A laser sterilisation apparatus

Abstract

A laser sterilisation apparatus 10 for sterilising an object 40 with a passive layer (42, fig. 1) and a biological contaminant (1, fig. 1) on the passive layer. The apparatus comprises a support 20 fo

Description

TECHNICAL FIELD The present disclosure relates to a laser sterilisation apparatus. Particularly, but not exclusively, the disclosure relates to a laser sterilisation apparatus for sterilising an object with a passive layer and a biological contaminant on the passive layer. Aspects of the disclosure relate to a laser sterilisation apparatus, to a method of sterilising an object, and to a sterilised object. BACKGROUND Sterilisation of surgical stainless-steel instruments is most commonly performed by steam sterilisation in an autoclave apparatus. The steam sterilisation process relies on high temperature steam at pressure which must be sustained for a minimum amount of time as dictated by various standards. Steam sterilisation is both a time-consuming process and utilises a substantial quantity of energy to heat water from liquid to gas. To sterilise using steam sterilisation instruments are typically held at a temperature of 120 degrees Celsius for 30-60 minutes at a pressure of 200 kPa. Reaching this temperature in a pressured steam environment takes time, as too does cooling to allow handling from this higher temperature this lengthens the overall processing time. A typical cycle time from instrument loading through to unloading after steam sterilisation may take around 3 to 6 hours. The present disclosure seeks to overcome or at least mitigate at least some of the problems of the prior art. SUMMARY OF THE DISCLOSURE Aspects and embodiments of the disclosure provide a laser sterilisation apparatus, a method of sterilising an object with a passive layer and a sterilised object as claimed in the appended claims. According to an aspect of the disclosure, there is provided a laser sterilisation apparatus for sterilising an object with a passive layer and a biological contaminant on the passive layer, the apparatus comprising: a support for removable receipt of the object, a controller, and at least one laser source configured to emit optical radiation to the object at a first set of operational parameters for absorption by the biological contaminant and to kill or destroy said biological contaminant, the laser source being controlled by the controller, and wherein the optical radiation configured to be emitted by the laser source has an intensity each second that is below an ablation threshold of the passive layer. The laser sterilisation apparatus enables the sterilisation of an object or surface of an object to kill biological contaminants located on the surface. Advantageously the apparatus in use undertakes the sterilisation of the object without laser ablating the surface of the object (or keeping any laser ablation to a minimum, for example such that virgin material below the passive layer is not revealed). Laser ablation of the object will damage the passive layer which can as a result lower the usable life of the object. For example, removal of the passive layer can reveal virgin material below which may corrode if passivation of the surface under atmospheric conditions is not possible. Moreover, laser ablation causes the removal of material from the surface of the object this can weaken the object especially if multiple laser ablation processes are employed over the useable lifetime of an object. The biological contaminant may be an organism and / or a product of an organism. The biological contaminants may be a potentially harmful organism and / or a product of an organism. Potentially harmful may mean potentially harmful to human or animal health, for example a potentially harmful organism may cause illness. Examples of a potentially harmful organisms include Escherichia coli (E. coli) and Bacillus, subtilis (B. subtilis). A potentially harmful product of an organism may be faecal matter or a toxin produced by an organism. The biological contaminant may be any one or combination of: a pathogen, a bacteria, a virus, a fungus, a fungal spore, a parasite, faecal matter, or a toxin produced by a pathogen. The object may be a medical instrument, or a part of a medical instrument, for example a surgical instrument. The laser sterilisation apparatus has a number of advantages over traditional sterilisation methods. For example, gamma radiation sterilisation requires the use of a sealed plastic 2 covering to cover a medical instrument inside which leads to large quantities of waste, the present laser apparatus does not require a sealed plastic covering but sterilises the surface directly and not through an interstitial component. Another traditional sterilisation method, steam sterilisation, takes a substantial length of time to sterilise a component which can be in the range of 3 to 6 hours, the heating of water to make steam requires a substantial amount of energy. Moreover, the long length of a single cycle time can be particularly onerous where medical equipment is required to be sterilised in a limited time, such as in an emergency surgery situation, or in limited quantities. The intensity may be an average intensity of the optical radiation or a peak intensity of the optical radiation. The peak intensity may be calculated from a: rectangular pulse, Gaussian pulse or sech2 pulse peak power. Optionally, the first set of operational parameters may comprise one or more of: a wavelength, a power level, a beam diameter, a scanning speed, a hatch distance, a focal length, laser frequency, a scan spacing, a scan island size and a scan island pattern. Utilising such operational parameters may enable the operator to tailor the laser to be used with a specific material. Optionally, the at least one laser source is configured to emit a wavelength in the range of 9.6 to 10.6 pm. The use of a wavelength in the range of 9.6 to 10.6 pm may reduce the likelihood of discolouration of the surface of the object, especially where the object may be made of a stainless steel, as compared to shorter wavelength laser beams which could lead to surface discolouration. Optionally, the at least one laser source is a CO2 laser. Utilising a CO2 laser source may provide the wavelength needed. CO2 laser sources may be cost effective compared to other more expensive laser sources. Optionally, wherein the laser source may be further configured to output the optical radiation at a power per area per unit time of 20 to 100 Jcm'2s'1. The optical radiation may be: 20 to 80 Jcm'2s'1, or 30 to 60 Jcm'2s'1, or 40 to 50 Jcm'2s'1, or 42 to 46 Jcm'2s'1, or 43.75 Jcm'2s'1. Optionally, the at least one laser source may have a beam position control device controllable by the controller. Advantageously this may enable the beam to move or scan over the object to sterilise at least a portion of its surface. Optionally, the beam direction control device is any one or combination of: a scanhead, a gantry, a focusing lens, a plurality of lenses, one or more mirrors, and one or more movable mirrors. Optionally, wherein the at least one laser source may comprise an F-theta lens. Advantageously the use of an F-theta lens may provide a laser been which has a flat field focal delivery. Optionally, the laser source may be a pulsed laser or a continuous laser. A pulsed laser may provide greater removal speed of biological contamination on the surface of an object for a first power level as compared to a continuous laser. A pulsed laser reduces the likelihood of heating the underlying material of the object, as a result may reduce the likelihood of recrystallisation or heat affected zones forming adjacent to areas which have been exposed to optical radiation from the laser. A continuous laser may enable finer control of the removal speed and enables more consistent intensity and power of the beam itself as compared to a pulsed laser which by necessity operates by short bursts of power. Optionally, wherein the first set of operational parameters comprises one or more of: a wavelength of 9.3 to 10.6 pm, a power level of 5 to 125 W, a beam diameter of 5.5 mm to 6.5 mm, and a scan speed of 5 mm / s to 2000 mm / s. Optionally, wherein the peak power of the laser is 200 to 500 W. For example, the peak