Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

Background: Plasma is a collection of active particles generated by dissociating molecules and ionizing atoms through applying high energy to a gas, such as high-sound heating or electrical shock. Recently, many reports have been published on the effectiveness of nonthermal atmospheric pressure gas discharge plasma (NTAPP) on living organisms. Furthermore, we have reported on the promotion of bone and tendon repair by NTAPP irradiation. We hypothesized that irradiation of NTAPP would promote the repair of the tendon-bone junction in a rotator cuff repair. This study investigated the effect of NTAPP irradiation on the healing process of the tendon-bone junction.

Methods: Among 36 Japanese white rabbits, the infraspinatus tendon was detached from the humeral insertion site. A 3.2 mm bone tunnel was then created at the original insertion site of the infraspinatus muscle. The left shoulder was irradiated with NTAPP at a distance of 1 cm from the bone tunnel for 5 minutes (plasma-treated group), while the right shoulder was not irradiated (control group). The rabbits were sacrificed at 2, 4, and 8 weeks postoperatively, and 6 of each were used for histological evaluation. Mechanical tests were also performed on 6 specimens each at 4 and 8 weeks.

Results: Histological evaluation showed that at 4 weeks, the histological tendon to bone maturing score was 6.8 1.3 in the plasmatreated group and 4.8 1.6 in the control group (P <.01); at 8 weeks it was 9.0 1.0 in the plasma-treated group and 5.2 1.1 in the control group (P <.01). Fibrocartilage formation and new bone formation were observed at both 4 and 8 weeks. In the mechanical test, the plasma-treated group had 75.0 18.9 N in ultimate load to failure at 8 weeks. In the control group, it was 51.1 7.9 N. (P ¼.04).

Conclusion: The repair of the rotator cuff at the tendon-bone junction was significantly improved at 4 and 8 weeks by irradiation with NTAPP.

DOI： 10.1016/j.jse.2024.07.039

Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

DOI： https://doi.org/10.1016/j.sab.2024.106972

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

This paper investigates how the duty cycle influences the production of hydrogen peroxide (H2O2) in an alternating current (AC)-driven plasma jet. H2O2 is a major reactive oxygen species produced by plasma jets in medicine and is a biological important molecule because it can intervene in cellular signaling processes important for disease treatment. In this study, duty cycles were varied from 9% to 72%, which correlated with an increase in the plasma's dissipated power and UV photon energy density, and consequently an increase in the production of high energy plasma components important for producing H2O2 through electron collision and UV photolysis reactions. Cell media treated with the plasma jet at higher duty cycles correlated with a decrease in the viability of HaCaT keratinocyte skin cells. The AC-driven plasma jets were shown to be operated optimally at a biocompatible gas temperature of below 40 °C whilst still maintaining efficiency in H2O2 production. Overall, the data presented in this study might find use for the future of optimization of the electrical properties of AC-driven plasma jets in plasma medicine.

DOI： 10.1088/1361-6463/ad5567

DOI： 10.1088/1361-6463/ad5567

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

Non-thermal atmospheric-pressure plasma (NTAPP) has been widely studied for clinical applications, e.g., disinfection, wound healing, cancer therapy, hemostasis, and bone regeneration. It is being revealed that the physical and chemical actions of plasma have enabled these clinical applications. Based on our previous report regarding plasma-stimulated bone regeneration, this study focused on Achilles tendon repair by NTAPP. This is the first study to reveal that exposure to NTAPP can accelerate Achilles tendon repair using a well-established Achilles tendon injury rat model. Histological evaluation using the Stoll’s and histological scores showed a significant improvement at 2 and 4 weeks, with type I collagen content being substantial at the early time point of 2 weeks post-surgery. Notably, the replacement of type III collagen with type I collagen occurred more frequently in the plasma-treated groups at the early stage of repair. Tensile strength test results showed that the maximum breaking strength in the plasma-treated group at two weeks was significantly higher than that in the untreated group. Overall, our results indicate that a single event of NTAPP treatment during the surgery can contribute to an early recovery of an injured tendon.

DOI： https://doi.org/10.1371/journal.pone.0301216

DOI： https://doi.org/10.1371/journal.pone.0301216

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

Non-thermal atmospheric-pressure plasma (NTAPP) is attracting widespread interest for use in medical applications. The tissue repair capacity of NTAPP has been reported in various fields; however, little is known about its effect on fracture healing. Non-union or delayed union after a fracture is a clinical challenge. In this study, we aimed to investigate how NTAPP irradiation promotes fracture healing in a non-union fracture model and its underlying mechanism, in vitro and in vivo. For the in vivo study, we created normal and non-union fracture models in LEW/SsNSlc rats to investigate the effects of NTAPP. To create a fracture, a transverse osteotomy was performed in the middle of the femoral shaft. To induce the non-union fracture model, the periosteum surrounding the fracture site was cauterized after a normal fracture model was created. The normal fracture model showed no significant difference in bone healing between the control and NTAPP-treated groups. The non-union fracture model demonstrated that the NTAPP-treated group showed consistent improvement in fracture healing. Histological and biomechanical assessments confirmed the fracture healing. The in vitro study using pre-osteoblastic MC3T3-E1 cells demonstrated that NTAPP irradiation under specific conditions did not reduce cell proliferation but did enhance osteoblastic differentiation. Overall, these results suggest that NTAPP is a novel approach to the treatment of bone fractures.

DOI： https://doi.org/10.1371/journal.pone.0298086

DOI： https://doi.org/10.1371/journal.pone.0298086

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

This paper presents and explains the principle behind anelectrochemical method to enhance the antimicrobial action of plasma-activated hydrogel therapy (PAHT) in the context of wound decontamination. The process involves grounding and hydratingpoly(vinyl alcohol) (PVA) hydrogel films during treatment with a helium (He) plasma jet. This electrochemically enhances production of hydrogen peroxide (H2O2), which is amajor antibacterial agent produced in the PVA hydrogel. Production of H2O2 is shownto be electrically enhanced through electron dissociation reactions, and through reactions associated with excited state species, metastables and ultra-violet (UV) photolysis. H2O2 production is chemically enhanced through the He flow of the plasma jet dehydrating the PVA hydrogel, which fuels the electrochemical dependent reactions associated with H2O2 production. The electrochemical process produces an unprecedented 3.4 mM of H2O2 in the PVA hydrogel. Production of other molecules such as reactive nitrogen species (RNS) are also enhanced by the same method. The electrochemically enhanced PAHT is highly effective ateradicating common wound pathogens Escherichia coli and Pseudomonas aeruginosa and mildly effective against Staphylococcus aureus. Overall, this study shows that the new PAHT dressing offers a promising alternative to antibiotics and silver-based dressings for controlling infection and stimulating healing in wounds.

