A key tenet of bone tissue engineering is the development of scaffold materials that can stimulate stem cell differentiation in the absence of chemical treatment to become osteoblasts without compromising material properties. At present, conventional implant materials fail owing to encapsulation by soft tissue, rather than direct bone bonding. Here, we demonstrate the use of nanoscale disorder to stimulate human mesenchymal stem cells (MSCs) to produce bone mineral in vitro, in the absence of osteogenic supplements. This approach has similar efficiency to that of cells cultured with osteogenic media. In addition, the current studies show that topographically treated MSCs have a distinct differentiation profile compared with those treated with osteogenic media, which has implications for cell therapies.

The control of human mesenchymal cell differentiation using nanoscale symmetry and disorder

http://files.janapv.webnode.cz/200000097-8a03f8afdf/ex_bias_nano.pdf

Exchange bias in nanostructures

Nanoimprint lithography (NIL) is a nonconventional lithographic technique for high-throughput patterning of polymer nanostructures at great precision and at low costs. Unlike traditional lithographic approaches, which achieve pattern definition through the use of photons or electrons to modify the chemical and physical properties of the resist, NIL relies on direct mechanical deformation of the resist material and can therefore achieve resolutions beyond the limitations set by light diffraction or beam scattering that are encountered in conventional techniques. This Review covers the basic principles of nanoimprinting, with an emphasis on the requirements on materials for the imprinting mold, surface properties, and resist materials for successful and reliable nanostructure replication.

/pdf/nanoimprint-lithography-methods-and-material-requirements-csc83swyi1.pdf

Nanoimprint Lithography: Methods and Material Requirements**

Electrochromic tungsten oxide films: Review of progress 1993–1998

One-dimensional (1D) ZnO nanostructures have been studied intensively and extensively over the last decade not only for their remarkable chemical and physical properties, but also for their current and future diverse technological applications. This article gives a comprehensive overview of the progress that has been made within the context of 1D ZnO nanostructures synthesized via wet chemical methods. We will cover the synthetic methodologies and corresponding growth mechanisms, different structures, doping and alloying, position-controlled growth on substrates, and finally, their functional properties as catalysts, hydrophobic surfaces, sensors, and in nanoelectronic, optical, optoelectronic, and energy harvesting devices.

/pdf/one-dimensional-zno-nanostructures-solution-growth-and-30xs4d6be7.pdf

One-dimensional ZnO nanostructures: Solution growth and functional properties

Electron beam lithography: resolution limits and applications

Molecular spin-crossover complexes of 3d–3d transitionmetal ions have been the focus of many researchers’ work because of their fascinating properties associated with the bistability of their electronic states (high spin (HS) or low spin (LS)). Although the origin of the spin-crossover phenomenon is purely molecular, the macroscopic behavior of these systems in the solid state is strongly determined by the interactions, of mainly elastic origin, between the transition-metal ions. Recently, remarkable progress has been made in the area of spin-crossover complexes with infinite one-, two-, or three-dimensional (1D, 2D, 3D) networks, the so-called coordination polymers. The purpose of this approach was the enhancement and fine tuning of cooperative properties by the strong covalent links between the metallic centers in the polymers. Indeed, a number of highly cooperative polymer systems have been reported in the recent literature that display hysteretic behavior (thermal and piezo), in some cases even at room temperature. In addition to this, we have recently demonstrated that 3D coordination polymers represent an attractive platform for growth of surface thin films with spin-crossover properties. In fact, the 3D network structure allows the sequential assembly, via stepwise adsorption reactions, of multilayer films based entirely on intraand interlayer coordination bonds. These films have opened up possibilities for investigating size-reduction effects, optical and dielectric properties, and device applications of spin-crossover materials. A further step in this direction is the generation of microand nanometer-sized lateral patterns. In fact, the multilayer sequential assembly (MSA) process (also called directed assembly or layer-by-layer assembly in the literature) has become increasingly popular not only for fabricating thin films but also many efforts have been devoted to generating distinct patterns of the multilayer films. Various lithographic and nonlithographic methods—such as deposition on chemically patterned surfaces, inkjet printing, lift-off processes, etching, direct photopatterning, and microcontact printing—have been explored with this aim. Each method has, of course, different merits, but the lift-off process remains an industry standard owing to its simplicity and reliability. Furthermore, when combined with electron-beam lithography (EBL), it allows patterns to be obtained in a wide size range down to the sub10 nm limit, and the alignment of the patterns is also possible with respect to structures that may already exist on the substrate. In this Communication, we report on a process for nanoand microscale assembly of the 3D spin-crossover coordination polymer Fe(pyrazine)[Pt(CN)4] (1) (Scheme 1) by using a combination of top-down (lift-off) and bottom-up (MSA) methods. We call attention to the 3D polymer nature of this system, which is the key aspect for 1) obtaining room-temperature hysteresis, 2) assembling multilayers, and 3) performing C O M M U N IC A IO N

A Combined Top‐Down/Bottom‐Up Approach for the Nanoscale Patterning of Spin‐Crossover Coordination Polymers

Large area arrays of dots have been patterned in Au/Co/Au(111) sandwiches with ultrathin Co layers (0.6 to 2 nm) and a perpendicular easy magnetization axis. Dot dimensions down to 0.2 μm have been achieved using x‐ray lithography, with either positive resist and direct ion beam etching or a lift‐off process with aluminum mask. Both processes have been tested against the damages they induce to the fragile structure of the samples. The magneto‐optical effects and magnetization reversal processes in the arrays have been characterized versus Co thickness, dot dimension, and lattice aspect ratio. For high quality samples, the domain walls propagation mechanism that drives magnetization reversal in as‐grown films is drastically modified in dot arrays, leading to a large increase of the coercive field with dot diameter reduction, together with changes in the shape of the hysteresis loops.

Study of large area high density magnetic dot arrays fabricated using synchrotron radiation based x‐ray lithography

Nanoimprint lithography for a large area pattern replication

A technology of proximity x‐ray lithography has been developed to replicate patterns of sub‐100‐nm feature size using synchrotron radiation. Process modeling has been done in advance in order to optimize the mask absorber thickness. It is shown that with tungsten absorber, a 0.3 μm thickness is the most desirable for 50 nm linewidth processing. Masks compatible with a Karl Suss stepper have been fabricated using 50 keV electron‐beam lithography and reactive ion etching techniques. As a result, well‐defined 50‐nm‐wide isolated W lines and small gratings of period down to 100 nm have been fabricated. Then they have been replicated under proximity condition using Super ACO synchrotron radiation. We present details of a replication procedure with gap settings down to 5 μm and show how sub‐100 nm structures can be 1:1 printed into both poly (methylmethacrylate) (PMMA) and (8.5%) MAA/PMMA resists. Finally, the results are analyzed in terms of a scaling rule to evaluate the resolution limit as a function of proximity gap using a synchrotron source.

Franck Carcenac

Papers

Electron beam lithography: resolution limits and applications

A Combined Top‐Down/Bottom‐Up Approach for the Nanoscale Patterning of Spin‐Crossover Coordination Polymers

Study of large area high density magnetic dot arrays fabricated using synchrotron radiation based x‐ray lithography

Nanoimprint lithography for a large area pattern replication

50‐nm x‐ray lithography using synchrotron radiation