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Polytetrafluoroethylene (PTFE) and fluorinated ethylene propylene (FEP) are typical fluoropolymers displaying several desirable technological properties such as electrical insulation and high chemical resistance. When their surfaces are irradiated with ion beams, dense micro-protrusions formed after the emergence and spread of micropores across the entire irradiated area, allowing culture cells to spread on the top of the protrusions. In this study, we investigate the morphological changes introduced in the fluoropolymer surfaces by ion beams as the energy of the beams is increased. When an FEP sample was irradiated with a nitrogen ion beam with an energy of less than 350keV at 1.0μA/cm2, protrusions were formed with a density between 2×107/cm2 and 2×108/cm2. However, at energies higher than 350keV, the protrusions became sparse, and the density dropped to 5×102/cm2. Protrusions appeared sporadically during irradiation at high energies, and the top of the protrusions appeared as spots inside the sample, which were difficult to etch and became elongated as the erosion of the surface progressed. Erosion was caused by sputtering of FEP molecules and evaporation at notably elevated temperatures on the surface. Analysis based on attenuated total reflectance/Fourier transform infrared spectroscopy showed the presence of C C bonds as well as –COOH, –C O, and –OH bonds on all irradiated samples. Their concentration on the surface densely covered with micro-protrusions was higher than that on the surface with sparse protrusions after irradiation at energies exceeding 350keV. Thus, we determined a suitable range for the ion energy for creating FEP surfaces densely covered with protrusions. [ABSTRACT FROM AUTHOR]

Abstract: An ion irradiation system in liquid has been developed using a tapered glass capillary with a thin window at the tip. Irradiation at a solid–liquid interface is interesting because it can be applied to novel analysis, radiation testing, and surface modification processes. In this study, polyethylene and polytetrafluoroethylene were irradiated with H+ ions in an aqueous solution containing acrylic acid monomers. The irradiated surfaces which were originally hydrophobic became hydrophilic due to the surface layer formed by the acrylic acid polymer. [Copyright &y& Elsevier]

Abstract: A polytetrafluoroethylene (PTFE) surface is smooth and biologically inert, so that cells cannot attach to it. Ion beam irradiation of the PTFE surface forms micropores and a melted layer, and the surface is finally covered with a large number of small protrusions. Recently, we found that cells could adhere to this irradiated PTFE surface and spread over the surface. Because of their peculiar attachment behavior, these surfaces can be used as biological tools. However, the factors regulating cell adhesion are still unclear, although some new functional groups formed by irradiation seem to contribute to this adhesion. To control cell behavior on PTFE surfaces, we must determine the effects of the outermost irradiated surface on cell adhesion. In this study, we removed the thin melted surface layer by postirradiation annealing and investigated cell behavior on the surface. On the surface irradiated with 3×1016 ions/cm2, cells spread only on the remaining parts of the melted layer. From these results, it is clear that the melted layer had a capacity for cell attachment. When the surface covered with protrusions was irradiated with a fluence of 1×1017 ions/cm2, the distribution of cells changed after the annealing process from ‘sheet shaped’ into multicellular aggregates with diameters of around 50μm. These results indicate that we can control cell behavior on PTFE surfaces covered with protrusions using irradiation and subsequent annealing. Multicellular spheroids can be fabricated for tissue engineering using this surface. [Copyright &y& Elsevier]

Abstract: Silicone (polydimethylsiloxane) sheets and tubes for medical use were irradiated with inert gas ions using plasma-based ion implantation (PBII). The affinity of the surface with tissue examined by an animal test was improved by the irradiation at optimal conditions. The cell attachment percentage increased at an applied voltage of less than −7.5kV; however, it decreased at higher voltage. The specimens irradiated at higher voltages were more hydrophobic than unirradiated specimens. The surface became rough with increasing voltage and textures, and small domains appeared. This effect was caused by different etching speeds in the amorphous and crystalline areas. [Copyright &y& Elsevier]

A compact neutron source using a particle accelerator is a promising tool for material analysis, infrastructural diagnostics, fissile material detection, and medical applications. For non-destructive, on-site inspection of the degradation of aged concrete and steel reinforcement it is essential to develop a light and compact neutron source system. To design a more compact RFQ linac for a transportable neutron source, we developed a 500 MHz RFQ linac. In this paper the design of a 500 MHz RFQ linac for a compact neutron source is described. First, using beam tracking simulation software, we designed the cell parameters of the 500 MHz RFQ linac, which can accelerate a proton beam from 30 keV to 2.49 MeV. Then, using three-dimensional electromagnetic simulation software and multiphysics simulation software, we optimized the cavity design of the 500 MHz RFQ linac, and investigated the thermal properties of the cavity with the cooling channels. [ABSTRACT FROM AUTHOR]

Fluorescent, ubiquitination-based cell cycle indicator-expressing HeLa cells have been irradiated with a microbeam set-up at RIKEN for examining the effect to cell cycle after bombarding with protons of 1 MeV incident energy. Here, single cells were exposed in their nucleus with different doses (100, 1000, 10,000 and 100,000 protons). Subsequently, the cells were monitored using time-lapse microscopy after irradiation. In this paper, we present the preliminary results for such irradiation for 8 cells. The irradiated cells with up to 10,000 protons showed the change in fluorescence from red to green. This indicates that the transformation from G 1 to S/G 2 in cell cycle seemed not to be affected by the irradiation up to 10,000 protons. However, the irradiated cell with 100,000 protons died in red fluorescence at ∼ 4 h after the irradiation. [ABSTRACT FROM AUTHOR]

