Électronique moléculaire

Résumé

L'électronique moléculaire (parfois appelée molectronique) est un thème interdisciplinaire qui couvre la physique, la chimie et la science des matériaux. L'élément unificateur est le recours à des « briques » moléculaires pour la fabrication de composants électroniques, qu'ils soient actifs ou passifs. Le concept de l'électronique moléculaire a suscité beaucoup d'enthousiasme parmi les scientifiques mais également parmi les aficionados de science-fiction, en raison de la perspective de réduction de la taille en électronique, grâce au contrôle des propriétés à l'échelle moléculaire. L'électronique moléculaire est à ce titre la brique qui permet d'étendre la loi de Moore au-delà de la limite prévue pour les circuits intégrés conventionnels en silicium. En raison de la large utilisation de l'expression, l'électronique moléculaire peut être divisée en deux disciplines distinctes mais connexes : les matériaux moléculaires pour l'électronique qui utilisent les propriétés des molécules pour

Source officielle

https://fr.wikipedia.org/wiki/%C3%89lectronique_mol%C3%A9culaire

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The formation of supramolecular structures is a central issue in bio- and nanotechnology and therein plays an important role for many novel developments such as biocompatible materials for integrating living cells or coating for implantable sensing devices as well as for designing smart molecular sensor surfaces for miniaturized bioanalytical techniques. The main focus of this thesis is the investigation of polypeptide layers on surfaces, in particular the formation of self-assembled monolayers (SAMs). SAMs made of long hydrocarbon chains or aromatic molecules comprising surface active and other functional groups have been deeply characterized over decades. Surprisingly, peptide SAMs did not meet the same strong interest despite their great potential in several areas. Natural (20) and artificial amino acids with different physical and chemical properties offer a plethora of novel possibilities to design coating of solid surfaces. In fact their combination in simple oligopeptide sequences provides a huge number of molecular components for the formation of SAMs. Control of SAM features such as density, flexibility, adaptability, interface properties, by tailoring the amino acid sequence opens a new route to manifold applications ranging from fundamental research to nano- and biotechnology. In this thesis different and complementary techniques have been used to investigate the self-assembling ability of polypeptides on surfaces with different physical and chemical properties. Infrared spectroscopy and circular dichroism allowed the determination of the peptide secondary structure on surfaces and in solution. Surface plasmon resonance provided the optical thicknesses of peptide SAMs on gold whereas contact angle measurements have been used to characterize their interfacial properties. In the first part of the thesis, a series of hydrophobic peptides (Ac-Cys-Alax-CONH2, x=3-6) have been self assembled on gold via the thiol group present in the cysteine. The main interest was whether these peptides formed densely packed SAMs with a defined secondary structure within the layer and how the properties of such SAMs depended on the length of the polypeptide backbone. The second part concerns the study of the interactions of an amphipathic helical peptide with various functionalized substrates. The aim was to investigate whether a proper design of the peptide could be used to predetermine its secondary structure on the substrate and whether the orientation of the peptide on the surface could be directly controlled via certain parameters of the surrounding medium. Since the hydrophilic residues of the peptide are histidines, a particular effort was spent in characterizing the peptide adsorption on substrates exposing nitrilotriacetic acid (NTA) moieties. Once established that the adsorption process did not alter its helical structure, the peptide was adsorbed on a substrate exposing two different functional groups: NTA, that could interact with the histidine residues, and methyl groups, that could interact with the hydrophobic ones. The goal was to bind the peptide in different orientation to the same substrate, exploiting the particular spatial distribution of its residues. The third part of this thesis concern the formation of nano- and micro-sized fibrils through molecular self-assembly of simple oligopeptides and protected amino acids. Such systems were chosen as models to investigate the role of the different driving forces in the formation of fibrillar structures. The aromatic protecting group being fixed, it could be shown that the protected amino acids formed fibrils with different sizes and morphologies, or did not form fibrils at all, depending on how strongly their side chains interact. The possibility of forming fibrils by using protected amino acids is of major importance not only in bio-related field but also in organic nanotechnology.

EPFL2008

Chargement

The field of micro electromechanical systems (MEMS) evolved from the microelectronic industry and the technologies developed to fabricate integrated circuits. As a result, MEMS are commonly fabricated on silicon wafers. The development of MEMS has been driven by three main merits: miniaturisation, microelectronics integration, and parallel fabrication with high precision. Many operational properties scale well with smaller sizes. In addition, integrated electronic circuitry allows embedding MEMS with computing or networking capabilities, while parallel manufacturing enables the fabrication of many identical devices on a single wafer, reducing the unit cost. The main MEMS application is transducers which transform signals from one form of energy to another, and can be used for perception (sensors) or to produce actions (actuators). Silicon and other microelectronic materials like metals have enabled very high-performance MEMS transducers because these materials can be used for a range of very effective actuating and sensing principles.More recently, polymers have started to be used in MEMS because of their unique electrical, physical and chemical properties which include biocompatibility, viscoelasticity and mechanical shock tolerance. They are also much softer than silicon or metals, and they can be processed using many techniques that allow unique low-cost, batch-style fabrication and packaging. However, polymers have relatively low glass-transition and melting temperatures. As a result, the advantages of polymers cannot easily be combined with high-performance actuating and sensing elements as these are based on silicon technology and require high-temperature fabrication steps. Here, a hybrid-MEMS fabrication process is used to address this issue. The developed devices are based on a trilayer structure, where a thick polymer core is sandwiched between two hard thin films, while electronic layers are embedded within in a fluid-compatible way.The objective of this thesis is to turn hybrid-MEMS into a benchmark MEMS technology. This involves many different aspects. First, sensing and actuation elements are integrated into trilayer devices, and their performance is analysed. Then, some more unique possibilities offered by hybrid-MEMS are exploited. A way to fabricate electronics on multiple layers is developed, which allows different electronic features to be integrated in parallel. In addition, three-dimensional bulk features fabricated at several levels are demonstrated. This is possible because the hybrid-MEMS process is based on the bonding of multiple wafers.All these new fabrication features are demonstrated in atomic force microscopy (AFM) applications. Self-actuated trilayer AFM cantilevers with sharp silicon tips are used to boost imaging speeds in the off-resonance tapping (ORT) mode, thanks to an order of magnitude faster surface probing rates. Furthermore, fully integrated ORT imaging is demonstrated with self-actuated piezoresistive cantilevers. Next, trilayer cantilevers with shielded conductive tips are introduced for electrical AFM modes. Finally, ongoing research projects are touched upon, including approaches to fabricate hybrid-MEMS with single crystal silicon piezoresistors for improved sensitivity, and an analysis of reproducibility of fabricated trilayer cantilevers.

EPFL2022

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The appearance of clinically detectable metastases is the end-point of a complex set of biological processes only few cancer cells are capable to complete. Metastatic colonization comprises the most inefficient metastatic steps as it requires a fine-tuned crosstalk between the disseminated cancer (stem) cells and their host microenvironment. The origin of the cancer cell and its intrinsic properties are factors that together with the organ microenvironment and circulation patterns determine the site of metastatic spread, the dormancy period and the extent of metastasis formation. Recent advances provide novel insights into the molecular components required for organ-specific infiltration, the composition of growth-supportive metastatic niches in different tissues and the cancer cell-niche crosstalk. (c) 2013 Elsevier Inc. All rights reserved.

Elsevier2013

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EPFL2022

EPFL2008