Jin-Heon Oh

Design and Characteristics of Bar Type Piezoelectric Micropump

Micropump is very useful component in micro/nano fluidics and bioMEMS applications. Using the flexural vibration mode of PZT bar, a piezopump is successfully made. The PZT bar is polarized along the thickness direction. The proposed structure for the piezo-pump consists of the input and output ports the piezoelectric ceramic actuator, the actuator support, and the diaphragm. The traveling flexural wave along the bar is obtained by dividing two standing waves which are temporally and spatially phase shifted by 90 degrees from each other. Fluid is drawn into a forming chamber, eventually the forming chamber closes trapping the fluid therein. Components of piezopump were made, assembled, and tested to validate the concepts of the proposed pump and confirm the simulation results.

SiGe Synthesis by Ge Ion Implantation

We report here the successful synthesis of SiGe by Ge ion implantation into Si-on-insulator (SOI) substrates. The fundamental principle for our SiGe synthesis is a chemical reaction preference by nature; oxygen molecules preferentially combine with Si atoms rather than Ge atoms since the formation energy of SiO2 is lower than GeO/GeO2, and the chemical bond strength of SiO2 is higher. This phenomenon consequently retards the diffusion of implanted Ge ions from the desired area, offering them sufficient time and chances to homogeneously unite with Si atoms and curing implantation damage during O2 gas annealing. Thus, the result is practical synthesis of SiGe that can flexibly create various Ge concentrations along with high crystalline quality. Ge ions with a dose of 1017 cm-2 are implanted at 100 keV into 193-nm-thick top Si layers of SOIs at room temperature. The Ge-implanted samples are subsequently annealed at 1100 or 1200 °C in an O2 gas ambient for 5 to 180 min. It is found that the implanted Ge ions mostly remain in the desired area during O2 gas annealing. An apparent increase in Ge concentration and a significant decrease in defect density by increasing annealing time are also observed. A theoretical basis and useful simulation for this material synthesis method are presented in this study, being supported by evidential experimental data and comparison of theoretical calculation and measured values.

Relativity of Electric Field to Resonance Characteristics and Piezoelectric Constants of Modified PZT Ceramics

Since piezoelectric phenomenon able to develop an electric charge proportional to a mechanical stress discovered by J. and P. Curie first, this material has been utilized as core material in diversity fields [1]. Generally, material properties of PZT ceramics are measured under the small signal input. Concrete concept and process are stated clearly in the international standards [2]. The various material constants, determined by these methods are accepted as being trustworthy. In high power devices, such as ultrasonic motors and PZT actuators need a high level or great vibration amplitude, large input signals should be provided to the PZT elements. In accordance with many previous researches, material properties of PZT ceramics shows the linear characteristics only limited ranges of input voltages [3-5]. Hence, it is difficult to estimate the suitability of PZT ceramic material in case of high power applications. In Institute of Radio Engineers (IRE) standards, the material properties are able to be acquired from frequency-impedance characteristics of PZT ceramics [2]. Therefore, if these relations are varied with the applied input voltage, the material constants, calculated by the method enshrined in the standards, undergo changes necessarily. This fact signifies that the material properties of PZT ceramics are affected by the applied electric fields. In this study, we fabricated the disk type PZT ceramic specimens by conventional methods and considered the electric field dependence of frequencyimpedance characteristics. And also, we calculated the PZT constant d33 using the resonance method of the IRE standards from those frequencies representatively.

Design of a Valveless Type Piezoelectric Pump for Micro-Fluid Devices

The operation principle of a traveling wave rotary type ultrasonic motor can be successfully applied to the fluidic transfer mechanism of the micro-pump. This paper proposes an innovative valveless micro-pump type that uses an extensional vibration mode of a traveling wave as a volume transportation means. The proposed pump consists of coaxial cylindrical shells that join the piezoelectric ceramic ring and metal body, respectively. In order to confirm the actuation mechanism of the proposed pump model, a numerical simulation analysis was implemented. In accordance with the variations in the exciting wave mode and pump body dimension, we analyzed the vibration displacement characteristics of the proposed model, determined the optimal design condition, fabricated the prototype pump from the analysis results and evaluated its performance. The maximum flow rate was approximately 595 μL/min and the highest back pressure was 0.88 kPa at an input voltage of 130 Vrms. We confirmed that the peristaltic motion of the piezoelectric actuator was effectively applied to the fluid transfer mechanism of the valveless type micro pump throughout this research.

