論文 - 寺川　光洋

Laser direct writing of graphene quantum dots encircling conductive structures for stimuli-responsive anti-counterfeiting label

Kosuke Tsukada, Mitsuhiro Terakawa

Optics Express （Optica）  33   19479 2025年04月

共著, 最終著者, 責任著者, 査読有り

Direct Writing of Conductive Microstructures inside a Thermoresponsive Hydrogel

Kashikawa K., Onoe H., Terakawa M.

ACS Applied Polymer Materials 7   4771 2025年

　概要を見る

The integration of soft electronic devices with biological systems has garnered increasing attention for applications such as bioinspired soft robotics and wearable health monitors. These devices are designed to interface with biological surfaces or tissues, mimicking the transmission of electrical signals through neural tissues while ensuring high biocompatibility and flexibility. Conductive polymer hydrogels, combining conductive polymers and hydrogels, have emerged as promising materials owing to their flexibility, stretchability, and biocompatibility. In the realization of advanced soft electronic devices, it is key to employ materials with high flexibility and biocompatibility and, moreover, develop techniques for the fabrication of precise and localized conductive structures inside hydrogels. In this study, we demonstrated the spatially selective polymerization of conductive polymers inside a thermoresponsive hydrogel. A poly(N-isopropylacrylamide) (PNIPAM) hydrogel was immersed in a precursor solution of polyaniline (PANI), and polymerization was induced by femtosecond laser pulse irradiation. Conductive polymer microstructures were successfully fabricated inside the hydrogel. Furthermore, using the thermal responsiveness of the PNIPAM hydrogel, we demonstrated that the electrical resistance of the PANI structures changed in response to temperature. The present method provides a strategy for the precise and localized fabrication of conductive structures inside hydrogels, offering an approach to the fabrication of soft electronic devices.

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High-resolution patterning of graphitic carbon structures in laser-induced graphitization of cellulose nanofiber film

Yosuke Kondo, Ken Kashikawa, Mari Kato, Mitsuhiro Terakawa

Optical Materials Express （Optica）  15 （ 1 ） 95 - 103 2024年12月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

　概要を見る

In laser-induced graphitization, decreasing the linewidth of patterned structures is key to enhancing the potential in microdevice fabrication. In this study, we demonstrated that graphitic carbon structures with narrow linewidth can be directly patterned in laser-induced graphitization of cellulose nanofiber (CNF) film by immersing the film in CaI2 solution. The linewidth of the structures increased with increasing laser power, indicating that the linewidth can be readily controlled. Based on the above findings, we patterned multiple concentric structures with precisely controlled linewidth to fabricate a Fresnel zone plate, which can focus laser light in the visible wavelength range.

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Laser-induced formation of fine porous graphitic carbon for eco-friendly supercapacitors

M. Kato, S. Hayashi, R. Funayama, Y. Kondo, Y. Hattori, M. Terakawa

Advanced Engineering Materials （Wiley）  26 （ 23 ） 2401301 2024年09月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  14381656

　概要を見る

An electric double-layer capacitor (EDLC), which is one of the pivotal energy storage devices, provides rapid charge–discharge capabilities and an extended cycle life. Areal capacitance, a key indicator of EDLC performance, increases with the specific surface area of its electrodes. This study demonstrates a method for significantly increasing the specific surface area in the laser-induced graphitization of biodegradable polymers by incorporating NaHCO3 into the composite sheet, generating not only microscale pores but also a large number of nanoscale fine pores. Furthermore, it shows that using these structures as EDLC electrodes leads to a substantial increase in areal capacitance. An increase in the number of fine pores formed in the structure and a corresponding rise in the areal capacitance of the fabricated EDLC are observed with the increase in the NaHCO3 weight ratio. Notably, the composite sheets are composed of natural-derived, biodegradable materials, while NaHCO3 is known for its low corrosivity and biotoxicity. The proposed method thus offers a pathway for fabricating energy storage devices with minimal environmental impact, ensuring their eco-friendly disposal post-use.

