Charge retention of self-assembled ferredoxin monolayer by the reduction-oxidation control for biomemory device.

The oxidation-reduction control to store charges in self-assembled ferredoxin layer was investigated by scanning electrochemical method. Micro sized spot arrays consisting of ferredoxin proteins which used as the storage element were formed on chemically modified gold coated glass by micro contanct printing method. The formation of ferredoxin array was confirmed by the atomic force microscopy. The charge store was investigated by external applied reduction potential to ferredoxin as a write function, and the stored reducing charge was measured as a read function of storage applications. In the reduction state, the stored charge was maintained for around 90 sec. This ferredoxin layer can be used as the molecular size information storage by applying the reducing potential and measuring the current flow when achieving the current of individual ferredoxin molecule.

Thick, three-dimensional nanoporous density-graded materials formed by optical exposures of photopolymers with controlled levels of absorption.

Three-dimensional (3D) intensity distributions generated by light passing through conformal phase masks can be modulated by the absorption property of photosensitive materials. The intensity distributions have extremely long depth of focus, which is proportional to the size of the phase masks, and this enables one to pattern thick (approximately 100 microm), nanoporous structures with precise control of grade density. Various density-graded 3D structures that result from computational modeling are demonstrated. Results of x-ray radiograph and the controlled absorption coefficient prove the dominant mechanism of the generated graded density is absorption of the photosensitive materials. The graded-density structures can be applied to a chemical reservoir for controlled release of chemicals and laser target reservoirs useful to shape shockless wave compression.

Molded transparent photopolymers and phase shift optics for fabricating three dimensional nanostructures.

This paper introduces approaches that combine micro/nanomolding, or nanoimprinting, techniques with proximity optical phase mask lithographic methods to form three dimensional (3D) nanostructures in thick, transparent layers of photopolymers. The results demonstrate three strategies of this type, where molded relief structures in these photopolymers represent (i) fine (<1 microm) features that serve as the phase masks for their own exposure, (ii) coarse features (>1 microm) that are used with phase masks to provide access to large structure dimensions, and (iii) fine structures that are used together phase masks to achieve large, multilevel phase modulations. Several examples are provided, together with optical modeling of the fabrication process and the transmission properties of certain of the fabricated structures. These approaches provide capabilities in 3D fabrication that complement those of other techniques, with potential applications in photonics, microfluidics, drug delivery and other areas.

Biomolecular photonic device consisting of Chl a/Chl b/phycoerythrin/phycocyanin hetero structure.

In living organisms the photosynthesis involves the absorption of light by the light-harvesting (LH) antenna complexes. By mimicking the photosynthesis process the artificial photonic device composed of bio-molecular hetero structure is developed. The proposed photonic device is composed of Chl a, Chl b, phycoerythrin and phycocyanin. To fabricate the highly ordered structure of biomolecules, the deposition of ordered Chl a/Chl b molecules onto solid substrates was done by the Langmuir-Blodgett (LB) technique, and the self-assembly technique was used for the deposition of phycocyanin molecule. To optimize the photocurrent generation, the photoelectric response characteristics of Chl a and Chl b LB films were measured according to the number of deposition layers, and effects of phycocyanin layer and various phycoerythrin concentrations on the photocurrent generation were analyzed. The biophotonic device was fabricated by the combination of the hetero biofilms and the photocurrent generation of the proposed device was observed. It was observed that the photocurrent generation of the proposed biodevice was improved by using the appropriate biopigments to be selected. The proposed artificial biophotonic device consisting of biopigments can be used to generate photocurrent by mimikng the photosynthesis in living system.

Bioelectronic device consisting of cytochrome c/poly-L-aspartic acid adsorbed hetero-Langmuir-Blodgett films.

A bioelectronic device consisting of protein-adsorbed hetero-Langmuir-Blodgett (LB) films was investigated. Four kinds of functional molecules, cytochrome c, viologen, flavin, and ferrocene, were used as a secondary electron acceptor (A2), a first electron acceptor (A1), a sensitizer (S), and an electron donor (D), respectively. To fabricate the cytochrome c adsorbed hetero-LB film, poly-L-aspartic acid was used as the bridging molecule. The hetero-LB film was fabricated by subsequently depositing ferrocene, flavin, and viologen onto the pretreated ITO glass. Cytochrome c-adsorbed hetero-LB films were prepared by the adsorption of cytochrome c onto the poly-L-aspartic acid treated-LB films by intermolecular electrostatic attraction. Finally, the MIM (metal/insulator/metal) structured molecular device was constructed by depositing aluminum onto the surface of the cytochrome c-adsorbed hetero-LB films. Hetero-LB films were analyzed by Atomic Force Microscopy (AFM), and cytochrome c adsorption onto the films confirmed. The photoswitching function was achieved and the photoinduced unidirectional flow was in accordance with the rectifying characteristics of the molecular device. The direction of energy flow was in accordance with the energy level profile across molecular films. Based on the measurement of the transient photocurrent of the molecular device efficient directional flow of photocurrent through the redox potential difference was observed. The photodiode characteristics of the proposed bio-electronic device were verified and the proposed molecular array mimicking the photosynthetic reaction center could be usefully applied as a model system for the development of the bio-molecular photodiode.