar exterior dimensions (e.g., â¼2.7 g, compared to â¼10.0 g) while providing equivalent heat spreading. Furthermore, the uHP operates at a 25% lower evaporator temperature, due to additional heat rejection to the surroundings through the ultrathin-walled envelope and wick.
ABSTRACT
A shellular is a micro-architectured material, composed of a continuous smooth-curved thin shell in the form of a triply periodic minimal surface. Thanks to the unique geometry, a shellular can support external load by co-planar stresses, unlike microlattice, nanolattice, and mechanical metamaterial. That is, the shellular is the only stretching-dominated material with the highest strength at a density of less than 10-2 g/cc. Therefore, it is expected to support internal pressure, too, by the bi-axial tensile stresses like a balloon. For more than 300 years, spherical and cylindrical vessels have been viable yet compromised options for storing pressurized gases. However, emerging green mobility necessitates a safer and more spatially conformable storage solution for hydrogen than spherical and cylindrical vessels these conventional vessels. In this study, we propose to use the shellular as a pressure vessel. Due to the distinct topological nature - periodic micro-cells constituting the triply periodic minimal surface, the alternative pressure vessel can be tailored individually for spatial requirements while ensuring safety with leak-before-break. For a given constituent material and prescribed pressure, the achievable internal volume-per-total weight of a P-surfaced, cold-stretched, double-chambered shellular vessel with a number of cells more than 15 × 15 × 15 can exceed the practical upper bound of both spherical and cylindrical vessels. For the applications, a thin shell with the large surface area of this micro-architecture is ideal for interfacial transfer of heat or mass between its two sub-volumes under internal pressure.
ABSTRACT
Recently, materials with micro-architecture of hollow trusses and ultralow density (less than 10-2 Mg/m3) have gained attention. The materials have been fabricated by forming templates based on 3D lithographical techniques, followed by hard coating on the surface, and finally etching out the template. Here, we describe a novel fabrication method for another micro architecture composed of a single continuous smooth-curved shell with D-surface, named Shellular; its template is prepared based on weaving flexible polymer wires. Compression test results reveal that these D-surfaced Shellulars have strength and Young's modulus comparable to those of their hollow truss-based competitors. The best virtue of this weaving-based technology is its mass-productivity and large-size potential. Also, this technology can be applied to fabricate not only D-surfaced but also P- or G-surfaced Shellular. The unique geometry of Shellular, composed of a single continuous, smooth, and interfacial shell or membrane separating two equivalent sub-volumes intertwined with each other, appears to possess huge application potential such as non-clogging tissue engineering scaffolds and compact light-weight fuel cells with high energy density.
ABSTRACT
A new type of cellular material named Shellular, in which cells are composed of a continuous, smooth-curved shell according to the minimal surface theory, is proposed. Shellular specimens are fabricated using 3D lithography with negative templates and hard coating, and exhibit superb strength and stiffness at densities lower than 10(-2) Mg m(-3), incorporating benefits from hierarchical structures and constituent materials with nanosized grains.
