Abstract:We demonstrate spectral filtering with state-of-the-art Bragg gratings in plasmonic V-groove waveguides fabricated by wafer scale processing based on nanoimprint lithography. Transmission spectra of the devices having 16 grating periods exhibit spectral rejection of the channel plasmon polaritons with 8.2 dB extinction ratio and −3 dB bandwidth of ∆λ = 39.9 nm near telecommunications wavelengths. Near-field scanning optical microscopy measurements verify spectral reflection from the grating structures, and the oscillations of propagating modes along grating-less Vgrooves correspond well with effective refractive index values calculated by finite element simulations in COMSOL. The results represent advancement towards the implementation of plasmonic V-grooves with greater functional complexity and mass-production compatibility.

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Fabrication of a seamless roll mold by direct writing with an electron beam on a rotating cylindrical substrate Fabrication of 100 nm metal lines on flexible plastic substrate using ultraviolet curing nanoimprint lithographyIn this work, we propose an innovative approach to the fabrication of a complete micro/nano fluidic system, based on direct nanoimprint lithography. The fabricated device consists of nanochannels connected to U-shaped microchannels by triangular tapered inlets, and has four large reservoirs for liquid input. A master silicon stamp with the multilevel structures is fabricated first, and then a negative replica is made, to be used as a stamp for ultraviolet nanoimprint lithography (UV-NIL). Afterwards, just one single UV-NIL step is necessary for patterning all the the micro and nanostructures. Furthermore, the devices are made of all-transparent materials, and the method allows flexibility for the type of substrates used. The active material (an inorganic-organic hybrid polymer) used for the fabrication of the device has been carefully chosen, so it has adequate surface properties (inert and hydrophilic) for its direct use for biological applications. Devices having 30 nm wide, 30 nm deep nanochannels have been fabricated, and the successful performance of the fluidic system and the continuity of the nanochannels have been proven by flow tests.

Propagation of channel plasmon-polariton modes in the bottom of a metal V groove has been recently demonstrated. It provides a unique way of manipulating light at nanometer length scale. In this work, we present a method based on nanoimprint lithography that allows parallel fabrication of integrated optical devices composed of metal V grooves. This method represents an improvement with respect to previous works, where the V grooves were fabricated by direct milling of the metal, in terms of robustness and throughput.

We present the results of optical characterization of metal V-groove waveguides using scanning near-field microscopy, showing broadband transmission with subwavelength confinement and propagation lengths exceeding 100 microm. An updated fabrication method using a combination of UV and nanoimprint lithography is presented. The developed approach is mass-production compatible, adaptable to different designs, and offers wafer-scale parallel fabrication of plasmonic components based on profiled metal surfaces.

Merkel Cell Polyomavirus (MCPyV) is the etiological agent of the majority of Merkel Cell Carcinomas (MCC). MCPyV positive MCCs harbor integrated, defective viral genomes that constitutively express viral oncogenes. Which molecular mechanisms promote viral integration, if distinct integration patterns exist, and if integration occurs preferentially at loci with specific chromatin states is unknown. We here combined short and long-read (nanopore) next-generation sequencing and present the first high-resolution analysis of integration site structure in MCC cell lines as well as primary tumor material. We find two main types of integration site structure: Linear patterns with chromosomal breakpoints that map closely together, and complex integration loci that exhibit local amplification of genomic sequences flanking the viral DNA. Sequence analysis suggests that linear patterns are produced during viral replication by integration of defective/linear genomes into host DNA double strand breaks via non-homologous end joining, NHEJ. In contrast, our data strongly suggest that complex integration patterns are mediated by microhomology-mediated break-induced replication, MMBIR. Furthermore, we show by ChIP-Seq and RNA-Seq analysis that MCPyV preferably integrates in open chromatin and provide evidence that viral oncogene expression is driven by the viral promoter region, rather than transcription from juxtaposed host promoters. Taken together, our data explain the characteristics of MCPyV integration and may also provide a model for integration of other oncogenic DNA viruses such as papillomaviruses.

Imprinted fluidic devices with nanochannels and transient inlets with smooth, gradually decreasing dimensions are used to analyze the flow of DNA single molecules.

Silicon nitride thin films deposited on silicon substrates are patterned by using atomic force microscopy (AFM) local oxidation nanolithography. The mechanism of the AFM-induced oxidation is studied by analysing the kinetics of the oxidation and by studying the electrical current during the oxidation process. We observe that the silicon substrate and the silicon nitride layer are simultaneously modified. Because of the significant technological relevance of silicon nitride film, the technique is applied for fabricating masks with nanometre-scale features by transferring the pattern to the silicon substrate.