Superhydrophobicity, water repellency, and self-cleaning properties of materials have recently attracted tremendous attention. [1][2][3] Superhydrophobic surfaces exhibit extraordinarily high water contact angles, by convention greater than 150°, and extraordinarily low contact-angle hysteresis (i.e., a low difference between advancing and receding contact angles), typically less than 5°-10°. Studies of superhydrophobicity realized by insects [4] and many plants, [5,6] particularly the lotus leaf, [6] show that these biological superhydrophobic surfaces not only have a low surface energy, but also a hierarchical surface roughness on at least two different (i.e., micro-and nanometer) length scales. Inspired by Nature, researchers have designed numerous synthetic superhydrophobic surfaces by creating nanometer-scale features on micrometer-scale roughened surfaces. [7][8][9][10][11] For example, Ming et al. [10] reported that a film containing raspberry-like particles (made by grafting 70 nm silica particles onto 0.7 lm silica particles) had a higher contact angle and lower contact-angle hysteresis than films composed solely of small (70 nm) or large (0.7 lm) particles with the same surface chemistry. Gao et al. [11] recently reported a significant increase in superhydrophobicity for hydrophobized surfaces containing micrometer-scale staggered rhombic posts, after imparting a second (nanoscale) topography onto the originally smooth surfaces of the posts with a solution reaction using methyltrichlorosilane. In this Communication, we describe two different strategies to make hierarchically roughened superhydrophobic surfaces, particularly in the form of electrospun nonwoven mats, by decorating micrometer-scale (ca. 1 lm) fibers with nanometer-scale (ca. 100 nm) pores or particles. These length scales are 1-2 orders of magnitude smaller than those exhibited by conventional woven textiles, including some composed of microfibers.[12]Electrospinning has become a popular method to generate continuous ultrathin fibers with micrometer and sub-micrometer diameters from a variety of polymeric materials. [13][14][15][16][17][18][19][20] Electrospun fibers intrinsically provide at least one length scale of roughness for superhydrophobicity because of the small fiber size. [21][22][23][24][25][26][27][28][29] For example, we previously showed that fiber mats composed solely of uniform fibers could be obtained by electrospinning a hydrophobic material (i.e., poly(styrene-blockdimethylsiloxane) block copolymer) blended with homopolymer polystyrene (PS).[23] The roughness of the nonwoven mat, resulting from the small diameters of the fibers (150-400 nm), combined with the enrichment of the dimethylsiloxane component at the fiber surfaces was sufficient to yield materials with a contact angle of 163°and a hysteresis value of 15°. Prior to that, Jiang et al. [21] reported a contact angle of 160.4°for a membrane consisting of micrometer-sized PS particles embedded within a fibrous PS matrix. Similarly, Acatay et al. [22] reported compa...

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Articles you may be interested inBroad-angle and efficient unidirectional excitations of surface plasmons with dielectric-coated subwavelength metallic periodic nanoslits Appl. Phys. Lett. 105, 091112 (2014); 10.1063/1.4893728 Strong coupling between surface plasmon polaritons and β-carotene in nanolayered system J. Chem. Phys. 138, 044707 (2013); 10.1063/1.4776233Efficient generation of surface plasmon by single-nanoslit illumination under highly oblique incidence

By engaging a compact asymmetric single slit coated with a photorefractive polymer, surface-plasmon-polariton (SPP) generation was efficiently controlled by a pump beam. In the structure, the nonlinear light-matter interaction is enhanced because of the cavity effect, which increases the sensitivity of SPPs to the surrounding dielectric. By variation of the real part of the refractive index together with an interferometric configuration, high on/off switching ratios are achieved. Moreover, the SPP generation and modulation processes are integrated in the same asymmetric single slit, which makes the device ultracompact. Experimentally, a high on/off switching ratio of >20 dB and phase variation of >π were observed with the device lateral dimension of only about 2 μm.

This paper presents a study of possible models to describe the relation between the scintillation light point-of-origin and the measured photo detector pixel signals in monolithic scintillation crystals. From these models the X, Y and depth of interaction (DOI) coordinates can be estimated simultaneously by nonlinear least-square fitting. The method depends only on the information embedded in the signals of individual events, and therefore does not need any prior position training or calibration. Three possible distributions of the light sources were evaluated: an exact solid-angle-based distribution, an approximate solid-angle distribution and an extended approximate solid-angle-based distribution which includes internal reflection at side and bottom surfaces. The performance of the general model using these three distributions was studied using Monte Carlo simulated data of a 20 x 20 x 10 mm lutetium oxyorthosilicate (Lu₂SiO₅ or LSO) block read out by 2 Hamamatsu S8550 avalanche photo diode arrays. The approximate solid-angle-based model had the best compromise between resolution and simplicity. This model was also evaluated using experimental data by positioning a narrow 1.2 mm full width at half maximum (FWHM) beam of 511 keV photons at known positions on the 20 x 20 x 10 mm LSO block. An average intrinsic resolution in the X-direction of 1.4 mm FWHM was obtained for positions covering the complete block. The intrinsic DOI resolution was estimated at 2.6 mm FWHM.