Photocatalytic Lithography Research Articles

Controllable construction of ZnO/TiO2patterningnanostructures by superhydrophilic/superhydrophobic templates

Position- and orientation-controllable micropatterned ZnO/TiO2 nanostructures with different morphologies have been fabricated using a novel and versatile superhydrophilic/superhydrophobic template. Scanning electron microscopy, optical microscopy, electron probe microanalysis and X-ray diffraction were systematically used to confirm the successful fabrication of the patterns and to characterize the structure and morphology. The selective growth of ordered ZnO nanostructured patterns on the TiO2 nanotube surface employs a simple photocatalytic lithography technique with mild reaction conditions and in the absence of seeds and noble metal catalysts. The photoelectrical properties of the micropatterned ZnO/TiO2 nanocomposites with unique heterojunction structure and different density and orientation of the ZnO crystals were also investigated. It is expected that this novel micropatterned technique based on the superhydrophilic/superhydrophobic template will become a powerful tool for fabricating various types of micropatterned nanomaterials and devices.

A micropatterned cell array with an integrated oxygen -sensitive fluorescent membrane

We propose a simple method for producing micropatterned cell spots by photocatalytic lithography on a Pt porphyrin-based oxygen-sensitive polystyrene membrane that enables real-time imaging of oxygen consumption of patterned cell spots with sub-millimetre resolution.

Superhydrophilic–Superhydrophobic Template: A Simple Approach to Micro- and Nanostructure Patterning of TiO2 Films

Vertically aligned nanotube (VATN) array micropatterns were fabricated based on a versatile superhydrophilic–superhydrophobic template. Scanning electron microscopy, optical microscopy, and an electron probe microanalyzer were systematically used to confirm the successful fabrication of the dual-scale (micro-/nanoscale) patterns and characterize their structure and morphology. The fabrication of the VATN patterning employed a simple photocatalytic lithography technique and mild reaction conditions at low temperature in the absence of a photoresist and a harmful chemical catalyst. This large-area dual-scale pattern based on the superhydrophilic–superhydrophobic template is expected to be a promising candidate for many applications in a broad range of scientific and technological areas, such as sensor arrays and optoelectronic devices.

Simultaneous evaluation of toxicities using a mammalian cell array chip prepared by photocatalytic lithography

A prototype of a mammalian cell array chip was developed on a flat glass surface. A superhydrophilic (water contact angle = 5°)/highly hydrophobic (120°) pattern was prepared on a fluorinated polymer-coated glass surface by means of photocatalytic lithography, and A549 (a human alveolar epithelial cell line), Hep G2 (a human hepatoma cell line) and mouse fibroblast 3T3 cells were inoculated onto the superhydrophilic regions. The cell populations were confined in the superhydrophilic regions for at least 24 h and separated from each other for at least one week. Organ-specific toxicity of aflatoxin B 1 and non-specific toxicity of adriamycin were successfully detected by using the cell array chip.

Photocatalytic lithography with image inversion

The feasibility of the inversion of metal images obtained by the chemical deposition of nickel onto Pd 2+ -loaded films of nanostructural TiO 2 exposed to high irradiation doses has been demonstrated. This permits the generation of both negative and positive metallic pictures by varying the irradiation dose, which expands the scope for obtaining planar metallic elements with complex structural organization.

Phototocatalytic lithography of poly(propylene sulfide) block copolymers: toward high-throughput nanolithography for biomolecular arraying applications.

Photocatalytic lithography (PCL) is an inexpensive, fast, and robust method of oxidizing surface chemical moieties to produce patterned substrates. This technique has utility in basic biological research as well as various biochip applications. We report on porphyrin-based PCL for patterning poly(propylene sulfide) block copolymer films on gold substrates on the micrometer and submicrometer scales. We confirm chemical patterning with imaging ToF-SIMS and low-voltage SEM. Biomolecular patterning on micrometer and submicrometer scales is demonstrated with proteins, protein-linked beads. and fluorescently labeled proteins.

Functional Evaluation of Cellular Populations with Different Size Prepared by Photocatalytic Lithography

not Available.

Wettability control of photocatalytic crystal layers by hydrophobic coating and subsequent UV light irradiation

Wettability of solid surfaces with water is governed by surface morphology and composition. In this study, a surface finishing technique consisting of three processes, that is, nanotexturing by nanosized photocatalytic crystal coating, hydrophobic coating by chemical vapor deposition and subsequent ultraviolet light photolithography, was employed to form ultrahydrophobic/ultrahydrophilic solid surfaces. Flux grown nanosized K 4Nb 6O 17 crystals were selected as a photocatalyst. A proper nanotexure of crystal layer surfaces enhanced their hydrophobicity. The rough solid surfaces modified by alkyl- and fluoro-alkyl silane were converted from ultrahydrophobic (> 150°) to ultrahydrophilic (< 10°) by photocatalytic oxidation using the K 4Nb 6O 17 crystal layer. Fine pitch ultrahydrophobic/ultrahydrophilic patterns were readily obtained by photocatalytic lithography by use of area-selective 254 nm-ultraviolet light irradiation.

