NON-THERMAL PLASMA

Abstract

A plasina-generation device for applying plasma to a human body, having a reservoir containing a gas, a plasma zone in fluid connection with the reservoir, and means for generating a plasma by electrical discharge in the plasma zone. The gas has a composition of 92% to 99.5% Helium and 0.5% to 8% Argon; or 95% to 99.5% Helium and 1% to 20% Neon; or 99.95% to 99.99% Helium and 0.01% to 0.05% Oxygen.

Claims

1. A plasma-generation device for applying plasma to a human body, the device comprising: a reservoir containing a gas, a plasma zone in fluid connection with the reservoir, and means for generating a plasma by electrical discharge in the plasma zone, wherein: the gas comprises from 92% to 99.5% Helium and from 0.5% to 8% Argon; or the gas comprises from 95% to 99.5% Helium and from I% to 20% Neon; or the gas comprises from 99.95% to 99.99% Helium and from 0.01% to 0.05% Oxygen.

2. The plasma-generation device of claim 1, wherein: the gas comprises from 95% to 99% Helium and from 1% to 5% Argon; or the gas comprises from 96% to 99% Helium and from 1 to 10% Neon or the gas comprises from 99.96% to 99.98% Helium and from 0.02% to 0.04% Oxygen.

3. The plasma-generation device of claim 1, wherein the means for generating a plasma comprises a power supply and a dielectric electrode for placing in proximity to a human body, and wherein, in use, the plasma zone is formed between the dielectric electrode and a surface of a human body.

4. The plasma.-generation device of claim 1, wherein the means for generating a plasma comprises a power supply, and first and second electrodes, and wherein, in use, the plasma zone is formed between the first and second electrodes and wherein a flow of gas from the reservoir through the plasma zone provides a flow of plasma to contact a surface of a human body.

5. The plasma-generation device of claim 1, wherein the means for generating a plasma comprises a power supply, and first and second electrodes sandwiching a dielectric material, and wherein, in use, the plasma zone is formed between the first or second electrode and a surface of a human body.

6. The plasma-generation device of claim 1, wherein the device is hand-held.

7. The plasma-generation device of claim 3, wherein the power supply comprises a battery integrated into a hand-held device.

8. The plasma-generation device of claim 1, wherein the gas is supplied through the means for generating a plasma at a flow rate of less than 51/min.

9. The plasma-generation device of claim 1, wherein the means for generating a plasma operates at a voltage of from 2-15 kV.

10. The plasma-generation device of claim 1, wherein the device is a hair straightener, a toothbrush, foot-spa or a hair-brush.

11. A refillable canister for use in a the plasma-generation device, the device comprising a reservoir containing a gas, a plasma zone in fluid connection with the reservoir, and means for generating a plasma by electrical discharge in the plasma zone, the canister comprising a reservoir and containing a pressurised gas, wherein: the gas comprises from 92% to 99.5% Helium and from 0,5% to 8% Argon; or the gas comprises from 95% to 99.5% Helium and from 1% to 20% Neon; or the gas comprises from 99.95% to 99.99% Helium and from 0.01% to 0.05% Oxygen,

12. The refillable canister of claim 11, wherein the gas consists essentially of Helium and Argon, Helium and Neon, or Helium and Oxygen, together with any unavoidable impurities.

13. The refillable canister according to claim 11, wherein the device is hand-held and wherein the canister is integrated into the hand-held device.

14. The use of a plasma for use in a treatment method, wherein the plasma is generated by electrical discharge through a gas, wherein the gas comprises from 92% to 99.5% Helium and from 0.5% to 8% Argon; or the gas comprises from 95% to 99.5% Helium and from 1% to 20% Neon; or the gas comprises from 99.95% to 99.99% Helium and from 0.01% to 0.05% Oxygen.

15. The use of a plasma of claim 14, wherein the treament method is for the cosmetic lightening of nails.

16. The use of a plasma of claim 14, wherein the treatment method is for the cosmetic whitening of teeth,.

17. The use of a plasma of claim 16, wherein the treatment method for the cosmetic whitening of a tooth comprises: plasma treating a surface of a tooth.

18. The use of a plasma of claim 14, wherein the treatment method is for the cosmetic bleaching of hair.

19. The use of a plasma of claim 18, wherein the treatment method for the cosmetic bleaching of a hair comprises plasma treating a surface of the hair applying a hair-dye to the plasma-treated hair.

