論文 - 寺川　光洋

Tailored Structure and Antibacterial Properties of Silica-Coated Silver Nanoplates by Pulsed Laser Irradiation

E. Takeda, W. Xu, M. Terakawa, T. Niidome

ACS Omega （American Chemical Society）  7 （ 8 ） 7251 - 7256 2022年02月

研究論文（学術雑誌）, 共著, 査読有り

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We coated triangular-shaped silver nanoparticles, a type of anisotropic nanoplate (NPL), with silica (i.e., prepared Ag@SiO2 NPLs). When we irradiated Ag@SiO2 NPLs with nanosecond-pulsed laser light for 10 s, the triangular shape changed to spherical because of the photothermal effect. A high laser power exposed the silver core, and the particles exhibited strong antimicrobial activity. In contrast, at a moderate laser power, the silica layer crystallized, and the particles’ antimicrobial activity decreased. Thus, a combination of Ag@SiO2 NPLs and an appropriately tuned power of pulsed laser irradiation facilitated a decreased or an increased antimicrobial activity.

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Multiphoton Photoreduction for Biomimetic Applications of Hydrogels

Nagano Y., Tsunemitsu K., Onoe H., Terakawa M.

Optics InfoBase Conference Papers （Optics InfoBase Conference Papers）  2022年

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Light-driven control of the flow velocity inside a hydrogel microchannel is demonstrated by fabricating metal microstructures by multiphoton photoreduction. A technique to evaluate the local strain and compression of the hydrogel will also be described.

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Laser Direct Writing of Graphene Quantum Dots inside a Transparent Polymer

Shuichiro Hayashi, Kaneto Tsunemitsu, Mitsuhiro Terakawa

Nano Letters （ACS Publications）  22 （ 2 ） 775 - 782 2021年12月

研究論文（学術雑誌）, 共著, 査読有り

　概要を見る

Graphene quantum dots (GQDs) have emerged as a promising new class of environmentally friendly quantum dots with unique properties. However, the limitations of synthesis and patterning methods have hindered GQDs from displaying their true potentials to date. Here, we demonstrate the simultaneous synthesis and patterning of GQDs for the first time inside a transparent polymer, polydimethylsiloxane (PDMS), using femtosecond laser pulses. By focusing and scanning femtosecond laser pulses, arbitrary fluorescent patterns such as a concealed fluorescent QR code can be readily patterned without pre- and/or post-treatment. In addition, the proposed method is applied to the fabrication of fluorescent three-dimensional structures inside a transparent polymer via multiphoton interactions. The proposed method realizes single-stepped and spatially selective patterning of GQDs directly inside polymer substrates and expands the possibilities of GQDs for applications in novel flexible three-dimensional optoelectrical devices.

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Nanosecond laser ablation of AlN ceramic

N. Nedyalkov, A. Dikovska, L. Aleksandrov, M. Terakawa

Applied Physics A （Applied Physics A: Materials Science and Processing）  127 （ 12 ） 951 2021年11月

研究論文（学術雑誌）, 共著, 査読有り

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In this work, the ablation rate and surface modifications are studied of aluminum nitride ceramic treated by a pulsed nanosecond Nd:YAG laser at four wavelengths—266 nm, 355 nm, 532 nm, and 1064 nm. The ablation depth is presented as a function of the laser fluence and the number of pulses applied. A decrease of the ablation efficiency with the increase of both laser fluence and number of pulses is observed for all wavelengths used. It is found that the laser treatment leads to the formation of a variety of micro and nanostructures on the surface of the material that are strongly dependent on the processing conditions. The laser ablation at the fundamental wavelength leads to the appearance of periodic structures on the surface. Such effect is not observed for the other wavelengths used. It is further found that the laser processing also leads to the formation a conductive layer for all wavelengths. Using a model based on the heat diffusion equation that takes into account the process of ceramic decomposition, the ablation dynamics is followed, and the dependence of the surface layers thickness on the processing conditions is estimated. The results obtained are used to explain the experimentally observed dependences.

