Air Plasma Treatment Research Articles

Effects of Atmospheric Air Plasma Treatment on the Surface Morphology, Wettability, Water Imbibition, and Germination of Zea Mays Seeds

Effects of Atmospheric Air Plasma Treatment on the Surface Morphology, Wettability, Water Imbibition, and Germination of Zea Mays Seeds

Polyetheretherketone and titanium surface treatments to modify roughness and wettability – Improvement of bioactivity and antibacterial properties

• PEEK and titanium both sustain cell adhesion, proliferation and differentiation. • Air-plasma treatment increases PEEK and titanium surface wettability. • Surface properties affect cell behavior depending on material nature. • Micropatterned titanium surface induce dental pulp stem cell differentiation. Among the materials available for implant production, titanium is the most used while polyetheretherketone (PEEK) is emerging thanks to its stability and to the mechanical properties similar to the ones of the bone tissue. Material surface properties like roughness and wettability play a paramount role in cell adhesion, cell proliferation, osteointegration and implant stability. Moreover, the bacterial adhesion to the biomaterial and the biofilm formation depend on surface smoothness and hydrophobicity. In this work, two different treatments, sandblasting and air plasma, were used to increase respectively roughness and wettability of two materials: titanium and PEEK. Their effects were analyzed with profilometry and contact angle measurements. The biological properties of the material surfaces were also investigated in terms of cell adhesion and proliferation of NIH-3T3 cells, MG63 cells and human Dental Pulp Stem Cells. Moreover, the ability of Staphylococcus aureus to adhere and form a viable biofilm on the samples was evaluated. The biological properties of both treatments and both materials were compared with samples of Synthegra® titanium, which underwent laser ablation to obtain a porous micropatterning, characterized by a smooth surface to discourage bacterial adhesion. All cell types used were able to adhere and proliferate on samples of the tested materials. Cell adhesion was higher on sandblasted PEEK samples for both MG63 and NIH-3T3 cell lines, on the contrary, the highest proliferation rate was observed on sandblasted titanium and was only slightly dependent on wettability; hDPSCs were able to proliferate similarly on sandblasted samples of both tested materials. The highest osteoblast differentiation was observed on laser micropatterned titanium samples, but similar effects, even if limited, were also observed on both sandblasted materials and air plasma treated titanium. The lowest bacterial adhesion and biofilm formation was observed on micropatterned titanium samples whereas, the highest biofilm formation was detected on sandblasted PEEK samples, and in particular on samples not treated with air-plasma, which displayed the highest hydrophobicity. The results of this work showed that all the tested materials were able to sustain osteoblast adhesion and promote cell proliferation; moreover, this work highlights the feasible PEEK treatments which allow to obtain surface properties similar to those of titanium. The results here reported, clearly show that cell behavior depends on a complex combination of surface properties like wettability and roughness and material nature, and while a rough surface is optimal for cell adhesion, a smooth and less hydrophilic surface is the best choice to limit bacterial adhesion and biofilm formation.

Controlled formation of topological defects of liquid crystals in micro-wells

ABSTRACT Topological defects in liquid crystals (LCs) have drawn attention because they frequently control their collective structure and motion. We have developed a robust and straightforward methodology to prepare well-organised isolated topological defects using the fabrication of micro-well structures. We could prepare multiple topological surface defects in each micro-well with high reproducibility. The micro-wells were prepared by capping a glass substrate on micro-molded polydimethylsiloxane (PDMS). The topological defects were stabilised by optimising the size and the shape and satisfying the boundary conditions inside each micro-well, which was controlled by the air-plasma treatment on the surfaces. We found the optimal conditions for the reproducible and stable formation of topological defects; a circular shape with its diameter <10 μm and the glass surface was treated by air-plasma, providing a proper balance of the elastic force to form topological defect at the centre.

