Some beetles in the Namib Desert collect drinking water from fog-laden wind on their backs. We show here that these large droplets form by virtue of the insect's bumpy surface, which consists of alternating hydrophobic, wax-coated and hydrophilic, non-waxy regions. The design of this fog-collecting structure can be reproduced cheaply on a commercial scale and may find application in water-trapping tent and building coverings, for example, or in water condensers and engines.

Fabry-Perot -like resonant transmission of microwave radiation through a single subwavelength slit in a thick aluminum plate is quantified for a range of slit widths. Surprisingly, and in contrast to previous studies [e.g., Y. Takakura, Phys. Rev. Lett. 86, 5601 (2001)], the resonant frequency exhibits a maximum as a function of slit width, decreasing as the slit width is reduced to less than 2% of the incident wavelength. This result accords with a new model based on coupled surface plasmon theory taking into account the finite conductivity, and hence permittivity, of the metal. This is contrary to a common assumption that metals can be treated as infinitely conducting in this regime.

In this report we discuss the impact of polarized foregrounds on a future CMBPol satellite mission. We review our current knowledge of Galactic polarized emission at microwave frequencies, including synchrotron and thermal dust emission. We use existing data and our understanding of the physical behavior of the sources of foreground emission to generate sky templates, and start to assess how well primordial gravitational wave signals can be separated from foreground contaminants for a CMBPol mission. At the estimated foreground minimum of -100 GHz, the polarized foregrounds are expected to be lower than a primordial polarization signal with tensor-to-scalar ratio r = 0.01, in a small patch (~ 1%) of the sky known to have low Galactic emission. Over 75% of the sky we expect the foreground amplitude to exceed the primordial signal by about a factor of eight at the foreground minimum and on scales of two degrees. Only on the largest scales does the polarized foreground amplitude exceed the primordial signal by a larger factor of about 20. The prospects for detecting an r = 0.01 signal including degree-scale measurements appear promising, with 5cr r -0.003 forecast from multiple methods. A mission that observes a range of scales offers better prospects from the foregrounds perspective than one targeting only the lowest few multipoles. We begin to explore how optimizing the composition of frequency channels in the focal plane can maximize our ability to perform component separation, with a range of typically 40 < v < 300 GHz preferred for ten channels. Foreground cleaning methods are already in place to tackle a CMBPol mission data set, and further investigation of the optimization and detectability of the primordial signal will be useful for mission design.

A slit in a thick metal plate that is extremely subwavelength will not transmit microwaves polarized parallel to it. It is shown here that cuts perpendicular to the slit allow parallel polarized radiation to resonantly transmit. Furthermore, a zero-order mode may be excited within the slit, the frequency of which, to first order, is independent of the plate depth. Remarkably, for this novel type of resonance, the field in the slit oscillates with a constant phase and little amplitude variation throughout the plate depth, while the resonant wavelength tends to infinity as the slit width approaches zero.

Selective transmission of radiation through a two-dimensional array of subwavelength slits in an otherwise opaque thin metal film is presented at microwave frequencies. Individual slits are modified with the addition of perpendicular cuts, which interestingly and perhaps counterintuitively leads to resonant transmission when the incident radiation is polarized parallel to the slits. Finite element modeling of the structure shows the transmission of radiation polarized parallel to the slit direction to be a result of induced surface currents exciting a zeroth-order Fabry-Pérot mode. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2745202͔ Electromagnetic ͑EM͒ pollution is currently one of the fastest growing forms of pollution due in part to the popularity of the mobile phone as a convenient communication device. As many environments such as hospitals and airports rely increasingly on sensitive electronic equipment, EM screening materials have generated much commercial interest. Indeed, a substantial body of work regarding frequency selective screens ͑FSSs͒ based on planar slit geometry exists. 1-8 However, for this geometry a Fabry-Pérot-like mode is utilized to mediate transmission at well defined frequencies, which imposes a characteristic thickness upon the transmitting structure ͑ജ 0 /2͒. 3 Here we present a structure that acts as a lightweight FSS formed from an otherwise opaque ultrathin aluminum film where the metal thickness t is much less than the skin depth ␦ at these frequencies.A one-dimensional array of subwavelength slits in metal will readily transmit radiation via coupled surface waves due to diffraction when the electric vector is polarized perpendicularly to the slit direction. 1 By contrast, radiation polarized with its electric vector parallel to the slits is reflected. Extending the array into two dimensions introduces fourfold symmetry, allowing transmission that is polarization independent since incident radiation will always have a component of the electric vector orthogonal to one of the slit directions. 5 If the slit array is deep with respect to the incident wavelength, i.e., d ജ 0 / 2, then it is also possible to couple to a series of Fabry-Pérot-type modes, 1 with the fundamental Fabry-Pérot mode existing at a wavelength corresponding to twice the slit depth. However, Suckling et al. 9 demonstrated that for incident radiation polarized parallel to the slit direction, it is possible to couple to a "zeroth-order" Fabry-Pérot mode. Here we propose a structure based on a planar subwavelength slit geometry that selectively transmits radiation at millimeter wavelengths via a coupled surface wave and remarkably allows coupling to a zeroth-order Fabry-Pérot mode while having a thickness of 1 / 100 of the operating wavelength. Coupling to both modes occurs for any azimuthal angle and is polarization independent.The structures presented here are formed from an array of slits cut into a 40 nm aluminum film. Despite being less than the skin depth at the operating wavelength, the aluminum...

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It is shown that microwave radiation can be transmitted through a wall of aluminium-alloy bricks even though the width of the gaps between the metallic elements is less than 5% of the radiation wavelength. Up to 90% of the radiation made incident upon the wall is transmitted, with both linear polarisations being passed. Experimental results are compared to theoretical predictions, proving that the transmission mechanism relies upon self-coupled surface plasmon resonances in what are effectively Fabry-Perot cavities.