DOI： https://doi.org/10.1002/adfm.202314345

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

Total reflection X-ray fluorescence (TXRF) analysis is used to determine the concentrations of trace elements in liquid samples. Solutions are generally added dropwise onto a flat substrate and dried. When liquids with low elemental levels are analyzed, a hydrophobic substrate is employed to prepare a small dome-shaped residue. In the analyses of high-level solutions (high elemental concentration solution), the quantitative accuracy and measurement sensitivity deteriorate because X-ray fluorescence (XRF) is absorbed inside the thick residue. By preparing a thin residue, it is possible to reduce this absorption effect. In our previous study, atmospheric pressure plasma jet (APPJ) treatment was used to prepare a superhydrophilic substrate. The time that super-hydrophilicity is maintained is not yet known and determining this value is important for performing TXRF analysis. Therefore, we measured the contact angles of the droplets and performed X-ray photoelectron spectroscopy of the substrate surfaces to determine the relationships between the experimental values and the elapsed time. The optimal APPJ-treated area has not yet been determined and is one of the most important factors for high-sensitivity analysis. In this study, we controlled the APPJ-treated area by preparing four polytetrafluoroethylene (PTFE) masks with different hole diameters and obtained recoveries, relative standard deviations, and minimum detection limits (MDLs) to identify the optimal APPJ-treated area. A PTFE mask with a diameter of 4 mm generated the best values, particularly for low-Z elements. By controlling the diameter of the dried residue to 4 mm, the MDL value in aluminum was improved by a factor of 1.7.

DOI： 10.1039/D3JA00168G

Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

Low-temperature atmospheric-pressure plasma jets are generally considered a safe medical technology with no significant long-term side effects in clinical studies reported to date. However, there are studies emerging that show plasma jets can cause significant side effects in the form of skin burns under certain conditions. Therefore, with a view of developing safer plasma treatment approaches, in this study we have set out to provide new insights into the cause of these skin burns and how to tailor plasma treatments to mitigate these effects. We discovered that joule heating by the plasma bullet currents is responsible for creating skin burns during helium plasma jet treatment of live mice. These burns can be mitigated by treating the mice at a further distance so that the visible plasma plume does not contact the skin. Under these treatment conditions we also show that the plasma jet treatment still retains its medically beneficial property of producing reactive oxygen species in vivo. Therefore, treatment distance is an important parameter for consideration when assessing the safety of medical plasma treatments.

DOI： https://doi.org/10.3390/plasma6010009

DOI： https://doi.org/10.3390/plasma6010009

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

Applicability of precise Raman spectral analysis of a-C:H films deposited using a plasma chemical vapor deposition (CVD) method has been discussed based on the sensitivity to initial conditions in peak separation. The spectral analysis offers to deconvolute the spectra into five peaks, while the as-deposited films prepared by plasma CVD is difficult to the five-peak separation. We found the peak position and the peak height ratio of the D-band to the G+-band can be employed to discuss the structure of the as-deposited films. We examined the structural difference between the films deposited at the powered electrode and that at grounded electrode. We found graphene nanoribbon-like structures may be formed in the films deposited on the grounded substrate. This result suggests that the substrate position is an important factor to form the graphene nanoribbon-like structure.

DOI： https://doi.org/10.1557/s43580-022-00310-6

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

Current methods used to treat non-muscle invasive bladder cancer are inadequate due to a high recurrence rate after surgery and the occurrence of adverse events such as interstitial pneumonia following intravesical instillation therapy. Low-temperature plasma is a new form of physical therapy that provides a rich source of reactive oxygen species (ROS). Oxidative solutions, created by pre-treatment of aqueous media with plasma before application to target cells, lead to the destruction of cancer cells through oxidative stress pathways. This study focuses on the effects of plasma-activated media (PAM) in bladder cancer cells. PAM treatment increases oxidative stress that leads to cell cycle arrest and concomitantly depolarises the mitochondrial membrane leading to increased mitochondrial ROS production. Cell cycle arrest and increased mitochondrial ROS production led to an increase in caspase 3/cytochrome c activity, which might explain the induction of apoptosis in bladder cancer cells in vitro and in a bladder cancer tumour in vivo. These observations highlight the potential of plasma activated solutions as a new adjuvant therapy in the clinical treatment of bladder cancer.

DOI： https://doi.org/10.3390/plasma5020018

DOI： https://doi.org/10.3390/plasma5020018

Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

Medical treatment using non-thermal atmospheric pressure plasma (NTAPP) is rapidly gaining recognition. NTAPP is thought to be a new therapeutic method because it could generate highly reactive species in an ambient atmosphere which could be exposed to biological targets (e.g., cells and tissues). If plasma-generated reactive species could stimulate bone regeneration, NTAPP can provide a new treatment opportunity in regenerative medicine. Here, we investigated the impact of NTAPP on bone regeneration using a large bone defect in New Zealand White rabbits and a simple atmospheric pressure plasma (helium microplasma jet). We observed the recovery progress of the large bone defects by X-ray imaging over eight weeks after surgery. The X-ray results showed a clear difference in the occupancy of the new bone of the large bone defect among groups with different plasma treatment times, whereas the new bone occupancy was not substantial in the untreated control group. According to the results of micro-computed tomography analysis at eight weeks, the most successful bone regeneration was achieved using a plasma treatment time of 10 min, wherein the new bone volume was 1.51 times larger than that in the plasma untreated control group. Using H&E and Masson trichrome stains, nucleated cells were uniformly observed, and no inclusion was confirmed, respectively, in the groups of plasma treatment. We concluded the critical large bone defect were filled with new bone. Overall, these results suggest that NTAPP is promising for fracture treatment.

DOI： 10.1371/journal.pone.0255861

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

DOI： 10.1039/D1JA00164G

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

To identify the key neutral species from atmospheric-pressure plasma for promoting the proliferation of fibroblast cells, an atmospheric-pressure radical generator was employed. A cell viability assay showed that the proliferation of fibroblasts was significantly promoted through radical treatment, resulting in the highest promotion ratio of 24%. The densities of the neutral radicals supplied by the radical generator were measured via mass spectrometry at atmospheric pressure. To determine an effective factor for the promotion, the dose dependencies of these radicals on the promotion ratio were investigated. The promotion ratio exhibited a strong correlation only with the NO• dose. These results confirmed that NO• is a direct trigger of plasma-enhanced cell proliferation.

DOI： https://doi.org/10.1002/ppap.202000225

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

As the application of nanotechnology increases continuously, the need for controlled size nanoparticles also increases. Therefore, in this work, we discussed the growth mechanism of carbon nanoparticles generated in Ar+CH4 multi-hollow discharge plasmas. Using the plasmas, we succeeded in continuous generation of hydrogenated amorphous carbon nanoparticles with controlled size (25–220 nm) by the gas flow. Among the nanoparticle growth processes in plasmas, we confirmed the deposition of carbon-related radicals was the dominant process for the method. The size of nanoparticles was proportional to the gas residence time in holes of the discharge electrode. The radical deposition developed the nucleated nanoparticles during their transport in discharges, and the time of flight in discharges controlled the size of nanoparticles.