Plasma-assisted template removal and consolidation of silica coatings on polycarbonate

This paper presents a fast and efficient method of removing the template from silica thin films on polycarbonate. Radiofrequency-generated oxygen plasma induced the decomposition of the non-ionic surfactant. The reference samples were silica coatings on silicon, which had different pore sizes. We removed the surfactant by solvent extraction and calcination from these samples. Grazing incidence angle X-ray diffraction analysis shows a highly ordered arrangement of mesopores. The formation of the face-centred cubic structure of mesopores is independent of the substrate and the template removal method. Atomic force microscopy analysis showed open-pore channels after oxygen plasma etching. It also proved that the ammonia treatment increases the hardness of the layer. A short air-plasma treatment is effective for the consolidation of the silica layer and improves the abrasion resistance of the layer on polycarbonate. Air plasma treatment is an alternative to the long heat treatment process. We performed environmental tests according to the relevant ISO standards for optical coatings. Air plasma treated silica coatings have passed all the weathering tests. Therefore, it can be used in outdoor applications, such as a protective layer for the plastic cover of LED street lights. These thin films on polycarbonate have at least one year of service life and are weather-resistant. Plasma treatment can consolidate the silica network and the thin films on polycarbonate have high light transmission (T = 98.8 %).

Highly Durable Gas Diffusion Electrodes Made from Non-Aqueous Catalyst Inks

In a PEM fuel cell, catalyst ink formulation and mixing processes are closely related to catalyst layer coating quality and the subsequent fuel cell performance and durability. Catalyst inks based on non-aqueous solvents such as glycerol and ethylene glycol (EG) have shown significant durability advantages over 1-propanol/water-based inks when using decal coating.1,2 Complex solvent-catalyst-ionomer interactions were used to direct the ink properties for coating requirements and optimize them for maximum fuel cell performance, matching the performance of 1-propanol/water-based CLs, while retaining improved durability. Ink rheology and catalyst particle size were used to monitor ink properties, which were later correlated to electrode morphology and structure. These methods were also used to monitor the ink quality and consistency from batch to batch, and from small lab scale to subsequent scale-up. The transition from coating EG-based catalyst ink on decals to coating on gas diffusion layers (GDLs), followed by a roll-to-roll (R2R) fabrication process are crucial for scale up and commercialization. However, coating EG-based catalyst inks on hydrophobic GDLs presented an initial challenge due to EG’s high boiling point and viscosity. Air plasma treatment was successfully used to allow coating of EG-based ink on hydrophobic GDLs. To establish the correlation between ink properties and MEA performance, gas diffusion electrodes made of 1-propanol/water and EG-based inks were tested for fuel cell performance and durability and compared to previously obtained results with decals. The performance and durability of EG-GDEs was better than that of the 1-propanol/water GDEs. The EG-GDE fabrication process was transferred from Giner to NREL for small scale ‘in-operando’ R2R trials. Multiple drying temperatures were evaluated, and the optimal drying temperature was identified. Finally, the electrode performance and durability of R2R fabricated GDEs was tested, and correlated to catalyst microstructures.This work provides a comprehensive understanding of interactions between Pt, carbon, ionomer, GDL and their impact on electrode structure, fuel cell performance and durability, as well as considerations for scale up to a R2R fabrication process. The attained information will be used to improve fuel cell electrode design, fabrication and scale-up. Acknowledgement: The project is financially supported by the Department of Energy’s Fuel Cell Technology Office under the Grant DE-SC0012049. References K-S. Lee, T. Rockward, A. Labouriau, N. Mack, Y. S. Kim, C. Johnston, 2009, Impact of Solvent on Ionomer Structure and Fuel Cell Durability. ECS Transactions. 25. 10.1149/1.3210717.C. Lei, F. Yang, N. Macauley, M. Spinetta, G. Purdy, J. Jankovic, D. Cullen, K. More, H. Xu, JES, 2021 168 044517.

Surface improvement of cotton/polyester blend textile using DC air glow discharge plasma

The surface properties of commercially cost-effective cotton/polyester blended textiles (50%/50%) are modified using dc low-pressure air discharge. Surface modifications are analyzed at different plasma conditions. The macroscopic effects are investigated by measurements of the contact angles, Fourier’s transform spectroscope (FTIR), x-Ray Diffraction (XRD), and the scanning electron microscope (SEM), which are examining the morphology of the treated surface and chemical shift. Atomic force microscopy (AFM) assesses the roughness of the treated textile surface. Furthermore, the mechanical characteristics of textiles are measured. The results indicate improved hydrophilicity of blend textiles and refinement of dyeability. In addition, the results of XRD, SEM images provided visual evidence that the dc air plasma treatment could be improved the wettability of blended textiles where the surface etching renders the blend textiles less crystalline and more hydrophilic and AFM results revealed that the plasma treatment was a good technique to increase the roughness of blend textile surface. In addition, the FTIR analysis indicated the presence of functional groups on the blend textile surface after plasma treatment. The results found that the improvements in surface properties are dependent on treatment time.

