論文

シリコンウエハ接合の性能を決定する要因の一つに，ナノスケールの表面粗さがある．本論文では，表面粗さの評価パラメータとして，表面の一番高い点からある深さまでに含まれる面積を表すBearing Ratioを導入した．適切な深さを選択すると，Bearing Ratioはウエハ接合における両ウエハの接触面積を表す．ウエハ接合の性能は接合エネルギにより定量化され，これは接触面積に比例すると考えられる．薬品により任意の表面粗さをもつウエハを製作し，これらの接合実験によりBearing Ratioと接合エネルギが比例することを示し，ナノスケール表面粗さとウエハ接合の性能を初めて定量的に関連付けた．

高性能Power MEMSデバイスの実現には，微小ロータの高速回転が不可欠である．ロータの回転性能を決定する要因の一つは，ロータのインバランスである．本論文において，ロータのインバランスがDeep Reactive Ion Etchingによる製作プロセスに依存していることを実験から証明した．さらにDRIEプロセスを最適化することにより，ロータのインバランスを軽減し，回転性能が向上することを示した．

微小機構の飛行には，外部場からのエネルギ供給が有効であり，外部交流磁場により回転する磁性体回転翼はその条件を満たす．磁性体材料としてMEMS製作技術により成膜が容易，かつ姿勢制御にも利用可能な軟磁性体が優れている．回転中の磁性体翼のダイナミクスを実験，計算を通じて解析した．また微小回転翼の飛行特性を評価し，微小飛行機構への応用可能性を示した．

シリコンウエハの直接接合プロセスは，強い接合力，および接着剤が必要ないことから，3次元構造をもつMEMSデバイス，特に　　Power MEMS デバイスなど高温，高圧下で使用されるMEMSデバイスの製作に有効である．本論文では，特に複数枚のシリコンウエハの直接接合によるMEMSデバイスの製作プロセスに付随する問題点，およびその解決方法を示した．

マイクロ燃焼システムにおいては，燃料のチャンバ内における滞在時間が短いことによる燃焼効率の低下が問題となる．本論文では，触媒を利用したマイクロ燃焼システムを提唱し，実験により有効性を示した．三木はこの論文において，シリコンベースのマイクロ燃焼システムの開発に携わった．

微小機構の安定した飛行には，姿勢制御が最も重要となる．本論文は，微小機構のボディ部分に形状磁気異方性をもつ磁性体を成膜し，交流磁場による磁気異方性トルクを利用した姿勢制御を提唱している．交流磁場は回転翼の駆動にも使用される．MEMS製作技術を用いて，微小飛行機構を製作し，交流磁場中において安定した飛行を実現した．また高速度カメラにより飛行を観察し，微小機構の飛行ダイナミクスを解析した．交流磁場により，同時に回転翼の駆動と姿勢制御をおこなうことにより，微小機構の簡素化，軽量化が可能となり，飛行が実現されたと結論した．

マイクロロボット移動用の回転翼に使用される磁性体は軟磁性体であり，回転中に磁化の大きさ，方向ともに変化する．本論文において，回転中の磁化および磁気トルクの変化を，計算および数ミリサイズのラージスケール磁性体翼による実験から解析した．磁性体の磁気特性とともに，形状磁気異方性が重要な役割を担っていることを明らかにした．また翼長0.9ミリメートルの磁性体回転翼をMEMS (Microelectromechanical Systems) 製作技術を用いて実現した．

マイクロロボットの移動には，地面との摩擦がなく，かつ３次元の移動が可能な飛行が有効である．本論文では，推力を得る方法として，交流磁場中で回転する磁性体回転翼を提唱し，数ミリサイズのラージサイズモデルによる実験を通じ，実現可能性を示した．

In this paper, we present a three-layered device for preparation of heterologous core layers linearly aligned in a hydrogel sheet by a simple four-step process without using pumps. Recently, cell-based sensors have been developed for detection of odorant molecules owing to the sensitivity and selectivity of olfactory receptors to chemical substances. To detect various odorant molecules with these sensors, it is necessary to array multiple types of sensor cells expressing different olfactory receptors. We therefore propose a sheet-shaped sensor chip for a sensor-cell array. Previously, hydrogel sheets with heterogeneous cell patterns were produced using microfluidic devices with syringe pump systems, causing loss of both sample volumes and time for settings. Here, we develop a device that enables preparation of hydrogel sheets with a small amount of samples and with a single manual pipette.

This paper reports successful re-formation of a lipid bilayer using an air bubble. Lipid bilayers have been used for membrane protein studies and biosensor applications. Droplet-contact-method is a simple and effective method to form the bilayers. A major challenge in using the bilayers originates from their vulnerability against physical and electrical disturbance, which leads the bilayer rapture and the droplet fusion. We previously proposed a concept to re-form a bilayer by introducing an air bubble to cut-and-split the merged droplet. In this work, we investigated the key parameters to guide the bubble and drastically enhanced the yield up to 97%.

Titanium is widely used in biomedical components. As a promising advanced manufacturing process, electropolishing (EP) has advantages in polishing the machined surfaces of material that is hard and difficult to cut. This paper presents the fabrication of a titanium microchannel using the EP process. The Taguchi method was adopted to determine the optimal process parameters by which to obtain high surface quality using an L9 orthogonal array. The Pareto analysis of variance was utilized to analyze the three machining process parameters: applied voltage, concentration of ethanol in an electrolyte solution, and machining gap. In vitro experiments were conducted to investigate the fouling effect of blood on the microchannel. The result shows that an applied voltage of 20 V, an ethanol concentration of 20 vol.%, and a machining gap of 10 mm are the optimum machining parameters by which to enhance the surface quality of a titanium microchannel. Under the optimized machining parameters, the surface quality improved from 1.46 to 0.22 µm. Moreover, the adhesion of blood on the surface during the fouling experiment was significantly decreased, thus confirming the effectiveness of the proposed method.

