Development of Fluid Devices for Soft Machine by the Use of Electro-sensitive Fluids

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The suspensions which undergo a rapid transition from Newtonian liquids to rigid solids on the application of electric fields, are referred to as electrorheological(ER) fluids. The secondary flow induced for insulating oils in high electric fields is called electrohydrodynamic (EHD) effects. The purpose of this study is the establishment of design method for new fluid devices such as liquid motor and micro pump, which can be applied to soft machines. (1) Two types of ER fluids are developed. One is the mesoporous silica(MPS) suspensions, the ER effect of? which is drastically improved by doping of copper phthalocyanine into mesopores of silica surfaces. The other is the suspensions of polymer blend particles. The ER effects can be enhanced by the blend of two polymers which are not ER-active. (2) When the ER suspensions which are placed on the comb pattern electrodes, are electrified, a fine pattern with a waveform is developed from the smooth surface. The surface profiles can be approximated by single sinusoidal waves or their superposition. The surface deformation can be expressed by a combination effect of electrophoretic and ER forces. (3) The ER suspensions were sandwiched between two flat disc electrodes with the radial line patterns. The change in electrification mode led to a motion of electrode. The parallel motion of electrodes can be actively regulated and therefore this technique is very attractive in application to new ER motors (4) It is well known that the EHD flow is induced for insulating oils in high electric fields, but we have succeeded in generating the EHD jet for water and developed the new ink jet devices. Although the velocity of EHD flow for oils is of the order of several cm/s, the EHD jet with a velocity of 1m/s can be quantitatively predicted by computer simulation