Tomoya Miyoshi

OHA Ceramic Electret for Vibration Energy Harvesting

With a motivation for developing oxy-hydroxyapatite (OHA) ceramic-electret applicable to vibration energy harvesting, the poling characteristics of OHA ceramics were investigated in terms of microstructure using thermally stimulated depolarization current (TSDC). OHA is a hydroxyapatite (Ca10(PO4)6(OH)2)-derivative material, in which the OH- ions are partially substituted by O2- ions and vacancies (Ca10(PO4)6(OH)2-xOx/2). Patterned electret using 14-mm diameter OHA ceramic was prototyped with stripe-shaped electrodes, which serve as the electrostatic shield on the surfaces. The relationship between surface potential and the pattern width of the electrodes was experimentally examined, and the power generation characteristics were investigated.

Development of Rotational Electret Energy Harvester Using Print Circuit Board

An improved 1-D electrostatic model is proposed for rotational electret energy harvester (EH). A test bench for rotational electret EH is developed, and the experimental data are compared with the prediction using the present model. A low-profile rotational electret EH is designed and prototyped using cost-effective PCBs. Ball bearings are used for the rotational support of a stainless steel rotor. In the rotational electret EH prototype with an air gap of 200µm, the output power of 80 µW is obtained at 2 rps.

A Dynamic Model of Arm-Equipped Rotational Energy Harvester During Human Locomotion

A dynamic model of arm-equipped rotational energy harvester (EH) during human walking is proposed. The model describes realistic arm swing based on a two link with shoulder and elbow joints rotation, and includes the electro-mechanical coupling with a rotational electret EH. It is found that output power around 77 µW can be obtained with a rotational electret EH at the walking speed of 1.22 m/s, with minimum outpour power of 40µW. Optimum design of rotational electret EH for human walking can be made with this type of model.

Development of a MEMS-based electro-rheological microfinger system with an alternating pressure source

This paper presents a novel MEMS-based electro-rheological (ER) microfinger system with an alternating pressure source for multiple microactuator systems. Based on rectifying alternating flow by the ER microvalves, the ER microfinger system enables half number and small size of supply and return pipes, which is suitable for multiple microactuator systems. The MEMS-based finger part was realized by newly developed PDMS micromolding process featuring high-aspect-ratio and three-dimensional structures. This is the first time demonstration of bi-directional, large-displacement of 1.1 mm and high-speed (rise time of 1.1 s) bending motion of the fabricated 1.6-mm long ER microfinger.