Catalyst Recovery, Regeneration and Reuse during Large-Scale Disinfection of Water Using Photocatalysis

The deployment of photocatalysis for remediation of water has not yet been realized, although laboratory-scale studies have demonstrated promise. Accomplishing this requires the development of photocatalysis as a process, including studying its efficiencies in remedying water when high volumes of water are processed, and addressing the recovery, possible regeneration and reuse of the photocatalysts. To that end, this work is aimed at demonstrating the use of a custom-built mobile platform for disinfecting large quantities of water. The benchtop platform built is capable of processing 15.14 L (4 gallons) per minute of water, with possibility for further scale-up. Preliminary studies on the catalyst recovery, regeneration and reuse via gravity-assisted settling, centrifugation and air plasma treatment indicated that 77% of Aeroxide® P25 titania (TiO2) nanoparticle and 57% of porous TiO2 nanowire photocatalysts could be recovered and regenerated for further use. Overall, this study indicated that process improvements, including increasing the kinetics of the photocatalysis, and optimization of the efficacies of the catalyst recovery and regeneration processes will make it useful for water remediation on any scale. More importantly, the portable and flexible nature of the benchtop photocatalysis system makes it amenable for use in conjunction with existing technologies for remedying large quantities of water.

Method and experimental characterization of the surface free energy of carbon fibers used in composite systems

AbstractSurface treatments are known to affect the interfacial properties in composite systems, including some mechanical properties, as well as the ease of handling. In this study, a simple surface free energy (SFE) characterization technique is proposed to assess the effect of fiber surface treatments on the wetting behavior and SFE of carbon fibers. Several fiber surface treatments were applied. Commercially available T300 carbon fibers from a unidirectional tape were desized and then subjected to nitric acid oxidation as well as air plasma oxidation. Functionalization of the fiber surface was confirmed via X‐ray photoelectron spectroscopy. Oxidation led to enhanced surface roughness as confirmed by measurements of the fibers' surface area using the Brunauer, Emmett, and Teller method. However, the wetting behavior of the fibers does not follow either the Wenzel or the Cassie–Baxter equations, possibly due to the dominant effect of the chemical interactions and the chemical heterogeneity of the fiber surface. It is shown that the polar component of the treated fibers' SFE increases while the dispersive component remains unaffected. The increase of the polar component is due to fiber surface functionalization. Both plasma and wet oxidation treatments enhanced the interfacial shear strength of carbon/epoxy specimens. Optimum conditions may result with treatment duration, as shown for a 2‐min air plasma treatment. The suggested technique to measure contact angles may prove beneficial for fast and accurate research work and also for quality control of surface treatments or coating processes.

Physical modification approaches to enhance cell supporting potential of poly (vinyl alcohol)‐based hydrogels

AbstractPVA‐based hydrogels with tissue engineered scaffolds application commonly need further modification to improve cell‐matrix interactions with respect to subsequent cell proliferation and differentiation. In this study, PVA‐modified hydrogels were formed by subjecting the solutions of PVA/Poly (R‐3‐hydroxybutyrate) (PHB), PVA/Extracellular Matrix (ECM), and PVA/PHB/ECM to freeze–thaw cycles and additive materials effect on cell supporting potential of the hydrogels was investigated. As, limited cell attachment and spreading were observed on PVA blended hydrogels, air plasma surface modification has been performed to promote cell attachment. Attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy revealed the presence of some reactive bonds such as carbonyl on pure and amide on ECM‐coated PVA after plasma exposure. Atomic force microscopy (AFM) also proved increased roughness of hydrogel surface due to the plasma treatment. Plasma modification positive effect on cytoskeleton arrangement of cultured equine adipose derived stem cells (eASCs) was then confirmed by DAPI/phalloidin staining and scanning electron microscopy (SEM) imaging. In summary, among different physical modification approaches, coating with ECM fallowed by air plasma treatment had the most significant effect on cell‐hydrogel interactions. Thus, this combined modification method can be utilized to improve initial attachment and subsequent phenotype of cultured cells on PVA hydrogels for tissue engineering applications.

