The control and modification of surface state is a major challenge in bioanalytical sciences, and in particular in electrokinetic separation methods, due to the importance of electroosmosis. This topic has gained recently a renewed interest, associated with the development of "lab-on-chips" systems that extend the range of materials in which separation channels are fabricated. The surface science community has developed through the years a large toolbox of characterization tools and surface modification protocols, which is not yet fully exploited in the bioanalytical world. In this paper, we try and present an overview of these tools, in order to stimulate new ideas for improved and more controlled surface treatment strategies for separations in capillaries and microchannels. We briefly describe some physical and chemical aspects of electroosmosis (global and spatially resolved), streaming current, and streaming potential. We also review the main strategies for surface coating, and compare the advantages of physisorption, well-organized thin self-assembled monolayers, or conversely thick polymer "brushes". Examples of existing applications to electrophoresis in microchannel are also given.

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An amphiphilic block copolymer poly(tert-butylacrylamide-b-(N-acryloylmorpholine-N-acryloxysuccinimide)) (poly(TBAm-b-(NAM/NAS)) and a random copolymer poly(NAM/NAS), synthesized by the reversible addition-fragmentation chain transfer (RAFT) polymerization process, have been used as support for oligonucleotide (ODN) synthesis, to elaborate polymer-oligonucleotide conjugates. In a first step, starters of ODN solid-phase synthesis were coupled to activated ester functions of polymers, and second, resulting functionalized polymers were covalently grafted onto hydroxylated controlled pore glass (CPG) support to further accomplish ODN synthesis. An efficient capping of residual hydroxyl functions of CPG was performed before synthesis, with both acetic anhydride and diethoxy-N,N-diisopropyl-phosphoramidite reagents, to suppress parasite-free ODN population present in conjugate crude material and resulting from syntheses directly initiated on silica beads. After purification, conjugates were evaluated in a DNA hybridization assay on a microarray, as macromolecules being able to favor capture of the target. Conjugate coating conditions were studied on the dT25/dA25 model. The role of the hydrophobic part (poly(TBAm)) of the conjugate synthesized with the block copolymer in the orientation of the conjugate after coating was revealed by spotting experiments achieved in a mixed solvent (DMF/H(2)O). The use of block copolymer-dT25 conjugate afforded a significant sensitivity improvement of the hybridization assay.

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A broad range of microfluidic applications, ranging from cell culture to protein crystallization, requires multilevel devices with different heights and feature sizes (from micrometers to millimeters). While state-of-the-art direct-writing techniques have been developed for creating complex three-dimensional shapes, replication molding from a multilevel template is still the preferred method for fast prototyping of microfluidic devices in the laboratory. Here, we report on a "dry and wet hybrid" technique to fabricate multilevel replication molds by combining SU-8 lithography with a dry film resist (Ordyl). We show that the two lithography protocols are chemically compatible with each other. Finally, we demonstrate the hybrid technique in two different microfluidic applications: (1) a neuron culture device with compartmentalization of different elements of a neuron and (2) a two-phase (gas-liquid) global micromixer for fast mixing of a small amount of a viscous liquid into a larger volume of a less viscous liquid.

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IntroductionThe development of controlled/living ionic and radical polymerization techniques during the last decades represents a major breakthrough in polymer chemistry and polymer science. Since these techniques lead to the synthesis of a wide range of tailor-made macromolecular architectures, significant improvements are expected in the current or future application fields of polymers. The industrial impact will however depend on the versatility and applicability of each technique, and of course on the extra cost for the final product.In this context, controlled radical polymerizations (CRP) and especially the reversible addition-fragmentation chain transfer (RAFT) process [1-3] have attracted a lot of attention since they combine the advantages of conventional radical polymerization and living ionic polymerizations. Conventional radical polymerizations are cost-effective techniques, easy to process with a low sensitivity to water and oxygen and applicable to a wide range of monomers. In addition, CRP techniques result in a very efficient control over molecular weight (MW), molecular-weight distribution (MWD), microstructure, chain-end functionality and macromolecular architecture.As shown in the previous chapters of this handbook, the RAFT process appears as one of the most interesting CRP techniques. First, RAFT polymerization is very similar to conventional radical polymerization since it only requires the addition of a chain-transfer agent (CTA) in the medium. Second, RAFT is a very versatile process able to control the (co)polymerization of a large variety of monomers leading to a virtually unlimited macromolecular design library.As a consequence, RAFT polymerization is a well-suited and promising technique to prepare high-performance polymers for a wide range of applications. Indeed, an efficient control at the macromolecular level is a very important step to control and improve the macroscopic properties of the final materials ( Fig. 13.1).