DOI： https://doi.org/10.3390/pr9010002

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

A brief history of the development of our plasma technology for the disinfection of agricultural harvests is presented in this review. We focused on the influence of reactive oxygen species (ROS), e.g. ground-state oxygen atoms [O(3Pj)], excited-state oxygen molecules [O2(1Δg)], and ozone (O3), generated from atmospheric-pressure plasmas on the inactivation of fungal spores under dry conditions. For elucidating the inactivation mechanisms, it is essential to reveal the key ROS. Using some powerful tools, we revealed that the dose of O(3Pj) strongly correlates with the inactivation of fungal spores when compared to those of another ROS, such as O2(1Δg) and O3. The balance of antioxidants in the spores is possibly modulated by O(3Pj), leading to oxidation of organelles in spores. Herein, we introduce and discuss how O(3Pj) contributes to the inactivation of fungal spores associated with in situ diagnostics of plasma generated ROS and in situ intracellular observations of a few fungal spore species.

DOI： https://doi.org/10.35848/1347-4065/abcbd1

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

To investigate the potential role of the hydroxyl radical (•OH) in cold atmospheric plasma (CAP) jet treatment, two fluorescence-based methodologies are utilised to measure DNA strand breaks. The first comprises a model system of a double-stranded DNA oligomer, where the respective strand ends are tagged with fluorophore and quencher molecules; and the second, a cell culture system reporting DNA strand breaks using the γ-H2AX assay. During the various CAP jet treatments, optical emission spectroscopy is used to detect the •OH in the gas phase and electron spin resonance is used to detect the •OH in solution. The CAP jet production of the •OH is shown to correlate to CAP jet induced DNA damage both with the DNA model and in biological cells. Results indicate that the CAP jet induces a higher degree of DNA damage when the CAP plume is in contact with the target solution. The potential of a ‘plasma screen’ based upon a hydrogel film, as a method to remove the DNA-damaging •OH species from reaching skin cells, is shown to significantly reduce DNA damage whilst facilitating the delivery of hydrogen peroxide. These findings could aid in the development of CAP jet-based applications where DNA damage is the objective (e.g. in cancer treatment) and others where it is to be avoided, e.g. in open-wound treatment and dermatology.

DOI： https://doi.org/10.1088/1361-6463/abb8ab

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

To understand the mechanisms for selective productions of NO2− and NO3− as reactive nitrogen species (RNS) in plasma activated water, we studied the oxidation reactions of NO as the primary species supposing O, O2, O3, OH, and H2O2 as possible oxidants. A coaxial-type dielectric barrier discharge reactor was employed in cascade connection to a reservoir and/or a water bubbler. First, the densities of NO and NO2 in the gas phase were measured with gas sensors in two gas systems: N2 admixed with water vapor and N2 admixed with O2, for comparison. It was found that while the density of NO in the latter case was one third of that in the former case owing to the difference in the first-step oxidation to NO2 or HNO2, the total yields of RNS in both cases were comparable. To investigate the oxidation pathways, admixing NO and NO2 in the downflow of the reactor was attempted to estimate their reactions with those oxidants and accomodation behaviours on the water surface. Injecting the effluent gas from discharge plasma into solutions of O2, O3, and H2O2, and injecting O3 into PAW, vice versa, were attempted to inspect the reactions in the liquid phase or at the gas–water interface. Based on the obtained results, it was found that, in the N2-H2O gas system, OH functions as the oxidant of NO to HNO2, exclusively yielding NO2− in solution with no effective second-step oxidation to NO3 or HNO3. On the other hand, in the N2-O2 gas system, O3 functions as the major oxidant in the successive oxidation from NO to NO2 to NO3, producing NO3− predominant PAW; however, the second-step oxidation in the gas phase is competing with the oxidation reactions in the liquid phase.

DOI： 10.1088/1361-6463/ab91eb

Other URL： https://iopscience.iop.org/article/10.1088/1361-6463/ab91eb/pdf

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

The inactivation mechanism of mould spores using plasma-generated neutral reactive oxygen species (ROS) was investigated in this paper. Typical cell viability using a counting of colony-forming unit assay indicated a major state of the spore cells. Both intracellular and extracellular damages have been investigated by a couple of well-established cell visualization techniques: confocal fluorescence emission microscopy, scanning electron microscopy, and transmission electron microscopy. It is revealed in this paper that the combination of the spore cell viability with those visualization results strongly suggested an early stage of the cell inactivation when ROS can induce intracellular lipid peroxidation through both nanometer-thick lipid cell membrane and less-damaged several hundred nanometer-thick cell wall.

DOI： https://doi.org/10.1002/ppap.202000001

Publishing type：Research paper (scientific journal)   Kind of work：Single Work  

Microplasma discharges in deionized water and artificial seawater were investigated using pin-to-plate electrodes with a gap of a several tens of microns. By using a pulse voltage source, microdischarge was operated in deionized water and diluted artificial seawater and compared with discharge in ambient air. To operate the microdischarge in undiluted artificial seawater, a pulse current source (impulse generator) was used to supply the breakdown voltage with sufficient current. Even in seawater with an electrical conductivity of 45 mS/cm, microplasma discharges were reproducibly ignited at applied voltages below 1 kV. In the optical emission spectrum for the microplasma in artificial seawater, the main components of Na, Mg, Ca, K, S, H, and O were observed as distinguishable isolated lines, including lines for Pd, Ag and Fe from the electrodes.

DOI： 10.34343/ijpest.2019.13.01.001

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

The mechanisms of plasma in medicine are broadly attributed to plasma-derived reactive oxygen and nitrogen species (RONS). In order to exert any intracellular effects, these plasma-derived RONS must first traverse a major barrier in the cell membrane. The cell membrane lipid composition, and thereby the magnitude of this barrier, is highly variable between cells depending on type and state (e.g. it is widely accepted that healthy and cancerous cells have different membrane lipid compositions). In this study, we investigate how plasma-derived RONS interactions with lipid membrane components can potentially be exploited in the future for treatment of diseases. We couple phospholipid vesicle experiments, used as simple cell models, with molecular dynamics (MD) simulations of the lipid membrane to provide new insights into how the interplay between phospholipids and cholesterol may influence the response of healthy and diseased cell membranes to plasma-derived RONS. We focus on the (i) lipid tail saturation degree, (ii) lipid head group type, and (iii) membrane cholesterol fraction. Using encapsulated molecular probes, we study the influence of the above membrane components on the ingress of RONS into the vesicles, and subsequent DNA damage. Our results indicate that all of the above membrane components can enhance or suppress RONS uptake, depending on their relative concentration within the membrane. Further, we show that higher RONS uptake into the vesicles does not always correlate with increased DNA damage, which is attributed to ROS reactivity and lifetime. The MD simulations indicate the multifactorial chemical and physical processes at play, including (i) lipid oxidation, (ii) lipid packing, and (iii) lipid rafts formation. The methods and findings presented here provide a platform of knowledge that could be leveraged in the development of therapies relying on the action of plasma, in which the cell membrane and oxidative stress response in cells is targeted.

DOI： https://doi.org/10.1039/C9CP03520F

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

DOI： 10.1109/ACCESS.2019.2928419

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

We treat deionized water using an atmospheric-pressure radical source to investigate the role of neutral radicals in the bactericidal efficacy of radical-activated water (RAW). The bactericidal efficacy of RAW is investigated using a colony-forming unit assay with Escherichia coli. Both the bactericidal efficacy and reactive oxygen and nitrogen species (RONS) concentration in stored RAW are investigated over a period of a month. E. coli was completely sterilized even in RAW stored for 7 days, indicating the strong bactericidal effect. However, deterioration of the bactericidal efficacy of RAW stored for 14 days is confirmed, which does not have a clear correlation with the time evolution of the RONS concentration. This result becomes a strong evidence that RAW has long-term bactericidal efficacy.