Improving the Physical and Mechanical Performance of Laminated Wooden Structures by Low-Temperature Plasma Treatment

This paper considers the effect of RF plasma on wood in improving the adhesion of binders to wood by increasing its surface wettability. Our study reveals that radiofrequency (RF) plasma treatment causes a greater than threefold decrease in the marginal wetting angle of wood. The greatest effect is achieved in RF plasma treatment in argon, which is on average 5% greater than that of RF plasma treatment in air or in propane/nitrogen mixture. In addition, the power of the RF plasma torch has the greatest influence, and the main influence comes from the voltage applied to the RF plasma torch; current does not have such a significant effect. To achieve a significant effect, the duration of exposure should be at least 5 min, with a total power of 4.05 kW. Studies have been conducted to determine the adhesive strength of wood. An increase in the strength of laminated beams made from RF-treated bars in relation to control samples was found. The greatest impact on the adhesion strength was revealed when using PVA-based glue, compared with the use of polyurethane-based adhesives and urea-formaldehyde resin.

Plasma treated carbon paper electrode greatly improves the performance of iron-hydrogen battery for low-cost energy storage

A novel iron-hydrogen battery system, whose Fe3+/Fe2+ cathode circumvents slowly dynamic oxygen reduction reaction and anode is fed with clean and cordial hydrogen, is systematically investigated. The maximum discharge power density of the iron-hydrogen battery reaches to 96.0 mW/cm2 under the room temperature. The capacity reaches to 17.2 Ah/L and the coulombic and energy efficiency are achieved to 99% and 86%, respectively, during the galvanostatic charge-discharge test. Moreover, stable cycling test is observed for more than 240 h and 100 cycles with the iron sulfate in the sulfuric acid solutions. It is found that air plasma treatment onto the cathode carbon paper can generate the oxygen-containing groups and increase the hydrophilic pores proportion to ca. 40%, enlarging nearly 6-fold effective diffusion coefficient and improving the mass transfer in the battery performance. The simple iron-hydrogen energy storage battery design offers us a new strategy for the large-scale energy storage and hydrogen involved economy.

Cold plasma hydrophilization of soy protein isolate and milk protein concentrate enables manufacturing of surfactant-free water suspensions. Part I: Hydrophilization of food powders using cold plasma

In this study, we found that treatment with cold plasma influenced the wetting properties of soy protein isolate and milk protein concentrate powders. Cold plasma treatment significantly decreased the apparent contact angle of the powders, indicating hydrophilization of the powders. Cold radiofrequency low-pressure plasma treatment had a larger effect on powder wettability than corona atmospheric plasma discharge. In addition, cold plasma treatment had a more noticeable effect on the wettability of the hydrophobic milk protein concentrate than on the inherently hydrophilic soy protein isolate. Both the soy protein isolate and milk protein concentrate demonstrated zero hydrophobic recovery over time. Scanning electron microscopy showed that cold air plasma treatment of food powders caused minor surface oxidation, though these changes were not observed using FTIR spectroscopy. We suggest that cold plasma treatment has important implications for the production of stabilizer-free food suspensions.

UV-Shielding TiO2 thin film deposition on flexible and heat-labile substrate using an open-air hybrid CVD/Plasma method

In this work, compact scratch resistant transparent amorphous TiO2 thin films are deposited at low temperature, i.e. as low as 50 °C, by a scalable hybrid method combining atmospheric pressure chemical vapor deposition and plasma treatment in open air. Thin film morphology, chemical composition and scratch resistance properties are investigated. The role of the plasma in the process is investigated through comparison with coatings deposited without plasma ignition. The versatile method enables film deposition on polymer film and shows good UV protection. This method, operating in open air shows promising results for the simple, large scale deposition of low carbon containing transparent TiO2 coatings at low temperature.

Influence of non-thermal plasma systems and two favorable surface treatments on the shear bond strength of PAEKs to composite resin

