Masataka Murahara

Protein adsorption on PTFE surface modified by ArF excimer laser treatment

Poly (tetrafluoroethylene) (PTFE) is a material that causes only a few rejections in a living body but has low tissue affinity. A soft tissue implant material that not only has high biocompatibility but also excellent bondability has been developed by photo-chemically incorporating OH functional groups on the PTFE surface with ArF excimer laser irradiation. Protein adsorption on untreated and treated samples was evaluated by scanning electron microscopy (SEM) and attenuated total reflection Fourier-transform infrared (ATR–FT-IR) spectroscopy, with bovine serum albumin (ALB) and fibrin (FIB) solutions. It has been found that protein adsorption increases with the increase in the OH group density on the PTFE surface. The maximum adsorption of both ALB and FIB was found on the PTFE sample treated with a laser fluence of 20 mJ/cm2 and a shot number of 2000, whose water contact angle was 28 degrees; the quantities of both ALB and FIB adsorbed increased by a factor 2 as compared with untreated sample.

Hard protective waterproof coating for high-power laser optical elements.

We developed a new method for making a waterproof coating by photooxidation of silicone oil. The silicone oil was spin coated onto the surfaces of optical elements, i.e., a plastic lens, a laser mirror, and a nonlinear optical crystal, and then irradiated with a xenon excimer lamp in air, which transformed the organic silicone oil into an amorphous glass film. This technique has enabled an optical thin film to transmit ultraviolet rays of wavelengths below 200 nm and to exhibit the characteristics of homogeneity, high density, and resistance to environmental effects and to corrosion by water, and a Mohs scale value of 5.

Fibrin-free intraocular lens for hindering secondary cataract with UV-photon-induced photochemical surface modification

A fibrin-free intraocular lens (IOL) has been developed for hindering secondary cataract. Hydrophilic and hydrophobic micro-domains were alternately generated on the poly(methyl methacrylate) [PMMA] IOL surface with UV photon irradiation. The modified IOL was soaked in aqueous fibrin solution, and the fibrin adsorption was measured by infrared spectroscopy (FT-IR). The results show that the fibrin adsorption on the sample with hydrophilic groups increased, while that on the sample with hydrophobic groups decreased. Moreover, the fibrin adsorption on the sample surface with hydrophilic and hydrophobic micro-domains arranged alternately was reduced to one-fifth of that on the untreated sample.

On-site electrolysis sodium metal production by offshore wind or solar energy for hydrogen storage and hydrogen fuel cycle

If hydrogen can be solidified at room temperature or under atmospheric pressure, its long-distance transportation and long-term storage become possible. It is, then, considered to convert hydrogen into sodium metal. This sodium metal will be produced by electrolyzing seawater salt or rock salt and stored in kerosene to transport to a consumption place; when water is added to the sodium metal, a large amount of hydrogen is generated instantaneously anywhere. Furthermore, a good thing is that the melting point of sodium hydride produced by reacting with hydrogen gas during the process of manufacturing sodium metal is 800°C, 8 times higher than 98°C of sodium metals melting point, so its handling risk becomes extremely lower. When adding water, the sodium hydride hydrolyzes vigorously to generate hydrogen in the same manner as sodium metal; the amount of the hydrogen generated is twice as large as the hydrogen produced by the reaction of sodium metal and water. Sodium hydride is a material that posses both functions of hydrogen absorption and hydrogen generation. Sodium metal, thus, is an economical, renewable, and sustainable fuel, which discharges neither CO2 nor radioactivity.

Water-resistant hard coating on optical material by photo-oxidation of silicone oil

Using photo-excited silicone oil developed a new protective hard coating method for high power laser to present the tolerance in water. The silicone oil was spin-coated onto the surface of an optical material and then irradiated with a xenon excimer lamp in the air, which transformed the organic silicone oil into inorganic glass. This technique has enabled an optical thin film capable of transmitting ultraviolet rays of wavelengths under 200 nm and possessing the characteristics of homogeneity, high density, resistance to environmental effects and to water, anti-reflective in water, and Mohs scale value of 5.