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Light-triggered transmittance control in thermoresponsive hydrogels by femtosecond laser direct writing

K. Kashikawa, H. Tomikawa, H. Onoe, M. Terakawa

ACS Applied Optical Materials （ACS）  2 （ 4 ） 565 - 573 2024年03月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

　概要を見る

Thermoresponsive hydrogels, which exhibit changes in their optical properties and volume due to temperature variations, are promising candidates for applications in soft devices. In this study, we demonstrate the modulation of transmittance in a thermoresponsive hydrogel through light stimulation employing gold microstructures fabricated via multiphoton photoreduction. The spatial integration of photoresponsiveness, attributed to high-density gold nanoparticles within the thermoresponsive hydrogel, was accomplished through the high-speed laser scanning of femtosecond laser pulses. The temperature measurement during the fabrication of the gold microstructure revealed that the high-speed and multiple scanning over the same path effectively reduced the temperature in the irradiated area of femtosecond laser pulses. The present approach enabled the mitigation of thermal effects during the fabrication, resulting in minimizing distortion in the fine lines of the structures. Upon exposure to stimulus light, a rapid change in the transmittance of the region where the structures were fabricated was prominently observed. The present method unveils a promising avenue for the advancement of light-responsive soft devices.

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Temperature measurement and morphological/crystalline differences in the laser-induced carbonization of polydimethylsiloxane

M. Kai, S. Hayashi, K. Kashikawa, M. Terakawa

Optical Materials Express （OPTICA）  14 （ 4 ） 955 - 964 2024年03月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  20102690

　概要を見る

Laser-induced carbonization, which allows for the facile generation of graphitic carbon, is considered a promising technique for fabricating arbitrary conductive microstructures. The morphology and crystallinity of the resulting product are acknowledged to be significantly influenced by laser irradiation conditions. However, unlike discussions pertaining to furnaces where detailed considerations of applied temperature and resulting products are common, discussions on the process of laser-induced carbonization are limited. In recent years, reports have shown that using polydimethylsiloxane (PDMS) as a precursor material not only produces graphitic carbon but also results in the formation of silicon carbide. In this study, we utilized a thermographic camera to measure temperature changes during laser-induced carbonization, aiming to elucidate the correlation between PDMS temperature fluctuations and the morphology and crystallinity of the resulting graphitic carbon. The results demonstrate that the morphology and crystallinity of the graphitic carbon formed through laser-induced carbonization are not solely determined by the maximum temperature in the laser-irradiated area. The temperature changes during laser irradiation play a crucial role in the selective generation of these materials.

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Defect-initiated formation mechanism of 3D carbon tracks on flexible transparent substrates by laser irradiation

S. Hayashi, X. Du, M. Rupp, K. A. Filsinger, M. Terakawa, C. B. Arnold

Optics and Laser Technology （ELSEVIER）  174   110686 2024年02月

共著, 査読有り,  ISSN  00303992

　概要を見る

Laser direct writing of 3D carbon structures onto flexible polymer substrates offers potential of rapid roll-to-roll manufacturing for a variety of key applications, including large area sensors, flexible electronics, robotics, energy storage/conversion, and other consumer applications. The specific formation mechanism of the carbon structures has been an issue of debate for many years with the prevailing notion of a simple photothermal conversion reaction that mainly depends on the total energy input. However, this view has been shown to be inconsistent with experimental observations of nonlinear changes in the resulting structures when multiple processing parameters are simultaneously changed. In this study, we propose a formation mechanism based on the nucleation and growth of laser-induced defects, which is experimentally validated by irradiating a continuous wave laser beam onto polydimethylsiloxane. The model is further validated by intentionally introducing controlled defects by femtosecond laser irradiation, and indicate the implications of a two-laser laser direct writing technique to go beyond the current processing limits. These results clarify the previously ambiguous mechanisms by which carbon structures form under laser irradiation and provide a deeper understanding of how to control photothermal processes for advanced material processing.