DOI： https://doi.org/10.1002/ppap.201900055

Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

This study assesses a potential use of the recently developed nonthermal atmospheric pressure plasma technology in hydroponic plant cultivation. Plasma‐activated liquid solutions were investigated, namely, L‐Phenylalanine (L‐Phe), which had a benzene ring structure. We found that the benzene ring structure in solution contributed to antimicrobial property. Further, colony forming unit (CFU) assay indicated that 99% of Escherichia coli (E. coli) were eliminated after 24‐h incubation and radish sprout growth increased by about 40% after 2 days of cultivation.

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

DOI： https://doi.org/10.3390/plasma2020010

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

Atmospheric-pressure plasma jets can be used to modify surfaces in a spatially-defined manner. Operating these jets in air is an efficient surface modification tool, however the resulting surface chemistries are limited by the plasma gases. In this study we demonstrate that plasma polymerization with heptylamine on polystyrene (PS) surfaces, using an atmospheric pressure plasma jet (APPJ), can enable mammalian cell attachment and growth. Importantly, the addition of the heptylamine monomer, in a helium carrier-gas, altered the spatially-defined treatment area in comparison to treatment with a helium plasma alone.

DOI： https://doi.org/10.1002/ppap.201800185

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

We employed UV–vis spectroscopy to monitor real-time changes in the oxygen tension and concentration of reactive oxygen and nitrogen species (RONS) in deionized (DI) water during treatments with helium (He) and argon (Ar) gas plasma jets. He and Ar gas jets are both shown to deoxygenate DI water with He being more efficient than Ar, whilst the plasma jets deliver and regulate the concentrations of hydrogen peroxide (H2O2), nitrite (NO2−) and nitrate (NO3−) in DI water. The H2O2 and NO3− production efficiency varied between He and Ar plasma jets, but was similar for NO2−. Whilst DI water fully equilibrated with ambient air prior to treatment (de-oxygenated by both plasma jets) when DI water was first de-oxygenated by an inert gas jet treatment, both plasma jets were found to be capable of oxygenating DI water. These insights were then used to show how different combinations of plasma jet and inert gas jet treatments can be used to modulate O2 tension and RONS chemistry. Finally, potential further improvements to improve control in the use of plasma jets in regulating O2 and RONS are discussed.

DOI： https://doi.org/10.7567/1347-4065/aaea6b

Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

© 2018 IEEE. Chemical components induced in water by irradiation to atmospheric pressure He plasma jet in ambient air has been investigated using UV absorption spectroscopy. There appears a characteristic absorbance peak in UV range for deionized water after irradiation to plasma jet. The UV absorbance peak can be well deconvoluted to 4 characteristic components assigned as O2, NO2-, NO3-, and H2O2, and from the analysis, the absolute concentration can be determined.

DOI： 10.1109/IEECON.2018.8712335

DOI： 10.1109/IEECON.2018.8712335

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

DOI： 10.1063/1.4999256

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

DOI： 10.1186/s13068-017-0979-6

Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

Plasma-activated water (PAW) is receiving much attention in biomedical applications because of its reported potent bactericidal properties. Reactive oxygen and nitrogen species (RONS) that are generated in water upon plasma exposure are thought to be the key components in PAW that destroy bacterial and cancer cells. In addition to developing applications for PAW, it is also necessary to better understand the RONS chemistry in PAW in order to tailor PAW to achieve a specific biological response. With this in mind, we previously developed a UV–vis spectroscopy method using an automated curve fitting routine to quantify the changes in H2O2, NO2−, NO3− (the major long-lived RONS in PAW), and O2 concentrations. A major advantage of UV–vis is that it can take multiple measurements during plasma activation. We used the UV–vis procedure to accurately quantify the changes in the concentrations of these RONS and O2 in PAW. However, we have not yet provided an in-depth commentary of how we perform the curve fitting procedure or its implications. Therefore, in this study, we provide greater detail of how we use the curve fitting routine to derive the RONS and O2 concentrations in PAW. PAW was generated by treatment with a helium plasma jet. In addition, we employ UV–vis to study how the plasma jet exposure time and treatment distance affect the RONS chemistry and amount of O2 dissolved in PAW. We show that the plasma jet exposure time principally affects the total RONS concentration, but not the relative ratios of RONS, whereas the treatment distance affects both the total RONS concentration and the relative RONS concentrations.

DOI： https://doi.org/10.7567/JJAP.57.0102B9

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

We review new trends of agricultural applications of atmospheric-pressure plasmas for decontaminating agricultural products and enhancing seed germination and growth of plants and beneficial microorganisms. We classify the decontamination techniques into three kinds of treatments, which are gas-phase, in-liquid, and plasma-activated liquid treatments, and introduce recent studies mainly after 2010, discussing the inactivation mechanism of microorganisms in each treatment. Likewise, we categorize the enhancement techniques into the same three kinds of treatments, and introduce the growth enhancements in detail, discussing the mechanisms and future prospects.

DOI： https://doi.org/10.1002/ppap.201700073

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

Electrically generated cold atmospheric plasma is being intensively researched for novel applications in biology and medicine. Significant attention is being given to reactive oxygen and nitrogen species (RONS), initially generated upon plasma–air interactions, and subsequently delivered to biological systems. Effects of plasma exposure are observed to millimeter depths within tissue. However, the exact nature of the initial plasma–tissue interactions remains unknown, including RONS speciation and delivery depth, or how plasma-derived RONS intervene in biological processes. Herein, we focus on current research using tissue and cell models to learn more about the plasma delivery of RONS into biological environments. We argue that this research is vital in underpinning the knowledge required to realize the full potential of plasma in biology and medicine.

DOI： https://doi.org/10.1016/j.tibtech.2017.07.012

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：Domestic journal  

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

DOI： 10.1088/1361-6463/aa7501

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

DOI： 10.1039/c7cc02927f

Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

DOI： 10.1088/1361-6463/aa61d7

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

We have developed a plasma cell treatment device called Plasma-on-Chip that enables the real-time monitoring of a single cell culture during plasma treatment. The device consists of three parts: 1) microwells for cell culture, 2) a microplasma device for generating reactive oxygen and nitrogen species (RONS) for use in cell treatment, and 3) through-holes (microchannels) that connect each microwell with the microplasma region for RONS delivery. Here, we analysed the delivery of the RONS to the liquid culture medium stored in the microwells. We developed a simple experimental set-up using a microdevice and applied in situ ultraviolet absorption spectroscopy with high sensitivity for detecting RONS in liquid. The plasma-generated RONS were delivered into the liquid culture medium via the through-holes fabricated into the microdevice. The RONS concentrations were on the order of 10–100 μM depending on the size of the through-holes. In contrast, we found that the amount of dissolved oxygen was almost constant. To investigate the process of RONS generation, we numerically analysed the gas flow in the through-holes. We suggest that the circulating gas flow in the through-holes promotes the interaction between the plasma (ionised gas) and the liquid, resulting in enhanced RONS concentrations.