power is 315 W. Optionally, wherein the apparatus may further comprise an object holder for removably retaining an object. By retaining the object in an object holder it may be more securely held in use and prevent or reduce the likelihood of any movement of the object during the sterilisation process. For example, when closing a door to the chamber forcefully which could cause the object to move. Optionally, the apparatus may further comprise a motor configured to move the object holder. By moving the object holder the object can be translated in use to focus the laser beam on different portions of the object without the need to move the laser beam. Alternatively, or optionally both the laser beam and the object may be moved. Optionally, the motor is configured to rotate the object holder. By rotating the object holder and therefore the object the user does not need to take the object and move it manually to expose a second portion of the object for sterilisation after a first portion has been sterilised. Optionally, the apparatus may further comprise a vision system configured to identify one or more of: a first sterilisation area; a second sterilisation area, an object type, and a number of objects to be sterilised. The vision system may be arranged to view at least a portion the object when the object is received in the support. By identifying a first and / or second sterilisation area different operational parameters may be utilised when sterilising different areas of the same object or different areas of two or more different objects. The identification of the object type may enable the apparatus to more quickly determine the type of sterilisational operational parameters to be utilised for that particular object. The identification of the number of objects to be sterilised enables the system to more accurately identify the number of objects which need to be sterilised to reduce the likelihood of objects not being sterilised. According to an additional aspect of the disclosure a method of sterilising an object with a passive layer and a biological contaminant on the passive layer is described. The method, utilising the apparatus of any embodiment of the aspect describing the apparatus, the method comprising the steps of: removably loading the object onto the support, emitting optical radiation using a first set of operational parameters at the object, wherein the optical radiation emitted by the laser source has an intensity each second that is below an ablation threshold of the passive layer, absorption of the optical radiation by the biological contaminant to kill or destroy the biological contaminant. The method enables the removal of biological contaminants from the surface of the object with minimal or no damage to the surface of the object. Optionally, the method may further comprise the steps of: receiving a first material parameters signal comprising materials data relating to the composition of the passive layer; determining in dependence upon the materials data the first set of operational parameters. The object may therefore be sterilised in dependence upon an input signal giving information on the composition of the passive layer and / or the composition of the object. The composition of the passive layer may be determined in dependence upon the composition of the object. Optionally the apparatus further comprises a vision system, and the further steps of: taking a first image of the object, determining a first sterilisation area in dependence upon the first image, and wherein the optical radiation is emitted to the first sterilisation area. By emitting optical radiation to specific areas the sterilisation may be tailored to specific objects, for example areas of objects which are more likely to come into contact with contaminants, e.g. touch points or blades of scalpels or the like. Optionally, the method may further comprise the steps of determining a limited sterilisation area different to the first sterilisation area in dependence upon the first image, and in response to determining the limited sterilisation area determine a limited set of operational parameters different to the first set of operational parameters, and emitting optical radiation using the limited set of operational parameters to the limited sterilisation area. By emitting limited optical radiation to specific areas the sterilisation may be tailored to specific objects, for example areas of objects which are less likely to come into contact with contaminants, e.g. not a touch point or a blades of scalpels or the like. Optionally, the apparatus further comprises an object holder and a motor configured to move the object holder, and the further steps of: removably loading the object in the object holder, after emitting optical radiation across the first sterilisation area using the motor to move the object, take a second image of the object, determine a second sterilisation area in dependence upon the second image, and emit optical radiation using the first set of operational parameters to the second sterilisation area. By utilising a object holder the optical radiation may be emitted to an object directly without the need for it to be manually rotated between sterilisation steps. Optionally, wherein the method further comprises the steps of: receiving a second material parameters signal comprising materials data relating to the composition of a portion of the object that does not have the passive layer; determining in dependence upon the materials data a second set of operational parameters, and emitting optical radiation using a second set of operational parameters at the portion of the object, wherein the optical radiation emitted by the laser source has an intensity each second that is below an ablation threshold of the composition of the second portion. As the method may take into consideration the different materials which make up the object the sterilisation method can be tailored to each material. Optionally, the first set of operational parameters comprise one or more of: a wavelength, a power level, a beam diameter, a scanning speed, a hatch distance, a focal length, a scan spacing, a scan island size and a scan island pattern. According to a further aspect of the disclosure a sterilised object obtained by the method of the aspect describing the method is provided. The object has the advantages as previously described with reference to the apparatus and / or method. Optionally, wherein the sterilised object has a decreased level of biological contaminant compared to the object pre-sterilisation of 99% or more, optionally 99.9% or more, optionally 99.99% or more, optionally 99.999% or more. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a cross-section of an object with a passive layer and a biological contaminant on said passive layer; Figure 2 is a schematic view of a laser sterilisation apparatus for sterilising an object, such as the object of Figure 1, according to an embodiment of the disclosure; Figure 3 is a schematic view of a laser sterilisation apparatus for sterilising an object according to another embodiment, the apparatus having a scanhead and an f-theta lens. The laser field of delivery is focused upon an object, in this case being a stainless steel disc that is supported by a sacrificial plate; Figure 4 is a plan view of the stainless steel disc and sacrificial plate of Figure 3. Figure 4 shows the lines of laser beam travel across the surface of the stainless steel disc and a portion of the sacrificial plate; Figure 5 is a schematic showing the fill line pattern applied to the stainless steel disc and portion of sacrificial plate in Figure 4. Depicted are two laser beam travel lines which partially offset; Figure 6 is a schematic view of a different laser sterilisation apparatus for sterilising an object, such as the object of Figure 1, according to an embodiment of the disclosure; Figure 7 is a schematic view of a controller for controlling the laser sterilisation apparatus of Figure 2 or Figure 3 or Figure 6 in accordance with an embodiment of the disclosure; Figure 8 is a flow chart of a method of sterilising an object with a passive layer and a biological contaminant using the apparatus of Figure 2 or Figure 3 or Figure 6; Figure 9a shows the object of Figure 1 at a first point