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Dark current in optical sensors has been one of their issues. The performance of these sensors can be improved by reducing their dark current. In this study, we investigated UV sensors based on ZnO nanorods (ZNRs), in particular, their current-voltage characteristics, response and recovery times, on-off current ratio, and responsivity as a function of the device process conditions. The number of seed layer coatings was changed and an oxygen (O₂) plasma treatment was applied to ZNRs. A microwave-assisted growth (MAG) method was used to grow ZNRs. The MAG method is one way to shorten device manufacturing time. The small number of seed layer coating processes played a role in reducing the dark current of the sensor. The O₂ plasma treatment further reduced the dark current. The crystal quality of ZNRs was affected by changes in the sensor fabrication process. Although the O₂ plasma treated device had an increased on-off current ratio, the response time was increased.

In this study, the fabrication of a wettability patterned surface for cellular micropatterning was investigated using step-wise ion beam processing. A perfluorinated poly(ethylene-co-propylene) (FEP) film was first irradiated using accelerated Xe+ ions with 100 keV of energy at the low current density of 1 μ A/cm² over the entire surface. Second, its confined regions were irradiated at the higher current density of 15 μ A/cm² at various ion fluences through the pattern mask to generate patterns with big differences in wettability. From the analytic results, it was clearly verified that the step-wise irradiation induced effective chemical and morphological changes on the FEP surface, resulting in the successful formation of well-defined micropatterns with relatively hydrophilic and superhydrophobic surfaces. Moreover, the results of in-vitro cell culture showed well-resolved formation of 200 μ m cell micropatterns on the wettability patterned FEP surface due to the individual effects of the relatively hydrophilic and superhydrophobic properties on the cell adhesiveness and proliferation.

In this paper, the simple and biocompatible micropatterning of cell-repellent poly(N-isopropylacrylamide) (PNIPAAm) on a cell-adhesive substrate by ion beam micropatterning to control cell adhesion is described. Cell-repellent PNIPAAm films spin-coated on cell-adhesive tissue culture polystyrene (TCPS) substrates were selectively irradiated by energetic proton ions at various fluences through a pattern mask, and subsequently developed to create the micropatterns of PNIPAAm. Well-defined negative-type PNIPAAm micropatterns were successfully created on the TCPS substrates at fluences higher than 5 x 10¹⁴ ions/cm², and their chemical properties were dependent on the fluence. Moreover, based on the results of the protein adsorption and in-vitro cell culture tests, 200 µm well-defined micropatterns of mammalian cells were clearly formed on the PNIPAAm-micropatterned TCPS substrates though the preferential adsorption and growth of cells on the TCPS regions due to the strong cell-repellency of PNIPAAm.

A simple and facile method for the patterning of gold nanoparticles (GNPs) was described via selective ion irradiation and oxygen plasma etching. Thin Pluronic films containing HAuCI4 as the precursor of GNPs were selectively irradiated through a pattern mask with 200 keV proton ions to generate GNP-embedded Pluronic patterns. The Pluronic was then removed by an oxygen plasma etching process for the pattern formation of GNPs. Based on the results of the UV-Vis, FE-SEM, and EDX analyses, 50 μm negative-tone line patterns of the GNP-embedded Pluronic were successfully generated at a fluence of less than 1 x 10(16) ions/cm2. The changes in the morphology and elemental composition of the formed GNP-embedded Pluronic patterns with different time periods of oxygen plasma etching were investigated using an FE-SEM with an EDX. The experimental results demonstrated that the patterns of GNPs were effectively generated by the oxygen plasma etching of the formed GNP-embedded Pluronic patterns for 15 min. Furthermore, the XRD results revealed that GNPs in the patterns formed by ion irradiation were further grown during the subsequent oxygen plasma etching.

In this study, a simple surface patterning method to create micropatterns of mammalian cells on indium tin oxide (ITO) substrates was developed using ion implantation. Thin polystyrene (PS) films spin-coated on an ITO glass was selectively implanted with accelerated proton ions through a pattern mask and then developed to generate PS micropatterns. Well-organized negative PS patterns were generated on the ITO glass. The results of the in vitro cell culture on the PS-patterned ITO glass with two types of cancer cell lines revealed the formation of well-defined cell patterns through a selective cell adhesion and proliferation only onto the ITO regions separated by PS regions. This facile method for cell patterning may be used to create a desired platform for cellular device applications, such as biosensors and cell microarrays.

