33 research outputs found

    Resist-free nanoimprinting on optical fibers for plasmonic optrodes

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    Nanostructure patterning on optical fibers enables miniaturized optrodes for photonic and plasmonic applications. Here we report a direct nanoimprint technique to produce high-quality nanostructure arrays on optical fiber endfaces. It has only one single step: imprinting optical fiber tips against a mold with nanostructures at the elevated temperature. This new method abandons resist used in traditional fiber-imprinting methods. Hundreds of fibers can be shaped simultaneously with one mold within minutes. The imprinted nanostructure arrays on optical fibers are transformed into plasmonic optrodes through metal deposition. Variation of imprint depths and mold patterns allows tailoring of the plasmonic resonances of these nanostructure arrays for high-performance refractometric sensing and on-fiber polarization. The sensitivity of 690 nm/RIU and figure of merit of 50 are both among the highest values for similar plasmonic nanostructure arrays. This resist-free nanoimprint paves the way towards a low-cost and high-throughput realization of plasmonic optrodes and their wide applications.Peipei Jia, Depeng Kong, Heike Ebendorff-Heideprie

    Anti-Reflective and Anti-Bacterial Properties of Biomimetic Nanostructures

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    In this thesis artificial nanostructured surfaces inspired by the moth eye were developed on both inorganic and organic substrates. Two properties, i.e. anti-reflective (AR) and anti-bacterial (AB) were studied in detail. On inorganic fused silica (Suprasil®) substrates, nanopillar arrays were fabricated by combining block copolymer micellar lithography (BCML) and reactive ion etching (RIE) techniques. The nanopillar arrays were fabricated on a large area and the parameters of the pillars were controlled. The substrates were used as molds to create nanostructures in organic substrates using two methods: replica molding and nanoimprinting. The first method transferred the pillar structure into a polyurethane substrate creating nanoholes. However, it was shown that this method was limited due to the low aspect ratio and difficulties in mold removal. Using nanoimprinting methods instead solved these problems. Both nanohole and nanopillar structures were homogeneously imprinted in a large area of the intermediate polymer stamp (IPS®) and polymethylmethacrylate (PMMA) materials. The AR properties of both organic and inorganic substrates were characterized using optical spectrometry. On Suprasil® surfaces, the transmittance was increased over a wide wavelength range of 200-1000 nm, with a maximum of 99.5% transmission per interface. Nanoimprinted IPS® and PMMA also depicted highly improved transmittance, with an increase from 91.5% to 95% with a single-sided nanohole array on IPS® and from 91.5% to 97.5% with a double-sided nanopillar array on PMMA. Excellent AR performance was achieved to a high incident angle of 60°, which significantly outperformed traditional thin-film AR coatings. A theoretical model was also set up matching the experimental results very well. The AB properties of the moth eye inspired structures were investigated on the nanostructured Suprasil®. The surface coverage of Staphylococcus sciuri (S. sciuri) bacteria was statistically analyzed by optical microscopy and the attachment sites between the bacteria and the nanostructures were observed by scanning electron microscopy (SEM). Although the surface coverage showed no significant difference between the nanostructured and planar surfaces, SEM images clearly revealed a different interaction of the bacteria and the nanostructures compared to plain surfaces. Nanofibers most likely fimbriae connecting the bacteria and the nanopillar tips were observed. Therefore, it was shown that the bacterium is able to sense the nano-scale features and respond with cell morphological alterations

    Ultrafast Fabrication of Metal Nanostructures Using Pulsed Laser Melting

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    Integration of block-copolymer with nano-imprint lithography : pushing the boundaries of emerging nano-patterning technology.

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    Molding and Replication of Ceramic Surfaces with Nanoscale Resolution

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    The design of reproducible and more efficient nanofabrication routes has become a very active research field in recent years. In particular, the development of new methods for micro- and nanopatterning materials surfaces has attracted the attention of many researchers in industry and academia as a consequence of the growing relevance of patterned surfaces in many technological fields, ranging from optoelectronics to biotechnology. In this work we explore, discuss, and demonstrate the possibility of extending the well-known molding and replication strategy for patterning ceramic materials with nanoscale resolution. To achieve this goal we have combined physical deposition methods, molecule-thick antisticking coatings, and nanostructured substrates as master surfaces. This new perspective on an “old technology”, as molding is, provides an interesting alternative for high-resolution, direct surface-relief patterning of materials that currently requires expensive and time-consuming lithographic approaches.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

    Nanooptics with surface plasmons and resonant nanoparticles

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