in time during the method of Figure 8; and Figure 9b shows the object of Figure 1 at a second point in time during a later step of the method of Figure 8. DETAILED DESCRIPTION A laser sterilisation apparatus 10, 100 for sterilising an object 40, 140 with a passive layer 42 and a biological contaminant 1, and a method 200 of sterilising an object 40, 140 according to the disclosure will be described with the aid of Figures 1 to 9b. Figure 1 shows an example of an object 40 in cross-section which has a passive layer 42 which covers the bulk non-passivated material 44. Figure 1 is not shown to scale and the depiction is for the purpose of teaching the disclosure. The object 40, 140 may be a medical instrument, or a part of a medical instrument, for example a surgical instrument. In Figures 2 and 3 the object 40, 140 is depicted as a knife or scalpel, however this is merely an example of one type of object 40, 140 which may be utilised with the present disclosure and is not intended to be limiting. The passive layer 42 of the object 40, 140 shown in Figure 1 may be a coating or outer shield layer of material created by a coating process, the result of a chemical reaction, or produced by the build-up of oxidation when virgin material is exposed to the air. The passive layer is a layer of material which is more corrosion resistant or less readily affected by the environment as compared to the virgin material which lies below it. An example of material and passive layer which the object 40, 140 may comprise may be stainless steel that has a passive layer comprising chromium oxide. The passive layer of chromium oxide may be formed by exposure of a virgin surface of the stainless steel to oxygen in the atmosphere. Alternatively, stainless steel may be immersed in an acid bath to dissolve free iron from the surface of the stainless steel to chemically remove the iron but leaving the chromium intact. The exposed chromium will then react with oxygen in the atmosphere and the result being a uniform surface of the stainless steel with a localised higher proportion of chromium (in wt% or atm%) than the bulk material. The use of acid bath passivation may lead to a thicker and more protective chromium oxide layer than ‘natural’ passivation without the step of removing free iron from the surface of the stainless steel. A stainless-steel object 40, 140 may have been passivated using the methods set out in the passivation standards as set out in ASTM A967 and / or AMS 2700 (or any updated version of either standard). A number of grades of stainless steel are provided in Table 1 below, this list however is not exhaustive and is intended to aid teaching of the present disclosure. The object 40, 140 may be at least partially made up of any material described in Table 1 in combination with other materials, however this list of materials is not intended to be limiting. As can be seen in Figure 1 on the surface of the object 40 there are one or more biological contaminants 1. In the example shown in Figure 1 the biological contaminants 1 are bacteria, however this is purely to aid teaching of the disclosure and is not intended to be limiting. The biological contaminant 1 may be an organism and / or a product of an organism. The biological contaminants may be a potentially harmful organism and / or a product of an organism. Potentially harmful may mean potentially harmful to human or animal health, for example a potentially harmful organism may cause illness. Examples of a potentially harmful organisms include Escherichia coli (E. coli) and Bacillus, subtilis (B. subtilis). A potentially harmful product of an organism may be faecal matter or a toxin produced by an organism. The biological contaminant 1 may be any one or combination of: a pathogen, a bacteria, a virus, a fungus, a fungal spore, a parasite, faecal matter, or a toxin produced by a pathogen. The biological contaminant 1 may become present on the surface of the object 40 during normal use and / or handling of the object 40. For example, when passing the object 40 hand-to-hand a biological contaminant 1 may become deposited on the surface of the object 40 from a person’s skin. Alternatively, the biological contaminant 1 may become deposited on the object 40 during normal use of the object 40, for example, where the object 40 is a scalpel use of the scalpel during a surgical procedure will impart biological contaminants 1 onto its surface. As will be apparent, in order to reuse the object 40 biological contaminants 1 should be destroyed or the presence of biological contamination 1 should be reduced to an acceptable level. An acceptable level may be defined by a standard known in the art or for a particular jurisdiction or an acceptable level may be the full removal of bacterial spores when samples are prepared, cultivated and examined under laboratory conditions with testing compared against positive control samples. Full removal may be defined as destroying or killing bacterial spores of 99% or more, or 99.9% or more, or 99.99% or more or 99.999% or more. As will be apparent to the skilled reader the specific standard recited here may only be suitable for a specific region / country, other jurisdictions may have different standards. The skilled person when utilising the present disclosure would understand that they may need to tailor various process parameters or parameters of the method 200 of using the apparatus as required under their jurisdictional requirements. As such, the recitation of any specific standard or regime to quantify sterilisation herein is not intended to limit the apparatus for use under only one standards regime. Figure 2 shows an example of a laser sterilisation apparatus 10 according to the disclosure which is used to sterilise the object 40. The laser sterilisation apparatus 10 has a support 20 that is used to removable receipt of the object 40, a controller 12, and at least one laser source 30 configured to emit optical radiation, laser beam L, to the object 40. The laser source 30 is controlled by the controller 20. The laser beam L is emitted by the laser source 30 at a first set of operational parameters for absorption by the biological contaminant 1 in order to kill said or destroy biological contaminant 1. The optical radiation L is configured to be emitted by the laser source 30 with an intensity each second that is below an ablation threshold of the passive layer 42. The support 20 may be a sacrificial plate 1020 onto which the object 40 is loaded. The sacrificial plate 1020 may be a consumable produce which may be utilised once or may be reused after it has been sterilised for example as part of a bulk autoclave process or by sterilising using the apparatus 10. Alternatively, the support 20 may be a mesh surface or planar surface. By emitting optical radiation L at an intensity each second that is below the ablation threshold of the passive layer 42 but at a level sufficient to kill or destroy the bacterial contamination 1 the apparatus 10 can be used to sterilise the surface of the object 40 without causing damage to the surface of the object 40. Or, at the very least, minimising damage to the surface of the object 40. The ablation threshold of a material or passive layer of a material may be obtained experimentally by device and methods known in the art for example utilising the method set out in the art. An example of an ablation threshold for some materials is shown below in Table 1: Material Femtosecond Pulse Ablation Threshold, Jem'2 Nanosecond Pulse Ablation Threshold, Jem'2 Stainless Steel (304) 0.15 ±0.03 0.8 ±0.2 Titanium 0.29 Aluminium Alloy 0.61 Table 1: Ablation threshold for different materials The laser source 30 is configured to emit pulsed or continuous optical radiation at a first set of operational parameters. The first set of operational comprise one or more of: a wavelength, a power level, a beam diameter, a scanning speed, a hatch distance, a focal length, a scan spacing, a scan island size and a scan island pattern. The power level may be a maximum power level of the beam as requested by a user, or it may be an average power of the beam where the beam is pulse laser. The beam diameter may be the requested diameter of the beam by the user at the surface of an object 40. The scan speed being the speed the