Molecular Microfluidic Bioanalysis: Recent Progress in Preconcentration, Separation, and Detection

This chapter reviews the state-of-art of microfluidic devices for molecular bioanalysis with a focus on the key functionalities that have to be successfully integrated, such as preconcentration, separation, signal amplification, and detection. The first part focuses on both passive and electrophoretic separation/sorting methods, whereas the second part is devoted to miniaturized biosensors that are integrated in the last stage of the fluidic device

Overview of Materials for Microfluidic Applications

For each material dedicated to microfluidic applications, inherent microfabrication and specific physico‐chemical properties are key concerns and play a dominating role in further microfluidic operability. From the first generation of inorganic glass, silicon and ceramics microfluidic devices materials, to diversely competitive polymers alternatives such as soft and rigid thermoset and thermoplastics materials, to finally various paper, biodegradable and hydrogel materials; this chapter will review their advantages and drawbacks regarding their microfabrication perspectives at both research and industrial scale. The chapter will also address, the evolution of the materials used for fabricating microfluidic chips, and will discuss the application‐oriented pros and cons regarding especially their critical strategies and properties for devices assembly and biocompatibility, as well their potential for downstream biochemical surface modification are presented

Macromolecular assemblies onto chemically nanopatterned surfaces

Among other things, the last decade has seen the emergence of two important techno-scientific features, which are the entry of semi-conductor integration technology in the nanometer range, and the explosion of chemical methods allowing to produce or to manipulate functional nano-objects such as macromolecules, proteins, clusters, nanotubes and colloids. It is therefore timely to develop ways to merge these two trends, which would allow significant progresses in these fields where the integration of soft-condensed matter with semi-conductor nanotechnology is of critical importance (biosensors, organic electro- and photo-active devices, molecular engines, etc.). In this context, there is currently an urgent need to succeed in placing organic nano-objects at specific addressable locations on a substrate. For fragile soft organic structures, letting Nature drive functional nano-objects to their docking locations could be a successful route for the fabrication of low cost nano-engineered devices in the near future. In this work, we precisely present a general route allowing to self-assemble macromolecules of varying natures at specific locations defined at the nanometer scale. Assembling instructions are first stored on a substrate, through the combination of electron-beam nanolithography and surface chemical reactions based on reactive silanes. In a subsequent step, the instructions are deciphered by organic molecules brought in contact with the patterned substrate, leading to controlled nanoscale deposition and assembly. The first part of this work consists of the production of surfaces chemically patterned with very high resolution (<<100 nm dimensions), by using gas phase silanation and electron beam lithography. The patterns were imaged and characterized to demonstrate that our technique allows us to obtain chemical templates down to 20-25 nm feature size level, comprising a wide range of chemical functionalities. These patterned surfaces were then used to direct the adsorption or the grafting of various macromolecular compounds, resulting in the formation of macromolecular 3D nanostructures from the 2D binary patterned surfaces. Different interactions were used to control the 3D assembly process, such as electrostatic interactions (layer-by-layer deposition of polyelectrolytes), combined hydrophobic and electrostatic interactions (for the selective adsorption of amphiphilic triblock copolymers), hydrophobic interactions for the local deposition of a protein (antigen 69K from Bordetella pertussis) and valence bond for the grafting of macromolecules at specific locations. For each of these assembling strategies, specific effects resulting from the nanoscale confinement of the macromolecules were evidenced, such as folding of chains of size larger than the 2D directing patches, tuning of antigen orientation, formation of complex block copolymer nanostructures decorating the edges of the 2D patterns, and reduced grafting probability for free radical polymerization on small patches. These results illustrate the rich behavior of macromolecules when approaching nano-patterned surfaces, and suggest that new rules govern macromolecules at this scale.Doctorat en sciences appliquées (FSA 3)--UCL, 200

Binary nanopatterned surfaces prepared from silane monolayers

We report on the fabrication of planar surfaces bearing nanoscale chemical patterns, obtained by combining electron beam lithography and gas-phase silanation, offering an unprecedented range of chemical functionalities down to the 20-25-nm feature size level. Compared to previously reported methods, this method combines a number of desirable features such as high resolution, a large range of accessible chemical functions, the possibility to pattern large surfaces, and the potential for higher throughput. The formation from the gas phase of silane monolayers of high quality and varying chemical functionality is shown to be achievable through the nanoholes of poly(methyl methacrylate) (PMMA) masks prepared by e-beam nanolithography on Si wafers. The removal of the mask and subsequent silanation of the background provides ultraflat surfaces chemically nanopatterned over large areas. The patterns were imaged and characterized by atomic force microscopy (AFM). The patterned surfaces can be used, for instance, to direct macromolecular assembly, as demonstrated by controlling the deposition of polyelectrolyte multilayers on the 150-nm scale

Nanoconfined polyelectrolyte multilayers

Lateral nanometer-scale control over the growth of polyelectrolyte (layer-by-layer) multilayers is demonstrated down to 40 nm, which is well below the natural size of the macromolecules in solution. Because of confinement upon adsorption, the molecules change conformation as compared with the usual, macroscopic case (see Figure). This work opens direct opportunities for transferring polyelectrolyte multilayer systems to nanotechnology

Polarised potential: Novel nanotech

International audienceScientists at the Laboratory for Photonics and Nanostructures have been developing a microfluidic device forthe control and measurement of electrokinetic phenomena that aims to blows previous models out of the water

Polarised potential: Novel nanotech

International audienceScientists at the Laboratory for Photonics and Nanostructures have been developing a microfluidic device forthe control and measurement of electrokinetic phenomena that aims to blows previous models out of the water

Nanopatterned self-assembled monolayers

We report on the fabrication of chemically nanopatterned gold surfaces by combining electron-beam lithography with gas and liquid phase thiolization. The line-edge roughness of the patterns is similar to 4 nm, corresponding to a limiting feature size in the range of 15 nm. Indications for a lower packing density of the self-assembled monolayers grown in the nanofeatures are given, and evidences for the bleeding of thiols along the grain boundaries of the gold substrate are displayed. A comparison is provided between nanopatterned thiol and silane monolayers on gold and on silicon wafers, respectively. The line-edge roughnesses are shown to be close to each other for these two systems, indicating that the limiting step is currently the lithography step, suggesting possible improvement of the resolution. The advantages and drawbacks of thiol versus silane monolayers are finally discussed with respect to the formation of chemically nanopatterned surfaces