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Spatially-selective enhancement of mechanical strength through localized cross-linking of double network hydrogels

Kaneto Tsunemitsu, Akira Watanabe, Hiroaki Onoe, Mitsuhiro Terakawa

Optical Materials Express （OPTICA）  13 （ 10 ） 2914 - 2924 2023年09月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

　概要を見る

To advance the development of flexible materials for soft robotics applications, it is crucial to enhance the elastic modulus and breaking the stress of soft materials, such as hydrogels. Double network hydrogels (DN gels) have displayed remarkable mechanical strength owing to their unique network structure composed of two types of polymer networks. However, current fabrication methods for DN gels entail cross-linking two distinct hydrogel polymers throughout the entire hydrogel matrix. In this study, we focused on employing multi-photon polymerization (MPP) with femtosecond laser pulses as a cross-linking method for hydrogels to achieve spatially selective formation of DN gel structures at the micrometer scale, along with the consequent improvement in local mechanical strength. We assessed the mechanical properties of the fabricated structures and confirmed that the mechanical strength varied within the regions where DN gel was locally formed.

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Laser-induced dielectric to conductor transformation on the surface of aluminium nitride ceramic

Nedyalkov N., Dikovska A., Nikov R., Koleva M., Grochowska K., Jendrzejewski R., Terakawa M.

Optics and Laser Technology （Optics and Laser Technology）  163 2023年08月

ISSN  00303992

　概要を見る

In this work formation of conductive lines on the surface of AlN ceramic induced by laser radiation is presented. The transformation to conductive state is done be ablation of the ceramic surface using nanosecond Nd:YAG laser. The dependences of the processing conditions as applied laser fluence and the pulse overlapping on the resistance value are obtained for different surface modifications including straight lines, ∟, and ┼ shapes. The formation of conductive structures is also studied for application of laser irradiation at the second (532 nm), third (355 nm) and fourth (266 nm) harmonics of the laser system. It is found that the resistance strongly depends on the processing conditions, as at appropriate choice it can be varied in a range of order of magnitude. Processing parameters windows are defined where the structure resistance has a minimal value. The performed analyses based on TEM, SEM, EDX, and Raman spectroscopy indicate that formation of aluminium layer, its oxidation and morphology define the processed areas conductivity. The role of oxidation is also confirmed by analyses of structures fabricated in vacuum, where significant reduction of the resistance is observed. It is found however, that a decrease of the ambient air pressure to 10 Torr is sufficient to obtain structures resistance of the same order as for processing in vacuum. Calculated data about the thickness of the conductive layer is also presented. The obtained results could be used in the design of microelectronic components, resistive elements, and novel optical materials.

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Cultivation and transplantation of three-dimensional skins with laser-processed biodegradable membranes

Yasuyuki Tsunoi, Izumi Takayama, Naonari Kondo, Yo Nagano, Hiromi Miyazaki, Satoko Kawauchi, Mitsuru Akashi, Daizoh Saitoh, Mitsuhiro Terakawa, and Shunichi Sato

Tissue Engineering Part A （Tissue Engineering - Part A）  29 （ 11-12 ） 344 - 353 2023年05月

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  19373341

　概要を見る

For the treatment of irreversible, extensive skin damage, artificial skins or cultured skins are useful when allogeneic skins are unavailable. However, most of them lack vasculature, causing delayed perfusion and hence delay or failure in engraftment of the tissues. We previously developed a prevascularized three-dimensional (3D) cultured skin based on the layer-by-layer cell coating technique (LbL-3D skin), in which cells are seeded and laminated on a porous polymer membrane for medium supply to the thick cultured tissue. Recent animal studies have demonstrated that LbL-3D skin can achieve rapid perfusion and high graft survival after transplantation. However, there were practical issues with separating LbL-3D skins from the membranes before transplantation and the handling separated LbL-3D skins for transplantation. To address these problems, in this study, we examined the use of biodegradable porous polymer membranes that enabled the transplantation of LbL-3D skins together with the membranes, which could be decomposed after transplantation. Thin films made from poly (lactic-co-glycolic acid) (PLGA) were irradiated with femtosecond laser pulses to create micro through-holes, producing porous membranes. We designed and fabricated culture inserts with the PLGA membranes and cultivated LbL-3D skins with 2 × 106 neonatal normal human dermal fibroblasts and 1 × 104 human umbilical vein endothelial cells in the dermis of 20 cell layers and 1 × 105 neonatal human epidermal keratinocytes in the epidermis. Histological analyses revealed that the skins cultured on the PLGA membranes had thickness of about 400 μm and that there were no defects in the quality of the skins cultured on the PLGA membranes when compared with those cultured on the conventional (nonbiodegradable) commercial membranes. The cultured LbL-3D skins were then transplanted together with the PLGA membranes onto full-thickness excisional wounds in mice. At 7 days posttransplantation onto a mouse, the tissues above and below the membrane were connected through the holes with collagen-positive fibers that appeared to migrate from both the host and donor sides, and favorable reepithelization was observed throughout the transplanted skin region. However, insufficient engraftment was observed in some cases. Thus, further optimization of the membrane conditions would be needed to improve the transplantation outcome.

