GB2433201A

GB2433201A - Sterilising a surface using portable light energy

Info

Publication number: GB2433201A
Application number: GB0525800A
Authority: GB
Inventors: Christopher Davies
Original assignee: Carglass Luxembourg SARL Zug Branch
Current assignee: Carglass Luxembourg SARL Zug Branch
Priority date: 2005-12-19
Filing date: 2005-12-19
Publication date: 2007-06-20
Also published as: GB0525800D0; WO2007071981A1

Abstract

Apparatus for sterilisation and/or destruction of biological contaminants present on a surface, the apparatus comprising a base unit 10 to which is attached a flexible cable 16 connected at its distal end to an optical assembly or head 18. In use, the optical head is arranged adjacent a surface 20 to be sterilised. The apparatus is then operated to transmit light energy onto the surface to effect sterilisation and/or destruction of biological contaminants present thereon. The light delivered is preferably in the ultra-violet region (200-400nm). The apparatus may include a power supply or a pulser 12 so that the light energy delivered is pulsed according to a predetermined regime. The power supply unit may convert AC mains voltage to high voltage DC (24, Fig. 2). The power supply unit 12 may house a pulse forming network (26, Fig. 2) including a capacitor. The DC output is used to charge the capacitor which remains charged until the user is ready to treat the surface. When the user pulses the optical output, the energy stored in the capacitor is delivered to flashlamp (18, Fig. 2) and converted into optical energy. A method of sterilising a surface comprising arranging the optical assembly adjacent a surface and operating the device to transmit light energy onto the surface is also claimed.

Description

Sterilisation This invention relates to the sterilisation of surfaces

and, in particular, to the sterilisation of surfaces by destroying biological contaminants thereon without damaging or otherwise altering those surfaces.

There are many environments in which surfaces are required to be sterile before certain processes can take place, for example, operating theatres, food preparation areas, and the like. Traditional sterilisation techniques include the use of chemical agents which are applied to the surface to be sterilised, thereby destroying contaminants, such as micro-organisms and bacteria, present thereon and rendering the surface sterile.

However, because such chemical agents are required to be toxic to biological contaminants present on the surfaces required to be sterilised, they are usually also toxic human contact. In any event, many such chemical cleaning agents can have a residual toxicity which is harmful to the environment.

Moreover, there is an emerging range of bacterial organisms which are resistant to the currently available chemical cleaning agents suitable for use in the above-mentioned environments. One such organism is the MRSA micro-organisms which is becoming increasingly common in operating theatre environments.

We have now devised an arrangement which seeks to alleviate the above-mentioned problems, and provides a means of effectively sterilising surfaces without causing surface damage or residual contamination.

Thus, in accordance with a first aspect of the present invention, there is provided the use of portable light energy delivery means to sterilise a surface, such use comprising the steps of: (i) arranging the light energy delivery means adjacent a surface to be sterilised; and (ii) operating the light energy delivery means to transmit light energy onto the surface to be sterilised to effect sterilisation and/or destruction of biological contaminants, such as micro-organisms and bacteria, present on said surface.

The light energy delivered to the biological contaminant(s) can have a photochemical interaction, a photothermal interaction or a combination of both, leading to the sterilisation and/or destruction of the contaminant(s). A photochemical interaction essentially refers to the situation whereby light interacts with the bacterial contaminant to initiate a chemical process which leads to a loss of viability for the organism to survive. An example of this is the breakdown of DNA when exposed to intense ultraviolet optical radiation. A photothermal interaction occurs when the light energy delivered to a biological contaminant produces a temperature rise which is sufficient to cause protein denaturing which leads to cellular death.

The light energy delivered is beneficially of a wavelength from a range between the ultra-violet region to the near infrared region, substantially in the range 200-l500nm, and more preferably of a wavelength from the ultra-violet region (typically substantially in the range 200-400nm) and most preferably substantially in the range 250nm-400nm.

The light energy delivered may comprise a plurality of wavelengths. Such wavelengths are absorbed by the biological contaminants which leads to a combination of photothermal and photochemical interactions and thus a breakdown in the biological material. If sufficient light impinges on the contaminant, no residual trace of viable material remains.