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Pulsed laser deposition of plasmonic structures in air by irradiation through the substrate

Nedyalkov N., Nikov R., Nikov R., Dikovska A., Karashanova D., Grochowska K., Karczewski J., Śliwiński G., Terakawa M.

Thin Solid Films （Thin Solid Films）  734 2021年09月

研究論文（学術雑誌）, 共著, 査読有り

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Laser-induced periodic structure formation in AlN ceramic

Nedyalkov N.N., Dikovska A., Nikov R., Atanasova G., Hayashi S., Terakawa M.

Optics and Laser Technology （Optics and Laser Technology）  144 2021年07月

研究論文（学術雑誌）, 共著, 査読有り

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Laser direct writing of highly crystalline graphene on PDMS for fingertip-sized piezoelectric sensors

Shuichiro Hayashi, Fumiya Morosawa, Mitsuhiro Terakawa

Advanced Engineering Materials （Wiley）  23 （ 10 ） 2100457 2021年06月

研究論文（学術雑誌）, 共著, 査読有り

　概要を見る

The patterning of electrically conductive structures directly onto the polydimethylsiloxane (PDMS) surface is crucial for the realization of flexible and elastic devices. Herein, defocused femtosecond laser pulses are irradiated for the fabrication of highly crystalline graphitic carbon structures on PDMS and a high electrical conductivity of ≈51.6 S m−1 is achieved. Utilizing the elasticity of PDMS and the high conductivity of fabricated structures, a fingertip-sized pressure sensor, which can detect pressures as low as ≈0.1 Pa, is realized. Moreover, a novel ring-shaped heart rate (HR) monitor, capable of measuring the HR from the index finger, is demonstrated, indicating the potential of fabricated structures in miniature and wearable healthcare applications.

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Electrically Conductive Porous Carbon Structures Fabricated by Laser Direct Carbonization of Bamboo

Miyakoshi R., Morosawa F., Hayashi S., Terakawa M.

2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021 （2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021）  2021年06月

　概要を見る

Porous carbon structures have attracted much interest for applications, such as catalyst carriers, energy storage devices, and chemical sensors, due to their chemical stability, high adsorptive property, and electrical conductivity. Among several methods to fabricate porous carbon structures, laser carbonization is a promising method for spatially-selective and high-resolution fabrication of electrically conductive porous carbon strucutres [1], [2]. Recently, the fabrication of porous carbon structures by laser carbonization using biomasses, materials derived from living or recently-living organisms, as the precursor have been reported [3]. In this study, we fabricated electrically conductive porous carbon structures by the femtosecond-laser carbonization of bamboo, which is a biomass with a well-connected three-dimensional porous structure by nature.

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Microfabrication of cellulose nanofiber-reinforced hydrogel by multiphoton polymerization

Hiroki Sugiyama, Kaneto Tsunemitsu, Hiroaki Onoe, Kotaro Obata, Koji Sugioka, Mitsuhiro Terakawa

Scientific Reports （Springer Nature）  11 （ 1 ） 10892 2021年05月

研究論文（学術雑誌）, 共著, 査読有り

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The mechanical strength of hydrogel microstructures is crucial for obtaining the desired flexibility, robustness, and biocompatibility for various applications such as cell scaffolds and soft microrobots. In this study, we demonstrate the fabrication of microstructures composed of cellulose nanofibers (CNFs) and poly(ethylene glycol) diacrylate (PEGDA) hydrogels by multiphoton polymerization. The stress of the fabricated microstructure during tensile testing increased with an increase in the CNF concentration, indicating that the mechanical strength of the microstructure was enhanced by using CNFs as fillers. Moreover, the swelling ratio of the microstructure increased with increasing CNF concentration in the PEGDA hydrogel. Our results show the potential of the technique for the microfabrication of advanced cell scaffolds and soft microrobots with the desired mechanical strength.