20. The use of a plasma of claim 14, wherein the treatment is for the cosmetic dyeing of hair, the method comprising: plasma treating a surface of the hair and applying a hair-dye to the plasma-treated hair.

21. A plasma generated by electrical discharge through a gas wherein: the gas comprises from 92% to 99.5% Helium and from 0.5% to 8% Argon; or the gas comprises from 96% to 99% Helium and from 1 to 10% Neon or the gas comprises from 99.96% to 99.98% Helium and from 0.02% to 0.04% Oxygen.

22. The use of a plasma according to claim 14, wherein the plasma heats a surface to be treated to a temperature of 48 C. or lower.

23. (canceled)

24. The plasma-generation device of claim 2, wherein the gas comprises from 96% to 99% Helium and from I to 3% Neon.

25. The plasma-generation device of claim 2, wherein the gas comprises from 96% to 99% Helium and from 1.5 to 2.5% Neon.

26. The plasma-generation device of claim 8. wherein the gas flow rate is less than 2.51/min.

27. The plasma-generation device of claim 26, wherein the gas flow rate is less than 1.51/min.

28. The plasma-generation device of claim 27, wherein the gas flow rate is from 0.1 to 0.51/min.

29. The use of a plasma of claim 14, wherein the treatment method is for treating a fungal infection in a nail.

30. The plasma-generation device of claim 21, wherein the gas comprises from 96% to 99% Helium and from 1 to 3% Neon.

31. The plasma-generation device of claim 30, wherein the gas comprises from 96% to 99% Helium and from 1.5 to 2.5% Neon. 32. The use of a plasma according to claim 22, wherein the temperature is 42 C. or lower.

Description

FIGURES

[0112] The present disclosure will be described in relation to the following non-limiting Figures, in which:

[0113] FIG. 1 depicts a device for the production of a plasma gas flow. The device is shown in full in Figure IA and in close cross-section in FIG. 1B. The device has an inner conductor and an outer conductive sheath sandwiching an inner conductor having gas channels for the passage of the plasma gas blend.

[0114] FIGS. 2A and 2B depict a device for the production of a plasma gas flow. The device includes a single electrode having through-holes for the passage of gas provided by and underlying tortuous gas conduit. There may further be provided a heater below the gas conduit to heat the whole assembly. Such a configuration would be suitable for hair-straighteners.

[0115] FIG. 3 shows an exemplary hair straightening tool employing the plasma device plates shown in FIG. 2.

[0116] FIG. 4 shows a schematic of the components which may be required for establishing a plasma flow for treatment.

[0117] FIG. 5 shows various views of a PF4 test rig as described herein. The rig includes a hand-held applicator 500 tethered to a gas supply 501 within the body of the rig. The body of the rig contains certain of the control electrics.

[0118] FIG. 6 shows two close-up view of the hand-held applicator 500 shown in FIG. 5. This shows the configuration of the device including the gas flow pathway from the gas supply 501 to the nozzle via a valve and between a pair of electrodes for the generation of the plasma.

[0119] Preferred embodiments of devices that apply the principles of the invention s out above will now be described with reference to the accompanying Figures.

[0120] Plasma application devices 100, 300, 400 may comprises: a source of gas in communication with one or more gas outlets 125, 325, 425, and a first electrode 110, 310, 410. Optionally, a second electrode 130, 330, 430 may also be provided. Alternatively, the second electrode may be formed by the article to which the plasma is to be applied (in which case it is not considered to form part of the device).

[0121] The source of gas may be a gas reservoir enclosed within the plasma application device, or may be a conduit in communication with a separate gas supply.

[0122] FIGS. 1 and 3 show plasma application devices 100, 300 for applying plasma to an article in which the device comprises a second electrode 130, 330. The article is to be located between the first electrode 110, 310 and the second electrode 130, 330. For this purpose, the second electrode 130, 330 may be movable relative to the first electrode 110, 310.

[0123] In the embodiment of FIG. 1, which may form a device for curling hair, at least two second electrodes 130a, 130b are provided, such that an electric field may be established between the first electrode 110 and either (or both) of the second electrode(s) 130a, 130b.