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Direct patterning of conductive structures on hydrogels by laser-based graphitization for supercapacitor fabrication

Rikuto Miyakoshi, Shuichiro Hayashi, Mitsuhiro Terakawa

Advanced Electronic Materials （Advanced Electronic Materials）  9 （ 5 ） 2201277 2023年03月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

　概要を見る

Hydrogels have emerged as promising supporting materials for wearable or implantable electronic devices, owing to their high biocompatibility. Among the many techniques for patterning conductive structures on supporting materials, laser-based graphitization allows the simultaneous synthesis and patterning of conductive structures. Here, it has been demonstrated for the first time, the direct patterning of conductive structures on hydrogels by laser-based graphitization, and the application of this method to the fabrication of hydrogel-based supercapacitors. Conductive graphitic carbon is formed on the hydrogel along the trajectory of laser scanning. One-step fabrication of supercapacitors is achieved by laser irradiation of hydrogels containing both lignin and NaCl electrolyte. Notably, the areal capacitance of the fabricated supercapacitor is retained after drying and swelling, indicating its reusability. The method realizes rapid fabrication of hydrogel-based supercapacitors that can be stored in a dry state, providing a facile method for storing and delivering energy-storage devices.

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Formation of gold nanoparticles inside a hydrogel by multiphoton photoreduction for plasmonic sensing

Keiki Muranaka, Takuro Niidome, Maria Leilani Torres-Mapa, Alexander Heisterkamp, Mitsuhiro Terakawa

Plasmonics （Plasmonics）  18 （ 2 ） 751 - 760 2023年02月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り,  ISSN  15571955

　概要を見る

Plasmonic sensing using metal nanoparticles has received considerable attention because of its high sensitivity for detection. In this study, gold nanoparticles (AuNPs) were formed near the focal point of femtosecond laser pulses inside a hydrogel containing gold chloride and glutamine for plasmonic sensing. The presence of glutamine suppressed the formation of AuNPs in the region outside of the laser focal point. The proposed method for the formation of AuNPs enables spatially selective fabrication of structures with optical properties attributed to localized surface plasmon resonance. Typical biomolecules present in sweat were detected using hydrogels with the fabricated structures. Among the biomolecules, the peaks of the absorbance spectra of the AuNPs inside hydrogels exhibited a blue shift only for urea. This result indicates that urea can be detected using hydrogels with fabricated structures. The method presented in this study facilitates spatially selective fabrication of biosensing structures inside the bulk of hydrogels.

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Laser-induced graphitization of lignin/PLLA composite sheets for biodegradable triboelectric nanogenerators

R. Funayama, S. Hayashi, M. Terakawa

ACS Sustainable Chemistry & Engineering （ACS Sustainable Chemistry and Engineering）  11 （ 7 ） 3114 - 3122 2023年02月

共著, 最終著者, 責任著者, 査読有り

　概要を見る

With the rapid development of the Internet of Things (IoT), numerous electronic devices are expected to be installed in the natural environment. Triboelectric nanogenerators (TENGs) can be reliable devices providing on-site, clean, and sustainable power generation in nature. The fabrication of metal-free, biodegradable TENGs will reduce the environmental burden and disposal cost after usage. In this study, we demonstrate the direct fabrication of conductive graphitic carbon on a biodegradable polymer composite by laser-induced graphitization and apply the structures for metal-free biodegradable TENGs. Laser-induced graphitization of poly(lactic acid) (PLA) composite sheets was achieved for the first time by mixing alkaline lignin powder as a filler. The fabricated TENGs could generate electricity, and the power density reached ∼1.98 mW/m2 at a load resistance of 200 MΩ when the fabricated TENG was driven at a contact frequency of ∼1 Hz and a contact pressure of 1 N. Power generation by contact with water and plants was also demonstrated, showing its applicability for power generation in natural environments. The proposed method in this study offers the facile fabrication of biodegradable devices and the development of sustainable power generation devices.