DOI： 10.1038/srep41953

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

DOI： 10.3389/fphy.2017.00001

Publishing type：Research paper (scientific journal)  

With ambient mass spectrometry, we followed the transport of neutral gas species and ionic species through a 3.2 mm thick agarose tissue model target during He non-thermal atmospheric pressure plasma (NT-APP) jet treatment. We found that the neutral gas species are unable to efficiently penetrate the agarose target. But both positively and negatively charged ionic species readily penetrate through the agarose target, following an initial time-lag period of several minutes. Interestingly, we also found that the ionic species are easily hydrated. The trends in the He NT-APP jet transport of ionic species observed in this study correlate well with the He NT-APP jet transport of reactive oxygen and nitrogen species (RONS) through agarose tissue model targets that was investigated in previous studies. Therefore, mass spectrometry might prove to be a useful tool in the future for analyzing the dosages of NT-APP-generated RONS in real biological tissues.

DOI： 10.2494/photopolymer.30.317

Publishing type：Research paper (scientific journal)  

The effect of oxidation, oxygenation, and de-oxygenation arising from He gas jet and He plasma jet treatments on the viability of skin cells cultured in vitro has been investigated. He gas jet treatment de-oxygenated cell culture medium in a process referred to as "sparging." He plasma jet treatments oxidized, as well as oxygenated or de-oxygenated cell culture medium depending on the dissolved oxygen concentration at the time of treatment. He gas and plasma jets were shown to have beneficial or deleterious effects on skin cells depending on the concentration of dissolved oxygen and other oxidative molecules at the time of treatment. Different combinations of treatments with He gas and plasma jets can be used to modulate the concentrations of dissolved oxygen and other oxidative molecules to influence cell viability. This study highlights the importance of a priori knowledge of the concentration of dissolved oxygen at the time of plasma jet treatment, given the potential for significant impact on the biological or medical outcome. Monitoring and controlling the dynamic changes in dissolved oxygen is essential in order to develop effective strategies for the use of cold atmospheric plasma jets in biology and medicine. Published by AIP Publishing.

DOI： 10.1063/1.4967880

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

The efficacy of helium (He) and argon (Ar) plasma jets are being investigated for different healthcare applications including wound and cancer therapy, sterilisation and surface disinfections. Current research points to a potential link between the generation of reactive oxygen and nitrogen species (RONS) and outcomes in a range of biological and medical applications. As new data accrue, further strengthening this link, it becomes important to understand the controlled delivery of RONS into solutions, tissue fluids and tissues. This paper investigates the use of He and Ar plasma jets to deliver three RONS (hydrogen peroxide-H2O2, nitrite-NO2- and nitrate-NO3- and molecular oxygen (O-2) directly into deionised (DI) water, or indirectly into DI water through an agarose target. The DI water is used in place of tissue fluid and the agarose target serves as a surrogate of tissue. Direct plasma jet treatments deliver more RONS and O-2 than the through-agarose treatments for equivalent treatments times. The former only deliver RONS whilst the plasma jets are ignited; the latter continues to deliver RONS into the DI water long after the plasmas are extinguished. The He plasma jet is more effective at delivering H2O2 and NO2- directly into DI water, but the Ar plasma jet is more effective at nitrating the DI water in both direct and through-agarose treatments. DI water directly treated with the plasma jets is deoxygenated, with the He plasma jet purging more O-2 than the Ar plasma jet. This effect is known as 'sparging'. In contrast, for through-agarose treatments both jets oxygenated the DI water. These results indicate that in the context of direct and indirect plasma jet treatments of real tissue fluids and tissue, the choice of process gas (He or Ar) could have a profound effect on the concentrations of RONS and O-2. Irrespective of operating gas, sparging of tissue fluid (in an open wound) for long prolonged periods during direct plasma jet treatment, could have implications for healthy tissue function; whilst through-tissue plasma jet treatment may provide a method to reperfuse oxygen-starved tissue. The assays described in this paper can be readily adopted (by others) and may support the future development of plasma sources to deliver specific (metered) doses of RONS.

DOI： 10.1088/0022-3727/49/30/304005

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

© 2016 The Japan Society of Applied Physics. Microplasma discharge in sea water for optical emission spectroscopy was investigated using a needle-to-plane electrode system. The electrodes of a Pd needle and a Pt plate were placed with a gap of 25 μm in typical artificial sea water or locally sampled natural deep sea water. A pulse current source, consisting of a MOSFET switch, a capacitor, an inductor and the resistance of the sea water between the electrodes, was used. The circuit parameters were optimized to decrease the breakdown voltage and the spark duration to suppress erosion of the electrodes. Using a microgap configuration, spark discharges were reproducibly ignited in the highly conductive sea water at low breakdown voltages. The ignition of spark discharges required not only a critical voltage sufficient for breakdown, but also a critical energy for preheating of the sea water, sufficient for bubble formation. The possibility of using optical emission spectroscopy of microplasma in water is shown for identifying elemental composition of sea water.

DOI： 10.7567/JJAP.55.07LC03

Publishing type：Research paper (scientific journal)  

Ozonated water was investigated using a conventional UV-Vis spectrophotometer. We compared the UV absorption spectra of ozone (O-3) in water generated by either O-2 or air plasma bubbling method. The results noted that the observing the entire absorption spectrum is important for understanding the composition of ozonated water. Using an in-situ with an O-2 plasma bubbling in water we monitored the time-resolved UV absorption spectrum of the ozonated water. It is well known that a typical UV absorption spectrum of ozonated water contains a broad absorption peak at 260 nm and a shoulder below 220 nm. In our time-resolved measurement, however, it initially contained a broad absorption at short wavelength range below 210 nm considerably from dissolved O-2. As increase of the ozonation time, it noted that the absorption spectrum indicated the presence of high concentration of H2O2 and O-2 as well as relatively lower concentration of O-3.

DOI： 10.2494/photopolymer.29.427

Publishing type：Research paper (scientific journal)  

DOI： 10.7567/JJAP.54.01AD04

Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.4930874

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

Using a versatile atmospheric-pressure helium plasma jet, diamond-like carbon (DLC) films were etched in ambientair. We observed that the DLC films are etched at a nominal rate of around 60 nm/min in the treated area (230 μm in diameter) during a 20-min exposure. The etching rate increased after the initial 10-min exposure. During this period, the flat DLC surface was structurally modified to produce carbon nanostructures with a density of ~2.4 × 10¹¹ cm⁻². With this increase in surface area, the etching rate increased. After 20 min, the DLC film had a circular pattern etched into it downto the substratewhere silicon nanostructureswere observed with sizes varying from 10 nm to 1 μm. The initial carbon nanostructure formation is believed to involve selective removal of the sp2-bonded carbon domains. The carbon etching results from the formation of reactive oxygen species in the plasma.

