WO2022033968A1

WO2022033968A1 - Methods and apparatus for generating gas mixtures using an electromagnetic radiation beam

Info

Publication number: WO2022033968A1
Application number: PCT/EP2021/071976
Authority: WO
Inventors: Harald Philipp
Original assignee: Harald Philipp
Priority date: 2020-08-14
Filing date: 2021-08-06
Publication date: 2022-02-17

Abstract

A carrier and an apparatus for use with the carrier (101). The carrier (101) contains one or more substances in a layer (105) formed on a substrate (103) which are retained bound to the carrier (101) in ambient conditions, but cause emission of a trace gas when locally irradiated with a beam (115) from an electromagnetic radiation source (111) that is part of the apparatus. The beam (115) transforms the substance locally to cause the trace gas to be emitted in a plume (117). The apparatus scans the beam (115) along a set path over the carrier (101) to controllably release amounts of the trace gas. The apparatus includes a flow generator that causes a transport gas (121) to flow past the carrier (101) so that when the trace gas is emitted it is conveyed away mixed in the transport gas.

Description

TITLE OF THE INVENTION

METHODS AND APPARATUS FOR GENERATING GAS MIXTURES USING AN ELECTROMAGNETIC RADIATION BEAM

FIELD OF THE INVENTION

[001] The present disclosure relates to methods and apparatus for generating gas mixtures or particulate aerosols within a transport gas such as air.

BACKGROUND

[002] A common method of storing a substance that is to be released as a gas is to use a pressure vessel (bottle, tank etc.). This is widely used for industrial gases, e.g. inert gases, synthetic air, hydrogen, oxygen etc. as well as for hydrocarbon fuels, such as butane, propane etc. The substance to be emitted as a gas is stored under pressure either with the substance in gaseous form or under high enough pressure for the substance to be liquified. Gas is released from the pressure vessel through an outlet conduit under control of associated pressure regulators and pressure valves.

[003] A gas production and emission method is generation of the gas through a chemical reaction of precursor molecules or elements. For example, US9649514B2 reacts sodium chlorate and iron at high temperature in an exothermic reaction to generate oxygen as well as byproducts of sodium chloride and iron monoxide.

[004] Another gas production and emission method is generation of the gas through decomposition. For example, US2004051535A1 discloses decomposition of a compound by oxidation, reduction or photolysis. It is also known that H2O2 readily decomposes into H2O and O2 spontaneously and especially when exposed to light.

[005] Another gas production and emission method is heat-driven sublimation of a bulk material (e.g. US 2015/083571 Al).

BRIEF SUMMARY OF THE INVENTION

[006] According to one aspect of the disclosure there is provided an apparatus for emitting a gas or particulates, the apparatus comprising: a holder configured to removably hold a carrier containing at least one substance, which responsive to the carrier being locally irradiated with an electromagnetic radiation beam causes the carrier to emit a trace gas or particulates; an electromagnetic radiation source operable to output an electromagnetic radiation beam; a scanning mechanism operable to direct the electromagnetic radiation beam onto a carrier held in the holder and thereby locally irradiate a location on the carrier sufficiently to emit the trace gas or the particulates; a flow generator operable to cause a transport gas to flow past a carrier held in the holder so that when the trace gas or particulates are emitted from the carrier they are conveyed away in the transport gas as a mixture of the transport gas and the trace gas or as an aerosol in which the particulates are in suspension in the transport gas; and a controller configured to control the electromagnetic radiation source and the scanning mechanism so that the beam is scanned to follow a path over the carrier, thereby to emit the trace gas or particulates into the transport gas at a controlled rate.

[007] According to another aspect of the disclosure there is provided a method of emitting a gas or particulates comprising: providing a carrier containing at least one substance, which responsive to the carrier being locally irradiated with an electromagnetic radiation beam causes the carrier to emit a trace gas or particulates; causing a transport gas to flow past the carrier so that when the trace gas or the particulates are emitted from the carrier they are conveyed away in the transport gas as a mixture of the transport gas and the trace gas or as an aerosol in which the particulates are in suspension in the transport gas; directing an electromagnetic beam onto the carrier to locally irradiate a location on the carrier sufficiently to emit the trace gas or the particulates; and scanning the electromagnetic beam to follow a path over the carrier, thereby to emit the trace gas or the particulates into the transport gas at a controlled rate.

