Kyung-Ho Cho

A flexible hybrid strain energy harvester using piezoelectric and electrostatic conversion

A new design of flexible energy harvester to utilize piezoelectric and electrostatic energy conversion mechanisms simultaneously from a single mechanical energy source is proposed. This non-resonant type harvester enables low-frequency mechanical inputs to be converted to electricity, and the polymeric structures make the harvester mechanically flexible, allowing it to be applied to non-planar surfaces. The fabricated harvester generated peak- and average power densities of 159 and 1.79 μW cm−2 respectively by piezoelectric conversion, and 52.9 μW cm−2 and 1.59 nW cm−2 respectively by electrostatic conversion from an input force of 1.2 N at 3 Hz. Considering its flexibility and ability to harvest mechanical inputs at frequencies below 3 Hz, low-frequency human movements could be a potential energy source for the proposed hybrid harvester to exploit.

The effect of polymer fill ratio in pillar structure for piezoelectric energy harvester

One method of energy harvesting is to use piezoelectric devices, which are able to interchange electrical energy and mechanical strain or vibration. This study is to experimentally investigate the behavior of a piezoelectric energy harvester that was constructed with an array of pillar structures made of 0.2(PbMg1/3Nb2/3O3)−0.8(PbZr0.475Ti0.525O3) with polymer fill. Additionally, the aim of this study is to optimize the fill ratio of the composite piezoelectric ceramics and polymer structure. 0.2(PbMg1/3Nb2/3O3)−0.8(PbZr0.475Ti0.525O3) ceramics were employed as piezoelectric ceramic pillars, prepared in a rectangular shape. These piezoelectric ceramic pillars were sintered separately and attached to a bottom metallic electrode with poled states. The optimum ratio of ceramic pillar and elastic polymer ratio will be discussed. Piezoelectric properties will be discussed including the piezoelectric constant, piezoelectric voltage constants, and electromechanical coupling coefficient. We will present how the harvested energy depends on the lead resistor.

Analysis on electric energy of EAP generator using Smartpice

In this research we proposed the circuit for storing electric energy by converting mechanical energy at capacitor using EAP Pad. We used the Smartspice program which is a circuit analysis program for checking level of electric energy. We mainly analyzed into 4 effecting factors to electric energy, and 4 factors are firstly applied voltage, secondly the capacitor of source part and the capacitor of capacitor part, thirdly capacitor of EAP and its change of capacitor value, and for last an applied frequency. For addition, research for EAP generators are needed electric power to circuit at all time till now. But different from that, this research focused on not all time.

A Simplified Process of PMN-PZT Energy Harvester Based on Flammable Materials

With the increasing demand of auxiliary power unit in portable electronic devices, the concept of renewable energy harvesting near human surrounding environmental circumstance arouses an interest. As the field of microelectromechanical system (MEMS) has advanced, a clear need for the integration of materials other than silicon and its compounds into micromachined transducers has emerged. Piezoelectric materials are high energy density materials that scale very favorably upon miniaturization and that has led to an ever-growing interest in piezoelectric films for MEMS applications. However, conventional powder processing and machining cannot meet the requirement of such fine ceramic structure. Advanced technologies such as those using lasers and soft PDMS modeling method have been available for micro-patterning of ceramics but are not viable for large-scale production. It is difficult and time-consuming to pattern fine scale ceramics. In this paper, we fabricated simple process of MEMS based energy harvester by employing the flammable materials with PMN-PZT micro-pillar structure. The optimum aspect ratio of thickness/length for the ceramic pillar dielectric properties and micro-structure will be discussed.

Multi-layer Ceramic-Pillar Composite Structures for Piezoelectric Energy Harvesters

In this paper, we will discuss piezoelectric energy harvesters of multi-layered ceramic-pillar composite structures to be used as the energy source of small size electronic devices. 0.2(PbMg1/3Nb2/3O3)-0.8(PbZr0.475Ti0.525O3) ceramics and polydi-methylsiloxane (PDMS) were employed as piezoelectric ceramic-pillar composite, which prepared in forms of rectangular pillar structures. The piezoelectric ceramic-pillar composites were sintered separately and attached on the metallic bottom electrode with poled states. Symmetric upper electrodes were attached on the other side. Subsequently, the ceramic-pillar structures of composite material were manufactured with single-layer, double-layer and triple-layer devices. Both of multi-layer and single layer devices will be compared with several analysis methods. Piezoelectric properties will be discussed including the piezoelectric constant. Also, the output power of the multi-layer and single layer devices will be studied.

(1-x)(PbMgNbO3-PbZrTiO3)-x(BaTiO3) Piezoelectric Ceramics

The Pb(Mn1/3Nb2/3)O3-Pb(Ti,Zr)O3 system near the morphotropic phase boundary (MPB) can be expected to provide high piezoelectric constant and electromechanical coupling coefficient. Therefore it has used as an excellent candidate for piezoelectric applications including the high-power application. In this study, electric field-induced phase transition in PMN-PZT-based ceramics at a relatively low field of 40 kV/cm will be discussed. The structural and electrical properties of (1-x)(PMN-PZT)-xBT ceramics were investigated as a function of the BaTiO3 content (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5). Phase formation behavior was studied by an X-ray diffraction method. Room temperature SEM investigation revealed common trends in the grain structure with increasing BaTiO3 content.

Impedance Spectroscopy Analysis of the Screen Printed Thick Films

In this study, we fabricate 3 wt% doped thick films on the Ag/Pd bottom electrode printed substrates for the LTCCs (low temperature co-fired ceramics) applications. From the X-ray diffraction analysis, 3 wt% doped BST thick films on the Ag/Pd printed substrates, which sintered at , showed perovskite structure without any pyro phase. The dielectric properties of 3 wt% doped BST thick films are measured from 1 kHz to 1 MHz. To investigate the electrical properties of 3 wt% doped BST thick films, we employ the impedance spectroscopy. The complex impedance of 3 wt% doped BST thick films are measured from 20 Hz to 1 MHz at the various temperatures.