beam L moves, hatch distance being the distance between adjacent tracks of a scan, focal length being the focal length of the beam, scan spacing being the spacing between two scans on an object 40, scan island size and scan island pattern take their normal definitions in the art. The wavelength is preferably a wavelength of 9.6 to 10.6 pm. The inventors have found that light emitted at this wavelength range provides a number of advantages, notably, the wavelength enables the elimination of bacteria and not merely their displacement whilst, at the same time, not damaging the surface of a stainless-steel object nor discolouring it. Whilst not depicted in the example of Figure 2, the laser source 30 may further comprise a beam position control device which is configured to direct the beam L towards a target (the object 40). The beam position control device may be a scanhead, or a gantry, a focusing lens, plurality of lenses, a mirror, a number of mirrors, or any combination thereof. The focusing lenses and / or mirror(s) may be driveable to enable automatic control of the beam L by the controller 12. The controller 12 will be described in more detail below. Where a scanhead or gantry is provided it may comprise one or more focusing lenses within or attached to the scanhead or gantry to enable focusing of the beam L whilst the beam L is being moved. The laser source 30 has an F-theta lens 32 which provides a flat field focal delivery. The F-theta lens 32 may be disposed in the laser source 30 as the last in the line of lenses where there is at least one other lens. The laser source 30 may be a CO2 laser. The CO2 laser may utilise a mixture of CO2 and one or more of nitrogen N2 and helium He to produce a laser beam L. In use the CO2 laser source 30 may be configured to emit optical radiation between 9.6 pm and 10.6 pm, a power level of 25 W or above and a scan speed of 1000 mm / s or slower, and / or a frequency of 40 kHz At this frequency (with the system used), a pulse duration of around 15 ps was achieved whilst the laser was operating in a ‘quasi-CW mode’ with a peak power of 315W. The intensity each second achieved was below the ablation threshold of stainless steel. Moreover, the range of wavelength of light emitted by the CO2 laser is in the ‘far-infrared spectrum’ and is more readily absorbed by organic materials than by metallic materials such as stainless steels. As such, biological contaminants 1 on the surface of an object 40, 140 will be destroyed with little to no damage of the passive layer on which they sit. Neodymium-doped yttrium aluminium garnet lasers (hereinafter Nd:YAG lasers) by comparison use a yttrium aluminium garnet crystal doped with neodymium ions as the laser source. Nd:YAG lasers emit light at 1.064 pm which is lower than the wavelength emittable by a CO2 laser source. Light at 1.064 pm is in the ‘near-infrared spectrum’ (that is closer to the wavelength of visible light than the far-infrared spectrum which is closer to the wavelength of microwaves than visible light in comparison to near-infrared spectrum light). 1.064 pm light is well absorbed by many metals including stainless steel. As such, Nd:YAG lasers are very effective at cutting metallic objects. The use of an Nd:YAG laser described here would not achieve the effect of destroying biological contamination 1 on the surface of an object 40, 140 without damaging the passive layer 42 underlying structure 44 of the object 40, 140. An example of a laser sterilisation apparatus 1000 utilising a CO2 laser source 30 that is configured to emit optical radiation between 9.6 pm and 10.6 pm according to the present disclosure is described in Figures 3, 4 and 5. The laser sterilisation apparatus 1000 comprises a number of the same features of the depiction of Figure 2, as such common features utilise the same feature reference numbers. The depicted apparatus 1000 of Figure 3 comprises a beam position control device 22, in this case a scanhead 22. The apparatus 1000 is a Multiscan (TM) VS setup from LUXINAR that comprises a Luxinar SR-10i 120 W CO2 Laser System (the laser source 30). The laser source 30 is fitted with a Scanlab Scancube 10 from Scanlab GmbH (the scanhead 22). The scanhead 22 is fitted with a 300 mm F-Theta objective lens (lens 32). Table 2 provides a number of parameters which were utilised with apparatus 1000 to sterilise object 1040 shown in Figures 3 to 5. The preparation of object 1040 of the purpose of evaluating the efficacy of apparatus 1000 and parameters in Table will be described in more detail below. The object 1040 in this example is loaded onto support 1020 which is a sacrificial plate 1020. Parameter Value Spot Size 720 pm Theoretical depth of field 20 mm Power level at duty cycle 72 W Scan Speed 1000 mms'1 Wavelength 10.6 pm Pulse Duration 15 ps Laser Frequency 40 kHz Average Power 120 W Spot Diameter 720 pm Duty cycle 0.6 Pulse Energy 3 mJ Peak Power 315 W Pulse Separation 2-400 ps Line Width, W 720 pm Line Offset, O 200 pm Table 2: Process Parameters for use with Apparatus 1000 The intensity each second of the laser pulse may therefore be calculated by dividing the peak power by area traversed by the laser beam each second (spot size multiplied by the 5 scan speed, i.e. 0.00072 m2s'1). Peak intensity each second is therefore 43.75 Jcm'2s'1. As will be understood by the skilled reader, the peak intensities may be theoretical maxima and the energy per unit area may not be imparted to the surface of an object 40, 140, 1040 one-to-one due to reflection or diffraction of optical radiation at the surface. The preparation of the object 1040 and the lab experiment to sterilise objects 1040 will now 10 be described in more detail. The object 1040 is a surgical stainless steel metal disc (316 stainless steel discs with an area of 452.39 mm2). A first set of objects 1040 were exposed to non-pathogenic bacterial contaminants namely Escherichia coli (E. coli) and a second set of objects 1040 were exposed to Bacillus, subtilis (B. subtilis). Prior to exposure with the pathogens the objects 1040 were first autoclaved at 121 °C for 15 minutes to ensure the 15 samples were free from unknown contamination. The bacterial strains were obtained from the bacterial culture stock of Professor Roy’s laboratory at the Department of Materials Science and Engineering, University of Sheffield. Under Class II microbiological safety cabinet, freshly grown single colonies of B. subtilis (spore-forming non-pathogenic bacteria) and E. coli on Luria-Bertani (LB) agar plates were used to inoculate sterile falcon tubes containing 10 mL of LB broth (primary culture) and incubated at 30 °C overnight with 200 revolutions per minute (rpm). The optical densities at 600 nm (OD600) were measured and fresh 20 mL LB broth (secondary culture) was inoculated by adjusting the initial OD600 to 0.1. The cultures were then incubated under the same growth conditions as the primary culture. Under sterile conditions, the objects 1040 were placed in six well plates (one per well) and labelled according. The cultures of E. coli and B. subtilis were independently coated on the surfaces of the first and second set of objects 1040 respectively at equal cell density. The ODs of respective bacterial cultures were adjusted to 1 and 100 pL was pipetted onto the metal disc and carefully spread across the entire surface. The cultures were allowed to air dry on the metal discs in the Class II microbiological safety cabinet for 2 hours. For creation of positive controls, the objects 1040 were coated with the respective cultures but were not subsequently scanned with laser. Negative controls had neither bacterial coating nor laser scanning. Following the drying of the objects 1040 they were loaded onto supports 1020 (the sacrificial plates 1020) as shown in Figure 4. A laser beam L was then emitted at the surface of the object 1040 from apparatus 1000 utilising the parameters of Table 2. Figure 4 shows the beam path P as a series of lines across the object 1040 and a portion of the sacrificial plate 1020. Figure 5 shows the beam path P schematically as a series of lines P which are superimposed onto the object 1040 and a portion of the sacrificial plate 1020. As will be apparent to the skilled reader these lines are ‘imaginary’ and would not be visible in practice