Delayed Lubricant Depletion of Slippery Liquid Infused Porous Surfaces Using Precision Nanostructures

Slippery liquid infused porous surfaces (SLIPS) are an important class of repellent materials, comprising micro/nanotextures infused with a lubricating liquid. Unlike superhydrophobic surfaces, SLIPS do not rely on a stable air-liquid interface and thus can better manage low surface tension fluids, are less susceptible to damage under physical stress, and are able to self-heal. However, these collective properties are only efficient as long as the lubricant remains infused, which has proved challenging. We hypothesized that, in comparison to a nanohole and nanopillar morphology, the "hybrid" morphology of a hole within a nanopillar, namely a nanotube, would be able to retain and redistribute lubricant more effectively, owing to capillary forces trapping a reservoir of lubricant within the tube, while lubricant between tubes can facilitate redistribution to depleted areas. By virtue of recent fabrication advances in spacer defined intrinsic multiple patterning (SDIMP), we fabricated an array of silicon nanotubes and equivalent arrays of nanoholes and nanopillars (pitch, 560 nm; height, 2 μm). After infusing the nanostructures (prerendered hydrophobic) with lubricant Krytox 1525, we probed the lubricant stability under dynamic conditions and correlated the degree of the lubricant film discontinuity to changes in the contact angle hysteresis. As a proof of concept, the durability test, which involved consecutive deposition of droplets onto the surface amounting to 0.5 L, revealed 2-fold and 1.5-fold enhancements of lubricant retention in nanotubes in comparison to nanopillars and nanoholes, respectively, showing a clear trajectory for prolonging the lifetime of a slippery surface

An array-based design methodology for 10GHz SiGe LC oscillators

In this paper, a mask programmable arraybased design methodology is used for the first time to implement a 10 GHz LC oscillator in a SiGe bipolar technology. The array used was not optimised prior to this design for the development of such circuits, and is used to highlight some of the restrictions faced by the designer when adopting an array-based approach. 10 GHz operation is demonstrated with a phase noise of –85.5 dBc/Hz @ 1MHz on first pass silicon. Whilst this performance is inferior to a full custom LC solution, the array-based design exceeds significantly the performance levels obtainable from a ring oscillator implemented using full custom techniques which meets the SONET jitter specifications. Detailed analysis of the various phase noise contributions to the 10 GHz LC oscillator show that the performance is not prohibitively compromised by the array-based design approach. Together with the improved time-to-market resulting from an array-based approach, this work makes a compelling case for the viability and adoption of arraybased design methodologies for a wide range of RF and microwave applications