Toshiharu Enomae

Paper substrate modification for rapid capillary flow in microfluidic paper-based analytical devices

The development of microfluidic paper-based analytical devices is the most promising emerging research globally, due to its main advantage of spontaneous liquid transport. Though many fabrication and detecting methods have been developed, there remain several challenges to overcome. In this paper, we present the findings of a simple and quick fabrication method that was developed by printing a modified poly(styrene-co-acrylic acid) solution using an ink jet printer. The formed hydrophobic barrier was then analyzed using a confocal laser scanning microscope and a scanning electron microscope. To overcome the problem of liquid analyte evaporation during long-distance delivery and long-time analysis, experiments were conducted on various conventional parameters in papermaking processes. To examine the influence of internal channel width, fiber orientation, plasma-etching treatment, beating degree and calendering, volumetric flow rates of channels were measured using an automatic scanning absorptometer. Consequently, internal channel width had no effect on the flow rate, and channels aligned along the machine direction exhibited higher volumetric and longitudinal flow rates than they did in the cross direction. Plasma-etching treatment was found to increase the longitudinal flow rate, but the volumetric flow rate remained virtually the same. It was also found that higher beating degrees decreased the flow rates, likely caused by the decreased radius of pores between fibers. Finally, it was found that calendering affected the flow rates only marginally.

Application of Biomaterials and Inkjet Printing to Develop Bacterial Culture System

We created an automated bioassay system based on inkjet printing. Compared to conventional manual bacterial culture systems our printing approach improves the quality as well as the processing speed. A hydrophobic/hydrophilic pattern as a container supporting a culture medium was built on filter paper using a toluene solution of polystyrene for hydrophobization, followed by toluene printing to create several hydrophilic areas. As culture media we used a novel poly(vinyl alcohol) based hydrogel and a standard calcium alginate hydrogel. The poly(vinyl alcohol) hydrogel was formed by physical crosslinking poly(vinyl alcohol) with adipic acid dihydrazide solutions. The conditions of poly(vinyl alcohol) gelation were optimized for inkjet printability and the optimum mixture ratio was determined. The calcium alginate hydrogel was formed by chemical reaction between sodium alginate and CaCl2 solutions. Together with nutrients both hydrogel solutions were successfully printed on paper by means of the modified inkjet printer. The amount of each solution was demanded simply by outputting CMYK values. In the last step bacterial cells were printed on both hydrogel media. For both media we achieved a stable bacteria growth which was confirmed by microscopical imaging of the developed bacterial colonies.

Traditional Papermaking Techniques revealed by Fibre Orientation in Historical Papers

Abstract This work aims to select adequate repair papers, based on fibre orientation information derived from paper objects during restoration, using non-destructive image analysis applied to micrographs of paper surfaces. Contemporary Japanese handmade papers exhibited high values of fibre orientation intensity, while contemporary Korean handmade papers exhibited low intensity values. This difference was assumed to be due to different sheet-forming actions. Model papers prepared in the laboratory by the still sheet-forming and flow sheet-forming methods had low and high values of fibre orientation intensity, respectively. Additionally, the screen side for the flow sheet-forming method had a value of fibre orientation intensity higher than the top side. This fact was logically explained in terms of fibre flow and dehydration rate, and consequently suggests its applicability to distinguishing the sides of ancient document papers. The application of this technique to the Shimadzu Family documents from 1606 to 1859 indicated high values of fibre orientation, suggesting that the flow sheet-forming method had already been established by the early seventeenth century in Japan. The papers of Korean Buddhist sacred books manufactured between the eleventh and sixteenth centuries exhibited low orientation intensity values, and the differences between the two sides were small. This indicates that the papers were manufactured by the still sheet-forming method concurrently with a sideways swing.

Electrical response of culture media during bacterial growth on a paper-based device

In this work, we evaluated the feasibility of a paper-based bacterial detection system. The paper served as a substrate for the measurement electrodes and the culture medium. Using a printing technique, we patterned gold electrodes onto the paper substrate and applied Luria broth (LB) agar gel as a culture medium on top of the electrodes. As the first step towards the development of a bacterial detection system, we determined changes in the surface potential during bacterial growth and monitored these changes over 24 h. This allowed us to correlate changes in the surface potential with the different growth phases of the bacteria.

Influences of saltwater immersion on properties of wood-cellulosic paper

The saltwater immersion method was developed to inhibit mould growth on flood- or tsunami-damaged paper. Commercially available fine paper used for printing and writing showed decreased tensile indices after saltwater immersion. The salt remaining in the paper tended to increase the moisture content because of the salt deliquescence and moisture in the air. The tensile index was restored by removing salt from the paper. Crystallization and distribution of salt in interfibre pores were also considered to influence interfibre rebonding. The difference in the fibre responses to saltwater depended on the relationship between nano-scaled pores in the fibre walls, osmotic pressure, and the degree of sizing, which resulted in low water retention values. More of the starch applied as a surface sizing agent was dissolved or dispersed during distilled water immersion than saltwater immersion. This loosened the fibre network, which was a factor that decreased the sizing degree of the paper.

International Conference Report

2005年11月17日に，フィンランドのヘルシンキで開かれた第5回ヨハンガリクセン討論会に参加した。この討論会は，現在ヘルシンキ工科大名誉教授であるJohan Gullichsen氏が，若手技術者や研究者に発表の場を提供するという趣旨で始めたものである。第5回を迎える今回は，“原料と製造工程―製品の視点から”というテーマで開かれ，5つのカテゴリーと8つの口頭発表が行われた。大規模ではないが，北欧だけでなく世界中からの発表が網羅されている。これらの発表の概要を報告する。