[0124] Preferably, the at least two second electrodes 130a, 130b substantially surround the first electrode 110. The at least two second electrodes 130a, 130b may comprise or be formed of a conductive polymer.

[0125] A housing 120 may surround the first electrode 110, with the one or more gas outlets 125 formed in the housing 120. Such a housing may comprise or be formed from a dielectric material such as a ceramic. Alternatively to the arrangement of FIG. 1, the housing 120 may itself form the first electrode 110 with the one or more gas outlets 125 forming a through-hole in the first electrode 110.

[0126] Preferably, a plurality of gas outlets 125 are provided spaced over a portion of the surface of the housing 120. Preferably, the gas outlets 125 are arranged such that gas passing through the gas outlets 125 will contact the second electrode 130.

[0127] The at least two second electrodes 130a, 130b may substantially surround the housing 120 so as to align with the plurality of gas outlets 125. The at least two second electrodes 130a, 130b may be movable (for example, pivotable) relative to the housing 120 for clamping an article (for example, hair) therebetween. A switch or sensor may be provided to trigger the device 100 to provide plasma when the second electrodes 130a, 130b are in a predetermined position relative to the first electrode 310.

[0128] The housing 120 may be generally cylindrical or generally conical or frusto-conical in shape. The at least two second electrodes 130a, 130b may be complementary in shape with the housing 120.

[0129] The device 100 may comprise a handle 140. The source of gas may be a reservoir located within the handle 140.

[0130] In use, the article may be passed between the housing 120 and the at least two second electrodes 130a, 130b. A plasma may be applied to the article by passing a gas from the source of gas via the one or more gas outlets 125 to the article at a location between the first electrode 110 and the second electrode 130. A voltage is applied between the first and second electrodes 110, 130 thus ionises the gas to form the plasma. Preferably, the second electrode 130 is connected to earth, while high frequency signal is applied to the first electrode 110.

[0131] In the embodiment of FIG. 3, which may form a device for straightening hair, the first electrode 330 may be mounted on or form a first component of a housing of the device 301 while the second electrode 330 may be mounted on or form a second component of a housing of the device 302. The first and second components of the housing 301, 302 may be pivotably connected, thereby allowing relative movement between the first and second electrodes 110, 310. Such movement may allow the user of the device to clamping an article (for example, hair) therebetween. A switch or sensor may be provided to trigger the device 100 to provide plasma when the second electrode 330 is in a predetermined position relative to the first electrode 310.

[0132] Preferably, the at least one gas outlet 325 is formed as a through-hole penetrating the first electrode 310. A suitable example of such an electrode is shown in FIG. 2A and described in detail below.

[0133] The device 300 may comprise a handle 340. The source of gas may be a reservoir located within the handle 340.

[0134] FIG. 2 depicts an electrode 200 for the production of a plasma gas flow. The electrode comprises a plurality of through-holes 225 for the passage of gas.

[0135] The electrode 200 may be formed a first conductive plates 201 and a second conductive plate 202. In use, the first plate 201 forms the article facing surface of the electrode. The plates 201, 202 may comprise a ceramic such as aluminium nitride.

[0136] The through-holes 225 may be formed in the first plate 201. A groove 230 may be formed in the second plate 202. The groove 230 is arranged to coincide with the through-holes 225. The first plate 201 may be affixed to the second plate 202 (for example, using fasteners or adhesive). The groove 230 extends from an edge of the second plate 202, at which edge it forms a gas inlet 203 for the electrode 200. Preferably, the groove 230 forms a single continuous conduit between the first and second plates 201, 202.

[0137] Optionally, there may be provided a heat source below the second plate 202, (for example, below the conduit) to heat the electrode 200. The use of a heater lowers the energy required for the gas to form a plasma.

[0138] Whereas the specific embodiments depicted in FIGS. 1 and 3 are preferably for applying plasma to an article located between two electrodes, the invention as described above can be applied to create a jet of plasma. FIG. 4 shows an example of such a plasma application device 400. The device may be used to apply plasma to a surface of an article, such as a hand or region of skin.

[0139] Plasma application device 400 comprises a source of gas. The source of gas may comprise in series: a needle valve 401; a pressure regulator 402; a mass flow meter 403; and a sintered element 404.

