Silver nanowires (AgNWs) surrounded by insulating poly(vinylpyrrolidone) have been synthesized by a polyol process and employed as transparent electrodes. The AgNW transparent electrodes can be fabricated by heattreatment at about 200 °C which forms connecting junctions between AgNWs. Such a heating process is, however, one of the drawbacks of the fabrication of AgNW electrodes on heat-sensitive substrates. Here it has been demonstrated that the electrical conductivity of AgNW electrodes can be improved by mechanical pressing at 25 MPa for 5 s at room temperature. This simple process results in a low sheet resistance of 8.6 Ω/square and a transparency of 80.0%, equivalent to the properties of the AgNW electrodes heated at 200 °C . This technique makes it possible to fabricate AgNW transparent electrodes on heat-sensitive substrates. The AgNW electrodes on poly(ethylene terephthalate) films exhibited high stability of their electrical conductivities against the repeated bending test. In addition, the surface roughness of the pressed AgNW electrodes is one-third of that of the heat-treated electrode because the AgNW junctions are mechanically compressed. As a result, an organic solar cell fabricated on the pressed AgNW electrodes exhibited a power conversion as much as those fabricated on indium tin oxide electrodes. These findings enable continuous roll-to-roll processing at room temperature, resulting in relatively simple, inexpensive, and scalable processing that is suitable for forthcoming technologies such as organic solar cells, flexible displays, and touch screens.

We demonstrate the fabrication of highly transparent conductive networks on a cellulose nanofiber paper, called cellulose nanopaper. Uniform coating of the conductive nanomaterials, such as silver nanowires (AgNWs) and carbon nanotubes, is achieved by simple filtration of their aqueous dispersions through the cellulose nanopaper, which acts as both filter and transparent flexible substrate. The as-prepared AgNW networks on the nanopaper offer sheet resistance of 12 X sq. À1 with optical transparency of 88%, which is up to 75 times lower than the sheet resistance on a polyethylene terephthalate film prepared by conventional coating processes. These results indicate that the 'filtration coating' provides uniformly connected conductive networks because of drainage in the perpendicular direction through paper-specific nanopores, whereas conventional coating processes inevitably cause self-aggregation and uneven distribution of the conductive nanomaterials because of the hard-to-control drying process, as indicated by the well-known coffee-ring effect. Furthermore, the conductive networks are embedded in the surface layer of the nanopaper, showing strong adhesion to the nanopaper substrate and providing foldability with negligible changes in electrical conductivity. This filtration process is thus expected to offer an effective coating approach for various conductive materials, and the resulting transparent conductive nanopaper is a promising material for future paper electronics.

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Optically transparent nanofiber paper containing silver nanowires showed high electrical conductivity and maintained the high transparency, and low weight of the original transparent nanofiber paper. We demonstrated some procedures of optically transparent and electrically conductive cellulose nanofiber paper for lightweight and portable electronic devices. The nanofiber paper enhanced high conductivity without any post treatments such as heating or mechanical pressing, when cellulose nanofiber dispersions were dropped on a silver nanowire thin layer. The transparent conductive nanofiber paper showed high electrical durability in repeated folding tests, due to dual advantages of the hydrophilic affinity between cellulose and silver nanowires, and the entanglement between cellulose nanofibers and silver nanowires. Their optical transparency and electrical conductivity were as high as those of ITO glass. Therefore, using this conductive transparent paper, organic solar cells were produced that achieved a power conversion of 3.2%, which was as high as that of ITO-based solar cells.

We have developed an environmentally benign large-scale (50 kg wood meal per batch) lignin production plant, operating based on acid-catalyzed polyethylene glycol (PEG) solvolysis of softwood biomass. The motivation for the proposed process was to promote technological innovation in biomass utilization systems in Japanese rural areas based on widely abundant Japanese cedar (sugi) biomass. In this study, the process was evaluated by investigating the effects of the source sugi wood meal size and the solvent PEG molecular mass on the yield, chemical structure, molecular mass, and thermal properties of the resultant PEG-modified lignin derivatives, glycol lignins (GLs). Reducing the source wood meal size and PEG solvent molecular mass not only promoted lignin PEGylation but also the subsequent acid-induced chemical rearrangements of the GLs as demonstrated by chemical analyses, 2D NMR, and size exclusion chromatography (SEC). Reducing the source wood meal size and/or increasing the solvent PEG molecular mass enhanced the thermal properties of GLs as determined by thermomechanical analysis (TMA) and thermogravimetric analysis (TGA). We considered that the proposed process can efficiently produce lignin derivatives with substantial control over the chemical structure and thermal properties to meet commercial and industrial needs for lignin-based advanced material production.

