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Light emission excited by stable tunnel junctions has attracted interest for potential use in optoelectronic device integration. However, these electrically driven sources cannot provide a high electroluminescence intensity. Here, we report a source with 2 orders of magnitude higher output power (1.4 nW). A well-designed optical antenna allows the electromigration process to be located accurately at the structure's center. Because of the subnanometer tunnel gap, the localized density of the optical states is greatly enhanced and contributes to high spontaneous emission rates. Combined with the antenna resonance and voltage bias, the localized surface plasmon energies can be tuned from 1.38 to 1.9 eV and provide a way to bridge the gap between plasmonic devices and integrated circuits.

Resin uptake plays a critical role in the stiffness-to-weight ratio of wind turbine blades in which sandwich composites are used extensively. This work examines the flexural properties of nominally half-inch thick sandwich composites made with polyvinyl chloride (PVC) foam cores (H60 and H80; PSC and GPC) at several resin uptakes. We found that the specific flexural strength and modulus for the H80 GPC sandwich composites increase from 82.04 to 90.70 kN Á m/kg and 6.03 to 7.13 MN Á m/kg, respectively, with 11.0% resin uptake reduction, which stands out among the four core sandwich composites. Considering reaching a high stiffness-to-weight ratio while preventing resin starvation, 32% to 38% and 40% to 45% resin uptakes are adequate ranges for the H80 PSC and GPC sandwich composites, respectively. The H60 GPC sandwich composites have lower debonding toughness than H60 PSC due to stress concentration in the smooth side skin-core interphase region. The ailure mode of the sandwich composites depends on the core stiffness and surface texture. The H60 GPC sandwich composites exhibit core shearing and bottom skincore debonding failure, while the H80 GPC and PSC sandwich composites show top skin cracking and core crushing failure. The findings indicate that an appropriate range of resin uptake exists for each type of core sandwich composite, and that within the range, a low-resin uptake leads to lighter blades and thus lower cyclic gravitational loads, beneficial for long blades.

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