[0140] The source of gas is arranged to provide a flow of gas between two electrodes 410, 430. Whilst the electrodes 410, 430 are depicted as being separated such that the flow direction is perpendicular to their separation, this is not essential. In fact, the electrodes 410, 430 may be separated in the direction of the gas flow. The gas may be ejected from the device 400 via one or more gas outlets 425. The one or more gas outlets 425 may be located downstream of the electrodes 410, 430. A nozzle may be provided downstream of the electrodes 410, 430. Alternatively, one of the electrodes 410, 430 may form the nozzle.

[0141] In an alternative embodiment, only a single electrode 410 is provided with the article acting as the second electrode. Thus, the source of gas is arranged to provide a flow of gas past the single electrode 410. The gas may be ejected from the device 400 via one or more gas outlets 425. The one or more gas outlets 425 may be located downstream of the electrodes 410, or may be formed as through holes in the electrode 410 (for example, in the manner depicted in FIG. 2. A nozzle may be provided downstream of the electrode 410. Alternatively, the electrode 410 may form the nozzle.

EXAMPLES

[0142] The present disclosure will now be described in relation to the following non-limiting examples.

[0143] There are many possible uses for cold atmospheric plasmas. The aim of these trials was is to analyse the bleaching efficacy of a variety of gas mixtures at different concentrations, whilst measuring the levels of ozone and nitrous oxide produced, recording the voltage deposition on a wet human test model and determining the temperature of the plume. Optical spectra were also taken in order to analyse the levels of certain metastable states and excited radicals.

[0144] Part AComparative Testing of Gas Mixes using ParaSure Plasma Indicator Strips

[0145] The objective was to find the most efficient plasma gas mix within necessary safety limits for a commercially viable device. This was done by assessing the bleaching efficacy of a variety of gas mixtures at different concentrations whilst also measuring the undesirable by-products of ozone and NOx and the temperature and electrical leakage down the plume.

[0146] The following tests were carried out using an experimental rig with the internal reference PF4. This includes a base control unit provides the required gas flow and electrical supply via an umbilical cord o a hand held unit. The hand held unit consists of concentric inner and outer bather electrodes mounted on quartz tubes to which a high voltage is applied and between which the gas is flowed. The discharge plasma gas flows down the open quartz flow tube and in to the atmosphere. The main discharge strikes across the narrow gas between the inner and outer electrodes but a secondary discharge occurs down the flow tube in to the plume formed by the flow of plasma gas mixing with the air at the end of the flow tube.

[0147] The gas flow rate used was 1.5 L/m. The power settings were varied to create different levels of plasma excitation and the gas mixes were varied by means of two mass flow controllers. The L*a*b* colour of the strips was measured using a spectrophotometer and the rate of bleach standardised to a measure of time to achieve a change of 2.5 or 5% L*SCI.

[0148] The best results per gas mix/power setting combination are presented.

TABLE-US-00001 Test A1 - Helium based mixes Test Voltage Bleach speed Temperature Ozone NOx sample Gas used kV (mins) (deg C.) (ppb) (ppb) Comments 1 He (control) 7 >120 38 35 25 Very slow 2 He 1% Ar 7 75 28 21 21 Quicker if pulsed 3 He 4% Ar 7 >120 28 27 20 4 He 8% Ar 7 65 29 41 340 He 1% Kr 7 16 40 50 20 5 He 2% Ne 7 9 30 25 210 Fast 6 He 8% Ne 7 9 30 4 130 Fast 7 He 20% Ne 7 18 28 5 85 He (control) 9 20 42 45 120 8 He 1% Kr 9 8 40 80 20 Fast 9 He 2% Kr 9 >120 44 65 16 10 He 1% H2 9 >120 35 4 120 11 He 2% H2 9 >120 36 5 <5 12 He 10% Xe 9 >60 34 35 13 He 20% Xe 9 >60 35 18 14 He 1% N2 9 14 35 17 360 15 He 250 ppm O2 7 <5 16 He 500 ppm O2 7 <5 17 He 2% N2O 7 5 High NOx

[0149] The data show that: [0150] Various additions of inert gases to He can significantly improve the oxidative effectiveness of the plasma beyond that possible with He alone. [0151] Different gas mixes produce significantly different oxidation results. [0152] Different concentrations of a gas mix produce different results and it can be seen that different concentrations work better for different gases. [0153] Kr, O.sub.2 and Ne are the most effective additions with the Ne mix being less sensitive to concentration.