Photochemical Bonding of Fluorocarbon and Fused Silica Glass for Ultraviolet Ray Transmitting

Fluorocarbon was photo-chemically combined to a fused silica glass with the silicon oil used as a bonding agent. Balsam, unsaturated polyester resins and UV hardening adhesives have been generally used for joining two optical glasses together. They, however, have a strong absorption band in the UV region. Therefore, a new bonding method was developed for optical materials to allow UV rays to pass through using silicone oil and excimer- lamp. This new method requires the fluorocarbon-polishing pad employed in our PCP (Photo-Chemical Polishing) method in hydrofluoric acid ambience, which is bonded with the silica glass. The silicone oil was put between the fused silica glass and the fluorocarbon (FEP), and an excimer- lamp was irradiated. When the excimer lamplight was irradiated vertically, the silicon oil ((-O-Si(CH 3 )-O-)n) was photo-dissociated and reacted with the oxygen adsorbed on the silica glass surface to produce a SiO 2 . On the other hand, the H atoms photo-dissociated from the silicon oil pulled out the F atoms of the FEP. As a result, the FEP and the silica glass were combined. The tensile strength of the sample bonded by the photo-chemical reaction was evaluated. The tensile strength of 5.4 [kgf/cm 2 ] was obtained, whereas that of the non-treatment sample was nil. Moreover, the transmittance of the vitrified silicone oil was measured at the 193 nm of ArF laser wavelength. It increased by 90.6% from 29.2% without the UV photon irradiation. The results showed that the silicon oil changed to silica glass by the excited oxygen, which improved the UV rays under 200nm transmittance.

Photochemical adhesion of fused silica optical elements with no adhesive strain

An adhesive method that creates properties of heatproof, waterproof, and transparent to ultraviolet ray of 200 nm and under in the wavelength without adhesive strain was developed by putting one silica glass to another with the silicone oil that had been photo-oxidized by Xe2 excimer lamp. The measurement by the ZYGO interferometer showed that there was neither adhesive strain nor bubbles, and the bonding strength of 18MPa was achieved. To compare the heat resistance of the photo-oxidized silicone oil with that of general-purpose adhesives such as silicone rubber, water glass, and epoxy resin, the shearing tensile strength test was conducted after exposing at high temperatures from 25 to 500 °C. As a result, the silicone rubber adhesive exfoliated at 110 °C, and the epoxy resin adhesive, at 150 °C; however, the photo-oxidized silicone oil had the bonding strength of 6.5MPa at 500 °C.

Role of oxidizing agent: thin film formation by photo-oxidizing silicone oil for vacuum UV rays transmittance and high hardness

An oxidizing agent is needed for silicone oil to be photo-oxidized with Xe2 excimer-lamp. However, the lamp light did not reach the silicone oil on the surface of the substrate satisfactorily, and the photo-oxidation reaction of the silicone oil layer was hard to take place properly. In order to find the appropriate conditions for supplying the proper amount of an oxidizing agent to silicone oil, the vacuum ultraviolet light that passed the silicone oil layer was made fluoresce in the phosphor to monitor the progress of the photo-oxidation reaction. As the vitrification by photo-oxidation reaction of the silicone oil layer improved, the fluorescence intensity of the phosphor increased. While monitoring the change of the fluorescence intensity, the supply of the oxidizing agent and the irradiation time of the vacuum ultraviolet light were controlled; as a result, the new method to efficiently form a transparent, photo-oxidized thin film has been established.

On site sodium manufacturing for energy storage with offshore wind power and seawater

Sodium metal reacts with water violently and generates a huge amount of hydrogen. Sodium metal has the role as a hydrogen storage material. The fossil fuel and nuclear fuel are deposited only in a limited region in the world and reserves are limited, whereas sodium exists plentifully as a salt in seawater and exists abundantly as a rock salt on the continents. Sodium (specific gravity, 0.971) is lighter than water and is stored safely in kerosene for electric power. The solution can then be transported to a location and with the addition of water can instantaneously generate a large amount of hydrogen for power generation.

On-site sodium metal production with electrolysis by offshore wind or solar cell power generation for hydrogen generation

Sodium metal reacts with water explosively to generate hydrogen. Therefore, sodium metal can have an important role as a hydrogen storage material. Seawater contains water most and sodium second. Seawater is electrolyzed by offshore wind or solar cell power generation to produce sodium; which is transported to a thermoelectric power plant on land and then is reacted with water to produce hydrogen for electric power generation. Sodium hydroxide, a by-product, is used as a raw material for soda industries. In the sodium production process, many by-products such as fresh water, magnesium, sodium hydroxide, hydrochloric acid, and sulfuric acid are produced. Thus, sodium metal is an economical, renewable, and sustainable fuel that discharges neither CO 2 nor radioactivity.