In this study, a facile route to fabricate micropatterns of cells is presented on the basis of electron irradiation of poly(dimethylsiloxane) (PDMS). PDMS films were irradiated with electron beams through a pattern mask with micrometer-sized grids. After irradiation, the changes in the chemical composition, morphology, and wettability of the PDMS surface were investigated by using an X-ray photoelectron spectrometer, an atomic force microscope, and a contact anglometer. The results of the surface analysis revealed that the hydrophobic PDMS surface was changed into a hydrophilic one by the electron irradiation. Furthermore, on the basis of cell culturing on the selectively-irradiated PDMS, cells such as NIH3T3 and L929 were selectively adhered to and proliferated on the irradiated regions of the PDMS surface, resulting in the micropatterns of the cells on the PDMS surface.

Micropatterning of titanium dioxide (TiO2) on the surface of thin poly(dimethyl siloxane) (PDMS) films was described by means of proton irradiation and liquid-phase deposition (LPD) techniques. The surface of thin PDMS films was irradiated with accelerated proton ions through a pattern mask in the absence or presence of oxygen in order to create hydrophilically/hydrophobically patterned surfaces. The results of the surface analysis revealed that the PDMS films irradiated at the fluence of 1 x 10(15) ions cm-2 in the presence of oxygen showed the highest hydrophilicity. The LPD of TiO2 particles on the patterned PDMS film surface showed a selective deposition of TiO2 on the irradiated regions, leading to well defined TiO2 micropatterns. The crystal structure of the formed TiO2 films was found to be in an anatase phase by X-ray diffraction analysis. This process can be applied for patterning various metal and metal oxide particles on a polymer substrate.

Poly(vinyl pyrrolidone) (PVP)-stabilized silver nanoparticles (NPs) were used as a new nanocomposite resist for electron beam lithography. A nanocomposite resist prepared by reducing silver nitrate in an alcoholic PVP solution was patterned by using a scanning electron microscope equipped with a nanometer pattern generation system. Well-defined negative tone patterns with a good sensitivity of 200 microC/cm2 and a contrast of 2.83 were obtained using the prepared nanocomposite resist. In addition, the changes in the morphology and structure of the resist patterns with a thermal treatment temperature were investigated by a FE-SEM with an EDX. The results revealed that the patterns of Ag NPs were formed through sintering the formed resist patterns at above 300 degrees C.

Patterned graft polymerization of a functional monomer on a hydrophobic polymer surface was proposed for biomolecule patterning. A poly(vinylidene fluoride) (PVDF) film surface was selectively activated by ion implantation through a pattern mask and acrylic acid (AA) was then graft polymerized onto the activated regions of the PVDF surfaces. The peroxide concentration on the implanted surface depended on the fluence, which had a considerable effect on the grafting degree of AA. Afterwards, amine-functionalized biotin and probe DNA were immobilized on the poly(acrylic acid)-grafted regions of the PVDF surfaces. Specific binding of biotin with streptavidin and hybridization of probe DNA with complimentary DNA proved successful protein and DNA patterning and well-defined 50 microm dot-type patterns of the streptavidin and DNA were obtained. These results confirmed the potential of this strategy for patterning of various biomolecules.

A convenient and effective method to pattern polymer-embedded metal nanoparticles by ion irradiation has been developed. The thin Pluronic films containing silver nitrate as a precursor of silver nanoparticles were irradiated through a pattern mask with accelerated proton (H+) ions. It was found from the UV-Vis measurement that the formation of silver nanoparticles in the Pluronic matrix was dependant on the amount of silver nitrate. The 50 microm line (pitch 150 microm) patterns of the Pluronic containing silver nanoparticles were obtained with the thin film irradiated to 1 x 10(16) ions/cm2. The heat treatment effect on the morphology of the patterns was investigated by using a scanning electron microscope with an energy dispersive X-ray spectrometer. The results confirmed that the silver nanoparticles were successfully embedded in the Pluronic patterns and the patterns were changed into large silver particles by a heat treatment above 350 degrees C.

This study describes a new patterning method of poly(vinyl pyrrolidone) (PVP) containing silver nanoparticles by using ion irradiation. The thin films prepared from PVP/silver nanoparticle solutions were irradiated through a mask with accelerated H+ ions. Well-defined 50 microm line (pitch 150 microm) patterns were generated from the film irradiated at 1 x 10(16) ions/cm2. The heat treatment effect on the morphology of the patterns was investigated by using a scanning electron microscope with an energy dispersive X-ray spectrometer. The results confirmed that the silver nanoparticles were successfully immobilized in the PVP patterns and the patterns were changed into silver particles by heat treatment above 300 degrees C.