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Direct writing of fluorescent semiconducting nanoparticles on polydimethylsiloxane by ultrashort-pulsed laser processing: Implications for electronic and photonic device fabrication

Shuichiro Hayashi, Mitsuhiro Terakawa

ACS Applied Nano Materials （ACS Applied Nano Materials）  6 （ 3 ） 2125 - 2132 2023年01月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

　概要を見る

Laser direct-write (LDW) methods offer the rapid, on-demand, and high-resolution patterning of a variety of nanocrystals (NCs). Out of the many LDW methods, the laser-induced modification method is an attractive method as NCs can be directly patterned on polymers without supplementary preparation steps. Previously, it has been indicated that the laser irradiation of polydimethylsiloxane results in composite structures composed of graphitic carbon crystals (GCs) and silicon carbide NCs (SiC-NCs). However, material properties distinctive of SiC-NCs have not been reported for the resulting structures owing to the low formation content relative to those of GCs. In this study by utilizing a high-repetition femtosecond laser, we demonstrate the controlled formation of GCs and SiC-NCs to achieve a composite structure exhibiting a measurable semiconducting behavior for the first time. Moreover, photoluminescence emissions distinctive of fluorescent molecular-sized SiC-NCs were observed from the resulting structures. The presented results will trigger a wave of ideas utilizing ultrashort-pulsed lasers for the laser-induced modification of polymers toward the fabrication of a wide range of electronic and photonic devices, such as memory storage devices, photovoltaics, and optical sensors.

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Fabrication of biodegradable triboelectric nanogenerator by laser-induced graphitization of lignin/PLLA composite sheets

Funayama R., Hayashi S., Terakawa M.

Proceedings of SPIE - The International Society for Optical Engineering （Proceedings of SPIE - The International Society for Optical Engineering）  12408 2023年

ISSN  0277786X

　概要を見る

We demonstrate the direct fabrication of graphitic carbon on a biodegradable polymer composite by laser-induced graphitization and applied the structures for the electrode of metal-free biodegradable triboelectric nanogenerators (TENGs). The laser-induced graphitization of fully biodegradable composite sheets composed of alkaline lignin powder and poly(L-lactic acid) (PLLA) was realized. The fabricated TENGs generated electricity by contact with synthetic polymers and natural materials such as water and plant leaves, indicating their applicability for on-site power generation in the natural environment. The proposed method provides the facile fabrication of biodegradable devices and the development of sustainable power generation.

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Direct writing of conductive and semiconductive structures via the femtosecond laser-induced carbonization of a silicone elastomer

Hayashi S., Terakawa M.

Proceedings of SPIE - The International Society for Optical Engineering （Proceedings of SPIE - The International Society for Optical Engineering）  12411 2023年

ISSN  0277786X

　概要を見る

In this study, we patterned structures composed of graphitic and silicon carbide nanocrystals by the laser-induced carbonization of polydimethylsiloxane. The average size of the observed silicon carbide nanocrystals varied depending on the energy per laser pulse, or pulse energy, used for patterning, where larger crystals were observed for structures patterned with higher pulse energies. Moreover, the electrical property of the patterned structure shifted from conductive to semiconductive, as the pulse energy for patterning increased. To the best of our knowledge, this is the first demonstration of the patterning of structures exhibiting measurable semiconducting properties by the laser-induced carbonization of polymers.

