| Enhaced inactivation of bacterial spores by atmospheric pressure plasm.. |
Enhaced inactivation of bacterial spores by atmospheric pressure plasma with catalyst TiO2
Appl. Catalysis B Environ. 93, 212 (2010)
Both atmospheric pressure plasma and photo-catalyst metal oxide titanium dioxide (TiO2) are well known for their microorganism inactivation and chemical material decomposition abilities. In this work, radio-frequency atmospheric pressure plasma and TiO2 are used together to inactivate Bacillus subtilis spores that have a very high degree of environmental resistance to ultra-violet (UV) photons and heat. The combinational use of the plasma and TiO2 demonstrates an enhanced performance of B. subtilis spore inactivation by showing a decrease in the decimal reduction time of as large as 40% compared with the use of plasma alone. A significant increase of hydroxyl (OH) and excited oxygen atomic emission line (O I) intensities in the presence of TiO2 suggests that the atmospheric pressure plasma assisted by TiO2 is very effective at generating reactive oxygen radicals, which is known to be a dominant factor in bacterial spore inactivation. Possible TiO2 activation mechanism by the plasma is investigated. |
| Feasibity study of the sterilization of pork and human skin surfaces b.. |
Feasibity study of the sterilization of pork and human skin surfaces by atmosphric pressure plasmas
Thin Solid Films 517, 4272 (2009)
Atmospheric pressure radio frequency (rf) glow discharge characteristics were studied aiming for the plasma treatment of living tissues such as pork and human skin. Electrical and optical measurements of the plasma gave reasonable values at low current of 4 mA and gas temperature of 60 °C at 100 W. The colorimetric measurement of the treated pork sample demonstrated negligible thermal effect from the plasma. In addition, the sterilization efficiency of Escherichia coli inoculated on pork surface was comparable with that of a conventional UV sterilizer. The experimental results promise that the atmospheric pressure rf plasma can be safely applied to human skin treatment without electrical and thermal damage. |
| Evaluation of atmospheric pressure plasma to improve the safety of sli.. |
Evaluation of atmospheric pressure plasma to improve the safety of sliced cheese and ham inoculated by 3-strain cocktail listeria monocytogenes
Food Microbiology 26, 432 (2009)
The objective of this study was to evaluate the efficacy of atmospheric pressure plasma (APP), which is capable of operating at atmospheric pressure in air, in sliced cheese and ham inoculated by 3-strain cocktail of Listeria monocytogenes (ATCC 19114, 19115, and 19111, LMC). The process parameters considered were input power (75, 100, 125, and 150 W) and plasma exposure time (60, 90, and 120 s). Microbial log reduction increased with increases of input power and plasma exposure time. After 120 s APP treatments at 75, 100, and 125 W, the viable cells of LMC were reduced by 1.70, 2.78, and 5.82 log in sliced cheese, respectively. More than 8 log reductions can be achieved in 120 s at 150 W. In contrast, reductions after 120 s ranged from 0.25 to 1.73 log CFU/g in sliced ham. Calculated D values, the exposure time required to inactivate 90% of a population, from the survival curves of 75, 100, 125, and 150 W of APP treatments were 71.43, 62.50, 19.65, and 17.27 s for LMC in sliced cheese, respectively, and those in sliced ham were 476.19, 87.72, 70.92, and 63.69 s. No viable cells were detected at 125 and 150 W of APP treatment in sliced cheese, irrespective of plasma exposure time, after 1 week at a detection limit of 10(1) CFU/g. These results indicate that the inactivation effects of APP on L. monocytogenes are strongly dependent on the type of food. |
| Escherichia coli deactivation study controlling the atmospheric pressu.. |
Escherichia coli deactivation study controlling the atmospheric pressure plasma discharge conditions
Cur. Appl. Phys. 9, 625 (2009)
Bio-applications of plasma have been widely studied in recent years. However, considering the high interests, the inactivation mechanisms of micro-organisms by plasma have not been clearly explained. The goal of this study was to find the sterilization mechanisms and define the major sterilization factors with the atmospheric pressure radio-frequency helium glow discharge. For the sterilization target the Escherichia coli was used. To begin with the sterilization study, the plasma characteristics were investigated by means of electrical and optical diagnostics. Especially, the gas temperature was controlled under 50 °C by keeping the input power less than 70 W to eliminate the thermal effects. Contribution of the UV irradiation from the plasma was studied and it turned out to be negligible. On the other hand, it was found that the sterilization was more effective up to 40% with only 0.15% oxygen addition to the helium supply gas. It indicates that the inactivation process was dominantly controlled by oxygen radicals, rather than heat or UV photons. |
| Plasma Surface Functionalization of Poly [bis(2,2,2-trifluoroethoxy)ph.. |
FPlasma Surface Functionalization of Poly [bis(2,2,2-trifluoroethoxy)phosphazene] Films and Nanofibers Langmuir 23, 8103 (2007)Polyphosphazenes are a class of hybrid organic-inorganic macromolecules with high thermo-oxidative stability and good solubility in many solvents. Fluoroalkoxy phosphazene polymers also have high surface hydrophobicity. A method is described to tune this surface property while maintaining the advantageous bulk materials characteristics. The polyphosphazene single-substituent polymer, poly[bis(2,2,2-trifluoroethoxy)phosphazene], with flat film, fiber mat, or bead mat morphology was surface functionalized using an atmospheric plasma treatment with oxygen, nitrogen, methane, or tetrafluoromethane/hydrogen gases. Surface chemistry changes were detected by static water contact angle (WCA) measurements as well as X-ray photon spectroscopy (XPS). It was found that changes in the WCA of as much as 150 degrees occurred, accompanied by shifts in the ratio of elements on the polymer surface as detected by XPS. Overall this plasma technique provides a convenient method for the generation of specific surface characteristics while maintaining the hydrophobicity of the bulk material. |