This study aimed to investigate the effect of non-thermal plasma systems with and without two favorable surface treatment techniques on the surface roughness (Ra) and shear bond strength (SBS) of polyaryletherketone (PAEK) polymers to veneering composite resin material. A total of 288 (n = 144 for each polymer) Polyetheretherketone (PEEK) and Polyetherketoneketone (PEKK) samples (7 73mm) were divided into the surface treatment methods (n = 16): untreated (CNT); dielectric barrier discharge air plasma treatment (DBD); atmospheric pressure plasma treatment with a plasma brush (APB); 98% sulfuric acid etching (SA); SA_DBD; SA_APB; tribochemical silica coating (TBC); TBC_DBD; TBC_APB. The Ra (n = 5) and scanning electron microscope (SEM) analyses (n = 1) were performed. A bonding agent was applied to the remaining samples (n = 10) and veneered with a composite resin. After storing in distilled water for 24 h at 37 °C, the SBS test was applied with a universal test machine, and the failure modes were examined with an optical microscope. The SBS and Ra data were statistically analyzed with Kruskal Wallis, two-way analysis of variance (ANOVA), and compared with Mann-Whitney_U and Tamhane tests (α = 0.05). The highest SBS value was observed in Groups SA (22.67 ± 1.48 MPa) for PEEK, Group TBC (18.91 ± 1.09 MPa) for PEKK polymer groups. The highest Ra values were determined in Group TBC_DBD for both polymers. While the TBC may enhance the SBS values of both polymers, the SA application is more effective for PEEK polymer regarding the SBS value. In contrast to the effect of DBD, APB application is beneficial for improving the bonding capacity of PAEKs.

Core-shell PLA/Kef hybrid scaffolds for skin tissue engineering applications prepared by direct kefiran coating on PLA electrospun fibers optimized via air-plasma treatment

Over the recent years, there is a growing interest in electrospun hybrid scaffolds composed of synthetic and natural polymers that can support cell attachment and proliferation. In this work, the physical and biological properties of polylactic acid (PLA) electrospun mats coated with kefiran (Kef) were evaluated. Gravimetric, spectroscopic (FTIR-ATR) and morphological investigations via scanning electron microscopy confirmed the effective formation of a thin kefiran layer wrapped on the PLA fibers with an easy-tunable thickness. Air plasma pre-treatment carried out on PLA (P-PLA) affected both the morphology and the crystallinity of Kef coating as confirmed by differential scanning calorimetry and X-ray diffraction analyses. Scaffolds were mechanically characterized with tensile tests to evaluate the reinforcing action of the Kef coating. The water resistance of Kefiran coating in distilled water at 37 °C evaluated on both PLA/Kef and P-PLA/Kef was carried out by gravimetric and morphological analyses. Finally, cell culture assays with embryonic fibroblast cells were conducted on selected hybrid scaffolds to compare the cell proliferation, morphology, and collagen production with PLA and P-PLA electrospun scaffolds. Based on the results, we can demonstrate that direct coating of PLA from Kef/water solutions is an effective approach to prepare hybrid scaffolds with tunable properties and that the plasma pre-treatment enhances the affinity between PLA and Kefiran. In vitro tests demonstrated the great potential of PLA/Kef hybrid scaffolds for skin tissue engineering.

Factors triggering germination in plasma-activated cotton seeds: water imbibition vs. reactive species’ formation

Plasma technology has emerged as an efficient, simple, and eco-friendly method for activating seed germination processes. Most studies on this subject have focused on the morphological and wetting effects on the surface state of seeds and attributed the improvement in germination occasionally found to the induced hydrophilicity and a higher water imbibition rate. Recently, the involvement of reactive oxygen and nitrogen species in the germination process has also been highlighted. In this work, we study the effect of a very low-power cold atmospheric air-plasma treatment on the germination and sterilization of cotton seeds in normal (i.e., water abundant) and simulated drought conditions. Optical emission spectroscopy of the plasma has revealed the formation of different excited species of molecular nitrogen and oxygen, as well as OH and NO radicals that are deemed responsible for the chemical functionalization and slight morphological changes observed on the surfaces of cotton seeds. The physicochemical changes of the seed surface were analyzed by scanning electron microscopy, energy-dispersive x-ray spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), and x-ray photoemission spectroscopy. This latter technique has shown the formation of a high surface concentration of oxygenated (i.e. –CO x , –C–OH, –O x ) and oxinitrided (i.e. –NO x ) functional groups which disappear from the surface upon exposure to vapor or liquid water. This process must entail the diffusion of these species (together with that of potassium ions that were plasma segregated to the surface) into the interior of seeds. The fact that the water uptake capacity of seeds is not significantly modified by the plasma treatment suggests that the observed in-diffusion of active oxygen and nitrogen species is an important factor in the enhancement of germination capacity induced by plasma activation, particularly under conditions of water scarcity, where germination differences of more than 60% could be found between pristine and plasma-treated seeds. The analysis by FT-IR of the adsorption of deuterated water (D2O) molecules is proposed as a useful procedure to directly monitor water uptake/release processes from seed surfaces.