[0154] Part BComparative Testing of Gas Mixes using Saccharomyces cerevisiae as a Model for Trichophyton Rubrum

[0155] The objective was to find whether any of the gas mixes from Part A could exhibit a biocidal effect against a cultured yeast under a variety of conditions.

[0156] The following tests were carried out using a plasma test device with gas flow rates of 1.5 L/min.

[0157] Test B1Qualitative Assessment of Direct Exposure to Agar Plates

[0158] A suspension of S.cerevisiae was prepared by adding colonies from an agar plate to 3 ml of PBS. This was prepared to an optical density of 0.2 measured using the spectrophotometer with PBS only as a blank.

[0159] To obtain an even growth of S. cerevisiae on the surface of the Malt Extract Agar, 200 ul of the 0.20 D suspension was pipetted on to the agar. This was spread evenly around the plate's surface using a plastic spreader.

[0160] The plasma plume was aimed at the centre of the inoculated agar plates for the specified durations and qualitative observations of the fungicidal effect were made following 48 hr incubation.

TABLE-US-00002 Test # Description He/1% Ar 1 10 seconds Very small zone of reduced growth 2 30 seconds Small zone of reduced growth 3 2 minutes Medium zone of inhibition 4 Control - no treatment No inhibition 5 Control - Gas only 2 mins No inhibition

[0161] The data show that: [0162] The gas mix plasmas did exhibit a zone of inhibition proportional to the duration of application. [0163] The gas only control produced no zone of inhibition.

[0164] Test B2Quantitative Assessment of Direct Exposure to Broth Cultures

[0165] Colonies from a plate containing S.cerevisiae were picked off and added to 10 ml of malt extract broth containing ceftazidime to create a broth culture. Microtitre wells containing 30 uL of 1.0 OD concentrated broth incubated for 48 hours were then exposed to plasma for differing time periods.The wells were then rehydrated with PBS, serially diluted and plated out to obtain cell counts.

[0166] Cell counts made before and after plasma treatment from average of 9 individual wells at 10.sup.1 dilution.

TABLE-US-00003 Test # Description He/1% Ar Initial broth >500 1 Control - gas only 5 mins 64 Control - no treatment 34 2 2 mins plasma 29 3 5 mins plasma 0

[0167] Test B3Quantitative Assessment of Exposure to Broth Cultures through Nail

[0168] 40 uL of the same broth culture used above was added to a modified Franz Cell within which a human nail clipping was secured. The Franz cell was inverted to allow the broth to remain in contact with the underside of the nail and the plasma applied for varying durations to the nail surface. The cell was then incubated and washed out using 100 uL of PBS, serially diluted and plated out for colony counting.

[0169] The seal around the edge of the nail meant that any measured reduction in the colony count in the broth would have to be as a result of plasma acting through the nail.

[0170] This test was done by applying plasma for 15 minutes using just the He/1% Ar mix in order to assess nail penetration. Each data point is the average cell count of 3 replicates.

[0171] Cell counts were taken before and after plasma treatment at different broth culture starting concentrations.

TABLE-US-00004 Test # Description Neat 10.sup.1 1 Nail 0.4 mm thick 42 4 2 Nail 0.7 mm thick 30 4 3 Nail 0.5 mm thick 2 0.3 Average across all nails 25 2.8 Control (0.5 mm thick) 390 39

[0172] The data show that: [0173] Over a duration of 15 minutes the He/1% Ar plasma is able to act through varying thicknesses of human nail to reduce the cell count by around 95%.

[0174] Part CComparative Testing of Gas Mixes using Medpharm Ltd Infected Nail Model using Trichophyton Rubruin

[0175] The objective was to apply the successful gas mixes from part B to an industry recognised onychomycosis nail model to identify the most efficacious mix using the actual pathogen responsible for the majority of infections, and to optimise the mix and the application regime to maximise efficacy.

[0176] All of the following tests were carried out by Medpharm Ltd using their infected nail model (ChubTur) whereby full thickness human nail samples are inoculated with spores of Trichophyton Rubrum and incubated for 14 days in a hydrated warm environment to allow the fungus to grow in to the nail. The nail is set in the ChubTur cell apparatus and exposed to various regimes of plasma treatment using different gas mixes.

