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only by the electrical discharge, have the leading inactivation role [57-112]. Nonetheless, the plasma-"based" sterilization has its important role in deter- mining the explosion of scientific research in real plasma sterilization systems, along with several other advantages. These can be synthesized in the low temperature of the processing cycle and the reduced treatment times (up to 3 hours). Overall, the use of such devices has improved the sterilization of thermosensitive category of the medical materials. Therefore, their efficiency and the effects on various materials have been closely monitored in many studies. On the other hand, the main concerning issue related to their operation is the use of powerful chemicals in the beginning of the treatment [50, 53, 54]. Despite of its high efficiency to sterilize endoscopic instruments, Plazlyte TM has presented difficulties during sterilization of the ophthalmic instruments. It is worth to mention also that the Plazlyte TM system was retreated from the market. 1.2.5.2 Plasma sterilizers The plasma sterilizers contains direct current (DC), alternative current (AC), radio frequency (RF) and microwave (MW) driven discharges produced at low, medium and high to atmospheric pressures. They were developed and tested for their potential as alternatives technologies to the existing conventional sterilization techniques. A schematic classification of low to atmospheric pressure plasma sources used for microbial inactivation is given in the Table 1.2 11
Table 1.2: Main plasma sources used for microorganism inactivation Low Pressure Atmospheric Pressure Direct Current (DC) sources Radio Frequency (RF) sources Microwave (MW) sources AC/DC glows, Coronas Dielectric Barrier Discharges (DBD) RF/MW torches The year 1968 came with the first patented device which used an electrical discharge for medical tools sterilization [113]. The plasma was produced to a pressure of 1 Torr using an inert gas and was sustained by an RF (13.56 MHz) electric power applied to a coil located outside the chamber. This first attempt has an historical importance in the sterilization by plasma field since the first mechanism of microorganisms destruction by an electrical discharge has been advanced in the same time. In this case the plasma ensured thermal destruction of the pathogen agents. A substantial progress of understanding the plasma killing mechanisms started with the early of 80 0 s when a series of hypotheses have began to be published. Studies regarding the importance of the gas mixtures within discharges were pointed out the effectiveness of the O2-based plasmas [58]. Due to the action of the atomic oxygen, which is a highly chemical reactive species, these discharges showed strong biocidal effects. Besides O atoms, other ground and excited species 12
Page 1 and 2: PLASMA STERILIZATION USING LOW PRES
Page 3 and 4: my appreciation especially for the
Page 5 and 6: Iis ion saturation current [µA] t
Page 7 and 8: CONTENTS 1 PRINCIPLES OF SURFACE DI
Page 9 and 10: 4 EFFECTS OF LOW TEMPERATURE PULSED
Page 11 and 12: and intuited to bring new important
Page 13 and 14: Figure 1.1: Schematic representatio
Page 15 and 16: Table 1.1: Common disinfection and
Page 17 and 18: the radiation energy is resonantly
Page 19: ers of heat, optical radiation and
Page 23 and 24: microorganism population as a respo
Page 25 and 26: UV Photon Before After DNA Figure 1
Page 27 and 28: to sterilize medical tools, but the
Page 29 and 30: sented by both theoretical and expe
Page 31 and 32: Plasma Sterilization Using Low Pres
Page 33 and 34: Figure 2.1: Experimental set-up. MB
Page 35 and 36: Figure 2.3: Electronic circuit of t
Page 37 and 38: such circumstances, the inactivatio
Page 39 and 40: ment time t is N = N0e −αt ≡ N
Page 41 and 42: shows the number of the viable micr
Page 43 and 44: has n −1 0 > 281.25 µm 2 availab
Page 45 and 46: 1 st 2 nd ( I) TNTC (II) TNTC (III)
Page 47 and 48: U LC blocking filter 19.74 pF 20.24
Page 49 and 50: Figure 2.8: Experimental set-up use
Page 51 and 52: the reactive species from plasma ar
Page 53 and 54: Temperature measurement Relative in
Page 55 and 56: MR MP SH Figure 3.2: Experimental a
Page 57 and 58: a fast temperature increasing rate.
Page 59 and 60: D h (min) 10 3 10 2 10 1 10 0 100 2
Page 61 and 62: MR QP SH Figure 3.6: Experimental a
Page 63 and 64: The contribution of photons and hea
Page 65 and 66: D (min) 10 3 10 2 10 1 10 0 Dν D h
Page 67 and 68: N/N 0 (%) 10 2 10 2 10 2 10 2 10 2
Page 69 and 70: D (min) 10 2 10 1 10 0 D h+ν+p D h
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holder is mainly given by particle
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3.5 Power sensitivity of spore inac
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If for a reference treatment temper
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of the sample was achieved. Moreove
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microorganisms were disposed in mon
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The pulse period covered a wide int
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in chapter 2. The treatment time of
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4.2.2 Injected RF power In order to
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ton =500µs, and the duty cycle was
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T ( 0 C) 120 100 80 60 40 20 I 0 5
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N/N 0 (%) 10 2 10 2 10 2 10 1 10 1
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elow 70 ◦ C. 3. Increasing the in
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the second phase of the inactivatio
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k 1, 2 (min -1 ) 1.2 1.0 0.8 0.6 0.
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I (arb. unit) 140 120 100 80 60 40
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I (arb. unit) 5 4 3 2 1 0 0.000 0.0
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I > (arb.unit) 1.0 0.9 0.8 0.7 0.6
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shown in Fig. 4.14. It can be seen
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I is (mA) 0.25 0.20 0.15 0.10 0.05
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value. When ton has been kept const
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survival curve characteristics were
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of the effects produced by differen
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solutely necessary for a profound u
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Conferences 1. Bacillus spores ster
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[9] W. A. Rutala, D. J. Weber, J. H
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[34] J. H. Young: Sterilization wit
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[57] M. K. Boudam, M. Moisan, B. Sa
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[79] J. Schneider, K. M. Baumgartne
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[100] S. Villeger, S. Cousty, A. Ri
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