Studies on the Surface and Wetting Properties of Poly(vinylidene fluoride)/Poly(acrylonitrile)/Multiwalled Carbon Nanotube-NH2 Blends as a Function of Air Plasma Treatment

Studies on the Surface and Wetting Properties of Poly(vinylidene fluoride)/Poly(acrylonitrile)/Multiwalled Carbon Nanotube-NH2 Blends as a Function of Air Plasma Treatment

Polyacrylamide mammary syndrome — specificity of the histological pattern of the focus before and after air-plasma treatment

BACKGROUND: At the end of the twentieth century, mammary gland contour correction using polyacrylamide gel (PAAG) became widely popular. The surgical approach must be improved because of the negative consequences associated with this technique.&#x0D; AIM: This study aimed to evaluate the possibilities of air-plasma technology in the treatment of long-term septic manifestations of polyacrylamide mammary syndrome as well as the prevention of its recurrence based on the analysis of histological examination findings.&#x0D; MATERIALS AND METHODS: Biopsy samples of eight women aged 38 to 59 years, who had undergone gel augmentation of the mammary glands six to 20 years ago, were studied. The complex treatment included air-plasma flow in cutting coagulation modes and nitric oxide therapy. A morphological study of the focus was performed before and after exposure to the plasma flow.&#x0D; RESULTS: Before treatment, chronic granulomatous inflammation and helioma were revealed in six cases; and acute phlegmonous-necrotic soft tissue inflammation in two cases. On the fifth day after combined necrectomy, single loci of the gel were visualized, the majority of which was vaporized. Chronic inflammation was less pronounced than the original histograms. During the sanitation with nitric oxide, the early appearance of foci of fibroblastic proliferation and marginal epithelialization was registered.&#x0D; CONCLUSIONS: Exposure to the air-plasma flow contributes to effective sanitation of purulent focus and gel total elimination Nitric oxide therapy (NO-therapy) accelerates the development of granulation tissue.

Improvement of Heat-Treated Wood Coating Performance Using Atmospheric Plasma Treatment and Design of Experiments Method.

The aim of this work is to improve the heat-treated wood coating performance using experimental design methodology and air–plasma treatment. Firstly, two different heat treatment processes were applied to the wood samples. In the second stage of the study, air–atmospheric plasma treatment was applied to heat-treated samples. These samples were coated with water-based varnish. Adhesion strength and colour change values of these samples before and after the artificial weathering test were measured. The design of experiments method was used to investigate the significant factors. The heat treatment process (212 °C—1 h and 212 °C—2 h) and atmospheric plasma treatment parameters (pressure, distance, and feed) were selected as independent variables, while adhesion strength and colour change were determined as dependent variables. The factors affecting the surface coating performance before and after the artificial weathering test were evaluated by analysis of variance (ANOVA) and Pareto plot. In addition, the factor levels that maximise the adhesion strength value and minimise the colour change were found using the multiobjective optimisation technique. According to the multiobjective optimisation method, results of treatment feed, working distance, and pressure of 60 mm/s, 7.69 mm, and 1 bar were considered as optimum plasma treatment conditions, respectively, for heat treatment process A. Corresponding values for the heat treatment process B were 60 mm/s, 10 mm, and 2 bar.

MEMS hydrogen gas sensor with wireless quartz crystal resonator

Abstract A highly sensitive hydrogen-gas sensor fabricated using MEMS technology is presented. The sensor chip consists of glass substrates, silicon substrate, and an AT-cut quartz crystal resonator, which is embedded in the microchannel constructed on the substrates. The quartz resonator has a fundamental resonant frequency of 165 MHz and a 200 nm palladium film deposited on its single surface as the hydrogen-gas sensing material. The MEMS hydrogen-gas sensor operates in a wireless manner by exciting and detecting the resonator vibration using the non-contacting antennas. The curvature induced resonant frequency change of the resonator plate caused by the expansion of the palladium film is used for the detection of the hydrogen gas. We succeeded in improving the hydrogen absorption rate and then the sensitivity for the hydrogen-gas detection by applying the air-plasma treatment method, and clarified the role of palladium oxide in lowering the energy barrier for the hydrogen-atom migration from surface to subsurface with the X-ray photoelectron spectroscopy. Thus sensitivity enhanced MEMS hydrogen-gas sensor exhibits a detection limit of 10 ppm or less at room temperature both in nitrogen and air.