DOI： 10.1016/j.diamond.2014.08.009

Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

Ambient molecular beam mass spectrometry (MBMS) has been used to study how different capillary widths (530 µm and 2.4 mm) and excitation waveforms (continuous wave kHz and pulsed dc) affect the ionic composition of atmospheric pressure plasma jets. It is shown from time-averaged ion intensities that reducing the width of the jet capillary results in a significant increase in the variety of both positive and negative ions detected within the discharge. We discuss this in terms of changes in flow velocity and the onset of turbulence within the plasma plume. Changing the mode of excitation had little effect on the ionic species detected from the microplasma jet; however, there was a notable shift in dominance towards higher mass ions when operated in a continuous wave kHz mode. The temporal evolution of the ions within the microplasma jet was observed for both excitation sources, operated at 5 and 15 kHz. Positive ions were created during periods correlated with the positive and negative peaks in discharge current, while negative ions were predominantly created at times when the discharge current peak was negative. This phenomenon was independent of the driving waveform. For pulsed dc excitation, considerably fewer positive ions were created in periods related to the negative current peaks, especially at higher frequencies. We propose a simple explanation for these processes based on ideas of streamer propagation and the influence of self-induced electric fields in the plasma plume.

DOI： 10.1088/0022-3727/46/46/464018

Authorship：Lead author   Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

This paper reports the spatially resolved surface modification of polystyrene (PS) using an atmospheric-pressure microplasma jet. Treatment of PS surfaces using a microplasma jet with a 100 µm diameter is investigated using contact angle, XPS, AFM and lens epithelial cell (LEC) growth. Microplasma jet treatment creates a defined reduction in contact angle of approximately 60° in a circular pattern with a diameter of 1.5 mm or more. Spatially resolved XPS analysis demonstrates that a reduction in contact angle is related to an increase in O1s peak intensity. AFM confirms that microplasma jet treatment causes no significant change in surface roughness. LECs are confined to a treated area.

DOI： 10.1002/ppap.201300052

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Kind of work：Single Work  

Using mass spectrometry we show that ion-molecule reactions in the gas phase produce heavy oligomers of the series [nM+H]⁺ (n up to 6) within the output plume of a heptylamine polymerizing plasma jet flowing into air and N₂ blankets. Optimal operating conditions for high yields of heavy oligomers are found.

DOI： 10.1002/ppap.201300042

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work  

A synthetic biological sensor was developed to monitor the interaction of plasma with soft, hydrated biological material. It comprises phospholipid vesicles in a hydrated proteinaceous environment comprising 5% (w/v) gelatin. The vesicles contained a self-quenched dye, which was activated by vesicle destruction giving a clear fluorescent switch on. The interaction of bacterial toxins with the sensor was measured in a proof of principle experiment, then the effect of atmospheric plasma jets with the sensor, was studied in order to assess the cytolytic effect of plasma jets in biological systems. When the plasma contacted the gelatin surface perpendicular to the surface, the treatment resulted in the formation of a star-shaped pattern of microchannels that radiated out from the centre of the treatment area within the gelatin matrix, and locally damaged vesicles within the microchannels at a depth of 150 µm below the gelatin surface. Plasma jets applied in parallel to the surface of the matrix resulted in the formation of a single microchannel with damage to the vesicles only evident at the walls of the channel, and a much reduced penetration depth within the gelatin. Our data show that the effects of plasma can be deep in the gelatin material and that the angle of treatment significantly influenced the nature and level of damage to the gelatin and vesicles. Potentially this gelatin model can be used to unravel the roles of different plasma species and the direct effect of whole plasma contact, from those of primary and secondary species—i.e. primary, those emanating directly from the plasma and secondary, those species created in the 'target' tissue. This type of insight could be useful in the future development of safe and effective plasma medical technologies.

DOI： 10.1088/0022-3727/46/18/185401

Authorship：Lead author   Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

A commercial current monitor has been used to measure the current associated with plasma bullets created in both the positive and negative half cycles of the sinusoidal driving voltage sustaining a plasma jet. The maximum values of the positive bullet current are typically ∼750 µA and persist for 10 µs, while the peaks in the negative current of several hundred μA are broad, persisting for about 40 µs. From the time delay of the current peaks with increasing distance from the jet nozzle, an average bullet propagation speed has been measured; the positive and negative bullets travel at 17.5 km s⁻¹ and 3.9 km s⁻¹ respectively. The net space charge associated with the bullet(s) has also been calculated; the positive and negative bullets contain a similar net charge of the order of 10⁻⁹ C measured at all monitor positions, with estimated charged particle densities n_b of ∼10¹⁰–10¹¹ cm⁻³ in the bullet.

DOI： 10.1088/0963-0252/21/3/034020

Publishing type：Research paper (scientific journal)  

Time-resolved ICCD images of discharge and plasma bullet formation in a capillary dielectric barrier discharge at atmospheric pressure have been obtained across the whole period in the voltage cycle. The images clearly show that the capillary discharge ignites at the inner edges of both electrodes, when each electrode is working as a cathode, and this leads to the formation of afterglow plasma bullets traveling upstream and downstream.

DOI： 10.1109/TPS.2011.2160290

Authorship：Lead author   Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

Using molecular beam mass spectroscopy, time-resolved measurements of the ionic species in the plasma plume of an atmospheric-pressure helium microplasma jet are made for a range of excitation frequencies (5, 10 and 25 kHz) and source–instrument orifice distances (1, 7 and 11 mm). Ionic species can only be observed in the visible plasma plume, with the main positive species being (65.26%) and (21.11%), and a few percentages of N⁺, O⁺, NO⁺ and He⁺. For the negative ions, the majority species are O₃^- (22.68%), O₂^-(H₂O) (10.49%) and a large range of minority species observed, namely O_n^-, OH_n^-, H₂O^-, CO_n^- and clusters, O_m^-(H₂O)_n, (OH)_m^-(H₂O)_n, O_n^-(CO₃) and CO₃^-(H₂O)_n. The flux of ions created from air species, such as NO⁺ and O₃^-, is seen to be maximized at a distance of several millimeters from the nozzle, whereas the He⁺ concentration continually decreases with distance from the exit orifice. The time-resolved measurements (time resolution down to 2 µs) show that positive ions appear twice in one full period of the voltage waveform, correlated directly with positive and negative current peaks. The rise and fall times of the positive ions are typically tens of us. In contrast, the appearance of negative ions is correlated only with the negative part of discharge current, with one main peak in the detected ionic flux seen per cycle. The rise time of the negative ions is about 10 µs, independent of mass; however, we observed longer decay times, from 100 to 150 µs, increasing with mass. With increased driving frequency, the time modulation in the ionic fluxes is reduced, particularly for the negative species that show almost constant fluxes at 25 kHz throughout the cycle. The observations can be understood through a simple picture of the interaction of the He jet and the moist ambient air. The results indicate that the discrete plasma 'bullets' and their afterglow tail, that forms the jet, carry an associated positive or negative current depending on the time of their creation in the voltage cycle.