The apatite forming ability of biopolymer bacterial cellulose (BC) has been investigated by soaking different BC specimens in a simulated body fluid (1.5 SBF) under physiological conditions, at 37 degrees C and pH 7.4, mimicking the natural process of apatite formation. From ATR-FTIR spectra and ICP-AES analysis, the crystalline phase nucleated on the BC microfibrils surface was calcium deficient carbonated apatite through initial formation of octacalcium phosphate (OCP) or OCP like calcium phosphate phase regardless of the substrates. Morphology of the deposits from SEM, FE-SEM, and TEM observations revealed the fine structure of thin film plates uniting together to form apatite globules of various size (from <1 mum to 3 mum) with respect to the substrates. Surface modification by TEMPO (2,2,6,6-tetramethylpyperidine-1-oxyl)-mediated oxidation, which can readily form active carboxyl functional groups upon selective oxidation of primary hydroxyl groups on the surface of BC microfibrils, enhanced the rate of apatite nucleation. Ion exchanged treatment with calcium chloride solution after TEMPO-mediated oxidation was found to be remarkably different from other BC substrates with the highest deposit weight and the smallest apatite globules size. The role of BC substrates to induce mineralization rate differs according to the nature of the BC substrates, which strongly influences the growth behavior of the apatite crystals.

In this study, we use nanostructured paper made from cellulose nanofibres (CNFs) as a flexible printable material for inkjet-printing of silver nanoparticle (AgNP) ink. The nanostructured paper is prepared by sheet casting of 10-40 nm wide mechanically fibrillated aqueous CNFs in suspension. The resulting nanostructured paper, in the form of densely packed laminar layers, has low surface roughness (40 AE 2.3 nm) and a nanoporous network structure. This unique surface feature helps the ink vehicles to permeate through the nanopores and also aids absorption along the fibril direction parallel to the surface while retaining the silver nanoparticles on the surface to compete with the initial spreading and final evaporation processes. As a result, well-defined inkjet-printed AgNP conductive tracks ($400 mm wide) on nanostructured paper show lower electrical resistance (1.57 AE 0.09 U cm À1 ) than those on commonly used plastics, including polyimide (PI, 2.07 AE 0.17 U cm À1 ) and poly(ethylene naphthalate) (PEN, 2.10 AE 0.16 U cm À1 ), at a moderate curing temperature of 150 C for 1 h. The inkjet-printed conductive tracks on nanostructured paper also show better electrical performance during and after folding than those printed on plastic substrates, such as PI, and exhibit stable electrical properties throughout a test period of 1000 h in a moisture resistance test (85 C and 85% relative humidity). The better overall electrical performance compared with that of tracks on plastic substrates highlights the potential of genuinely nanostructured paper as a printing substrate for flexible printed electronics.

Requirements for flexible electronic substrate are successfully accomplished by green nanocomposite film fabricated with two natural components: glycol-modified biomass lignin and Li montmorillonite clay. In addition to these major components, a cross-linking polymer between the lignin is incorporated into montmorillonite. Multilayer-assembled structure is formed due to stacking nature of high aspect montmorillonite, resulting in thermal durability up to 573 K, low thermal expansion, and oxygen barrier property below measurable limit. Preannealing for montmorillonite and the cross-linking formation enhance moisture barrier property superior to that of industrial engineering plastics, polyimide. As a result, the film has advantages for electronic film substrate. Furthermore, these properties can be achieved at the drying temperature up to 503 K, while the polyimide films are difficult to fabricate by this temperature. In order to examine its applicability for substrate film, flexible electrodes are finely printed on it and touch sensor device can be constructed with rigid elements on the electrode. In consequence, this nanocomposite film is expected to contribute to production of functional materials, progresses in expansion of biomass usage with low energy consumption, and construction of environmental friendly flexible electronic devices.