| Feasibility study of material surface treatment using an atmospheric l.. |
Feasibility study of material surface treatment using an atmospheric large area glow plasma
Thin Solid Films 506–507, 355 (2006)
Application of atmospheric large-area plasma of a volume of 200 × 50 × 4 mm3 to various material surfaces was attempted for modification of surface properties. Based on the electrical and optical diagnostics, the plasma used for the treatment exhibited normal glow discharge characteristics with relatively low gas temperature, which might enable surface modification without thermal effect. Contact angle measurement showed that the plasma treatment, in general, changed surface characteristics such as wettability of paper, glass, and a silicon (Si) wafer from being hydrophobic to hydrophilic. In addition, ashing of the photoresist coated on a Si demonstrated that the measured ashing rate was found to vary depending on the plasma exposure time and the oxygen amount added to the argon supply gas. Based on the results, it is expected that the atmospheric plasma can be effectively utilized to some processes to which conventional low-pressure plasmas are employed. |
| Hydrophilic surface modification of PDMS using atmospheric RF plasma. |
Hydrophilic surface modification of PDMS using atmospheric RF plasma
J. Phys. Conference Series 34, 656 (2006)
Control of surface properties in microfluidics systems is an indispensable prerequisite for the success of bioanalytical applications. Poly(dimethylsiloxane) (PDMS) microfluidic devices are hampered from unwanted adsorption of biomolecules and the lack of methods to control electroosmotic flow(EOF). Among the various methods of hydrophilic treatment, a new cleaner technology was chosen to treat PDMS. By using atmospheric RF plasma, hydrophilic surfaces can be created. Thus, analysis was conducted with AFM, XPS, and contact angle before and after plasma treatment. Constructing hydrophilic surfaces without changing the true character of that surface has previously been costly and time consuming. But by using atmospheric plasma cost and time are both greatly reduced. There are many other benefits of hydrophilic surface treatment, including the capability to increase adhesion and capillary effects, etc. Also, with hydrophilic treatment of the micro channels on the PDMS surface, surface tension is reduced thus allowing fluids to move easily along those channels. However, the most important aim is to increase the capillary effects without any deposition or chemical treatment. |
| Control of radio frequency atmospheric pressure argon plasma character.. |
control of radio frequency atmospheric pressure argon plasma characteristics by helium gas mixing Phys. Plasmas 13, 013504 (2006)
The control of plasma characteristics is one of the important issues in many atmospheric pressure plasma applications. In order to accomplish this control, a feasibility study was performed by investigating the role of helium gas in an argon glow plasma that were produced in ambient air by 13.56 MHz radio-frequency power. Optical emission spectroscopy was used to measure rotational temperature and emission spectra acquired between 300 and 840 nm. Based on electrical and optical measurements, parameters such as gas temperature, breakdown voltage, power coupling efficiency, spatial uniformity of rotational temperature, and the sum of the emission intensity were controlled by varying the argon and helium gas mixing ratio. The addition of helium gas from 0 to 10 pm to the argon flow of 10 pm lowered the breakdown voltage from 430 to 300 V pk and the rotational temperature from 465 to 360 K. However, an excessive addition of helium resulted in a reduction of the spatial uniformity and efficiency of power coupling. When the ratio of helium to argon flow was between 0.3 and 0.5, a high spatial uniformity with a relatively low gas temperature and breakdown voltage was achieved. This suggests that mixing of the supply gas is a useful way of controlling the plasma characteristics that may be utilized for applications with specific required discharge conditions. |
| Superhydrophobic CFx Coating via In-Line Atmospheric RF Plasma of He-C.. |
Superhydrophobic CFx Coating via In-Line Atmospheric RF Plasma of He-CF4-H2
Langmuir 21, 11213 (2005)
Stable superhydrophobic coatings on various substrates are attained with an in-line atmospheric rf plasma process using CF4, H2, and He. The coating layer is composed of CFx nanoparticulates and has an average roughness of ∼10 nm. This roughness is much smaller than other surfaces reported for superhydrophobicity in the literature. The superhydrophobic coatings are produced on both metallic and insulating substrates without any need of separate microroughening or vacuum lines. |
| A uniform glow discharge plasma source at atmosphric pressure. |
A uniform glow discharge plasma source at atmosphric pressure
Appl. Phys. Lett., 84, 188 (2004)
An atmospheric-pressure, uniform, continuous, glowplasma was produced in ambient air assisted by argon feeding gas, using a 13.56 MHz rf source. Based on the measured current–voltage curve and optical emission spectrum intensity, the plasma showed typical glow discharge characteristics, free from streamers and arc. The measured rotational and vibrational temperatures were in the range of 490 to 630 K and 2000 to 3300 K, respectively, within the operation range of argon flow rate and rf power. From the spatial measurement of total optical emission intensity, and rotational and vibrational temperatures, the plasma shows very high uniformity (over 93%) in the lengthwise direction. The plasma size for this study was 200 mm×50 mm×5 mm, although a plasma was produced in the scaled-up version of 600 mm in length, aiming for large-area plasma applications. |
