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We examined the slicing technique of silicon wafers with little kerf loss using an ultrafine wire tool. As the first step, we performed microgrooving with an ultrafine wire tool. The thinning of the wafer and the decrease in kerf loss can minimize production costs. We discuss the strength characteristics and the microgrooving performance of the ultrafine wire tool. The main results are as follows. The relative velocity greatly affects the grooving properties. The ultrafine wire tool easily breaks when the relative speed is high. When the ultrafine wire tool and abrasives with large diameter grains are used, the ultrafine wire easily breaks and chipping in the work material easily occurs; furthermore, the ultrafine wire strays.

A microbial chip is demonstrated that immobilises microbes into micro holes using positive dielectrophoresis (DEP) for efficient screening. The DEP frequency was set at 10 MHz, which was found to be most effective to selectively immobilise live bacteria. The media including reactive agents can be flown into the chip continuously and therefore the reaction products can be continuously collected. Immobilisation of microbes enables quantification of the number of microbes involved in the reaction and makes their reactions conditions consistent. These advantages enable the proposed microbial chip to evaluate the production capacity of a single bacterium. To demonstrate it, the developed microbial chip was used to characterise microbes and evaluate biological activity. First, Corynebacterium bacterium was used as a sample bacteria. The chip successfully revealed the production capacity of lactic acid by a single C. bacterium . It was experimentally found that the production rate of lactic acid of Corynebacterium glutamicum increased 1.7 times and 3.8 times by adding pyruvic acid and sodium bicarbonate, respectively. Secondly, microbes belonging to the Corynebacterium group with respect to the lactic acid production were screened. Corynebacterium variabile was experimentally found to be the most productive among three tested members. The proposed microbial chip is readily applicable to an efficient microbial screening platform and potentially a reliable microbial sensor given the capacity of quantifying the total number of bacteria involved in the microbial reaction.

In this paper, the immobilization of bacteria in micropores is demonstrated using positive dielectrophoresis (DEP) in a microfluidic device. The device uses a hot melt sheet in which a microfluidic channel is formed, sandwiched between upper and lower electrodes. The sheet was patterned using a cutting machine with a precision of 5 μm and was successfully bonded to ITO electrodes at 100 °C. During experiments that took place over the course of 2 days, no erosion of the sheet was observed. The ultimate goal is to characterize bacteria while precisely controlling their number and reaction conditions. By effective screening of such bacteria, it is hoped that useful chemicals such as organic acids, antibiotic drugs, and foodstuffs can be efficiently produced by fermentation. Corynebacterium glutamicum was chosen as the sample bacterium in this study. An optimum DEP frequency of 10 MHz was first experimentally determined for preferentially driving live bacteria to areas with stronger electric fields. The proposed device was then used to immobilize the bacteria in micropores with diameters of 5 and 10 μm. An average of 7.5 and 24.4 bacteria were successfully immobilized in the 5- and 10-μm pores, respectively, with a live/dead ratio of greater than 10. The proposed microfluidic device allowed the lactic acid productivity of C. glutamicum to be evaluated while immobilizing them in the microporous carrier. It is thus readily applicable as an efficient bacteria screening platform.

This paper demonstrates a microbial-robot that migrates in low Reynolds number fluidic environments powered by motile flagellated bacteria. To immobilize the flagellated bacteria strongly, we utilized bacterial cellulose (BC), which was produced by Gluconacetobacter xylinus. We evaluated the adhesion between the BC and the flagellated bacteria, Aliivibrio fischeri using a microfluidic shear device and confirmed that the superiority of BC over conventional MEMS materials. Conical-shaped BC was produced by Gluconacetobacter xylinus in conical microholes with a help of oxygen concentration gradient. A. fischeri were successfully immobilized onto the BC structure to form a microbial-robot, which could swim in culture media at an average speed of 4.8 μm/s.

In this paper we demonstrate highly dense immobilization of bacteria into nanoimprinted holes. Nanoimprinting enables micro holes smaller than 2 μm in diameter with a high accuracy, which cannot be patterned using conventional UV photolithography. In our prior work, we developed a microbial reactor immobilizing bacteria into micro holes, which facilitated collection and evaluation of reaction products while the number of bacteria involved in the reaction could be quantified. However, the holes were made by photolithography and the minimum size was limited to be 3 μm in diameter. Large holes allow multiple bacteria to be immobilized in a hole, which resulted in errors in quantification. The number of bacteria immobilized in a nanoimprinted hole was found to have smaller deviation than in photolithographically formed holes. In addition, density of the immobilized bacteria was experimentally found to be largest in case of 2-μm-holes. The proposed processes will be of great help for precise evaluation of bacteria reaction.

In this paper we demonstrate a continuous-flow microbial microreactor that immobilizes microbes into microporous carrier. First, bacteria are trapped into 3, 5, 10, 20-μm-diameter pores using positive dielectrophoresis (DEP). After non-immobilized bacteria are flushed, the continuous-flow microreactor generates reaction products when culture media including reactive substrate are supplied. Continuous-flow type reactors facilitate collecting and evaluating reaction products. We used the developed microreactor to characterize microbes belonging to Corynebacterium group by measuring generated lactic acid when glucose was supplied. The amount of lactic acid produced by a single bacterium was deduced and we found Corynebacterium variabile to be most productive among three tested members. The microbial reactor proposed herein is readily applicable to an efficient microbial screening platform.

Micro-fabrication technologies have been extensively studied to achieve smaller sizes and higher aspect ratios. When the features have sizes of a couple of micrometers or below, nano-imprinting can be an effective method for micro-fabrication at low cost. However, it is difficult to achieve aspect ratio greater than 1. In this research, we propose micro fabrication of super absorbent polymer (SAP) as a new material for micro devices. SAP swells by adding deionized water, which can be used as a post patterning process to enhance the aspect ratio of micro structures. Micropatterning of SAP must be conducted under thoroughly dry conditions and we used nano-imprinting processes. We successfully augmented an aspect ratio of the nano-imprinted micro holes of SAP from 0.65 to 1.2 by the swelling process. The proposed patterning and swelling process of SAP can be applicable to micro-fabricate high-aspect-ratio structures at low cost for high performance lab-on-a-chip.

In this study, we experimentally revealed that the microscale surface geometry of anodes strongly affects the performance of microbial fuel cells (MFCs). MFCs have much need to be improved in their power. The power generated by an MFC is considered to be strongly affected by the interaction between the organic bacteria and the inorganic electrode surfaces. In prior work, the nanoscale surface roughness of the anode was discussed; however, we consider that the microscale surface geometry may play a crucial role given the bacteria size of micrometer order. We used a two-chamber MFC and the direct electron transfer bacteria Shewanella putrefaciens. We prepared seven types of anode electrodes with different microscale surface geometries and experimentally found that the MFC performance depended on the contact area between the bacteria and the anode. The MFC generated the maximum power when the contact area between the anode and bacteria was the largest.

Amorphous films in the system of AlPO4-Al2O3 were prepared by rf sputtering, and their physical properties such as density, refractive index and thermal expansion coefficient, and the infrared absorption spectra were measured. The physical properties and the infrared absorption spectrum of an amorphous AlPO4 were very similar to those of SiO2 glass. All the physical properties of the amorphous AlPO4-Al2O3 films had the same compositional dependence; that is, they increased linearly with increasing Al2O3 content up to about 80mol% Al2O3, beyond which they increased more rapidly. The results of infrared spectra indicated that the coordination number of aluminum ions was 4 below about 80mol% Al2O3 content, but increased rapidly to about 5 above 80mol% Al2O3, reaching to the value of an amorphous Al2O3 film.