[0177] Measurements of effectiveness are derived from an ATP assay following 24 hrs incubation. In this model, the amount of luminescence measured is directly proportional to the amount of ATP present, where the level of ATP detected is an indication of the viability of T. Rubrum. Most experiments are based on a sample size of 6.

[0178] Test C1Gas Mix Comparisons

[0179] Through numerous tests it was determined that the maximum result measurable with the model was 95% kill of the organism. Therefore the time that various gas mixes took to achieve this level was assessed alongside the kill level achievable through a 6 minute application.

TABLE-US-00005 Time to achieve 95% kill Kill achieved in 6 Test # Gas used (mins) minutes (%) 1 He/1% Ar 15 82% 2 H2/250 ppm O2 10 90%

[0180] The data shows that: [0181] A number of gas mixes can achieve 95% kill of the fungus through the nail given enough time.

[0182] Test C2Comparisons with Commercial Products

[0183] The aim of the study was to compare the in-vitro efficacy from a single 6 minute application of the various plasmas with single applications of commercial comparators as per the manufacturer's instructions a topical anti-fungal cream and a cold laser device.

TABLE-US-00006 Test # Description Fungal kill achieved 1 He/1% Ar 82% 2 H2/250 ppm O2 90% 4 Loceryl (topical anti-fungal by Galderma) 10% 5 Non-thermal laser 60%

[0184] The data also shows that: [0185] Single doses of plasma from a variety of gas mixes are significantly more effective than single doses of the commercial topical and cold laser comparators. [0186] The most significant advantage over commercial comparators is achieved by the Ar/4% Kr mix.

[0187] Part DCosmetic Bleaching of Hair

[0188] The objective was to apply the successful gas mixes to demonstrate the potential for their use in the cosmetic bleaching of hair.

[0189] Test D1Effect on Melanin

[0190] To examine the effect of plasma on hair colour an initial experiment was carried out to determine whether plasma would have an effect on the primary colour agent in hair, melanin.

[0191] Hydroxyapatite (HAP) disks were stained with melanin (CAS: 8049-97-6) and treated using a gas blend of 500 ppm O2 in He. Incremental 2 minute treatments were applied with the disk colour being measured before and after as above.

[0192] All other experimental set-ups and device variables were as above

[0193] Delta L* colour change of melanin stained HAP disks following rounds of 2 minute plasma treatments.

TABLE-US-00007 Delta L* Round 1 2 3 4 5 9.57 16.20 19.85 23.09 25.23

[0194] The data shows that: [0195] Melanin is highly susceptible to bleaching by plasma.

[0196] Test D2Effect on Human Hair

[0197] Using the same experimental set-up, two samples of human hair, one dark (L*=17, Wella chart 4/07), one light (L*=34, Wella chart 6/43) were plasma treated in 15 minute long sessions and delta L* assessed as above.

[0198] Delta L* colour change of light and dark human hair following rounds of 15 minute plasma treaments were measured and are set out in the table below.

TABLE-US-00008 Delta L* Round 1 2 3 4 5 6 Light 0.63 1.54 0.58 0.14 2.43 2.72 Dark 2.59 5.66 6.75

[0199] The data shows that: [0200] The effect on dark hair is quicker and more pronounced

Further Examples

[0201] A plasma device rig was connected to two different gases and the gas concentration measured by way of two mass flow controllers operated via a computer, as described in the methodology below. The plasma plume was first measured for temperature, ozone and nitrous oxide emissions, and voltage deposition, before attempting to bleach a ParaSure plasma indicator strip. The device head was left at a distance of 10 mm from the strip and the L*a*b* colour was measured at given intervals to a maximum of 1 hour. Results were found for a number of inert gas mixes, in addition to some molecular gas and inert gas mixtures.