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Femtosecond laser-induced graphitization of transparent cellulose nanofiber films

Fumiya Morosawa, Shuichiro Hayashi, Mitsuhiro Terakawa

ACS Sustainable Chemistry & Engineering （ACS Sustainable Chemistry and Engineering）  9 （ 7 ） 2955 - 2961 2021年02月

研究論文（学術雑誌）, 共著, 査読有り

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© 2021 American Chemical Society. Laser graphitization allows for the spatially targeted modification of biomasses into electrically conductive structures and is a promising technique for the development of sustainable electronic devices. Out of the many biomasses, cellulose nanofiber (CNF) is a sustainable biomass which exhibits unique properties, such as mechanical strength and optical transparency. In this study, we demonstrated the fabrication of highly conductive graphitic carbon from CNFs using a high-repetition femtosecond laser. A conductivity as high as 6.9 S/cm was obtained by single scanning of the laser beam, which is estimated to be more than 100 times higher than the conductivity reported previously. From the Raman analysis of the structure, the formation of highly crystalline graphitic carbon was indicated, which contributes to the high conductivity. In the case of high-repetition femtosecond laser irradiation, it is considered that strong optical effects, in addition to thermal effects, contribute to the degradation of CNFs, resulting in the formation of highly crystalline graphitic carbon. Our presented technique allows for the direct writing of highly conductive graphitic carbon on CNF films, and the development of sustainable electronic devices, using mechanically robust and transparent CNF films as the substrate, should be realized.

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Charged fluorophores-assisted fabrication of metallic structures inside hydrogel by multi-photon photoreduction

Machida M., Shen W., Onoe H., Heisterkamp A., Mazur E., Terakawa M.

Proceedings of SPIE - The International Society for Optical Engineering （Proceedings of SPIE - The International Society for Optical Engineering）  11676 2021年

　概要を見る

We demonstrated the fabrication of gold microstructures inside a PEG-based hydrogel with different charged fluorophores by multi-photon photoreduction. By adding an anionic charged FITC-dextran or a cationic charged Rhodamine110 to the metal ion solution, line width of the fabricated gold microstructures increased compared to that of the structures fabricated in fluorophore-free hydrogel. The photobleaching could enhanced the reduction of gold ions accompanying the oxidation of the fluorophores. Notably, the inhibition of reduction of gold ions at a site other than the focal point was observed with FITC-dextran, which may be attributable to the coordination of gold ions to FITC-dextran.

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Fabrication of hollow channels surrounded by gold nanoparticles in hydrogel by femtosecond laser irradiation

Izumi Takayama, Akito Katayama, Mitsuhiro Terakawa

Nanomaterials （Nanomaterials）  10 （ 12 ） 2529 - 10 2020年12月

研究論文（学術雑誌）, 共著, 査読有り

　概要を見る

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. The fabrication of hollow channels surrounded by gold nanoparticles in poly(ethylene glycol) diacrylate (PEGDA) is demonstrated. The absorption spectra show that gold nanoparticles were formed at the periphery of the focus by reduction of gold ions. The microscope observation and Raman spectroscopy analyses indicate that the center of the channels were void of PEGDA, which can be attributed to the femtosecond laser-induced degradation of the hydrogel. Since both the hydrogel and gold nanoparticles are biocompatible, this technique of fabricating hollow channels surrounded by gold nanoparticles is promising for tissue engineering, drug screening, and lab-on-a-chip devices.

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Anionic fluorophore-assisted fabrication of gold microstructures inside a hydrogel by multi-photon photoreduction

Manan Machida, Weilu Shen, Hiroaki Onoe, Yuki Hiruta, Alexander Heisterkamp, Eric Mazur, and Mitsuhiro Terakawa

Optical Materials Express （The Optical Society (OSA)）  11 （ 1 ） 48 - 58 2020年12月

研究論文（学術雑誌）, 共著, 査読有り

　概要を見る

© 2020 Optical Society of America. All Rights Reserved. The fabrication of accentuated gold microstructures is demonstrated by multi-photon photoreduction inside an anionic fluorophore-containing hydrogel. We attempted to facilitate gold-ion photoreduction near the focal point of laser pulses, expecting the donation of electrons by the oxidation of fluorophores in the vicinity of gold ions. The presence of anionic FITCdextran also inhibited the spontaneous reduction in untargeted zones, which is attributed to the coordination of gold ions and the anionic FITC-dextran. Simultaneous facilitation and inhibition are promising for the fabrication of dense metal microstructures in the targeted zone while maintaining the hydrogel's light permeability.