[008] According to another aspect of the disclosure there is provided a carrier for use in combination with the above-described apparatus. The carrier serves as a store for at least one substance capable of producing a trace gas or particulates. The carrier comprises a support to which is bound at least one substance for producing a gas or particulates, wherein the at least one substance is retained bound to the support in ambient conditions, e.g. at an ambient temperature range up to at least 40°C, and in response to being exposed to an electromagnetic radiation beam to locally irradiate a location on the carrier emits the trace gas or the particulates.

[009] Further aspects of the disclosure relate to the above-defined apparatus adapted for use with the above-defined carrier, to a combination of the apparatus and one or more of the carriers and to the apparatus loaded with the carrier.

[0010] The path followed by the electromagnetic beam over the carrier may alternatively be considered to be a track on the carrier that the beam has already followed and/or is intended to follow in the future under control of the controller.

[0011] In the above-defined apparatus, the controller may be configured to record what portion of the path has already been followed over any given carrier that is loaded into the apparatus. In particular, the controller may be configured to output a signal to cause removal of a carrier held in the apparatus when the path has been followed completely or nearly completely. The output signal may be transmitted by at least one of: a display indicator; a sound emitter; and a data transmitter.

[0012] In the above-defined apparatus, the electromagnetic radiation source may be a laser.

[0013] Beam-shaping optics may be provided to bring the electromagnetic radiation beam into an elongate cross-section for irradiating the carrier. The elongate cross-section has major axis and a minor axis and the major axis can be aligned transverse to at least most of the path, with the minor axis therefore aligned with at least most of the path.

[0014] In some embodiments, the scanning mechanism consists of a single linear drive assembly for moving the electromagnetic radiation beam relative to a carrier held in the holder along a linear axis. Such a scanning mechanism is optimal for embodiments in which the controller is configured to describe the path as a line.

[0015] In other embodiments, the scanning mechanism comprises first and second drive assemblies for moving the electromagnetic radiation beam relative to a carrier held in the holder along a linear radial axis and a rotational axis. Such a scanning mechanism is optimal for embodiments in which the controller is configured to describe the path as a spiral. For example, the coordinate system may be a 2D polar coordinate system for describing a spiral over a rotating disc-shaped carrier.

[0016] In other embodiments, the scanning mechanism comprises first and second drive assemblies for moving the electromagnetic radiation beam relative to a carrier held in the holder along first and second linear axes that are transverse to each other. Such a scanning mechanism is optimal for embodiments in which the controller is configured to describe the path as a serpentine or otherwise with a path composed principally of linear sections. For example, the first and second linear axes may be orthogonal to each other in a Cartesian coordinate system for describing a serpentine over an arbitrarily shaped flat carrier, such as a rectangular carrier.

[0017] The apparatus may further comprise a sensor configured and arranged to measure concentration of the trace gas or particulates emitted from the carrier. The sensor is operable to supply a sensor signal indicative of the concentration to the controller. The controller is configured to control the electromagnetic radiation source, e.g. by adjusting its output power, and/or the scanning mechanism, e.g. by adjusting the speed of beam scanning, responsive to the sensor signal so as to maintain the concentration of the trace gas or particulates at a desired level.

[0018] For trace gas emission in some embodiments, the substance is a solid or liquid form of the trace gas species to be emitted. For trace gas emission in other embodiments, the substance or substances may produce the trace gas as a reaction product in a chemical reaction. Specifically, the carrier may include two or more of said substances which are precursors of a chemical reaction which has the trace gas as a reaction product. The chemical reaction may be endothermic and thus activated by the local irradiation locally heating the carrier. If air is used as the transport gas, the chemical reaction may involve oxygen present in the air as a reactant to combine with at least one substance on the carrier as the other reactant(s). The at least one substance may emit an aroma compound as the trace gas.