but are used to teach the present disclosure. Figure 5 shows a zoomed in view of the beam path P and shows a first path P1 and a second path P2. The two paths P1, P2 partially offset with a line offset O which is given in Table 2. The line width W is given in Table 2 also, as can be seen, the line width W is equal to the spot diameter in the example described by Figures 3 to 5. The first path P1 was created by the laser beam L tracking across the surface of the object 1040 in beam direction T1. The second path P2 was created by the laser beam L tracking across the surface of the object in beam direction T2. T1 and T2 are anti-parallel to each other. After exposing the objects 1040 to optical radiation L from apparatus 1000 using the parameters in Table 2 it was observed that there was no E. coli growth observed when plated immediately after scanning nor after 24 hrs of incubation for the first set of objects 1040. The same result was achieved with respect to the B. subtilis samples and the second set of objects 1040. The experiment was repeated with a second laser source. The second laser source was not a CO2 laser source which outputs a beam of optical radiation at a different wavelength. When the experiment was repeated with this second laser source significant growth of both E. coli and B. subtilis was observed after 24 hours. Moreover, observation of the posttreatment objects 1040 showed the presence of corrosion, e.g. pitting corrosion. The presence of the observed corrosion indicates that surface ablation had occurred resulting in the exposure of virgin material below the passive layer of the object 1040. As a result, the second laser source is not suitable for use in laser sterilisation of medical equipment as not only did it not perform suitably to sterilise the objects 1040 but it also caused damage to the surface of the object 1040. With the aid of Figure 6 another laser sterilisation apparatus 100 will now be described. The laser sterilisation device 100 comprises a number of the same features as the laser sterilisation apparatus 10 of Figure 2 and apparatus 1000 of Figure 3, as such common features are referred to by the same reference numerals. Additional optional features will now be described. As will be apparent to the skilled reader, any of the individual the additional optional features of Figure 6 may be included in the embodiment depicted in Figure 2 without departing from the scope of the disclosure. Figure 6 shows the device 100 which has a chamber 150. The chamber 150 surrounds and encloses a working area or working volume which contains the support 20. The chamber 150 may be made of a material which does not permit optical radiation of the type emitted by laser source 30 therethrough. For example, the chamber 150 may be a metal box with a port for loading and / or unloading an object 40, 140 therein. The chamber 150 may have a window 152 through which the laser beam L is directed. Alternatively, laser source 30 may be located within the chamber 150. In the depicted example of Figure 6 there is a different object 140 located on the support. The object 140 has a first region 142 and a second region 144. The first and second regions 142, 144 are made of two different materials. In the example the object 140 is a knife or scalpel which has a metallic blade with a passive region (first region 142) and a handle connected to the blade made of a second material (second region 144). The second material may be another material from Table 1, or the second material may be any one or combination of: a polymer In this example the support 20 has an object holder 124 for removably holding the object 40, 140. The object holder 40 depicted in Figure 6 is a clamp which retains the object 40, 140 between the jaws of the clamp. This form of object holder 124 is merely for the purpose of teaching the disclosure and is not intended to be limiting. In alternative devices 100 the object holder 124 may be a hook, a peg, a stand, or any other suitable device for holding an object 40, 140. In Figure 6 the object holder 124 is located on a turntable 122 which is driven by a motor (not shown). The motor may be controlled by the controller 12. The motor and turntable 122 enable the object 40, 140 located in the object holder 124 to be turned to expose different surfaces to the laser beam L. In alternative configurations the object holder 124 may be directly, or indirectly, coupled to an output shaft of the motor such that the output shaft of the motor causes the object holder 124 to turn. An indirect coupling may be by means of a gear train or gearbox between the output shaft and object holder 124. The motor may be a stepper motor configured to move in a plurality of discrete steps which may be instructed by the controller 12. The object holder 124 may further comprise a tilt table (not shown) or other such pivot mechanism to pivot the object holder 124 and therefore an object 40, 140 contained therein. By providing a tilt table or pivot mechanism the object 40, 140 located in the object holder 124 to be turned to expose different surfaces to the laser beam L. The combination of tilt table and turntable 122 may enable the object 40, 140 to be moved in a plurality of axes (e.g. x, y and z axes). Figure 6 shows an object holder 124 removably holding a single object 140. However, optionally the object holder 124 may comprise multiple devices for holding objects 40, 140 such that multiple objects may be held by a single object holder 124. Whilst the depicted embodiment shows a single object holder 124 holding a single object 140 the apparatus 100 may comprise more than one object holder 124 or a plurality of object holders 124. Each of the plurality of object holders 124 being configured to retain one object 140 or multiple objects. The device 100 may optionally further comprise a vision system 150 that is connected to the controller 12. The vision system 150 is configured to identify various aspects of the object 40, 140 located on the support 20. The vision system 150 depicted in Figure 6 may be a camera suitable for use in a laser system and able to withstand bright reflections from the laser beam L. The camera may be located on a moveable support enabling the camera to be pointed or positioned facing the object 40, 140 or another point of interest of the device 10 that the user would like to observe. The vision system 150 may be further configured to undertake in process visual confirmation that a surface or area of the object 40, 140 is being sterilised. The apparatus 10, 100 may further comprise an air extraction system such as a fume hood or vacuum system. The air extraction system is fluidly connected to the support 20 and object 40, 140 in use so that any particulates or vaporised matter may be extracted from the apparatus 10, 100 for ease of disposal or collection. As will be apparent to a skilled reader from careful review, the present disclosure is not a ‘laser cleaning device’ within the normal understanding of the phrase. A laser cleaning device of the prior art removes dirt along with a surface layer of an object to reveal virgin material which was covered by the now removed surface. There is also the potential that virgin material located beneath the surface layer is also removed by the laser cleaning device depending upon the penetration depth of the laser into the bulk material. A virgin material in this context is a non-passivated material which has not previously been exposed to the atmosphere. Laser cleaning devices have a power level an order of magnitude greater than the apparatus 10, 100 of the present disclosure and may utilise a pulse duration in the nano-to-femtosecond range. Laser cleaning devices are not suitable for sterilisation of objects 40, 140, not least because they would cause permanent damage to objects 40, 140 such as medical equipment for example by damaging or removing the passive layer 42. A common use of laser cleaning is the removal of rust (an iron oxide) from the surface of an iron alloy or steel component whereby a laser emitting optical radiation greater than the ablation threshold of the rust. This causes the rust to become vaporized. Subsequently the virgin material in such an example will become passivated due to reaction with oxygen in the atmosphere