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Figure 1.4: Schematic representation of the erosion process meaning photodes- orption by photons impact and the synergetic action of reactive species and UV photons translated into UV-induced etching. After [81]. 1.3.3 Topical issues in sterilization research As a sterilization tool, plasma dominates the existent classical methods with its impressive properties. Unfortunately, the application of plasmas in industry and commerce requires several issues to be solved. These have a starting point coming of the controversies which still dominate the mechanisms of microorganism inactivation and of various technological difficulties meet in the processing of the whole range of medical instruments. For example, there have been many attempts 17
to sterilize medical tools, but their various internal lumens or hollow parts still fails [106]. The difficulties it seems to arise of the weak possibility to produce an uniform discharge along small but long diameter tubes or pipes. Another problem is the treatment temperature, especially when the samples or instruments are closed to the plasma production region. Within the discharge itself the gas temperature can reach few hundreds Celsius degrees, therefore, the decrease of surfaces heating is important when heat sensitive materials are processed [70, 84]. Moreover, the sterilization itself needs a good understanding of the physical and biochemical complex phenomena which occur during this process. Until now, the vast majority of the studies have pointed out the importance of UV photons or reactive neutral species, usually abundant in plasma discharges than other species. More than this, it is emphasized their synergic action on the microbial extinction [17, 57, 60, 81]. Regardless of the tentative decontamination mechanisms already proposed, it is clear that plasma acts on bacteria with all its three inactivation agents: heat, optical radiation, and plasma particles [70]. In the last years, there have been a few attempts to assess the relative effectiveness of these inactivation agents in low pressure and atmospheric pressure discharges. However, the number of studies on this topic is still very small, and the reported obtained results are highly different. Therefore, our research has a purpose to rule out controversies related to the role of each plasma inactivation agent in the process of microorganisms inactivation. 18
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 and 24: microorganism population as a respo
Page 25: UV Photon Before After DNA Figure 1
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
Page 75 and 76: If for a reference treatment temper
Page 77 and 78:
of the sample was achieved. Moreove
Page 79 and 80:
microorganisms were disposed in mon
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The pulse period covered a wide int
Page 83 and 84:
in chapter 2. The treatment time of
Page 85 and 86:
4.2.2 Injected RF power In order to
Page 87 and 88:
ton =500µs, and the duty cycle was
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T ( 0 C) 120 100 80 60 40 20 I 0 5
Page 91 and 92:
N/N 0 (%) 10 2 10 2 10 2 10 1 10 1
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elow 70 ◦ C. 3. Increasing the in
Page 95 and 96:
the second phase of the inactivatio
Page 97 and 98:
k 1, 2 (min -1 ) 1.2 1.0 0.8 0.6 0.
Page 99 and 100:
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
Page 105 and 106:
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
Page 109 and 110:
value. When ton has been kept const
Page 111 and 112:
survival curve characteristics were
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of the effects produced by differen
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solutely necessary for a profound u
Page 117 and 118:
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
Page 123 and 124:
[57] M. K. Boudam, M. Moisan, B. Sa
Page 125 and 126:
[79] J. Schneider, K. M. Baumgartne
Page 127 and 128:
[100] S. Villeger, S. Cousty, A. Ri
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