Kazuyoshi Tsuchiya

Development of RF magnetron sputtering method to fabricate PZT thin film actuator

Abstract PZT piezoelectric very thin films suitable for a microactuator have been deposited onto Invar alloy substrate using a high-temperature RF magnetron sputtering technique. PZT thin films must be deposited onto conductive substrate for a monomorph or a bimorph actuator. The chemical composition and the crystalline structure of these films were measured by ESCA and XRD, respectively. The chemical composition of PZT deposited stoichiometrically was almost the same as commercially-produced bulk PZT. Crystal planes (1xa01xa00) and (1xa01xa01) of PZT perovskite structure were observed in XRD analysis. When the substrate was heated to above 600xa0°C, SEM revealed only a very small number of pinholes on the surface. A thin (500xa0nm) film actuator has been characterized by measuring the piezoelectric property using a Laser Doppler Vibrograph. It was confirmed that the piezoelectric property has a linear relationship with the grain size, which also increased with the substrate temperature. The piezoelectric property of deposited PZT thin films showed a good agreement with a quoted value of bulk PZT, when the substrates were heated to 600xa0°C.

Development of blood extraction system designed by female mosquito’s blood sampling mechanism for bio-MEMS

A compact and wearable wristwatch type Bio-MEMS such as a health monitoring system (HMS) to detect blood sugar level for diabetic patient, was newly developed. The HMS consists of (1) a indentation unit with a microneedle to generate the skin penetration force using a shape memory alloy(SMA) actuator, (2) a pumping unit using a bimorph PZT piezoelectric actuator to extract the blood and (3) a gold (Au) electrode as a biosensor immobilized GOx and attached to the gate electrode of MOSFET to detect the amount of Glucose in extracted blood. GOx was immobilized on a self assembled spacer combined with an Au electrode by the cross-link method using BSA as an additional bonding material. The device can extract blood in a few microliter through a painless microneedle with the negative pressure by deflection of the bimorph PZT piezoelectric actuator produced in the blood chamber, by the similar way the female mosquito extracts human blood with muscle motion to flex or relax. The performances of the liquid sampling ability of the pumping unit through a microneedle (3.8mm length, 100μm internal diameter) using the bimorph PZT piezoelectric microactuator were measured. The blood extraction micro device could extract human blood at the speed of 2μl/min, and it is enough volume to measure a glucose level, compared to the amount of commercial based glucose level monitor. The electrode embedded in the blood extraction device chamber could detect electrons generated by the hydrolysis of hydrogen peroxide produced by the reaction between GOx and glucose in a few microliter extracted blood, using the constant electric current measurement system of the MOSFET type hybrid biosensor. The output voltage for the glucose diluted in the chamber was increased lineally with increase of the glucose concentration.

Development of Blood Extraction System for Health Monitoring System

The purpose of this research is to develop the compact human blood sampling device applied for a health monitoring system(HMS), which is called “Mobile Hospital”. The HMS consists of (1) a micro electrical pumping system for blood extraction, (2) a bio-sensor to detect and evaluate an amount of Glucose, Cholesterol and Urea in extracted blood, by using enzyme such as Glucoseoxidase (GOD), Cholesteroloxidase and Urease. The mechanical design elements of the device are bio-compatible microneedle, indentation unit using a shape memory alloy(SMA) actuator and pumping unit using a piezoelectric microactuator. The design concept is the biomimetic micromachine of female mosquito’s blood sampling mechanism. The performances of the main mechanical elements such as indentation force of the microneedle, actual stroke of the indentation unit using a SMA actuator and liquid sampling ability of the pumping unit using PZT piezoelectric microactuator were measured. The 3 mm stroke of the indentation load generated by SMA actuator was 0.8mN. The amount of imitation blood extracted by using bimorph PZT actuators was about 0.5 microliters for 10 sec. A 60-micrometer outer diameter and 25-micrometer inner diameter Titanium microneedle, which size is same as female mosquito’s labium, was produced by sputter deposition.

Piezoelectric-fluid interaction finite element analysis of a valve-less piezoelectric pump

In this paper, a new composite actuator, which consists of a bimorph piezoelectric plate and a metal cap, was proposed for micro-TAS (Total Analysis Systems) which is widely used for chemical, biological and medical devises. The main objective of this work is to verify the displacement amplification introduced by a new design of composite actuator. At first, the proposed disc-shaped composite actuator was modeled and the static deflection was compared with conventional ones which are monomorph, bimorph actuators and a composite actuator called Moonie. Additionally, the proposed composite actuator was applied to a valve-less pump in a Y-shaped fluid channel and a piezoelectric-fluid interaction finite element simulation was performed. Computations demonstrated the superior performance of the new composite actuator compared with conventional ones.

Study for piezoelectricity characterization of PZT actuators deposited by RF magnetron sputtering for MEMS

Pb(Zr,Ti)O3 piezoelectric material(PZT) has been utilized for a microactuators or microsensors. Because PZT piezoelectric materials have higher power or larger displacement than the other piezoelectric materials such as BaTiO3. The PZT thin films were deposited onto a heated Invar alloy by using a high temperature RF magnetron sputtering. The chemical composition and the crystalline structure for deposited PZT were measured by ESCA and XRD, respectively. The chemical composition of PZT deposited stoichiometrically was almost same as the commercial based bulk PZT composition. Crystal planes (110) and (111) of PZT Perovskite structure were observed in XRD analysis. Employing over 600 degree heating, almost no pinhole on the surface was observed by SEM. Thin film actuator with 500 nm thickness has been also characterized by measuring the piezoelectric property using Laser Doppler Vibrograph. It was confirmed that the piezoelectric property has a linear relationship with the grain size, which also increased with the substrate temperature. Therefore, it is possible to control piezoelectric properties by the sizes of PZT grain, which is grown by heating substrate. The piezoelectric property of deposited PZT thin films showed a good agreement with a quoted value of bulk PZT, when the substrates were heated up at 600 degree.