Porphyrin-Based Photocatalytic Lithography

Photocatalytic lithography couples light with photoreactive coated mask materials to pattern surface chemistry. We excite porphyrins to create radical species that photocatalytically oxidize, and thereby pattern, chemistries in the local vicinity. The technique advantageously is suited for use with a wide variety of substrates. It is fast and robust, and the wavelength of light does not limit the resolution of patterned features. We have patterned proteins and cells to demonstrate the utility of photocatalytic lithography in life science applications.

Photocatalytic Lithography using Zinc Oxide Nanoislands

Resist-free photocatalytic lithography has been studied. We attempted to etch aluminum (Al) thin films in deionized water using zinc oxide (ZnO) nanoislands as the photocatalyst deposited on Al thin films by reactive RF magnetron sputtering. The etching samples (ZnO/Al/glass) were irradiated with UV light in deionized water. We measured Al concentration in deionized water after UV irradiation and calculated Al etching rate. It was found that Al can be etched using ZnO nanoislands as the photocatalyst in deionized water and that Al etching rates were from 0.28 to 0.53 nm/min. These values were on the atomic size order. The activation energy of reaction for Al etching by photocatalysis of ZnO was 31.32 kJ/mol. Al etching rate can be increased by adding hydrogen peroxide (H2O2) to deionized water.

Photocatalytic lithography based on thin films of amorphous hydrated titanium dioxide

The mechanism of photoactivation of amorphous hydrated titanium dioxide thin films containing palladium ions toward the reaction of electroless deposition of nickel was studied. It was shown that the photocatalytic reduction of palladium ions during UV irradiation results in the formation of intermediate Pd(I) states that subsequently disproportionate, yielding a Pd nanophase. The palladium nanoparticle-catalyzed electroless deposition of nickel on exposed areas of the titanium dioxide photolayer makes it possible to fabricate metal patterns having a 5-μm resolution, with the fast and irreversible capture of photoelectrons at the latent image formation step preventing the image from blurring, including the process on conducting substrates.

Photocatalytic Lithography Processing via Poly(vinyl butyral)/TiO2 Photoresists by Ultraviolet (UV) Exposure

Photolithography of a pattern-forming process was developed with ultraviolet (UV) exposure and lithography methods, using poly(vinyl butyral) (PVB) with a nano-TiO2 composite as a photoresist. The PVB/TiO2 photoresist with high mechanical strength can be photodegraded because of the photocatalytic reaction during UV irradiation. After the PVB was removed from the exposed region, the TiO2 particles left after the photoreaction were easily removed by solvent, because of the low mechanical strength in this region. Results show that a pattern was able to be formed on substrates using this photolithography technique. The surface morphology of the PVB/TiO2 films associated with different exposure times was demonstrated. The dynamic intensities of functional groups for the residues (solid phase) and the volatile products (gas phase) during PVB/TiO2 photodegradation were analyzed. In addition, design of a photoreactor to shorten the UV-exposure time and improve the quality of the pattern-forming requirement was d...

Active-Matrix Backplane with Inkjet Printed Organic Thin-Film Transistors (OTFTs) for QR-LPD

Active matrix organic-TFT(OTFT) array for Quick-Response Liquid Powder Display (QR-LPD) was fabricated by use of inkjet printing technology.To define the shape and size of patterns formed by inkjet printing, we adopted a novel surface modification technique called photocatalytic lithography. Photocatalyst such as TiO2 oxidizes various organic materials in an excited state. Therefore photomask with a photocatalytic layer, irradiated with ultraviolet (UV) light, can oxidize selectively the surface of the organic material layer facing the phtocatalytic and then form hydrophobic and hydrophilic patterns. Ink-droplets ejected from ink jet print head spread only on the hydrophilic area and set like the mask pattern.We have developed to apply this technique to fabricating flat panel display components such as color filter, biomedical tools, and so on. The combination of inkjet printing and photocatalytic lithography enables fine patterns to be formed in a few steps and at low cost.In this study, we obtained well-defined source and drain electrode in which the channel length is below 10 micron by use of inkjet and photocatalytic lithography. As a result, high contrast image consist of 10 inch, 80 dpi QR-LPD active matrix array was refreshed successfully.

Superhydrophilic–superhydrophobic micropattern on TiO 2 nanotube films by photocatalytic lithography

The present paper describes an unconventional approach to fabricate the superhydrophilic–superhydrophobic micropatterns on the TiO 2 nanotube structured film by photocatalytic lithography with a two-step process. At the first step, the superhydrophobic TiO 2 nanotube film is fabricated through electrochemical and self-assembled techniques. And at the second step, the superhydrophobic film is selectively exposed to UV light through a photomask to locally photocatalyse the organic monolayer assembled on the TiO 2 nanotube surface. The superhydrophilic–superhydrophobic micropatterns have thus been developed, as a novel template to fabricate a define micropatterned coating of nano octacalcium phosphate by electrochemical deposition. It is indicated that these combined processes reveal a very promising approach for constructing well-defined micropatterns of various functional materials.