producing a new rust layer (the passive layer) on the surface. As will be apparent the ‘new’ surface level will not be the same as the ‘original’ surface level. As will become clear to the skilled reader, the present disclosure, if used on the same rust covered object, would not remove rust from the surface. Instead, bacterial contamination 1 would be vaporized with minimal or no damage to the rust layer or virgin material below. The controller 12, as shown in the example of Figures 2, 3 and 6 and in more detail in Figure 7, is connected to the laser source 30 in order to control the laser source 30. The controller 12 will be described now in more detail. The controller 12 comprises one or more processors 50 which are configured to control the device 10. The controller system 12 comprises one or more processors 50, represented by dot-dashed line 50 in Figure 7. The processor(s) 50 comprise an input device 52 and an output device 54. The input device 54 is arranged to receive one or more input signals 60, such as a signal containing operational parameters for a sterilisation session or an instruction to carry out a preprogrammed sterilisation session which is retrievable from a memory 59 stored in the controller 12. The output device 54 is arranged to output one or more output signals 70, such as a signal to instruct the laser source 30 to emit optical radiation. The input and output device 52, 54 may be any input / output device as known in the art suitable for the purpose of input and / or output of a signal. For example, the input and / or output device may be a data bus connector. The processor(s) 50 comprise an interface 56, a data processor 58 and a memory 59. The interface 56 comprises the input and output device 52, 54. The interface 56 is electrically connected to the data processor 58 to enable two-way communication of data between the interface 56 and the data processor 58. The data processor 58 is electrically connected to the data storage 59 to enable one or two-way communication between the data storage 59 and the data processor 58. Two-way communication is indicated by the two-headed arrows in Figure 7 between the interface 56 and the data processor 58 for example. One way communication is indicated by a single-headed arrow, for example between the inputs 60 and the input device 52 and between the output device 54 and the outputs 70. The data storage 59 may be a read only memory or a read-writable memory. Where the data storage 59 is a read-writable memory the processor 12 may be configured to write data, such as data relating to an operational parameter. The data storage 59 comprises instructions that when executed by a computer (the controller 12) cause the controller to carry out a method as will be described in more detail below. The controller 12 may comprise: a data processor 58 and / or control circuitry; and / or processor circuitry; and / or at least one application specific integrated circuit (ASIC); and / or at least one field programmable gate array (FPGA); and / or single or multi-processor architectures; and / or sequential / parallel architectures; and / or at least one programmable logic controllers (PLCs); and / or at least one microprocessor; and / or at least one microcontroller; and / or a central processing unit (CPU), to perform the described methods. The controller 12 may include a data storage 59 and / or an associated memory, the memory may be located locally to the controller or remotely. The memory may be a non-volatile flash memory. A method 200 of sterilising an object 40, 140 with a passive layer 42 and a biological contaminant 1 on the passive layer 42, utilising any previously described laser sterilisation apparatus 10, 100 will now be described with the aid of Figures 8, 9a and 9b. The method enables the sterilisation of an object 40, 140 by using a laser beam L which enables the destruction of biological contamination 1 located on the surface of on an object which may be to an acceptable level as set out above. The method 200 comprises step 210 whereby a user, or alternatively an automated object loading system removably loads the object onto the support 20. The support 20 and object 40 may be located in the line of fire of the laser beam L emitable from the laser source 30, alternatively the laser source 30 may be positioned of controlled by means of the beam control device to enable the laser beam L to be targeted at the object 40. Subsequently at step 220 the laser source 30 emits optical radiation (laser beam L) using a first set of operational parameters at the object 40. This step is shown in Figure 9a. The optical radiation emitted by the laser source has an intensity each second that is below an ablation threshold of the passive layer 42. The ablation threshold of the passive layer 42 may optionally be determined in dependence upon the first set of operational parameters in order to set an upper limit of intensity each second threshold that the laser beam L is not to pass. The first set of operational parameters may contain materials parameter data indicative of the material of which the passive layer 42 comprises and / or materials parameter data indicative of the material of which the non-passivated layer 44 is made of. Next at step 230 the optical radiation is absorbed by the biological contaminant 1 to kill or destroy the biological contaminant 1. This is indicated in Figure 9b which follows Figure 9a. In Figure 9a the laser beam L is moving in a beam direction of travel indicated by the arrow v. As can be seen in Figure 9a the beam has not yet reached either of the depicted biological contaminants 1. In the second figure, Figure 9b, the laser beam L has reached and passed through one of the two biological contaminants 1. The laser beam L has killed or destroyed the first biological contaminant 1 to form a destroyed biological contaminant 2 which may be a vapour, dust, particulates or other emission from the vapourised biological contaminant 1. As will be apparent after the biological contaminant 1 is killed it is no longer alive nor able replicate to form new biological contaminants 1. Where the apparatus 10, 100 comprises an air extraction system the destroyed biological contaminant 2 may subsequently be removed from the apparatus 10, 100 by the air extraction system. Optionally, the method 200 may comprise further steps for automated determination of the first set of operational parameters. This is particularly advantageous where the apparatus 10, 100 may be used with a number of different material types as it may enable the apparatus to quickly retrieve or determine suitable operational parameters for that particular material. The following steps may occur before step 210 or between steps 210 and 220, that is at any point prior to the emission of the optical radiation L by the laser source 30. The step comprises receiving a first material parameters signal comprising materials data relating to the composition of the passive layer; and determining in dependence upon the materials data the first set of operational parameters. The method 200 may further comprise the steps of receiving a second material parameters signal comprising materials data relating to the composition of a portion of the object that does not have the passive layer. Receiving a second materials parameter signal may be useful where there are more than one material making up the object 40, 140. Subsequently the method 200 determines in dependence upon the materials data a second set of operational parameters, and then emits optical radiation using the second set of operational parameters at the portion of the object 40, 140, wherein the optical radiation emitted by the laser source has an intensity each second that is below an ablation threshold of the composition of the second portion. Optionally, where the apparatus 10, 100 further comprises a vision system the method 200 may have additional optional steps for determining a first sterilisation area to be sterilised, this may advantageously enable the focus on one area for sterilisation in preference to a second or identify only one area for sterilisation. For example, the first sterilisation area may be determined by segmenting an image into foreground (object 30) and background (support 20). Or alternatively, the