The light energy preferably attenuates/defuses rapidly with distance from the energy delivery means apparatus. This provides for user safety preventing physical damage to the user via accidental discharge, providing the output window of the energy delivery means is spaced by a few centimetres from the user. This contrasts use of other comparable light delivery systems such as laser systems, where the energy density attenuation distance would not be comparable.

The light energy delivered is beneficially pulsed preferably according to a predetermined regime. It may be necessary to direct a plurality of pulses on one section of the surface to be sterilised in order to effect sterilisation and/or destruction of the biological contaminants. Alternatively, a single pulse of light energy delivered may be of sufficient energy to effect the sterilisation and/or destruction. Thus, in accordance with a preferred embodiment of the invention, by using a relatively high intensity pulse of light, at a suitable energy density wavelength spectral range and pulse duration, bacterial contaminants can be selectively destroyed, whereas the intensity and duration of the pulse of light is such that the surface to be sterilised has minimal interaction with the incoming light, thus limiting the potential for damage.

The light energy delivery means is preferably hand-held and positionable relative to the surface to be sterilised manually by a user. This is particularly suitable for sterilising smooth surfaces. However, in another embodiment of the invention, it is envisaged that the light energy delivery means may be incorporated in the head of vacuum cleaner or vacuum cleaner-like arrangement, with a rotary brush progressively pulling sections of the pile of, for example, a carpet upwards and the light energy delivery means delivering a pulse of light energy to each section of the carpet to destroy organisms such as dust mites, fleas and the like.

The energy delivery means may comprise electrical gas discharge apparatus, which is preferably controlled to limit the pulse rate and/or duration of the light pulse.

In a preferred embodiment the operation of the gas discharge apparatus is controlled by: (i) charging a capacitor arrangement; (ii) initiating a trigger pulse to discharge the capacitor arrangement; and (iii) discharging the capacitor arrangement through an inductor to the gas discharge apparatus.

Also in accordance with the present invention, there is provided apparatus for sterilisation and/or destruction of biological contaminants present on a surface, the apparatus comprising portable light energy delivery means arrangeable adjacent the surface, and operable to transmit ultra-violet light energy onto the surface to effect sterilisation and/or destruction of biological contaminants present thereon.

The light energy delivered is beneficially of a wavelength substantially in the range 200-400nm, and more preferably 250 -4 00 nm.

The apparatus is preferably controllable to deliver the light energy in the form of a pulse of light, and preferably includes means to adjust and/or limit the pulse repetition rate of successive light pulse events, and/or the duration of a light pulse event, and/or the intensity of the light delivered.

The light energy delivery means preferably includes a manual trigger for initiating a light pulse when the delivery head is positioned to the user's satisfaction.

Means may be provided for selectively adjusting the intensity of the light delivered.

The light energy delivery means preferably comprises electrical gas discharge device which preferably includes a light emitted discharge tube, or more preferably a pair of light emitting discharge tubes arranged in side by side relationship.

The apparatus preferably includes a pulse forming network having a capacitor and inductor arrangement in which the capacitor discharges through the inductor to drive the electrical gas discharge apparatus to produce a light pulse, and beneficially includes a trigger network for initiating the capacitor of the pulse forming network to discharge.

The apparatus preferably includes a reflector arranged to direct emitted light in a predetermined direction.

A preferred embodiment of the apparatus comprises: (i) a light energy delivery head including an electrically operable light emitting element; (ii) a base unit remote from the delivery head, the base unit including electrical power supply for the light emitting element of the delivery heads; and (iii) a flexible umbilical extending between the base unit and the delivery head permitting connection of the delivery head to the base unit.

The light emitting element of the delivery head preferably comprises an electrical gas discharge light emitting device, the base unit including an electrical power arrangement having a capacitor for discharging through the electrical gas discharge light emitting device in the head via the umbilical.

An exemplary embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic block diagram showing generally an exemplary embodiment of apparatus suitable for use in the performance of the present invention; Figure 2 is a schematic block diagram showing more specifically an exemplary embodiment of apparatus suitable for use in the performance of the present invention; Figure 3 is a circuit diagram of an exemplary embodiment of a pulse forming network suitable for use in the apparatus of Figure 2; Figure 4 is a graph showing the variation in light output for a typical flashlamp when pulsed at two different energy levels; Figure 5 is a graph showing the typical spectral transmission levels of five common flashlamp envelope materials; and Figure 6 is a schematic diagram of a reflector arrangement for optimising the collection of light from a flashlamp.

