Published papers

An electro-conjugate fluid (ECF) is a kind of functional fluid, which generates a powerful jet flow (ECF jet) when subjected to a high DC voltage. This study applies the ECF on a novel liquid rate gyroscope. The gyroscope has a liquid flow inside generated by the ECF jet When a rate is applied to the gyroscope, the flow drifts due to the Coliolis force. The gyroscope senses this drift by using hotwires to detect the applied rate. A prototype could successfully detect the applied rate with appropriate response.

There has been some amount of confusion over the origin of electrohydrodynamic phenomena responsible for the actuation of dielectric fluids in the presence of an electric field. Previous studies have accounted for the possibility of conduction pumping, ion drag pumping and induction pumping as driving mechanisms but have ignored the possibility of Maxwell (electric) pressure driven flow. Until recently, this mechanism has been poorly understood and as a result has often been overlooked. This paper demonstrates how a Maxwell pressure gradient can induce flow in dielectric liquids in the presence of a non-uniform field. We derive, from first principles using lubrication theory, an expression for the flow velocity which exhibits a quadratic dependence on the applied voltage and also proportionality to the ratio of the permittivity and viscosity. The theoretical predictions are supported by experimental results. Although we have examined the phenomenon for a particular class of dielectric liquids, it is believed that this mechanism could well be responsible for the actuation of other low conductivity dielectric fluids previously attributed to conduction or ion drag pumping. In any case, we discuss ways to identify the dominant mechanism by comparing the salient features for a given type of flow.

We propose in this study a novel concept of a liquid rate gyroscope using electro-conjugate fluid. The electro-conjugate fluid (ECF) is a dielectric fluid which works here as a functional/smart fluid generating a powerful jet flow (ECF jet) under a high DC electric field. The ECF liquid rate gyroscope proposed senses the drift of the liquid flow due to Coriolis force when an angular rate is applied. The contribution of the proposed concept on gyroscope technology is to provide a possibility for a low cost micro gyroscope with impact resistance. This paper describes a design of ECF micro liquid rate gyroscope and performance evaluations. The results of experiments show the ECF micro liquid rate gyroscope could possibly be a next generation standard of micro gyroscope for consumer products.

電界共役流体に発生するジェット流に角速度が加わるとコリオリ力により偏流する．この偏流量をホットワイヤの抵抗値の変化として検出する液体レートジャイロを開発した．

電界共役流体を流動の圧力源として，ノズルにより生成されるジェット流に角速度が加わった際に生じる偏流を検出するレートジャイロを開発し，実験的に特性を明らかにした．また，アラン分散解析によってジャイロのドリフト特性を明らかにし，次世代マイクロジャイロのスタンダードとしての可能性を示した．

電界共役流体を利用して，液圧駆動でありながらポンプ，アクチュエータ部，タンクを一体化した人工筋を開発し，これを複数個集積化した際の駆動とくしを明らかにした．

電界共役流体を流動の圧力源として，ノズルにより生成されるジェット流に角速度が加わった際に生じる偏流を検出するレートジャイロを開発し，実験的に特性を明らかにした．

電界共役流体を用いてミミズの運動パターンおよび構造的柔軟性を模倣した新たな移動ロボットを開発し，駆動特性を実験的に明らかにした．

電界共役流体に発生する流動は工学的に有効なパワー源と成りうるもののその流動メカニズムは不明であった．本研究ではマクスウェル応力を流体の基礎式に導入し，電界共役流体の流動モデルを提案し，実験と比較した．

An artificial muscle is one of the key technologies for soft robots. This paper describes design, fabrication, and characterization of an artificial muscle cell using an electro-conjugate fluid (ECF) and integration of the cells. The ECF is a kind of dielectric and functional fluid, which generates a powerful jet flow or ECF jet under an electrostatic field applied with an electrode pair. It is experimentally clarified that the smaller electrodes generate a more powerful ECF jet with constant voltage applied. The authors propose in this study a new type of micro artificial muscle cell using electro-conjugate fluid (ECF micro artificial muscle cell). This soft actuator having a power source inside is compact enough for integration. By integrating a large number of cells, we can realize a macro-sized artificial muscle. In this paper, we fabricate a prototype of ECF micro artificial muscle cell (emptyset 12.5 mm x 13 mm), and integrate four cells into a 2 x 2 ECF artificial muscle actuator showing larger stroke and force. The maximum stroke and force are 1.56 mm and 320.5 mN with a single cell, and they are increased to be 2.8 mm and 504.1 mN with the 2 x 2 ECF artificial muscle actuator. (C) 2008 Elsevier B.V. All rights reserved.

We propose a novel liquid rate gyroscope using an electro-conjugate fluid in this study. The electro-conjugate fluid (ECF) is a dielectric fluid that works here as a functional/smart fluid generating a powerful jet flow (ECF jet) when subjected to high DC voltage. Using the ECF jet, we developed a liquid rate gyroscope based on the principle of a conventional gas rate sensor operated by Coriolis force. Because the ECF jet is generated only with a tiny electrode pair, the pumping part of proposed ECF gyroscope needs no mechanically moving parts, resulting in making the ECF gyroscope suitable for micro sensor compared to the gas rate sensor having a pumping mechanism inside. We fabricated a prototype of liquid rate gyroscope (40mm x 60mm x t7mm) and confirmed its characteristics by experiment. The experimental results confirm the effectiveness of the proposed liquid rate gyroscope. The scale factor of -29 mV/(degrees/s) is obtained with applied voltage of 4.5 kV.

For surgical devices used in minimally invasive surgery, compact multi-degree-of-freedom (multi-dof) actuators are required due to a small work space in the patient body. With conventional single-dof actuators such as electromagnetic motors, a multiple number of actuators are required to generate multi-dof motion. Moreover, additional transmission mechanisms make the total system even larger and heavier. In contrast, a single unit of multi-dof ultrasonic actuator can generate multi-dof rotation of a spherical rotor by utilizing three natural vibration modes of a bar-shaped stator. In our previous work we designed and built a surgical forceps with a wrist capable of two-dof motion, using a single multi-dof ultrasonic motor. The present study proposes a novel control scheme to generate three-dof motion of the surgical instrument for minimally invasive surgical procedures. Through experiments we have confirmed the system performance of the developed device. (c) 2007 Elsevier Ltd. All rights reserved.

電界共役流体を用いると，簡便な構造でマイクロ人工筋を構成できる．本研究では，タンク，ポンプ，アクチュエータを一体化したマイクロ人工筋セルを提案した．繊維強化チューブとタンク膜を二重円筒構造とすることによって外部に大規模なタンクやポンプを必要としない直径10 mmのセル構造を実現した．

An electro-conjugate fluid (ECF) is a kind of dielectric fluid, which works as a smart fluid. The fluid generates a powerful jet flow, which we call an ECF jet, when subjected to high DC voltage with a highly non-uniform electric field. This means the ECF works as a fluid power source for mechanical components without any bulky pumps. This paper develops a high-performance ECF micromotor having novel saw-toothed electrode series. The motor has four disk plates with the electrode series as a rotor. The inner diameter and length of the motor are 9 and 10.6 mm, respectively. Experimental results confirm that the output power and torque of the motor are 21 times and 7.5 times larger than those of a previous ECF micromotor having bar-shaped electrode pairs. (C) 2007 Elsevier B.V. All rights reserved.