Tetsuro Sawadaishi

Mesoscopic patterns of molecular aggregates on solid substrates

Abstract A two-dimensional micron-sized honeycomb structure was formed when a chloroform solution of an amphiphilic polymer was cast on solid surfaces at high atmospheric humidity. This simple method is widely applicable for patterning of molecular aggregates on solid surfaces. Mesoscopic patterns are demonstrated to be formed spontaneously from a variety of amphiphilic polyion complexes, amphiphilic covalent polymers, and organic–inorganic hybrid materials. Size and structure of the patterns can be regulated by concentration, atmospheric humidity, etc.

Bottom-up strategy of materials fabrication: a new trend in nanotechnology of soft materials

Recent progresses in nanometer-scale molecular self-organization and mesoscopic pattern formation are reviewed from the view point of nanotechnology of bottom-up materials fabrication. Nanometer-scale layer-by-layer self-assemblies on nanoparticles will provide wide applications in many fields. The micro-contact printing technique is effectively used for up-sizing the nanostructured molecular assemblies as submicrometer- and micrometer-scale patterns. Dissipative structures formed in non-equilibrium systems as self-organized spatio-temporal structures are newly employed for the mesoscopic patterning of the nanostructured molecular assemblies.

Mesoscopic pattern formation of nanostructured polymer assemblies

Abstract Hierarchical mesoscopic structures of the nanoscopic supramolecular assemblies, which consist of polyelectrolytes and bilayer-forming amphiphiles, are prepared by a simple and new solvent-casting method. Submicron scale 2-D structures, e.g. regular dots, stripes, and networks, are formed when highly diluted organic solutions of polymer assemblies are cast on solid surfaces. Dynamic mesoscopic regular structures, the so-called ‘dissipative structures’, formed in the non-equilibrium processes of solvent-casting are fixed as hierarchically structured polymer assemblies.

Utilization of DNA as functional materials: Preparation of filters containing DNA insolubilized with alginic acid gel

Thin films composed of DNA and alginic acid were prepared by casting their mixed solution on glass plate followed by coagulation with aqueous solution of calcium chloride. DNA could be conveniently insolubilized by this method. DNA in the films adsorbed intercalating materials, such as ethidium bromide. This phenomenon was successfully applied to the preparation of filters for the selective removal or accumulation of harmful intercalating pollutants.

Two-Dimensional Patterning of Nanoparticles Using Dissipative Structures

Abstract Two-dimensional regular patterns of nanoparticles were formed on solid substrate by casting colloidal dispersion. Periodic stripes were formed on mica surface parallel to the receding direction of casting solution. The thickness of each stripe was estimated to be comparable to that of monolayer of particles. From atomic force microscopy (AFM) and scanning electron microscopy (SEM), it was cleared that the monolayer of silica particles were hexagonally packed.

Control of Structures of Two-dimensional Patterns of Nanoparticles by Dissipative Process

In this report, we will describe about control of structures of two-dimensional patterns of nanoparticles. When the glass substrate was dipped into and withdrawn from highly concentrated dispersion of nanoparticles, stripe-crack patterns were formed parallel to the receding direction. The patterned assembly of nanoparticles was spontaneously removed from glass substrate. From scanning electron microscopy (SEM), it was clear that the assembly of silica particles had strap-like structure. The thickness of the assembly consisting of silica particles could be controlled by deposition speed and size of particles.

PREPARATION OF MESOSCOPIC PATTERNS OF NANOPARTICLES BY SELF-ORGANIZATION

Two-dimensional regular patterns consisting of ultra-fine particles were formed on honeycomb-patterned polymer film. Ultra-thin polymer films were prepared by simple casting of diluted amphiphilic polymer solution onto solid substrate. In the cast film, honeycomb patterns were observed as a result of evaporative cooling in the casting solution. Ultra-fine particles were introduced into the hole of honeycomb-patterned films by simple casting or dip-coating of aqueous ultra-fine particles dispersion. Densely packed ultra-fine particles were observed in only the hole of honeycomb pattern but not on the limb. The patterns of ultra-fine particles were expected to be the novel functional optical materials containing photonic crystals.

Fabrication and photoconductivity measurements of mesoscopic 2-D patterned DNA

Abstract Regularly arrayed mesoscopic lines of DNA, parallel to the receding direction of the solvent, can be prepared by simple casting from an aqueous solution. Photocurrent of single line of DNA assemblies containing intercalators, acridine orange, was generated when the patterned cast film was irradiated by the light at 480nm, through the excitation of the intercalators.

A novel microfabrication process of polymer materials and nanoparticles based on self-organization

Dissipative structures formed in the casting polymer solutions are utilized for micro- and nano-patterning of polymer materials. We have found that the typical dissipative structures were formed in the casting process of polymer solutions on solid surfaces. Dynamic regular structures formed in casting polymer solutions are fixed as regular patterns, stripes, and lattices, etc., of polymer materials. We have also found regular pattern formation in casting solutions of nanoparticles.