Microcontact printing process for the patterned growth of individual CNTs

We report an original approach to pattern a substrate with isolated carbon nanotubes. Through the improvement of the microcontact printing technique by the use of a new composite stamp, we were able to produce on flat substrates micrometric features of a catalyst suitable for the localised growth of single-walled carbon nanotubes by catalytic chemical vapour deposition. This catalyst material is for the first time prepared via an original sol–gel process. The growth of straight carbon nanotubes between the patterns was observed and a method to promote the controlled growth of such isolated nanoobjects is thus conceivable

Does MPTP intoxication in mice induce metabolite changes in the nucleus accumbens? A 1H nuclear MRS study: A severe DA denervation in VTA induces metabolite changes in the NAc

International audienceUsing in vivo 1H NMR spectroscopy in a mouse model of Parkinson's disease, we previously showed that glutamate concentrations in the dorsal striatum were highest after dopamine denervation associated with an increase in gamma-aminobutyric acid (GABA) and (Gln) glutamine levels. The aim of this study was to determine whether the changes previously observed in the motor part of the striatum were reproduced in a ventral part of the striatum, the nucleus accumbens (NAc). This study was carried out on controls and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-intoxicated mice. In vivo spectra were acquired for a voxel (8 L) in the dorsal striatum, and in the NAc (1.56 L). NMR acquisitions were first performed 10 days after the last MPTP injection in a basal condition [after saline intraperitoneal (i.p.) injection] and then in the same animal the week after basal NMR acquisitions, after acute levodopa administration (200 mg kg1, i.p.). Immunohistochemistry was used to determine the levels of (Glu) glutamate, glutamine synthetase (GS) and glutamic acid decarboxylase (GAD) isoform 67 in these two structures. The Glu, Gln and GABA concentrations obtained in the basal state were higher in the NAc of MPTP-intoxicated mice which have the higher dopamine denervation in the ventral tegmental area (VTA) and in the dorsal striatum. Levodopa decreased the levels of these metabolites in MPTP-intoxicated mice to levels similar to those in controls. In parallel, immunohistochemical staining showed that glutamate, GS and GAD67 immunoreactivity increased in the dorsal striatum of MPTP-intoxicated mice and in the NAc for animals with a severe dopamine denervation in VTA. These findings strongly supported a hyperactivity of the glutamatergic cortico-striatal pathway and changes in glial activity when the dopaminergic denervation in the VTA and substantia nigra pars compacta (SNc) was severe. Copyright (c) 2012 John Wiley & Sons, Ltd

Alignment and nano-connections of isolated carbon nanotubes

We report a new approach for the alignment and the electrical nano-connection of isolated carbon nanotubes (CNTs). Through a novel combination of proven technics, we have been able to align isolated carbon nanotubes and selectively contact those CNTs by high resolution electron beam lithography (HREBL). Resistance versus temperature (R(T)) experiments have been carried out to determine the reliability of the metal–CNTs interface and to probe the electronic conductance of the CNT

Probing the electronic properties of individual carbon nanotube in 35 T pulsed magnetic field

After optimization of the alignment and the nano-contact processes of isolated single wall and double-walls carbon nanotube, we investigate the high magnetic field effects on the electronic transport properties of an individual metallic CNT. We develop pioneer multi-probes magneto-transport experiments under a 35 T pulsed field which reveal an unexpected oscillatory behavior of RðHÞ inconsistent with existing theories

Using polydimethylsiloxane as a thermocurable resist for a soft imprint lithography process

International audienceNanoimprint lithography has been investigated using polydimethylsiloxane as a thermocurable resist. This novel process allowed us to reduce both pressure (<10 bars) and temperature (80 °C) when compared to a conventional imprinting process with a thermoplastic polymer resist such as polymethylmethacrylate. Using a new formulation of the elastomeric material, we have demonstrated high quality imprinting of both micronic and nanometric structures with no evidence of any viscous flow problems. The excellent etching resistance of the polydimethylsiloxane structures to a reactive ion etching silicon process and the compatibility with a lift-off procedure for pattern transfer are also presented

Self-aligned patterns of multiple biomolecules printed in one step

International audienceWe describe an adaptation of the microcontact printing technique for generating self-aligned patterns of two different molecules in one printing step. Elastomeric stamps exhibiting different levels of topography are designed and fabricated so that, by external pressure, their deformation enables two planes, selectively inked with two different molecules, to contact the surface. The fabrication of 1 μm wide biomolecular patterns aligned into 5 μm wide patterns of another biomolecule is demonstrated through fluorescence imaging and atomic force microscopy

Micro-Contact Printing of Two Different Biomolecules in One Step Using Deformable Poly(dimethylsiloxane)-Based Stamp

International audiencePatterning biomolecules at the micron or nano-scale presents a major challenge for the elaboration of integrated biochips. Among the different techniques that are emerging, Microcontact printing (µCP) appears as one of the most promising due to its simplicity and low cost. However, µCP exhibits a severe limitation because only one type of molecule can be deposited at a time using a poly(dimethyldiloxane) (PDMS) stamp. We present a new process called one-step-multiple-µCP (OSM-µCP) using a specific multilevel PDMS stamp which allows the patterning of two different molecules in one step. Our method based on the elastomeric properties of a PDMS stamp can print self aligned patterns of two different molecules by pressuring homogenously the top side of the stamp. The stamp levels inked by two different molecules contact the surface sequentially. OSM-µCP of two proteins, here bovin serum albumin BSA and streptavidin is demonstrated and this method can be applied to others couples of molecules. These results show that patterning biomolecules with OSM-µCP process opens new perspectives for soft lithography by enabling the fabrication of complex patterns of different molecules

Aluminum Bowties for Plasmonic‐Enhanced Infrared Sensing

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Towards greener nanoimprint processes

The purpose of this work is to develop nano-imprint processes using “greener” polymers. PLA, a bio-sourced, bio-degradable and bio-compatible polymer, will be directly nano-structured via a thermal nano-imprint process (T-NIL). PVA, a synthetic bio-compatible and bio-degradable polymer, will be used as water-soluble sacrificial layers for lift-off process

Porous silicon membrane, with an integrated aqueous supply, for two chamber AFM

International audienceImaging membrane proteins in aqueous solution in their native configuration remains a challenge for atomic force microscopy (AFM). Usually, supported lipidic bilayer membranes decorated with proteins have been imaged most of the time on mica surfaces. However, for proteic transmembrane structures, the presence of the underlying substrate can be detrimental inducing a denaturation process. In this paper we present a full silicon process enabling the fabrication of free standing suspended lipidic membranes on nanoholes suitable for liquid AFM imaging. A simple microfluidic device gives access to both sides of the membranes enabling dynamical chemical changes to be performed during AFM imaging