Yoshiaki Yasuda

Control of protein orientation in molecular photoelectric devices using Langmuir—Blodgett films of photosynthetic reaction centers from Rhodopseudomonas viridis

A photoelectric device was prepared using Langmuir—Blodgett (LB) films of photosynthetic reaction centers (RCs). Monolayers of RCs from Rhodopseudomonas viridis were deposited on transparent electrodes. The orientation of the RCs on the electrode surface was controlled using various substrates with different surface wettabilities. The degree of alignment was evaluated by measuring the polarities of light-induced electric responses. The orientation was also measured by means of an enzyme-linked immunosorbent assay that uses antibodies to distinguish opposite sites of the RCs. Photocells comprised of RC-LB films showed a steady-state photocurrent. The direction of the current flow was regulated by altering the orientation of the RCs.

A two-axis piezoelectric tilting micromirror with a newly developed PZT-meandering actuator

In this paper, we propose a new mechanical design of piezoelectric unimorph actuator that generate large static deflection angle by accumulating angular displacement in a cascaded piezoelectric cantilever formed in a meandering shape. The new actuator design was adopted in a double-gimbal two-dimensional optical scanner of a 4 mm times 6 mm foot print. The scanner delivered a relatively large static angle of mechanical plusmn8.6deg at an applied voltage of 20 Vdc at a non-resonant operation.

PIEZOELECTRIC 2D-OPTICAL MICRO SCANNERS WITH PZT THICK FILMS

ABSTRACT A piezoelectric 2D-optical micro scanner was fabricated with PZT thick-film actuators prepared using Arc Discharge Reactive Ion-Plating method. Two orthogonal pairs of unimorph actuators were used to compose a double-gimbal structure. The inner and outer actuators were controlled independently. A large elliptical mirror (1 mm × 2 mm) was scanned two-dimensionally. The scanner showed large optical scan angles of 23 degrees (4.3 kHz for X-scan) by 52 degrees (90.3 Hz for Y-scan) at low driving voltages of typical 10–20 V AC with a 5 V dc offset. The frequency ratio provided 47 scanning lines. Using the 2D scanner, we demonstrated laser image-projection of some characteristics.

Langmuir-Blodgett films of reaction centers of Rhodopseudomonas viridis: photoelectric characteristics

Abstract A stable monolayer of the isolated reaction centers (RCs) from a photosynthetic bacterium, Rhodopseudomonas viridis was prepared on a water subphase. The behavior of the monolayer was studied with reference to their surface pressure-area isotherms. The results show that a densely packed monolayer could be obtained by optimizing the initial spreading densities. Langmuir-Blodgett (LB) films which had a dense, close-packed structure could be produced with high initial density of material and high surface pressure. The absorption spectrum of this LB film was similar to that of solubilized RCs. Upon illumination with near infrared light, a sandwich device of LB films exhibited an initial current or voltage transient followed by a steady component. These results indicated that the function of photon/electron conversion of RCs was still retained in the LB films. The LB film fabrication described, giving a steady photocurrent, provides a possible method for the application of membrane proteins in biodevices.

Self-Assembling Photosynthetic Reaction Centers on Electrodes for Current Generation

Photosynthetic reaction centers (RCs) made from photosynthetic organisms can be used in solar batteries because their molecules cause light-induced charge separation. We present a simple immobilization system of the intact RCs from Rhodobacter sphaeroides on an electrode that uses nickel ligand binding by the hexameric histidine tag on H subunit (HHisRC). The binding constant of HHisRC to the nickel-nitrilotriacetic acid (Ni-NTA) chip measured with a surface plasmon resonance instrument was 1.6 x 10(8) M-1. HHisRCs were immobilized on an indium tin oxide electrode overlaid with an Ni-NTA gold substrate. The photoinduced displacement current of this electrode was measured to estimate the orientation of HHisRC on the electrode, and the detachability of HHisRC from the electrode was determined by using an imidazole solution wash. The direction of the flash-light-induced displacement current suggested that the H subunit side of the immobilized HHisRC faced the surface of the electrode. The photoinduced current disappeared after the electrode was washed in the imidazole solution. This simple immobilization and detachment of HHisRC to the electrode might be useful for making a reproducible photocurrent device.

