The interaction of cells and bacteria with surfaces structured at the nanometre scale.

Block copolymer thin films can be used as soft templates for a wide range of surfaces where large area patterns of nanoscale features are desired. The cylindrical domains of acid-sensitive, self-assembled monolayers of polystyrene−poly(2-vinylpyridine) block copolymers on silicon surfaces were utilized as structural elements for the production of parallel metal nanowires. Metal ion loading of the P2VP block with simple aqueous solutions of anionic metal complexes is accomplished via protonation of this basic block, rendering it cationic; electrostatic attraction leads to a high local concentration of metal complexes within the protonated P2VP domain. A subsequent brief plasma treatment simultaneously removes the polymer and produces metallic nanowires. The morphology of the patterns can modulated by controlling solution concentration, deposition time, and molecular weight of the block copolymers, as well as other factors. Horizontal metallic nanoarrays can be aligned on e-beam lithographically defined sil...

Using cylindrical domains of block copolymers to self-assemble and align metallic nanowires.

We demonstrated a self-assembly of two different kinds of nanoparticles simultaneously directed on a monolayer film of diblock copolymer micelles via physical and chemical arrangements. We first incorporated gold nanoparticles physically around the micelles of a monolayer film of PS-PVP micelles having a short-range hexagonal order. Iron oxide nanoparticles were then synthesized chemically in the PVP core area of the ordered micelles, resulting in a mosaic nanopattern of magnetic iron oxide nanoparticles surrounded by metallic gold nanoparticles. Thus, we were able to direct two kinds of nanoparticles to self-assemble in the specific positions as an example of controlled fabrication of nanometer-sized building blocks.

Directed self-assembly of two kinds of nanoparticles utilizing monolayer films of diblock copolymer micelles.

Membranes can be fabricated either from lipid or polymer molecules, leading to the formation of liposomes or polymersomes. In all types of liposomal membranes, the issue of phase separation plays a central role not only in the membrane-formation itself, but also in the resulting structural features taking place within or at the surface of such membranes. When nanoparticles or polymers interact with lipid membranes, the final morphology is strongly determined by the charge, composition and size of the interacting components, which in turn induce phase separation processes. The present review assembles investigations on lipid/polymer/nanoparticle interaction with the main focus directed towards model membrane systems published in the recent literature starting from ∼2005, providing a deeper and more thorough understanding of these complex interactions and their effects on membrane properties.

Beyond the lipid-bilayer: interaction of polymers and nanoparticles with membranes

The driving forces behind the development of flexible electronics are their flexibility, lightweightedness, and potential for low-cost manufacturing. However, because of physical locations, traditional thermal processes cause deformations in the flexible substrate. As a result, the adhesion quality of the printed wires is deteriorated. This article reviews recent developments in printing circuits on a flexible substrate by combining self-assembled polyelectrolytes, ink-jet printing of a catalyst, and electroless plating of metals. The limitations and potential applications of this technology are also discussed. Experiments implementing this technology demonstrated significant results. By a vibration-induced assistance during an ink-jet printing catalyst process, line width and blurring can be controlled to within ′3% variation. Following the IPC 6013 standard for flexible electronics, the results after thermal cycling (288 °C, 6 times) and a hot oil test (260 °C, 3 times) indicated that the metallic circuit had retained excellent adhesion properties and electric characteristics. We also report the first successful demonstration of a metal film in a via-hole inner wall on a flexible substrate. This novel fabrication method is ideal for the realization of large area, flexible electronics and furore multilayer flexible substrate Application, such as flexible display, chip on flexible substrate, etc. particularly where traditional lithographic processes can not be applied.

Ink-Jet Printing, Self-Assembled Polyelectrolytes, and Electroless Plating: Low Cost Fabrication of Circuits on a Flexible Substrate at Room Temperature

A polystyrene−poly(ethylene oxide) containing diblock copolymer, when spread at the air/water interface, spontaneously forms surface aggregates. This surface aggregation is shown to be neither compression-induced, associated with micellization in the spreading solvent, nor induced by the Langmuir−Blodgett film transfer process. We have previously found that such two-dimensional surface aggregation occurs for diblock copolymers with a polystyrene block and a hydrophilic block of quaternized poly(vinylpyridine), poly(tert-butyl acrylate), poly(n-butyl acrylate), or poly(dimethylsiloxane). The phenomenon has also been observed in films of polystyrene−poly(methyl methacrylate) by Rice and co-workers.1 Indeed, whenever an appropriate imaging technique has been used, phase-separated domains with 30−100 nm length scales have been observed, when amphiphilic diblock copolymers are spread at the air/water interface and transferred to solid substrates at appreciable surface pressures. We therefore believe that the f...

Polystyrene−Poly(ethylene oxide) Diblock Copolymers Form Well-Defined Surface Aggregates at the Air/Water Interface

The self-assembly of block copolymers, homopolymers and surfactants on surfaces often leads to well-defined patterns with topologically or chemically distinct regions. Important recent developments in controlling the nature of the pattern include methods to produce patterns via passive adsorption of a solid substrate; coupling of substrate topology and polymer phase separation in order to effect control over pattern formation; and methods to `tune' the surface potential of the substrate to eventually control pattern formation. The use of the polymer-patterned surface as a nanolithography mask has also been demonstrated in two very interesting systems. © 1999 Elsevier Science Ltd.

Patterned surfaces via self-assembly

We have investigated the effect of surface compression on the form of surface aggregates of diblock copolymers of polystyrene and poly(ethylene oxide) formed on a water subphase. The hexagonal order found in the surface aggregates at low surface pressures is disrupted as the surface pressure increases up to the transition in the surface pressure–area isotherm. We show that the PEO block does not go into the aqueous subphase to form a brush. Three models describing the conformation of the copolymer in the surface aggregates are proposed and their relative merits in terms of the experimental evidence are discussed. The most favored model is one where the polystyrene core of the surface aggregates sits on top of a coherent film of PEO. There is a good correlation between the behavior of the diblock copolymer and previous work by Shuler and Zisma on spread films of homopoly(ethylene oxide). In this description the PEO undergoes a dehydration process and a conformational change upon compression.

Compression of polystyrene–poly(ethylene oxide) surface aggregates at the air/water interface

Block polyelectrolytes P(Sx-b-VP/RXy) composed of polystyrene (PS) blocks (x = 200, 260) and alkylated (R = Cn) poly(vinylpyridine) (PVP) (X = I or Br; y = 119−270; n = 4, 10, and 18) have been studied using the Langmuir film balance technique and in situ X-ray and neutron reflectivity measurements. Previous studies showed that the self-assembled surface micelles (with PS core and RPV+PX- corona) at the air/water interface revealed a characteristic transition (when n > 6) without any significant hydration or the submersion of the corona chains. Combined X-ray and neutron reflectivity studies of P(Sx-b-VP/RXy) polyelectrolytes show that although the polyelectrolyte block is water soluble, it remains adsorbed to the water surface. The thickness of the adsorbed layer measured by X-ray reflectivity is in agreement with that measured using neutron reflectivity. This agreement indicates that the counterions are closely associated with the alkylated PVP chains, localized at the air/water interface, and are not d...

Juliet K. Cox

Papers

Polystyrene−Poly(ethylene oxide) Diblock Copolymers Form Well-Defined Surface Aggregates at the Air/Water Interface

Patterned surfaces via self-assembly

Compression of polystyrene–poly(ethylene oxide) surface aggregates at the air/water interface

Observation of Surface Ordering of Alkyl Side Chains in Polystyrene/Polyelectrolytes Diblock Copolymer Langmuir Films