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Femtosecond-laser-induced graphitic carbon from transparent cellulose nanofiber films

Morosawa F., Hayashi S., Terakawa M.

2020 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2020 - Proceedings （2020 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2020 - Proceedings）  2020年08月

　概要を見る

© 2020 IEEE. The fabrication of electrically conductive structures by femtosecond-laser irradiation of a cellulose nanofiber (CNF) film was demonstrated. Raman analyses indicated the formation of graphitic carbon, which is attributable to the electrical conductivity of the structures.

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Multiphoton photoreduction for dual-wavelength-light-driven shrinkage and actuation in hydrogel

Kosuke Mizuguchi, Yo Nagano, Hiroaki Nishiyama, Hiroaki Onoe, Mitsuhiro Terakawa

Optical Materials Express （The Optical Society (OSA)）  10 （ 8 ） 1931 - 1940 2020年07月

研究論文（学術雑誌）, 共著, 査読有り

　概要を見る

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement. The dual-wavelength-driven shrinkage of metal microstructures and hydrogel actuation are demonstrated by the fabrication of multi-metal microstructures in hydrogels by multiphoton photoreduction. Silver and gold microstructures were fabricated in a poly-Nisopropylacrylamide (PNIPAm) hydrogel. Because of the different optical resonances of the metals, wavelength-dependent shrinkage of metal microstructures was demonstrated concurrently with the volume change of the supporting hydrogel by light stimulation. Furthermore, the direction of actuation of the hydrogel was controlled by switching the wavelength of light stimulation. The results indicate the potential of multiphoton photoreduction for applications in light-driven optical components and micro-robots fabricated with soft materials.

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Myoblast adhesion and proliferation on biodegradable polymer films with femtosecond laser-fabricated micro through-holes

Takayama I., Kondo N., Kalies S., Heisterkamp A., Terakawa M.

Journal of Biophotonics （Journal of Biophotonics）  13 （ 7 ）  2020年04月

研究論文（学術雑誌）, 共著, 査読有り

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© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Controlling cell adhesion and cell differentiation is necessary to fabricate a tissue with arbitrary properties for tissue engineering applications. A substrate with a porous structure as a cell scaffold allows the diffusion of the cell culture medium through the scaffold. In this work, we show that the femtosecond laser fabricated micro through-holes in biodegradable polymer films, enhance myoblast adhesion, and accelerates proliferation and differentiation. ChR2-C2C12 and UT-C2C12 cells were seeded on the films with micro through-holes each fabricated by a single femtosecond laser pulse. Cell adhesion was enhanced on films with holes fabricated by laser irradiation. In addition, cell proliferation was accelerated on films with micro through-holes that penetrate the film, compared to on films with micro craters that do not penetrate the film. On films with arrays consisting of micro through-holes, cells aligned along the arrays and cell fusion was enhanced, indicating the acceleration of cell differentiation.

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Synthesis of silicon carbide nanocrystals and multilayer graphitic carbon by femtosecond laser irradiation of polydimethylsiloxane

Hayashi S., Morosawa F., Terakawa M.

Nanoscale Advances （Nanoscale Advances）  2 （ 5 ） 1886 - 1893 2020年03月

研究論文（学術雑誌）, 共著, 査読有り

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© The Royal Society of Chemistry 2020. Laser-based modification of polymer materials has been emerging as a versatile and efficient technique to simultaneously form and pattern electrically conductive materials. Recently, it has been revealed that native polydimethylsiloxane (PDMS) can be modified into electrically conductive structures using femtosecond laser irradiation; however, the details regarding the structures formed by this method have yet to be revealed. In this work, structures were fabricated by focusing and scanning femtosecond laser pulses onto the surface of PDMS. Raman Spectroscopy and Transmission Electron Microscopy (TEM) analyses revealed the formation of silicon carbide (SiC) nanocrystals, as well as multilayer graphitic carbon, in the modified regions of PDMS. The state of the formed material differed depending on the distance from the focal spot, suggesting that photo-thermal effects contributed to the degradation of PDMS into conductive material. Electrical conductivity measurements, in addition to Raman results, indicated that the amount of disorder in the formed graphitic carbon contributes to the electrical conductivity of the fabricated structures.