DOI： 10.1088/0022-3727/44/36/365202

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Kind of work：Single Work   International / domestic magazine：International journal  

Time-resolved ICCD images of discharge and plasma bullet formation in a capillary dielectric barrier discharge at atmospheric pressure have been obtained across the whole period in the voltage cycle. The images clearly show that the capillary discharge ignites at the inner edges of both electrodes, when each electrode is working as a cathode, and this leads to the formation of afterglow plasma bullets traveling upstream and downstream.

Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Kind of work：Single Work   International / domestic magazine：International journal  

Using Schlieren photography, the helium outflow configuration from a fine capillary-based microplasma jet discharge has been captured for free-stream conditions. The transition
from laminar to turbulent flow is clearly identified with and without operation of the plasma. At a flow rate of 2.3 L min⁻¹ with no plasma operating, this transition occurs 54 mm from the nozzle; however, with plasma struck (peak voltages of 8 kV_p−p), this reduces to 40 mm.

DOI： 10.1109/TPS.2011.2157940

Publishing type：Research paper (scientific journal)   Kind of work：Joint Work   International / domestic magazine：International journal  

This paper reports on the correlation between gas flow and plasma behaviour in the outflow of a micro-atmospheric pressure plasma jet operating in helium using both 2D optical imaging and Schlieren photography. Schlieren photography shows that the helium outflow changes from laminar to turbulent conditions after distances between 20 and 50 mm from the nozzle. Above a flow rate of 1.4 slm, the length of the laminar region decreases with increasing flow rate. However, by contrast the visible plasma plume increases in length with increasing flow rate until its extension just exceeds that of the laminar region. At this point, the plasma becomes turbulent and its length decreases. Exposing polystyrene (PS) samples to the plasma jet significantly alters the water contact angle in a defined area, with the hydrophobic PS surface becoming more hydrophilic. This modification occurs both with and without direct contact of the visible glow on the surface. The radius of the treated area is much larger than the width of the visible jet but much smaller than the area of the turbulence on the surface. The treated area reduces with increasing nozzle–substrate distance.

DOI： 10.1088/0022-3727/44/15/155206

Publishing type：Research paper (scientific journal)  

DOI： 10.1541/ieejfms.131.344

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Kind of work：Single Work   International / domestic magazine：International journal  

The potential of using water-vapor plasmas excited by microwaves as a ultraviolet (UV) light source has been investigated by using various pressures and input powers. The UV irradiation power increased and saturated at a pressure range dependent on the input power. On the other hand, other visible and infrared emissions corresponding to four atomic lines, i.e., the Balmer series of hydrogen at 486.1 nm ( H beta) and 656.3 nm (H alpha) and oxygen atoms at 777.2 and 844.6 nm, were clearly decreased with an increase in the total gas pressure. It was found that pressures (1.4-2.0 kPa) near the saturated water-vapor pressure were found to give the most intense UV irradiation. With a vapor pressure of 1.6 kPa and a total microwave power of 300 W, the power density of UV (Gamma uv ) was measured to be 10.5 uW cm^-2 at a distance of 30 cm from the center of the discharge tube as measured through an optical viewing port on the cavity discharge applicator. This value for UV is comparable to that for a mercury lamp. However, the efficiency was estimated to be considerably lower than that of a mercury lamp.

DOI： 10.1109/TPS.2008.2007732

Publishing type：Research paper (scientific journal)   Kind of work：Single Work  

We have studied the effects of ternary gas mixtures of Xe(10%)–Kr(20% and 40%)–Ne on the luminous efficiency in ac plasma display panels. Spatiotemporal behaviors of near infrared (IR) emission was measured by an intensified charge-coupled device camera equipped with a narrow bandpass filter and absolute densities of excited Xe∗ and Kr∗ atoms in the lowest resonance (1s₄) and metastable (1s₅) levels were measured by a technique of microscopic laser absorption spectroscopy. We have found interesting features from both emission and absorption experiments, such as longer near-IR emission (0.3–0.4 us) and different temporal behaviors between the excited Kr^∗(1s₅) atoms and Xe^∗(1s₄,1s₅) atoms. We have also found that the order of magnitude of the peak density of excited Kr^∗(1s₅) atoms (∼10¹² cm⁻³) was ten times smaller than that of Xe^∗(1s₄,1s₅) atoms, and that their decay time was remarkably short (∼0.3 us). These results have then been compared with those for a binary gas mixture of Xe(10%)–Ne. At a certain range of the sustain voltage, the production rate of Xe^∗(1s₄,1s₅) atoms and the luminous efficiency have turned out to be slightly improved for the ternary gas mixtures, compared to the binary gas mixture.

DOI： https://doi.org/10.1063/1.2786609

Publishing type：Research paper (scientific journal)   Kind of work：Single Work   International / domestic magazine：International journal  

The effects of the driving frequency of the sustaining-voltage pulses on microplasmas in a cell of an ac plasma-display panel (ACPDP) were investigated using spectroscopic diagnostics [optical emission spectroscopy (OES) and laser-absorption spectroscopy (LAS)]. The unit discharge cell has a structure similar to that of a general commercial ACPDP, but it is prepared for three-dimensional (3-D) observation using a pair of micro-prisms. When the near-IR emission by OES and the absorption signal by LAS were observed in the front and side views simultaneously, it was determined that the discharge was concentrated at the center of the discharge space and quickly responded to an applied electrical potential as the sustaining frequency increases. The production efficiency of excited Xe^**(2p) atoms and vacuum-ultraviolet (VUV) photons, which was estimated from the spectroscopy results with the measured power dissipated in the discharges, increased as the frequency of the sustain pulses increases to 100 kHz. At 250 kHz, however, the efficiency remarkably decreased because of an inefficient time for excimer formation and, possibly, for wall-charge formation. From the quantitative analysis of the efficiency, the most-efficient frequency for the sustain voltage was around 100 kHz in the case of Xe(5%)–Ne at 500 Torr, i.e., the efficiency depended on both the priming particles [excited Xe^*(1s₅) atoms] in space and the charged particles on the dielectrics.

DOI： https://doi.org/10.1889/1.2739799

Publishing type：Research paper (scientific journal)   Kind of work：Single Work  

Performances of microplasmas in unit discharge cells with grooved structures in the dielectric layer covering the coplanar electrodes were investigated in alternating current (ac)-type plasma display panels filled with Ne-Xe(10%) mixture at 450 torr. The diagnostics are based on a microscopic laser-absorption spectroscopy technique for the spatiotemporally resolved measurements of absolute densities of Xe^*(1s₅,1s₄) atoms, from which the production rate and the efficiency of the vacuum ultraviolet photons were estimated. These results were compared with previously reported data obtained in conventional phosphor coated panels with the same structures for the dependences on the applied sustain voltages. As the result, the following conclusions were ascertained. The grooved structure does not help to improve the luminous efficiency but it helps to lower the firing and sustaining voltages by about 20 V if the electrode gap is kept constant. Therefore, it provides additional possibilities for the selection of other operating conditions such as the gas composition and pressure for the improvements of the luminance and the luminous efficiency.