Fabrication of Multiscale Surface-Chemical Gradients by Means of Photocatalytic Lithography

We describe a new method for the fabrication of surface-chemical gradients. A film of titanium dioxide is brought into close proximity to a uniformly monolayer-covered surface and exposed to UV light to produce oxygen radicals. The use of a gradated grayscale mask between the UV source and the TiO2 allows the production of surface-chemical gradients via oxidation of the monolayer. The technique is demonstrated on gold surfaces bearing alkanethiol SAMs. Oxidation and subsequent replacement of the oxidized thiols has been used to produce surface-chemical gradients with lengths on the submillimeter to centimeter scales. The oxidation, removal, and replacement of the thiols during the process have been demonstrated by means of XPS. This oxidative process may be applied to other surface chemistries. Similarly, other shapes and slopes of gradients may be produced, depending on the photomask employed.

Photocatalytic Lithography Based on Photocatalytic Remote Oxidation

Photocatalytic lithography is a method for surface patterning based on photocatalytic remote oxidation. A TiO2-coated photomask is faced with a surface to be patterned, and irradiated with UV light. If a glass plate modified with alkyl chains is used, hydrophilic/hydrophobic patterns can be obtained. The alkyl chains in the irradiated regions are removed by oxidative decomposition, and those in the non-irradiated regions are left. Irradiation time is 30-60 s, and resolution is about 5 μm. This technique is potentially applicable to fabrication of biochips, lab-on-a-chip devices and simple electronic circuits.

Super-hydrophobic/super-hydrophilic patterning of gold surfaces by photocatalytic lithography

Super-hydrophobic and super-hydrophilic gold surfaces were prepared by modifying microstructured gold surfaces with thiols. The perfluorodecanethiol (PFDT)-modified rough gold surface was converted from super-hydrophobic (water contact angle = 150–160°) to super-hydrophilic (0–10°) by photocatalytic remote oxidation using a TiO2 film. During the remote oxidation, oxygen-containing groups were introduced to the thiol, and finally, even sulfur atoms were removed. Super-hydrophobic/super-hydrophilic patterns were also obtained by photocatalytic lithography, by using a TiO2-coated photomask. On the basis of this technique, enzymes and algal cells were patterned on the gold surfaces to fabricate biochips.

Conversion of a solid surface from super-hydrophobic to super-hydrophilic by photocatalytic remote oxidation and photocatalytic lithography

A super-hydrophobic surface, of which contact angle was 151°, was obtained by modifying a SiO 2 microparticle film-coated glass plate with octadecyltriethoxysilane (ODS). The super-hydrophobic surface was converted to super-hydrophilic by remote oxidation using a TiO 2 photocatalyst for 40 min, due to oxidative decomposition of the ODS monolayer. The increase in the wettability of the super-hydrophobic surface with water was faster than that of a normal hydrophobic surface. Patterning of the super-hydrophobic surface was also possible by means of photocatalytic lithography based on the remote oxidation using a photomask. It was possible to entrap water in the oxidized regions.

Mechanisms and Resolution of Photocatalytic Lithography

Remote oxidation via the gas phase by the TiO2 photocatalyst was exploited for a novel technique for solid surface patterning, photocatalytic lithography. A TiO2-coated photomask was placed on an organic or inorganic substrate to be patterned with a small gap (12.5−100 μm), and irradiated with UV light. Heptadecafluorodecyltrimethoxysilane-, octadecyltriethoxysilane-, and methyltriethoxysilane-coated glass plates, a silicon plate, and a copper plate could be patterned in ≥10 min with resolution of 10 μm or better. Such resolution could be obtained even when the intervening gap between the TiO2 film and the substrate was 100 μm. This may be explained in terms of a double excitation scheme, in which not only TiO2 but also a chemical species diffusing from the TiO2 surface or the substrate to be oxidized is excited by the incident light.

A new patterning method using photocatalytic lithography and selective atomic layer deposition.

We report a new patterning method using photocatalytic lithography of alkylsiloxane self-assembled monolayers and selective atomic layer deposition of thin films. The photocatalytic lithography is based on the fact that the decomposition rate of the alkylsiloxane monolayers in contact with TiO2 is much faster than that with SiO2 under UV irradiation in air. The photocatalytic lithography, using a quartz plate coated with patterned TiO2 thin films, was done to prepare patterned monolayers of the alkylsiloxane on Si substrates. A ZrO2 thin film was selectively deposited onto the monolayer-patterned Si substrate by atomic layer deposition.