This paper reports a cartridge-type device to produce sensor cells with spontaneous solution exchange. Our group has developed a cell-based odorant sensor expressed olfactory receptors. These sensor cells presented excellent sensitivity and specificity, which would be useful for a wide range of sensor applications. However, production of such sensor cells requires multiple times of aseptic solution exchanges. In this work, we develop a cartridge-type cell culture device that utilizes capillary force for spontaneous solution exchange without pumps or tubes. When the cartridge is set to the exchange stage, the specified volume of solution is exchanged immediately. We experimentally examine the solution exchange, and demonstrate the response of a sensor cell to a chemical stimulus in the exchanged solution. We consider that the device would be useful to produce multiple types of sensor cells.

In order to improve the quality of life of dialysis patients, our group have been developing an implantable hemofiltration device (IHFD) composed of multiple layers of dialysis membranes and microfluidic channels. To improve the hemodialysis performance of IHFD, preventing the negative filtration, which is caused by the oncotic pressure of blood, is mandatory. In this study, we fabricated IHFDs with five different microchannel designs and experimentally investigated the performance of each device in in vitro experiment. In addition, the successful IHFD was further evaluated by ex vivo experiments with a beagle dog. The experiments verified the effectiveness of the microchannel design, which will be used for the IHFD for in vivo experiments with pigs in the future.

This paper describes a method capable of individual and selective re-formation of ruptured BLMs (bilayer lipid membranes) by using air bubbles in arrayed devices. BLMs play an important role in membrane protein studies, biosensor applications, and drug screening. In such applications, data throughput is a key issue, but BLMs are easily ruptured by physical/electrical disturbance, which makes it difficult to operate a large BLM array. In this work, we propose a bubble-assisted BLM re-formation method: An aqueous phase is divided by a small air bubble covered with a lipid monolayer. After the bubble departed, the divided aqueous phases are brought into contact with the lipid monolayer, resulting in formation of BLM. This method enables selective BLM re-formation in a multichannel device. To verify individual and selective BLM re-formation using this method, we developed a 4ch bubble-assisted device and demonstrated repetitive BLM re-formation.

This study describes a gas-flow device that enhances the solubility of gas-phase odorants into aqueous solution for cell-based sensors. Cell-based sensors using olfactory receptors have attracted attention because of their high sensitivity and selectivity. However, most of previous studies used liquid-phase odorants as a target sample due to their low solubility of gas-phase odorants even though the applications expect the gas-phase sensing. Therefore, we focus on gas-phase odorant detection using the gas-flow device. Here, we clarify the impact of the velocity of convection inside the solution to enhancement of the solubility, based on computational simulation. Moreover, we experimentally verify efficiency of odorant dissolution in two types of devices, compared with the negative control using a sample odorant.

Cell-based sensors using olfactory receptors have attracted attention because of their high sensitivity and selectivity. A challenge is efficient partition of gaseous samples to the aqueous solution where the cell-based sensors reside. In this paper, we developed a device with a gas-flow channel, which allowed inflow of gaseous odorants over a well filled with aqueous solution. We considered that shear stress induced by the gas-flow at the gas-liquid interface initiate convectional mixing inside liquid and in turn, promotes partitioning of gaseous odorants into the solution. Solubility of a gaseous odorant was experimentally found to increase with the mixing strength. We further demonstrated efficient detection of a gaseous odorant using the sensor cells with the developed gas-flow device.

Tactile displays, which present virtual surfaces and tactile information to the users, can potentially augment quality and quantity of information in human-computer interaction. In this presentation, we discuss how we solve the inverse problems of the tactile displays, i.e., how to derive the control parameters of the displays when the target tactile sensations are given, in which we propose the microfabricated tactile samples to deduce quantitative correlation between the surface properties and tactile perception.

In the present study, we propose a largely deformable and miniaturized soft actuator that is made by an elastic rubber bladder (called a pouch) with a low-boiling-point liquid. When the temperature of the low-boiling-point liquid reaches 34 - C, the liquid inside the pouch evaporates, and the whole structure inflates. Thanks to the proposed fabrication method, we can make a miniaturized pouch of approximately 5 mm in diameter with a thin rubber membrane, and the pouch can inflate to a volume of 86 times or more compared to its initial volume and can generate approximately 20 N at maximum. We calculated the deformation model and developed the fabrication process through investigation of the thickness and the inflation volume of the pouch with respect to the process parameters. We then experimentally characterized the actuator with respect to the generated force, time response, and repeatability of the inflation. We believe that micro elastic pouch motors will contribute to soft robotic systems as a new component as a result of having unique characteristics, such as millimeter size and large deformability.

An artificial cell membrane is applied to study the pore formation mechanisms of bacterial pore-forming toxins for therapeutic applications. Electrical monitoring of ionic current across the membrane provides information on the pore formation process of toxins at the single pore level, as well as the pore characteristics such as dimensions and ionic selectivity. However, the efficiency of pore formation detection largely depends on the encounter probability of toxin to the membrane and the fragility of the membrane. This study presents a bilayer lipid membrane array that parallelizes 4 or 16 sets of sensing elements composed of pairs of a membrane and a series electrical resistor. The series resistor prevents current overflow attributed to membrane rupture, and enables current monitoring of the parallelized membranes with a single detector. The array system shortens detection time of a pore-forming protein and improves temporal stability. The current signature represents the states of pore formation and rupture at respective membranes. The developed system will help in understanding the toxic activity of pore-forming toxins.