A Combination of Fast Resonant Mode and Slow Static Deflection of SOI-PZT Actuators for MEMS Image Projection Display

A new type of MEMS optical scanner for image projection display has been developed by using the ADRIP (arc discharge reactive ion plating) technique of PZT piezoelectric material on an SOI wafer. Stable and wide range 2D scan was made possible by combining resonant motion for the fast horizontal axis (11.2 kHz, optical 39 degrees) and quasi-static operation for the slow vertical axis (DC ~60 Hz, optical 29 degrees) operated at 40 Vpp voltage

A novel ISFET-type biosensor based on P450 monooxygenases.

We made a biosensor based on ion-sensitive field effect transistor (ISFET) using P450 monooxygenase. ISFETs are electrical devices and have been used as pH sensors. We used genetically engineered P450 monooxygenase for our research because of its high enzymatic activity. The fusion enzyme between rat CYP1A1P450 monooxygenase and yeast NADPH-cytochrome P450 oxidoreductase was expressed in yeast Saccharomyces cerevisiae strain AH22. Yeast microsomal membranes were immobilized in an agarose layer on the ISFET. o-Deethylation of 7-ethoxycoumarin to 7-hydroxycoumarin was catalyzed by the enzyme in the presence of nicotinamide adenine dinucleotide phosphate reduced form (NADPH). Formation of 7-hydroxycoumarin from 7-ethoxycoumarin was also measured by fluorescence. The difference of the voltage between the ISFET device and control device without enzymes showed a voltage increase along with the enzymatic reaction of P450 monooxygenases, and this voltage increase in the device was inhibited by addition of MnCl(2), an inhibitor of P450 monooxygenase. There was a positive correlation between the voltage increase in the ISFET device and the fluorescence intensity. This is the first electrochemical biosensing using P450 monooxygenases immobilized on the ISFET, and is applicable to the sensing of chlorophenol compounds.

Effects of counterions on the orientation control of photosynthetic reaction center proteins in an applied bias-voltage Langmuir–Blodgett method

Abstract Molecular orientation of photosynthetic reaction center protein (RC) was controlled during film deposition in Langmuir–Blodgett (LB) film preparation by the polarity of an applied bias voltage. The orientation of RCs was examined by measuring a displacement current. The effects of counterions in the subphase (including both bivalent cations and polyions) were studied to clarify the mechanism involved in orientation control by an applied bias voltage. Results confirmed that the orientation of an RC at the water surface was governed by the electrostatic repulsion between the electric double layer near the substrate and the dipole of the RC.

A laser display using a PZT-actuated 2D optical scanner

We report an image projection display using a MEMS 2D optical scanner driven by the PZT unimorph actuators developed by the ADRIP method. Improved contrast ratio of optical scan speeds with relatively large angles (horizontal: optical 27 degrees at 16.4 kHz, vertical: optical 31 degrees at 77.4 Hz, frequency ratio of 210) has made it possible to project monotone bitmap animations

A biaxial piezoelectric MEMS scanning mirror and its application to pico-projectors

In this paper, we report a two-dimensional MEMS optical scanner that actuate and detect the angular motion through the piezoelectric effect of thin film PZT. Typical scan ranges were ±12° at 25 kHz for the horizontal resonance and ±8° at 60 Hz for the vertical non-resonance, and the overall power consumption was 100 mW or less. A newly designed mechanical rib structure on the backside of the mirror was found to suppress the dynamic deformation of the mirror to the level compatible with a high definition of 720 pixels or more. A scanning laser type pico-projector was developed for demonstration.