first sterilisation area may be an object first region 142. The method 200 may have the following steps which may occur between steps of taking a first image of the object and determining a first sterilisation area in dependence upon the first image, which occurs after step 210 when the object 40, 140 is loaded and prior to step 220. Subsequently step 220 is modified such that the optical radiation L is emitted to the first sterilisation area. In the case where the object 30 is segmented from the support 20, it is ensured that the apparatus 10 is used time and energy efficiently to sterilise only those areas that require sterilisation. Once the area has been determined, the controller 12 may then utilise suitable algorithm to determine a path of the laser beam L to cover the area that has been obtained by the vision system 160 in an efficient manner. Optionally, the method 200 may further comprise additional steps to determine an area for limited sterilisation which can be utilised to limit the intensity of sterilisation in areas which are less likely to have come into contact with a biological contaminant 1. The additional step of determining a limited sterilisation area different to the first sterilisation area may be made in dependence upon the first image. As a result of this determination, the method 200 determines a limited set of operational parameters different to the first set of operational parameters, and then emits optical radiation using the limited set of operational parameters to the limited sterilisation area. Optionally where the apparatus 10, 100 has an object holder 120 and a motor configured to move the object holder, the method 200 may comprise further steps to rotate or move the object 40, 140 in the object holder 120 to expose a second area of the object 40, 140. The method 200 has the further steps of: removably loading the object 40, 140 in the object holder 120, subsequently after emitting optical radiation L across the first sterilisation area using the motor to move the object, then take a second image of the object. After taking the second image determine a second sterilisation area in dependence upon the second image, and emit optical radiation L using the first set of operational parameters or second set of operational parameters or the limited set of operational parameters as appropriate to the second sterilisation area. This process can be repeated multiple times to sterilise the whole object 40, 140, e.g. both sides or a series of rotational slices. A method of determining the ablation threshold is also disclosed. Whilst the operator may set the laser sterilisation apparatus 10, 100, 1000 to emit optical radiation L which is below the ablation threshold of Table 1 the ablation threshold may also be determined by the operator by tailoring one or more of the operational parameters of the laser apparatus 10. Whilst this may not result in a specific value of the ablation threshold per se, it enables a number of operational parameters which can be used in practice by the operator and / or stored in a memory of the controller. For example, the inventors of the present disclosure were able to determine through experimentation that processing a Ferritic 300-grade stainless steel was not ablated using operational parameters of 72 Watts, a scan speed of 1000 mm / s and a spot diameter of 720 pm. Such parameters were able to sterilise the Ferritic 300-grade stainless steel sample. The example given is however not intended to be limiting. As will be apparent, the skilled reader will understand that by careful reading of the present disclosure they will be able to arrive at similar operational parameters for other materials (i.e. other than Ferritic 300-grade stainless steel) which they may wish to use with the laser sterilisation apparatus 10, 100, 1000. For example, the method of determining a laser ablation threshold operational parameter may comprise the steps of: loading a sacrificial disc or plate of a material into the laser sterilisation apparatus 10, 100, 1000. The material may be any one of: a steel, a high carbon steel, a low carbon steel, a stainless steel (including: austenitic, martensitic, ferritic, duplex, precipitation, austenitic-ferritic), titanium and alloy steels, non-ferrous metals and non-ferrous metal alloys. Subsequently emitting optical radiation L from the laser source 30 at utilising a first test set of operational parameters. The operational parameters may be any previously described, e.g. scan speed, power, etc. Then after the emission of optical radiation L has completed the operator may then confirm whether laser ablation has occurred, for example by visual inspection using microscopy equipment or the like. The operator may be able to confirm that no laser ablation has occurred as they may not be able to observe any one of the following features in an area which had been passed over by the optical radiation L: surface discoloration, surface degradation, removal of surface material, pits, trenches, or other such features. Surface discoloration may take the form of regions which have a different colour to adjacent regions which had not been exposed to optical radiation (this may for example be due to the presence of oxides in the area exposed to laser radiation). The step of emitting optical radiation L may optionally be repeated multiple times for a second test set of operational parameters and optionally further through to an nth test set of operational parameters on the sacrificial disc or plate at different locations of the sacrificial disc or plate. As will be apparent the second test set of operational parameters is different to the first set and each subsequent test set would be different to the first or second set. In order to confirm that the first, second, ..., nth test set of operational parameters are sufficient to sterilise the sacrificial plate the operational parameters may be used on sacrificial discs or plates exposed to non-pathogenic bacterial contaminants, for example, Escherichia coli (E. coli) or Bacillus, subtilis (B. subtilis) as is described in more detail with reference to laser sterilisation apparatus 1000. The operational parameters, once confirmed that they meet the requirements for sterilisation as set out above or by other quantification means known within the art, the operational parameters may be utilised in practice by the operator on an object 40, 140 for the purpose of sterilisation. It will be understood that numerous changes may be made within the scope of the present disclosure. For example, alternative paths for the laser beam may be used, such as a first pass of non-overlapping parallel paths P, and a second pass of non-overlapping parallel paths P at a transverse offset and / or angular offset from the first pass. Alternatively, a spiral, circular or other curved path may be used. To provide an audit trail for the sterilisation, the path may be recorded and stored, e.g. in the memory, and the power output of the laser beam L may be periodically checked, e.g. at the start, finish and / or at intermediate points in the process using a suitable sensor (not shown). Rather than using a vision system, the apparatus may store one or more standard shapes of objects to be sterilised and the objects may be positioned in a known location on the support 120 using a suitable object holder 124. The apparatus may comprise two or more laser beams being emitted from different locations (from one or more lasers) to provide suitable coverage for three-dimensional objects instead of, or in addition to, a moveable support. NO. FEATURE L Laser Beam P, P1, P2 Beam Path O Line Offset T1 Path Direction T2 Path Direction v Beam Direction of Travel W Line Width 1 Biological Contaminant 2 Destroyed Biological Contaminant 10, 100, 1000 Laser Sterilisation Apparatus 12 Controller 20, 120, 1020 Support 22 Beam Position Control Device, Scanhead 30 Laser Source 32 Lens 40, 140, 1040 Object 42 Passive Layer 44 Non-Passivated Material 50 Processor 52 Input Device 54 Output Device 56 Interface 5 58 Data processor 59 Memory 60 Input Signal 70 Output Signal 122 Turntable 10 124 Object Holder 142 Object First Region 144 Object Second Region 150 Chamber 152 Window 15 160 Vision System 200 Method 210 Method Step 220 Method Step 230 Method Step 20