[0202] Apparatus: [0203] Plasma Device [0204] Two Alicat Mass Flow Controllers C-10SLPM-D [0205] Alicat USB Bus BB9 [0206] Laptop with FlowVisionMX control software [0207] Konica Minolta Spectrophotometer CM-2600d [0208] Tektronix Oscilloscope TDS2024C [0209] TIM USB Thermal Camera [0210] Fluke Thermometer 52 K/J [0211] 2B Technologies Ozone Monitor 106-L [0212] EnviroTechnology Nitrous Oxide Chemiluminescence Monitor 200E [0213] Ocean Optics UV-NIR Spectrometer HR4000CG [0214] Wet Human Test Model [0215] 1) Select correct gases on mass flow controllers and using the FlowVisionMX control software, select the appropriate gas concentration. [0216] 2) Set up nitrous oxide monitor. Ensure pump is running to draw sample gas through the system and sample tube is a close to the plume as possible. [0217] 3) Set up ozone monitor to record 10 minute averages during plasma treatment. The ozone monitor sample tube should also be placed as close to the plume as possible. [0218] 4) Set up Plasma device with the selected gas mixture using a flow rate of 1.51/min. Let gas flush through the 20-30 mins. [0219] 5) Switch on power to produce plasma, with power set to DC voltage 9.00 kV. [0220] Then measure: [0221] a. Peak to peak voltage on the human test model [0222] b. RMS voltage on the human test model [0223] c. Frequency on the human test model [0224] d. Frequency of the handpiece [0225] 6) After 10 minutes, record the nitrous oxide and ozone average readings. [0226] 7) Set up thermal imaging camera to find the temperature of the plume at the human test model. Allow sufficient time for the reading to stabilise before recording. [0227] 8) Record the temperature at the human test model using the thermometer, ensuring that the thermocouple is not directly in the plume. [0228] 9) Align optical fibre to ensure maximum readings for spectral data and record the spectrum with the electric dark spectrum over 1 second. Save the spectrum in spc format for later analysis. [0229] 10) Repeat 5-9 at 7.00 kV and 5.00 kV. [0230] 11) Repeat 1-10 for all necessary gas concentrations. [0231] 12) After completing the measurement matrix for each gas mixture, select the best two or three gas concentrations for bleach testing. [0232] 13) Calibrate the spectrometer and record the calibration data. [0233] 14) Mark a 3 mm target area on the plasma indicator. [0234] 15) Measure I.,*a*b* of the target using the spectrometer. Take 3 measurements for each sample, rotating sample by 90 degrees each time, Quote the average of these readings. [0235] 16) At 15 minutes, 30 minutes and 60 minutes, repeat 15.

[0236] Colour measurements using a spectrometer to observe *b* values are well known in the art.

[0237] The spectral emissions for each gas concentration were measured to indicate which chemical species were being excited by the plasma plume at each voltage. It was discovered that the main bleaching agent in these tests was singlet Oxygen, although there is a notable bleaching effect that can be attributed to hydroxyl radicals.

[0238] In the Helium with added Argon gas mixtures, it was seen that the proportion of metastable Argon is strongly related to the amount of excited singlet Oxygen but less to the number of hydroxyl radicals. The highest levels of metastable Argon were found at 9.00 kV. There was found to be little relationship between the bleaching agents and metastable Helium.

[0239] A similar relation was found in the Helium/Neon gas mixtures; it was seen that the proportion of metastable Neon is linked to the amount of excited singlet Oxygen and hydroxyl radicals. The highest levels of metastable Neon were again found at 9,00 kV. This trend was not continued in the Argon/Krypton gas mix, as high levels of metastable Krypton led to varying levels of the bleaching agents. There was also a similar correlation with the bleaching gases in this mix and metastable Argon.

[0240] Helium/Xenon also did not fit the general trend, as the Xenon metastable was disproportionately high and did not seem to excite any other products. The limited results gained from Nitrogen gas mixes suggest that they also follow an alternative trend, however due to significant quenching giving such a small sample of data, the true method of bleaching remains unclear. The results from Hydrogen gas mixes show that hydroxyl radicals are the main bleaching agent in the plume. However this is likely due to the increased levels of hydrogen in the plasma itself.

[0241] The effectiveness of bleaching test varied considerably across the different gas mixtures and compositions. In general, the most efficient inert gas mixture was Argon/Krypton. However, it was seen that one particular composition of Helium/Neon was more effective. The least effective gas mixture was Helium/Argon, which was less than a tenth as effective as the Argon/Krypton mix.

[0242] Of the molecular gas mixtures, the most effective was Argon/Hydrogen. The molecular gases performed much worse when partnered with Helium. The Argon/Hydrogen mixtures are much more bleaching than the Helium/Hydrogen mix.

[0243] All percentages and ratios recited herein are by volume, unless otherwise stated.

[0244] The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art, and remain within the scope of the appended claims and their equivalents.