Referring to Figure 1 of the drawings, in general, an exemplary embodiment of apparatus suitable for use in the performance of the present invention comprises a base unit in which is housed a power supply 12 and a control unit 14. Attached to the base unit 10 is a flexible cable 16 connected at its distal end to an optical assembly or head 18. In use, the optical head 18 is arranged adjacent a surface 20 (or part of a surface) to be sterilised, and is then operated to transmit light energy onto the surface 20 to effect sterilisation and/or destruction of biological contaminants present thereon.

Mains electricity 22 is supplied to the base unit 10 and the power supply 12 converts the AC mains voltage to high voltage DC 24. Referring to Figure 2 of the drawings, the power supply unit 12 also houses a pulse forming network 26 including a capacitor. The high voltage DC output is used to charge the capacitor for storage of electrical energy.

The capacitor remains charged until an operator or user is ready to treat a surface. When the operator pulses or triggers the optical output, the energy stored in the capacitor is delivered to the flashlamp 18 through a suitable high voltage switch 28. The electrical energy is converted by the flashlamp 18 into optical energy, the duration and intensity of the optical pulse being determined by the amount of energy stored in the capacitor and the rate of discharge.

Referring to Figure 3 of the drawings, a typical pulse forming network comprises a capacitor 30 -inductor 32 network configured such that the values of capacitance and inductance regulate the duration and intensity of the electrical pulse supplied to the flashlamp 18. Table 1 gives details of typical parameters of components suitable for use in pulse forming network 26.

Parameter Value Unit Capacitance (C) 1000 /AFarads Charge Voltage (V) 1500 Volts Stored Energy (J)= CV2 1125 Joules Inductance (L) 300,uHenrys Pulse Duration(T)=3(LC)' 1.64 Milliseconds Table 1: Pulse Forming Network Typical Values The wavelength distribution of light from the flashlamps is governed by the physical properties of the flashlamp 18 and the amount and duration of the electrical pulse supplied to it. Figure 4 shows the variation in light output for a typical flashlamp when pulsed at 2 different energy levels.

The key physical properties of the flashlamp to consider are gas type, typically Krypton or Xenon, the gas fill pressure, normally in the range of 100-1000 Torr, and the physical dimensions of the lamp.

A key factor to consider when selecting a suitable flashlamp is the glass type used in the construction in the lamp envelope. Typically, the wavelength range produced by the flashlamp covers the ultra-violet to the infra-red region of the spectrum. By choosing suitable glass envelope types, certain wavelength ranges can be filtered by the envelope. For the application described, typical materials include Clear Fused Quartz which transmits wavelengths from 200nm to 400nm, and UV absorbing Titanium doped Quartz which can be used to filter out wavelengths below 250nm, this type of glass being suitable for filtering out wavelengths that can produce Ozone when pulsed with sufficient intensity in air. Figure 5 shows the typical spectral transmission of common flashlamp envelope materials, and Table 2 details typical flashlamp parameters.

Parameter Value Unit Arc Length 50 mm Lamp Bore 7 mm Gas Type Xenon Gas Fill Pressure 450 Torr Envelope Type Titanium Doped Quartz Table 2: Typical Flashlamp Parameters The light output from the flashlamp may be directed to the surface to be sterilised via a reflector and or optical arrangement designed to optimise the collection of the light, as shown in Figure 6. The light from the flashlamp 18 emerges in a radial direction, for optimum efficiency, the light emitted in the area of the lamp 18 facing away from the treatment surface 20 is reflected (by reflector 34) towards the treatment surface 20. The reflector material is such that it is capable of reflecting wavelengths in the stated ranges. The energy density delivered per unit area is dependent upon the aperture area and the total delivered energy, and typical optical output parameters are given in Table 3.

Parameter Value Unit Aperture Length (L) 50 mm Aperture Width (W) 20 mm Area (LxW) 10 cm2 Total Electrical Energy (E) 1125 Joules Electrical to Optical 50 % Conversion Efficiency Total Optical Energy (Eo) 562.5 Joules Optical Energy Density 56.25 Joules per cm2 Table 3: Typical Optical Output Parameters An optional focusing element 36 can be used to increase the intensity of the light impacting on the treatment surface by focusing the incoming light to a smaller area. This can also be used to alter the distance from the reflector 34 to the treatment surface 20. If the device is used without the focusing element 36, it is preferable that a window is placed at the exit of the reflector 34 to protect the reflector 34 or flashlamp 18 from contamination or damage.

