A new type of functionally graded (FG) piezoelectric bending actuator was proposed by the present authors in their former study and the advantage of the new actuator over the traditional bimorph and unimorph actuators in internal stress distribution was illustrated by simulation results. In this study, the fabrication process of FG piezoelectric bending actuators is developed and the characteristics of the fabricated actuators are investigated. The material compositions with different dielectric and piezoelectric constants were selected from the Pb(Ni 1/3 Nb 2/3 )O 3 -PbZrO 3 -PbTiO 3 family and used as the four layers in the new FG piezoelectric actuator. The piezoelectric constant and dielectric constant were graded oppositely in the thickness direction. The durability of the fabricated FG piezoelectric actuators was measured in a vibration test and compared with that of the traditional bimorph actuator to evaluate the improvement of performance. The results show that the durability of the FG piezoelectric actuators is much higher than that of the bimorph actuator.
The artificial microswimmer is a cutting-edge technology with applications in drug delivery and micro-total-analysis systems. The flow field around a microswimmer can be regarded as Stokes flow, in which reciprocal body deformation cannot induce migration. In this study, we propose a microcapsule swimmer that undergoes amoeboidlike shape deformations under fluid oscillation conditions. This is a study on the propulsion principle using a capsule with a solid membrane, and one of only a few studies using fluid oscillation. The microswimmer consists of an elastic capsule containing fluid and a rigid sphere. Opposing forces are generated when fluid oscillations are applied, because the densities of the internal fluid and sphere are different. The opposing forces induce nonreciprocal body deformation, which leads to migration of the microswimmer under Stokes flow conditions. Using numerical simulations, we found that the microswimmer propels itself in one of two modes, i.e., stroke swimming or drag swimming. We discuss the feasibility of the proposed microswimmer and show that the most efficient swimmer can migrate tens of micrometers per second. These findings pave the way for future artificial microswimmer designs.
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