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Effect of Pd-decoration on the sensing properties of ZnO nanostructures

Dilova T., Atanasova G., Og. Dikovska A., Avdeev G., Machida M., Terakawa M., Stefanov P., Nedyalkov N.

Thin Solid Films （Thin Solid Films）  693   137693 2020年01月

　概要を見る

© 2019 Elsevier B.V. In this work, we present fabrication and studies of pure and Pd-decorated ZnO nanostructures on Ag-coated substrates in view of gas-sensing application. The sensor elements consist of a dense structure of ZnO nanobelts. The chemical composition of the surface and gas-sensing properties of pure and Pd-doped nanostructures were studied and compared. On the surface of the Pd-decorated ZnO samples, the presence was found of Pd and Pd-Ag clusters, as well as isolated Pd2+ ions were incorporated into the ZnO lattice. The Pd-ZnO sensor element showed a better response to CO, NH3, and acetone compared to the pure ZnO sample. The Pd-ZnO sample exhibited its highest response to exposure to acetone at room temperature. We associate the improvement of sensing performance of the Pd-decorated ZnO nanostructures with the increased number of adsorption centers on the surface due to the Pd nanoparticles.

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Luminescence properties of laser-induced silver clusters in borosilicate glass

Nedyalkov N., Dikovska A., Koleva M., Stankova N., Nikov R., Borisova E., Genova T., Aleksandrov L., Iordanova R., Terakawa M.

Optical Materials （Optical Materials）  100 2019年12月

研究論文（学術雑誌）, 共著, 査読有り

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© 2019 Elsevier B.V. This paper describes the luminescence properties of small silver clusters formed by laser treatment of silver-doped borosilicate glass. Using irradiation by a Nd:YAG nanosecond laser system operating at the fourth harmonic wavelength (266 nm), areas are formed in the glass samples that emit bright luminescence peaking at about 600 nm when excited by UV light in the spectral range 300–390 nm. The influence is presented and discussed of the glass composition and the laser processing parameters on the emission characteristics. It is further shown that the luminescent properties are affected by the fluence of the excitation source, namely, a complete quenching of the emission is achieved above a certain value. The luminescence of the irradiated areas is explained by the formation of Ag clusters due to irradiation-induced reduction of Ag ions and increased atom mobility resulting from the local heating. The limited stability of the luminescent areas upon UV radiation can be related to heat-induced cluster decomposition and re-oxidation. The results obtained provide a new insight in the optical properties of noble-metal nanostructures and could form the basis of fabrication of complex optical systems and luminescent component used in the study of, e.g., biological systems.

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Fabrication of a monolithic lab-on-a-chip platform with integrated hydrogel waveguides for chemical sensing

Torres-Mapa M., Singh M., Simon O., Mapa J., Machida M., Günther A., Roth B., Heinemann D., Terakawa M., Heisterkamp A.

Sensors (Switzerland) （Sensors (Switzerland)）  19 （ 19 ）  2019年10月

　概要を見る

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. Hydrogel waveguides have found increased use for variety of applications where biocompatibility and flexibility are important. In this work, we demonstrate the use of polyethylene glycol diacrylate (PEGDA) waveguides to realize a monolithic lab-on-a-chip device. We performed a comprehensive study on the swelling and optical properties for different chain lengths and concentrations in order to realize an integrated biocompatible waveguide in a microfluidic device for chemical sensing. Waveguiding properties of PEGDA hydrogel were used to guide excitation light into a microfluidic channel to measure the fluorescence emission profile of rhodamine 6G as well as collect the fluorescence signal from the same device. Overall, this work shows the potential of hydrogel waveguides to facilitate delivery and collection of optical signals for potential use in wearable and implantable lab-on-a-chip devices.

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