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Simultaneous laser-based graphitization and microstructuring of bamboo for supercapacitors derived from renewable resources

Rikuto Miyakoshi, Shuichiro Hayashi, Mitsuhiro Terakawa

RSC Advances （Royal Society of Chemistry）  12 （ 46 ） 29647 - 29652 2022年10月

研究論文（学術雑誌）, 共著, 最終著者, 責任著者, 査読有り

　概要を見る

Utilizing renewable resources for electrodes realizes the sustainable fabrication of a supercapacitor with high environmental friendliness. Laser-based graphitization of biomass has been emerging as a promising technique for patterning the electrodes of a supercapacitor with renewable resources. Herein, simultaneous patterning and microstructuring of laser-induced graphene (LIG) on a renewable biomass resource, bamboo, by a laser-based graphitization technique was demonstrated. By irradiating femtosecond laser pulses onto bamboo, graphitization and microstructuring were both induced simultaneously, forming conductive structures with high surface area. Furthermore, LIG patterned on bamboo by our method was used as the electrodes of supercapacitors. NaCl was selected as the electrolyte for the fabrication of supercapacitors. The proposed method realizes the fabrication of environmentally-friendly supercapacitors comprised of all renewable biomass resources.

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Light-driven flow control in the hydrogel microchannel by utilizing a metal microstructure fabricated by multiphoton photoreduction

Yo Nagano, Hiroaki Onoe, and Mitsuhiro Terakawa

Optical Materials Express 12 （ 8 ） 3303 - 3312 2022年08月

共著, 最終著者, 責任著者, 査読有り

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Laser-based molecular delivery and its applications in plant science

Heinemann D., Zabic M., Terakawa M., Boch J.

Plant Methods （Plant Methods）  18 （ 1 ）  2022年06月

　概要を見る

Lasers enable modification of living and non-living matter with submicron precision in a contact-free manner which has raised the interest of researchers for decades. Accordingly, laser technologies have drawn interest across disciplines. They have been established as a valuable tool to permeabilize cellular membranes for molecular delivery in a process termed photoinjection. Laser-based molecular delivery was first reported in 1984, when normal kidney cells were successfully transfected with a frequency-multiplied Nd:YAG laser. Due to the rapid development of optical technologies, far more sophisticated laser platforms have become available. In particular, near infrared femtosecond (NIR fs) laser sources enable an increasing progress of laser-based molecular delivery procedures and opened up multiple variations and applications of this technique. This review is intended to provide a plant science audience with the physical principles as well as the application potentials of laser-based molecular delivery. The historical origins and technical development of laser-based molecular delivery are summarized and the principle physical processes involved in these approaches and their implications for practical use are introduced. Successful cases of laser-based molecular delivery in plant science will be reviewed in detail, and the specific hurdles that plant materials pose will be discussed. Finally, we will give an outlook on current limitations and possible future applications of laser-based molecular delivery in the field of plant science.

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Nanosecond laser-induced oriented periodic structures on AlN ceramic

Nedyalkov N., Dikovska A., Nikov R., Nikov R., Dliova T., Atanasova G., Aleksandrov L., Karashanova D., Strijkova V., Terakawa M.

Applied Surface Science 585 （ 30 ） 152712 2022年05月

研究論文（学術雑誌）, 共著, 査読有り

　概要を見る

This work presents results on nanosecond laser-induced surface structuring of AlN ceramic. The process under investigation is performed using the fundamental wavelength of Nd:YAG laser system. It is shown that the change of the ambient air pressure from atmospheric one to 10-4 Torr, leads to modification of the surface morphology – from ripples structure with a periodicity of about the incident irradiation wavelength, to an oriented periodic microstructure with a characteristic period in the range 10–15 µm. In all cases when the periodic structures are formed, a clear orientation perpendicular to the incident irradiation polarization is observed. The properties of the oriented periodic microstructures (OPMSs) formed at the lowest pressure condition are studied in more details, as the influence of the processing conditions on their characteristics is presented. It is found that the formation of OPMS requires a minimal laser pulse number and application of laser fluence above certain threshold. The surface of the fabricated structures is conductive, as the performed analyses indicate that the effect is related to presence aluminium in the processed areas. Possible mechanisms of formation of these structures are discussed. Ablation experiments using irradiation at 532 and 266 nm are also reported and discussed. The presented results may have significant impact when laser processing of AlN ceramics is considered, and for the design of structures with potential applications in microelectronics, tribology, and aluminium-based UV plasmonics.

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