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inside the spores was measured trying to confirm these results. On the other hand, the role of optical radiation in atmospheric pressure discharges was recently confirmed by other scientists and it was shown that UV photons lead the microbial inactivation process [57]. 1.3.2 Mechanisms of plasma sterilization at low pressure At low pressure, a detailed sterilization mechanism has been developed taking into account the microorganism survival curves (i.e., the number of microorganisms as a function of the treatment time) [17, 18, 70-75, 81]. The physical processes responsible for the observed temporal dynamics of the bacteria population were found to be carried out mainly by UV photons and radical species created in plasma. The last ones are getting adsorbed on the microorganism surface in such a way that volatile compounds are formed. Such an erosion mechanism of sur- faces is known as etching [61, 82-84]. Following the steps of the survival curve, the inactivation process takes place in three phases detailed below: 1. In the first phase the destruction of microorganism genetic material (i.e., DNA) by UV photons dominates the inactivation process as it is shown in Fig 1.3; 2. The erosion of the microorganism through etching takes place in the second phase. Here, the reactive species are adsorbed on the microorganisms surface and start chemical reactions (chemical etching) forming compounds 15
UV Photon Before After DNA Figure 1.3: Destruction of the DNA molecule by photon direct impact. as CO2, COandH2O which are harmless. In parallel, a photo-desorption process takes place where UV photons are breaking chemical bonds overall contributing to the etch rates. More than this, it is believed that the photons are acting synergistically with reactive species, accelerating the elimination rate of microorganism organic materials [17, 18, 57, 64, 65]. The schematic representation of the physical processes which take place in this phase is showninFig.1.4; 3. The last phase starts when the surface of microorganisms has been eroded enough that the UV photons can finally kill the last survivals leading to total inactivation of the entire population. 16
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 and 20: ers of heat, optical radiation and
Page 21 and 22: Table 1.2: Main plasma sources used
Page 23: microorganism population as a respo
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
Page 71 and 72: holder is mainly given by particle
Page 73 and 74: 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
Page 127 and 128:
[100] S. Villeger, S. Cousty, A. Ri
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