DOI： 10.1109/TPS.2006.872431

Publishing type：Research paper (scientific journal)   Kind of work：Single Work  

Ne–Kr gas mixtures with high Kr concentrations were applied to ac plasma display panels. Spatiotemporal behaviors of excited Kr atoms in the 1s5 metastable state and the 1s₄ resonance state were measured by microscopic laser-absorption spectroscopy in the binary mixtures with Kr concentrations of 20% and 40%. A systematic comparison was done between the characteristics of Ne–Kr-filled panels and those of conventional Ne–Xe panels with the same structure but with lower Xe concentrations of 5% and 10%. For example, the total number of Kr^∗(1s₅) atoms in a unit cell ranged from 7.4×10⁷ to 2.0×10⁸, at the peak was apparently smaller than the value of Xe^∗(1s₅) atoms. However, when the difference in the decay rate of the excited atoms by three-body collision processes is taken into account, the production efficiency of vacuum-ultraviolet (VUV) emission from Kr^∗₂ excimers is as large as that from Xe^∗₂ excimers in a usual panel since these processes lead directly to the formation of excimers. From the measured density of Kr^∗(1s₄) atoms, it is estimated that the contribution of the atomic resonance line is smaller than the excimer band at those high Kr concentrations. In any case, by summing up those two contributions to the VUV emission, the overall efficiency in the Ne–Kr(40%) panel is estimated to be comparable to that in the Ne–Xe(10%) one.

DOI： http://dx.doi.org/10.1063/1.2131194

Publishing type：Research paper (scientific journal)  

We have investigated the influence of microscopic surface structures of the MgO protective layer on the ion-induced secondary electron emission coefficient in alternating-current plasma display panels (AC-PDPs). The microscopic surface structures of the MgO protective layer have been formed by using a mesh mask with an electron beam evaporation method. The ion-induced secondary electron emission coefficient γ of the MgO protective layer with mesh-patterned microscopic surface structures has been measured by the γ-FIB (focused ion beam) system. It is found that the MgO protective layer with microscopic surface structures has a higher γ than those without any surface structures.

DOI： https://doi.org/10.1143/JJAP.43.L1154

Publishing type：Research paper (scientific journal)  

The change in work function was studied on Indium-tin-oxide (ITO) surface after O-plasma treatment using γ-focused ion beam (γ-FIB). As the surface of ITO experienced more O-plasma treatment, both the surface resistivity and the work function got higher. Auger electron spectroscopy identified the increase of oxygen as well as the decrease of Sn. The rise of work function and surface resistivity is considered to be due to the change in oxygen and Sn on the surface of ITO

DOI： https://doi.org/10.1016/S0921-5107(03)00115-6

Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

The work functions of MgO single crystals with its respective orientation (111), (200), and (220) have been investigated from their ion-induced secondary electron emission coefficient γ, respectively, using various ions with different ionization energies in a γ-focused ion beam system. The work function for MgO single crystal with (111) orientation has the lowest value, 4.22 eV, whereas it is 4.94 eV for (200) and the highest value is 5.07 eV for (220). These work functions of MgO single crystals can explain the nonzero values of the ion-induced secondary electron emission coefficient γ for Xe+ ions, whose ionization energy is 12.13 eV.

DOI： http://dx.doi.org/10.1063/1.1581376

Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

調査・活動報告

CiNii Research

Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

調査・活動報告

CiNii Research

Presentation type：Poster presentation  

Venue：Chubu University, Aichi, Japan  

Presentation type：Poster presentation  

Venue：Chubu University, Aichi, Japan  

Presentation type：Poster presentation  

Venue：Chubu University, Aichi, Japan  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Venue：Yokohama, Japan  

Presentation type：Poster presentation  

Venue：大阪公立大学中百舌鳥学術交流会館  

Presentation type：Poster presentation  

Presentation type：Poster presentation  

Venue：Chitose Civic Culture Center, Hokkaido, Japan  

Presentation type：Oral presentation (invited, special)  

Venue：立願寺温泉ホテル 湯里  

Presentation type：Oral presentation (general)  

Venue：朱鷺メッセ 新潟  

Presentation type：Oral presentation (general)  

Venue：朱鷺メッセ 新潟  

Presentation type：Oral presentation (general)  

Venue：朱鷺メッセ 新潟  

Presentation type：Oral presentation (general)  

Venue：朱鷺メッセ 新潟  

Presentation type：Oral presentation (general)  

Venue：朱鷺メッセ 新潟  

Presentation type：Poster presentation  

Venue：朱鷺メッセ 新潟  

Presentation type：Poster presentation  

Venue：朱鷺メッセ 新潟  

Presentation type：Poster presentation  

Venue：朱鷺メッセ 新潟  

Presentation type：Poster presentation  

Venue：朱鷺メッセ 新潟  

Presentation type：Poster presentation  

Venue：朱鷺メッセ 新潟  

Presentation type：Poster presentation  

Venue：朱鷺メッセ 新潟  

Presentation type：Oral presentation (invited, special)  

Venue：Jeju, Korea  

Presentation type：Oral presentation (general)  

Venue：Makuhari Messe, Chiba, Japan  

Presentation type：Oral presentation (general)  

Venue：Makuhari Messe, Chiba, Japan  

Presentation type：Oral presentation (invited, special)  

Venue：Seoul, Korea  

Presentation type：Poster presentation  

Venue：Seoul, Korea  

Presentation type：Oral presentation (general)  

Venue：東京  

Presentation type：Oral presentation (general)  

Venue：東京  

Presentation type：Oral presentation (general)  

Venue：東京  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Venue：Nagoya, Japan  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Venue：Jeju, Korea  

Presentation type：Poster presentation  

Venue：大阪公立大学  

Presentation type：Poster presentation  

Venue：Nagoya  

Presentation type：Oral presentation (general)  

Venue：横浜  

Presentation type：Poster presentation  

Presentation type：Oral presentation (general)  

Venue：熊本  

Presentation type：Oral presentation (general)  

Venue：熊本  

Presentation type：Oral presentation (invited, special)  

Venue：熊本  

Presentation type：Poster presentation  

Venue：熊本  

Presentation type：Poster presentation  

Venue：熊本  

Presentation type：Oral presentation (general)  

Venue：熊本  

Presentation type：Poster presentation  

Venue：熊本  

Presentation type：Poster presentation  

Venue：熊本  

Presentation type：Poster presentation  

Venue：熊本  

Presentation type：Poster presentation  

Venue：熊本  

Presentation type：Oral presentation (general)  

Venue：熊本  

Presentation type：Oral presentation (general)  

Venue：千葉  

Presentation type：Poster presentation  

Presentation type：Poster presentation  

Venue：Kyoto  

Presentation type：Poster presentation  

Venue：Kyoto  

Presentation type：Oral presentation (general)  

Venue：東京  

Presentation type：Poster presentation  

Venue：Gifu  

Presentation type：Poster presentation  

Venue：Gifu  

Presentation type：Poster presentation  

Venue：Gifu  

Presentation type：Oral presentation (invited, special)  

Venue：Yokohama  

Presentation type：Oral presentation (general)  

Venue：Yokohama  

Presentation type：Oral presentation (general)  

Venue：Yokohama  

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Presentation type：Poster presentation  

Venue：Osaka  

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Presentation type：Oral presentation (general)  

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