Design of valveless type piezoelectric pump for micro-fluid devices

Abstract The operation principle of travelling wave rotary type ultrasonic motor can be applied to fluidic transfer mechanism of micro-pump successfully. In this paper, we propose a novel type valveless micro-pump that uses extensional vibration mode of travelling wave as a volume transporting means. The proposed pump is consisted of coaxial cylindrical shells that joined piezoelectric ceramic ring and metal body respectively. To confirm the actuation mechanism of proposed pump model, a numerical simulation analysis on the proposed model was implemented. In accordance with the variation of exciting wave mode and pump body dimension, we analyzed the vibration displacement characteristics if proposed model, determined the optimal design condition, fabricated the prototype pump from the analysis results and evaluated its performance. The maximum flow rate was about 580[μl/min] and the highest back pressure was 0.85[kPa] at 120[Vrms] input voltage. We confirmed that peristaltic motion of piezoelectric actuator was able to be applied to the fluid transferring mechanism of valveless type micro pump effectively through this research.

Electric Field Dependence of Piezoelectric Constants and Resonance Characteristics in Modified PZT Ceramics

The practical application of piezoelectric ceramics is applied not only under low electric fields. Therefore, an examination for characteristics of piezoelectric ceramics under high electric fields can contribute to reducing the susceptibility of multifarious applications and to facilitating production of control circuits. These contributions can lead to the expansion of industrial applications. In this research, we fabricated disk-type piezoelectric ceramic samples using conventional methods, measured the resonance characteristics of these samples from low to high voltages driving conditions, and calculated the piezoelectric constants. Resonance frequency and voltage reduction ratio decreased steeply in the specific input voltage sections in PZT-PMNS ceramics.

An Analysis of the Resonance Characteristics of a Traveling Wave Type Ultrasonic Motor by Applying a Normal Force and Input Voltage

Piezoelectric ceramics, constituting an active element, make a stator vibrate generating a rotational force in ultrasonic motors. In the drive of ultrasonic motors, many factors exist that can affect the resonance characteristics of piezoelectric ceramics. For example, those factors are the bonding conditions with the elastic body, the magnitude of the electric field, the normal force for the frictional drive, the emission of heat due to vibration and friction, and so on. Therefore, it is important to properly research the inclination for variation of piezoelectric ceramics in the circumstance where complex elements are involved. In this paper, we focus on the analysis of the resonance characteristics of an ultrasonic motor due to the magnitude of the input voltage and normal force.

Haptic Actuator Design Using PMN-PT Ceramic

The study is aimed to design the haptic actuator powered by piezoelectric actuation. Prototype actuator consists mainly of two metallic plate joined with rubbers. PMN-PT ceramics are connected to each of one side of metallic plate and tungsten mass joined at centre of plate to control resonance frequency and vibration force of prototype actuator. This prototype actuator has evaluated 3D finite element method simulation program and has conducted an experiment. The result of experiment has shown vibration acceleration with frequency. This actuator has given 0.15∼0.25 g of vibration acceleration at 180∼230 Hz.

Fabrication and Characteristics of Ring Type Valveless Piezoelectric Micro-Pump using Peristaltic Motion

The operation principle of travelling wave rotary type ultrasonic motor can be applied to fluid transfer mechanism of micro-pump successfully. In this paper, we propose a novel type valveless micro-pump that uses extensional vibration mode of travelling wave as a volume transporting means. The proposed pump consists of coaxial cylindrical shells that joined piezoelectric ceramic ring and metal body respectively. In accordance with the variation of the pump body dimension, we analyzed the vibration displacement characteristics of pump model, determined the optimal design condition, fabricated the prototype pump from the analysis results and evaluated its performance. The maximum flow rate was about 530 μl/min and the highest back pressure was 0.83 kPa at 120Vrms, 35 kHz input voltage.

A Valveless Piezoelectric Micro-Pump Using Peristaltic Motion of Two Sided Disk Type Vibrator

Piezoelectric micro-pump should contain the physical running parts like check valves for acquiring the unilateral motion of fluid from the alternating motion of actuators. But the check valves raise many problems such as abrasion or exhaustive destruction by the recursive mechanical displacement. And the performances of micro pump are deteriorated by them. To solve these problems, we propose a novel type piezoelectric valveless micro-pump using peristaltic motion due to the travelling wave excitation. Proposed pump model consists of two piezoelectric ceramic plates, elastic metal body, caps for covering flow path, rubber rings for tight sealing and disk springs for the pressurization of pump body. The FEM simulation analysis of the proposed pump model was carried out to verify its operation mechanism. And a prototype pump was fabricated and evaluated to validate the proposed concepts. Maximum back pressure was 0.97kPa and flow rate was 640μl/min under 130Vrms, 67.5kHz of driving voltage.