Claims

1. A laser sterilisation apparatus for sterilising an object with a passive layer and a biological contaminant on the passive layer, the apparatus comprising:a support for removable receipt of the object,a controller, andat least one laser source configured to emit optical radiation to the object at a first set of operational parameters for absorption by the biological contaminant and to kill or destroy said biological contaminant, the laser source being controlled by the controller, andwherein the optical radiation configured to be emitted by the laser source has an intensity each second that is below an ablation threshold of the passive layer.

2. The apparatus of claim 1, wherein the first set of operational parameters comprise one or more of: a wavelength, a power level, a beam diameter, a scanning speed, a hatch distance, a focal length, laser frequency, a scan spacing, a scan island size and a scan island pattern.

3. The apparatus of claim 1 or 2, wherein the at least one laser source is configured to emit a wavelength in the range of 9.6 to 10.6 pm.

4. The apparatus of any preceding claim, wherein the at least one laser source is a CO2 laser.

5. The apparatus of any preceding claim, wherein the laser source is further configured to output the optical radiation at a power per area per unit time of 20 to 100 Jcm'2s'1.

6. The apparatus of any preceding claim, wherein the at least one laser source has a beam position control device controllable by the controller.

7. The apparatus of claim 6, wherein the beam direction control device is any one or combination of: a scanhead, a gantry, a focusing lens, a plurality of lenses, one or more mirrors, and one or more movable mirrors.

8. The apparatus of any preceding claim, wherein the at least one laser source comprises an F-theta lens.

9. The apparatus of any preceding claim, wherein the laser source is a pulsed laser or a continuous laser.

10. The apparatus of any preceding claim, wherein the first set of operational parameters comprises one or more of: a wavelength of 9.3 to 10.6 pm, a power level of 5 to 125 W, a beam diameter of 5.5 mm to 6.5 mm , and a scan speed of 5 mm / s to 2000 mm / s.

11. The apparatus of any preceding claim, wherein the peak power of the laser is 200 to 500 W.

12. The apparatus of any preceding claim, wherein the apparatus further comprises an object holder for removably retaining an object.

13. The apparatus according to claim 12, further comprising a motor configured to move the object holder.

14. The apparatus according to claim 13, wherein the motor is configured to rotate the object holder.

15. The apparatus of any preceding claim, further comprising a vision system configured to identify one or more of: a first sterilisation area; a second sterilisation area, an object type, and a number of objects to be sterilised.

16. A method of sterilising an object with a passive layer and a biological contaminant on the passive layer, utilising the apparatus of any preceding claim, the method comprising the steps of:removably loading the object onto the support,emitting optical radiation using a first set of operational parameters at the object, wherein the optical radiation emitted by the laser source has an intensity each second that is below an ablation threshold of the passive layer,absorption of the optical radiation by the biological contaminant to kill or destroy the biological contaminant.

17. The method of claim 16 further comprising the steps of:receiving a first material parameters signal comprising materials data relating to the composition of the passive layer;determining in dependence upon the materials data the first set of operational parameters.

18. The method of claim 17, wherein the apparatus further comprises a vision system, and the further steps of:taking a first image of the object,determining a first sterilisation area in dependence upon the first image, and wherein the optical radiation is emitted to the first sterilisation area.

19. The method of claim 18 further comprising the steps of determining a limited sterilisation area different to the first sterilisation area in dependence upon the first image, and in response to determining the limited sterilisation area determine a limited set of operational parameters different to the first set of operational parameters, and emitting optical radiation using the limited set of operational parameters to the limited sterilisation area.

20. The method of any of claims 18 or 19, wherein the apparatus further comprises an object holder and a motor configured to move the object holder, and the further steps of: removably loading the object in the object holder, after emitting optical radiation across the first sterilisation area using the motor to move the object,take a second image of the object,determine a second sterilisation area in dependence upon the second image, and emit optical radiation using the first set of operational parameters to the second sterilisation area.

21. The method of any of claims 17 to 20, further comprising the steps of: receiving a second material parameters signal comprising materials data relating to the composition of a portion of the object that does not have the passive layer;determining in dependence upon the materials data a second set of operational parameters, andemitting optical radiation using a second set of operational parameters at the portion of the object, wherein the optical radiation emitted by the laser source has an intensity each second that is below an ablation threshold of the composition of the second portion.

22. The method of any of claims 16 to 21, wherein the first set of operational parameters comprise one or more of: a wavelength, a power level, a beam diameter, a scanning speed, a hatch distance, a focal length, a scan spacing, a scan island size and a scan island pattern.

23. A sterilised object obtained by the method of any one of claims 16 to 22.

24. The sterilised object of claim 23 wherein the sterilised object has a decreased level of 5 biological contaminant compared to the object pre-sterilisation of 99% or more, optionally 99.9% or more, optionally 99.99% or more, optionally 99.999% or more.s

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