Kaori Kamata

Fabrication of left-handed metal microcoil from spiral vessel of vascular plant.

Silver microcoil is fabricated through a biotemplating process combined with electroless plating. Spiral vessels in Lotus root are employed as a biotemplate because of their left-handed coil structure. The silver microcoil exhibits a solenoidal microcoil showing self-inductance in the level of picohenry, which could be applied for electromagnetic-responsive materials in the high-frequency region such as millimeter waves or terahertz waves.

Smart block copolymer masks with molecule-transport channels for total wet nanopatterning

Total wet nanopatterning on silicon wafer surface by using liquid-crystalline (LC) integrated amphiphilic block copolymer (BC) masks with perpendicularly aligned poly(ethylene oxide) (PEO) cylindrical domains as molecule-transport channels is demonstrated. This smart BC mask enables us to fabricate hexagonally arranged nanohole arrays, by nanopatterning of silicon wafer surfaces, with tunable periodicity in a range of 16–40 nm and precise transcription with an accuracy of a few nanometers. Blending poly(ethylene glycol) monomethyl ether into the PEO cylinders to be nanochannels is a key trick to induce effective transportation of both etching reagents and products in the successful wet nanopatterning. The BC lithography with our smart BC masks and wet etching processes may be evaluated as a low-cost and mass-productive wet nanopatterning of silicon wafers, and may be applied to wide variety of substrates such as metals, semiconductors, glasses, and polymers by choosing appropriate etching reagents.

Spirulina -Templated Metal Microcoils with Controlled Helical Structures for THz Electromagnetic Responses

Microstructures in nature are ultrafine and ordered in biological roles, which have attracted material scientists. Spirulina forms three-dimensional helical microstructure, one of remarkable features in nature beyond our current processing technology such as lithography in terms of mass-productivity and structural multiplicity. Spirulina varies its diameter, helical pitch, and/or length against growing environment. This unique helix is suggestive of a tiny electromagnetic coil, if composed of electro-conductive metal, which brought us main concept of this work. Here, we describe the biotemplating process onto Spirulina surface to fabricate metal microcoils. Structural parameters of the microcoil can be controlled by the cultivation conditions of Spirulina template and also purely one-handed microcoil can be fabricated. A microcoil dispersion sheet exhibited optically active response attributed to structural resonance in terahertz-wave region.

Stable macroscopic nanocylinder arrays in an amphiphilic diblock liquid-crystalline copolymer with successive hydrogen bonds

In bulk films of a novel well-defined amphiphilic diblock liquid-crystalline copolymer with aramid moieties, a stable perpendicularly orientated hydrophilic nanocylinder array with hexagonal packing was formed in a large area by supramolecular self-assembly.

Nanodimple Arrays Fabricated on SiO2 Surfaces by Wet Etching through Block Copolymer Thin Films

Block copolymer thin films are promising nanotemplates because highly ordered periodic structures are spontaneously formed through microphase separation on a deca-nanometer scale and over a large area. An amphiphilic block copolymer, which consists of poly(ethylene oxide) (PEO) and poly(methacrylate) (PMA) with azobenzene mesogens and is denoted by PEOm-b-PMA(Az)n, indicates a strong chemical contrast between the corresponding microdomains, which offer structurally reliable nanotemplates for fabricating nanostructured materials. Thermally annealing a PEOm-b-PMA(Az)n thin film provides hexagonally arranged, perpendicularly oriented PEO cylinders, which perform as ion-conductive nanochannels. In this study, a SiO2 layer on a silicon wafer substrate is etched by NH4F through a PEO114-b-PMA(Az)54 thin film as a nanomask. The SiO2 layer is patterned with a 24-nm-periodic hexagonally arranged nanodimple array. Atomic force microscope (AFM), field emission scanning electron microscope (FESEM), and cross-sectional transmission electron microscope (TEM) observations reveal that the nanodimple array has a 2-nm depth and is spread over the entire SiO2 surface on centimeter scale.

Roll-to-Roll Processable PEO-LC Block Copolymer Template Films with Normally Oriented Nanocylinder Array Structures

This paper reports the first demonstration of roll-to-roll coating of a series of poly(ethylene oxide) (PEO)-liquid crystalline (LC) block copolymers by using microgravure coating. Highly ordered hexagonal dot structure was revealed on the whole surface of the coated surface by AFM imaging. Cross sectional TEM observation of the microtomed specimen of the film exclusively exhibited normally oriented PEO nanocylinder array structure, consistent with those prepared in a conventional laboratory procedure by spin-coating, bar coating, and cast.

Nanocylinder Array Structures in Block Copolymer Thin Films

An overview of the microphase separation of block copolymers is described here ranging from their syntheses and basic phase behaviors to the recent progress in the fabrication of ultrafine self-organized nanostructures. Since the synthesis of block copolymers with a narrow polydispersity and a wide variety of backbones such as a rod-coil or a coil-coil block copolymer has undergone considerable development over the last 20 years, the morphology of self-organized nanostructures in block copolymer melts can be controllable from the viewpoint of polymer design and treatment conditions generating the desired phases. The self-organized nanostructure with cylindrical phase has especially attracted much interest due to the structural character of its domains, which are either continuous or noncontinuous in the solid state, i.e., the anisotropic distribution of the elements, and due to its ability to control the cylinder direction against the film. The nanocylinder array structures in block copolymer samples have also been shown to be promising for the design of electric and photonic devices.

Hexagonally Arranged Nanopore Film Fabricated via Selective Etching by 172-nm Vacuum Ultraviolet Light Irradiation

Abstract Highly ordered nanopore arrays were successfully fabricated using poly(ethylene oxide) (PEO) and polymethacrylate with azobenzene mesogen in side chains [PMA(Az)] block copolymer film based on irradiation of 172-nm vacuum ultraviolet (VUV) light. The block copolymer forms a highly ordered microphase-separated film with perpendicularly oriented PEO cylinders just by thermal annealing through a self-assembling process. We found that the etching rate of the PEO homopolymer was much higher than that of the PMA(Az) homopolymer at a chamber pressure of 102 Pa of atmosphere under VUV irradiation. The etching rate of the PEO component in the two systems of microphase separation and macrophase separation of the homopolymer blend crucially depended on the feature size of phase separation. In the PEO selective etching process of the block copolymer film, the water-contact angle of the film dramatically increased due to elimination of hydrophilic PEO. The resulting nanopore array film will be useful for low-density target materials.

Nanopatterning of Si wafer surface using microphase-separated structure of block copolymer as wet etching mask

This report presents a new lithographic process utilizing the microphase-separated structures as an etching mask for wet chemical etching of Si wafer. The process demonstrated in this study could open easy tuning of pattern size by changing molecular weight of block copolymers and large area nanopattern transcription with high throughput.