Abstract: Application of nano and micro fabrication techniques in industry requires solution to some crucial problems. One of the significant problems is the sticking interface between mold surface and imprinted polymer. In this study, we report a solution to the sticking interface problem by modification of nano imprinting mold using fluorine ion implantation. After the fluorine implantation, anti sticking layer appeared on the nano imprinting mold surface. After the implantation, a mold made from glass like carbon was patterned by focused ion beam lithography. The pattern was made up of word “TIRI”. The line width was varied with 300nm, 500nm, and 1μm. The line depth was about 200∼300nm. The average depth of implanted fluorine was approximately 90nm. After imprinting, the resin was removed from the mold by mechanical lift-off process. Transferred pattern was observed and confirmed by a scanning electron microscope (SEM) and an atomic force microscope (AFM). The pattern transferred from mold to resin was found to be successful. [Copyright &y& Elsevier]

Abstract: Ar or Xe ions were implanted into the fractured-faces or surfaces of as-carbonized glass-like carbon (GC) specimens for modification of the structure of them. Microstructural changes were examined by Raman spectroscopy, by scanning tunneling microscope (STM) and by transmission electron microscopy (TEM). It was found that the as-carbonized surfaces and fractured-faces of the specimens were changed to an amorphous structure by ion implantation. Implanted as-carbonized surfaces of specimens were restored nearly pristine structures after re-heat-treatment at 3000°C. On the other hand, implanted fractured-faces of specimens resulted in well-developed structures after re-heat-treatment at 3000°C. After re-heat-treatment at 3000°C, the degree of graphitization on the implanted fractured-faces was higher than that on the pristine fractured-faces. It can be concluded that mobility of carbon atoms, or free face, seemed to play an important role on surface graphitization. [Copyright &y& Elsevier]

InGaP solar cells are popularly used as detectors that output a current signal due to incident radiation. The device has a bare surface structure having a thickness of approximately 1 µm, which may facilitate the detection of high-energy charged particles with short ranges. When neutrons react with boron, they emit alpha rays and charged particles of lithium nuclei. This study demonstrates that InGaP solar cells can be applied as neutron-detection devices by installing a boron-conversion film on the surface of the cell. In addition, its performance in high-temperature environments is also investigated to develop its applicability as a detector in nuclear reactors and space exploration. InGaP solar cells irradiated with neutrons at the compact accelerator neutron source RANS exhibited an increase in the current signal proportional to the flux. A slight degradation was also observed after long-term neutron irradiation. The temperature dependence of the current behavior was also evaluated by fabricating a chamber that can perform neutron irradiation in a high-temperature environment. The current behavior of the InGaP solar cell at 275 °C presents a slightly higher sensitivity than that at 20 °C, thus confirming the narrow-band-gap effect in high-temperature environments. [ABSTRACT FROM AUTHOR]

Solute cluster induced hardening plays a dominant role in the irradiation embrittlement of reactor pressure vessel. For Cu-rich clusters, the Russell and Brown model (1972) is often applied for their correlation with hardening, but many parameters of the model are taken as adjustable to fit specific experimental data. In this work, a correlation is attempted and discussed between Cu-rich clusters and hardening in a series of reactor pressure vessel model alloys. Compared with the Cu clusters of the same size, Cu-rich clusters containing Ni and Mn may have lower obstacle strength and cause lower hardening. [ABSTRACT FROM AUTHOR]

Abstract: Teflon surfaces were modified using a combination of 3MeV proton microbeam scanning and subsequent 250keV N2 + ion beam irradiation. When a Teflon surface is irradiated using only an N2 + ion beam, micro-protrusions are densely formed in the irradiated area. It has been previously confirmed that these protrusions aid the attachment of biological cells, which then spread on the surface. Therefore, modification of the Teflon surface patterning is necessary in order to enhance its functionality as cell culture substrata. In this study, flat areas and depressed structures were created among the dense micro-protrusions by bubbles that were generated inside the sample using proton beam scanning. This modification will contribute to the fabrication of cell culture dishes with the advantages of micro-protrusions. [Copyright &y& Elsevier]

Abstract: Polytetrafluoroethylene (PTFE) and fluorinated ethylene propylene (FEP) are fluoropolymers that have several desirable technological properties, such as electrical insulation and chemical inertness. Nitrogen ion beam irradiation at high fluence forms dense microprotrusions on PTFE and FEP surfaces. Such unique surface structures are useful in cell culture dishes where cells can attach and spread on top of the protrusions. To enhance this functionality, control of surface morphology is necessary. In this study, we create smooth patterns between micro-protrusions by using focused MeV proton beam scanning and subsequent keV nitrogen ion beam irradiation. As a result, many double bonds (C C) and oxygen-containing groups were detected by attenuated total reflectance/Fourier infrared spectroscopy, particularly in the smooth areas. [Copyright &y& Elsevier]

Abstract: Polytetrafluoroethylene (PTFE) is a typical fluoropolymer and it has several desirable technological properties such as electrical insulation, solid lubrication etc. However, the conventional microstructuring methods have not been well applied to PTFE due to its chemical inertness. Some effective micromachining using synchrotron radiation or ion beam irradiation has been reported. In this study, we create micro-prominences by raising the original surface using proton beam writing (PBW) without chemical etching. A conical prominence was formed by spiral drawing from the center with a 3MeV proton beam. The body was porous, and the bulk PTFE below the prominence changed to fragmented structures. With decreasing writing speed, the prominence became taller but the height peaked. The prominence gradually reduced in size after the speed reached the optimum value. We expect that these porous projections with high aspect ratio will be versatile in medical fields and microelectromechanical systems (MEMS) technology. [Copyright &y& Elsevier]