Additionally, either a vacuum or air purge system (not shown) can be incorporated into the optical head to prevent debris from impinging on the optical aperture.

An embodiment of the present invention has been described above by way of example only. It will be apparent to persons skilled in the art that modifications and variations can be made without departing from the scope of the invention.

Claims

CLAIMS: 1. A method of sterilising a surface using portable light

energy delivery means, the method comprising the steps of: i) arranging the light energy delivery means adjacent a surface to be sterilised; and ii) operating the light energy delivery means to transmit light energy onto the surface to be sterilised to effect sterilisation and/or destruction of biological contaminants, such as micro-organisms and bacteria, present on said surface.

2. A method according to claim 1, wherein the light energy delivered to biological contaminant(s) on the surface has a photochemical interaction.

3. A method according to claim 1 or claim 2, wherein the light energy delivered to biological contaminant(s) on the surface has a photothermal interaction.

4. A method according to any preceding claim, wherein the light energy delivered is of a wavelength from a range between the ultra-violet region to the near infrared region, substantially in the range 200-l500nm.

5. A method according to claim 4, wherein the wavelength delivered is in the ultra-violet region (typically substantially in the range 200-400nm) 6. A method according to any preceding claim, wherein the light energy delivered comprises a plurality of wavelengths.

7. A method according to any preceding claim, wherein the light energy delivered attenuates/defuses rapidly with distance from the energy delivery means.

8. A method according to any preceding claim, wherein the light energy delivered is pulsed according to a predetermined regime.

9. A method according to any preceding claim, wherein light energy parameters are tailored to provide a relatively high intensity pulse of light, at a suitable energy density wavelength spectral range and pulse duration, to selectively impair or destroy bacterial contaminants, whereas the intensity and duration of the pulse of light is such that the surface to be sterilised has minimal interaction with the incoming light, thus limiting the potential for damage.

10. A method according to any preceding claim, wherein the light energy delivery means is hand-held and positionable manually by a user relative to the surface to be sterilised.

11. A method according to any preceding claim, wherein the energy delivery means comprises electrical gas discharge apparatus.

12. A method according to claim 11, controlled to limit the pulse rate and/or duration of the light pulse.

13. Apparatus for sterilisation and/or destruction of biological contaminants present on a surface, the apparatus comprising portable light energy delivery means arrangeable adjacent the surface, and operable to transmit light energy onto the surface to effect sterilisation and/or destruction of biological contaminants present thereon.

14. Apparatus according to claim 13, wherein the light energy delivered is of a wavelength substantially in the range 200-400nm.

15. Apparatus according to claim 13 or claim 14, wherein the apparatus is controllable to deliver the light energy in the form of a pulse of light (pulse event) 16. Apparatus according to any of claims 13 to 15, wherein the apparatus includes means to adjust and/or limit the pulse repetition rate of successive light pulse events, and/or the duration of a light pulse event, and/or the intensity of the light delivered.

17. Apparatus according to any of claims 13 to 16, wherein the light energy delivery means includes a manual trigger for initiating light delivery when the delivery head is positioned to the user's satisfaction.

18. Apparatus according to any of claims 13 to 17, wherein means is provided for selectively adjusting the intensity of the light delivered.

19. Apparatus according to any of claims 13 to 18, wherein the light energy delivery means comprises electrical gas discharge device.

20. Apparatus according to any of claims 13 to 19, wherein the apparatus includes a reflector arranged to direct emitted light in a predetermined direction.

21. Apparatus according to any of claims 13 to 20, wherein the apparatus comprises: i) a light energy delivery head including an electrically operable light emitting element; ii) a base unit remote from the delivery head, the base unit including electrical power supply for the light emitting element of the delivery head; and iii) a flexible umbilical extending between the base unit and the delivery head permitting connection of the delivery head to the base unit.

22. A method substantially as herein described with reference to the accompanying drawings.

23. Apparatus substantially as herein described with reference to the accompanying drawings.