Isaku Kanno

Development of Deformable Mirror Composed of Piezoelectric Thin Films for Adaptive Optics

In this paper, we report a piezoelectric deformable mirror composed of piezoelectric thin films for low-voltage adaptive optics (AO). A 2-mum-thick piezoelectric Pb(Zr,Ti)O3 (PZT) film was deposited on a Pt-coated silicon-on-insulator (SOI) substrate, and a diaphragm structure of 15 mm in diameter was fabricated by etching a Si handle wafer. A 19-element unimorph actuator array was produced on the PZT films with an Al reflective layer over the backside of the diaphragm. Measurements of the displacement profile using a laser Doppler vibrometer demonstrated that a large displacement of approximately 1 mum was obtained by applying a voltage of 10 Vpp on one actuator. To examine the application feasibility of the deformable mirror to AO, we reproduced low-order Zernike modes by calculating the voltage on each individual electrode using an influence function matrix. The measurements demonstrated that the deformable mirror could produce the Zernike modes up to the seventh term. Considering the low-voltage actuation as well as the capability for miniaturization of the electrode size, deformable mirrors (DMs) actuated by PZT films are desirable for low-cost AO

Concepts for a new class of all-polymer micropumps

This paper presents a polymer-based micropump addressing the cost, performance, and system compatibility issues that have limited the integration of on-chip micropumps into microanalysis systems. This pump uses dielectric elastomer actuation to periodically displace fluid, and a pair of elastomeric check valves to rectify the fluids resulting movement. Its significant features include the use of a transparent substrate, self-priming capability, insensitivity to gas bubbles, and the ability to admit particles. A pump occupying less than 10 mm2 of chip space produced a 77 microl min(-1) flow rate. The pump has a high thermodynamic efficiency and exhibits little performance degradation over 10 hours of operation. In addition to its notable performance, the pump can be fabricated at low cost and directly integrated into microfluidic chips that use planar softlithography-formed structures. The new pump concept, fabrication, and experimental performance are discussed herein.

Electromechanical coupling factors of single-domain 0.67Pb(Mg1∕3Nb2∕3)O3–0.33PbTiO3 single-crystal thin films

Thin films of single c-domain/single-crystal (1−x)Pb(Mg1∕3Nb2∕3)O3−xPbTiO3 (PMN-PT) with x≅0.33 near a morphotropic boundary composition were heteroepitaxially grown on (110)SRO∕(001)Pt∕(001)MgO substrates. The heteroepitaxial growth was achieved by rf-magnetron sputtering at the substrate temperature of 600°C. After the sputtering deposition, the substrates were rapidly cooled from 600°C to room temperature by atmospheric air gas at a cooling rate of 100°C∕min. The rapid cooling process enhanced the heteroepitaxial growth of the single c-domain/single crystal PMN-PT thin films. Their electromechanical coupling factor kt measured by a resonance spectrum method was 45% at resonant frequency of 1.3GHz with phase velocity of 5500 to 6000m∕s for the film thickness of 2.3μm. The d33 and d31 were 194pC∕N and −104pC∕N, respectively. The observed kt,d33, and d31 were almost the same to the bulk single-crystal values. The present PMN-PT thin films are applicable for a fabrication of GHz planar bulk acoustic wave t...

Intrinsic crystalline structure of epitaxial Pb(Zr,Ti)O3 thin films

We report on the intrinsic crystalline structure of epitaxial ferroelectric Pb(Zr,Ti)O3 (PZT) films, which are fully relaxed from the stress of the substrate. The PZT films with the rhombohedral composition of Zr∕Ti=68∕32 were epitaxially grown on (001)Pt∕(001)MgO substrates. Four-circle x-ray diffraction measurements revealed that the films showed not only perfect c-axis orientation, but also a tetragonal phase due to a clamping effect of the substrate. Successively, x-ray diffraction measurements using synchrotron radiation were carried out to examine the intrinsic structure of stress-free PZT films, which were powdered after substrate removal. The structure refinement by Rietveld analysis demonstrated that the films without substrates returned to a rhombohedral phase, however, 19% of the B site in the perovskite structure was occupied by Pb atoms. The phase-transition temperature from rhombohedral to cubic slightly decreased due to the anomalous structure of the stress-free PZT films. These results sug...

Electric Field-Induced Strain of PbZrO3 Films

In this paper, we report an electric field-induced strain of antiferroelectric (AFE) PbZrO3 (PZ) films deposited by rf-sputtering. The PZ films grown on the (001)Pt/(001)MgO substrate are preferentially oriented along the c axis in a tetragonal system which is perpendicular to the AFE polar direction. On the other hand, the PZ films on the (111)Pt/Ti/Si substrate have a random orientation, and they show clear double P–E hysteresis loops, representing the AFE–ferroelectric (FE) phase transition caused by the application of an electric field. The transverse strain induced by the electric field is evaluated by the measurements of tip displacement of PZ/substrate unimorph cantilevers. The PZ films on the Pt/Ti/Si substrate exhibit clear strain jump corresponding to the AFE–FE phase transition, and a maximum transverse strain of 5×10-5 is obtained at an electric field of -150 kV/cm.

Improving the Performance of a Traveling Wave Micropump for Fluid Transport in Micro Total Analysis Systems

Micropumps are one of the most important microfluidic components in Micro Total Analysis System (μTAS). The authors have developed a traveling wave micropump that demonstrates high energy efficiency and does not require valves. A prototype valveless micropump was fabricated using microfabrication techniques to validate the pumping principle. The micropump uses piezoelectric bimorph cantilevers to deform a flexible microchannel wall. Traveling waves are induced on the surface of the microchannel by applying properly phased sinusoidal voltage to the piezoelectric cantilevers. The resulting peristaltic motion of the channel wall transports the fluid. The fluid flow in the micropump was numerically simulated with the computational fluid dynamics code, FLUENT. Comparing the experimental and numerical results confirmed that the proposed modeling method can accurately evaluate the performances of the traveling wave micropump. Based on the flow obtained in numerical analysis, an improvement in the pump efficiency is expected with optimization of the shape of the moving wall.

Characterization of Transverse Piezoelectric Properties of c-Axis Oriented PbTiO3 Thin Films

In this study, we evaluated transverse piezoelectric properties of c-axis oriented PbTiO 3 (PT) thin films from the actuation of the PT/MgO unimorphs. The PT films were grown on Pt/MgO substrates using rf-sputtering technique. X-ray diffraction measurements revealed that the PT films exhibited highly c-axis orientation with a-axis domains, suggesting epitaxial growth of the PT films. The piezoelectric characteristics of the PT films were estimated by the measurements of tip deflection of the unimorph cantilevers composed of PT films and MgO substrates. The PT cantilevers showed excellent linear piezoelectric deflection even with the application of large reverse voltage to the polar direction. The stable piezoelectricity of the PT films is attributed to not only large coercive field larger than their break down field but the highly c-axis orientation of PT films. We estimated piezoelectric coefficient e 31 of the PT thin films and obtained large transverse piezoelectricity of e 31 = −1.77 C/m 2 which is two times larger than that of the PT single crystals.