[0019] For particulate emission, one particulate type of interest for an aerosol is a metal which has disinfection properties. The metal may be silver, zinc, copper or bismuth. The at least one substance then comprises a metal for emitting metal particulates as the particulates. For particulate release, local heating caused by the local irradiation may be used to ablate the substance from the carrier as particulates.

[0020] It is also possible for the carrier to be designed to emit more than one trace gas or more than one kind of particulates, or a combination of trace gas and particulates, through inclusion of multiple substances or multiple groups of substances for each trace gas and each particulate type.

[0021] For the carrier, one type of trace gas of interest is halogens, in particular for use in disinfection. For example, the at least one substance may comprise a halogen selected from the group iodine, chlorine and bromine for emitting a halogen gas as the trace gas. In particular, the at least one substance may comprise iodine for emitting iodine gas as the trace gas. The iodine may be provided by the at least one substance being molecular iodine (I2) or including iodine as a dissociable part of a complex. If molecular iodine is used, this may be deposited on a substrate as a coating. The deposition process may be sublimation and condensation of gaseous I2 or the application of a liquid solution containing iodine, the solvent being evaporated away to leave the solute, I2, behind. One solvent suitable for this purpose for example is ethanol. If the molecular iodine is in pure crystal form, then it is necessary to cover the crystalline molecular iodine with a protective barrier to prevent it from sublimating prior to use, given that crystalline molecular iodine readily sublimates at room temperature. The protective barrier may be provided by a protective layer or by microencapsulation. An alternative is to dissolve molecular iodine into a suitable host, such as paraffin wax or polyethylene; the resulting solid solution when heated melts and readily emits sublimated iodine from the surface. An alternative to using molecular iodine is to include the iodine as a dissociable part of a complex. As an example, iodophores such as povidone-iodine provide a more stable yet still inexpensive alternative to molecular iodine, that readily gives up I2 when irradiated with an electromagnetic radiation beam. Another example provides the iodine in a complex which dissociates when irradiated with electromagnetic radiation; an example is the chemical diiodomethane, which dissociates into iodine when exposed to intense light. Another possibility is to use dissociable iodine complexes, such as amyloseiodine, and cellulose-iodine, which like iodophores weakly bind I2 and release the I2 again upon heating. The iodine may also be bound to a binder material for adhesion and concentration control.

[0022] The support may comprise a substrate and the at least one substance is present in a layer arranged on the substrate. The support may have a porous structure providing pores that are filled with the at least one substance. In some embodiments, the porous structure is provided by an aerogel. In some embodiments, the porous structure is provided by expanded PTFE.

[0023] The at least one substance may be present as solid particles or liquid droplets microencapsulated in microcapsules. The microcapsules are configured to release the at least one substance when irradiated by the electromagnetic radiation beam. Microencapsulation is for example a suitable approach in use cases that are based on storing a solid or liquid substance on the carrier that sublimates or evaporates to a gaseous form of the same substance. This is the case for solid or liquid substances that spontaneously sublimate or evaporate in ambient conditions as well as for cases in which the solid or liquid substance is stable in ambient conditions and the phase change to gas is induced by the local irradiation. For a substance that spontaneously sublimates in ambient conditions, the microcapsules thus serve to bind the substance to the support in ambient conditions, and the local irradiation acts to disrupt the thin film coating of the microcapsules, e.g. by rupturing. [0024] The carrier comprises a support to which is bound at least one substance for producing a gas or particulates, wherein the at least one substance is retained bound to the support in ambient conditions

[0025] For structural rigidity, the carrier may include a frame, such as a ring-shaped frame, that is arranged to hold the support. The carrier may further comprise a protective layer arranged to provide a barrier between the at least one substance and the surroundings of the carrier.

[0026] A given apparatus will be designed to be used with a particular physical format of carrier. A wide variety of carrier formats are possible. Suitable formats include a strip intended to be scanned uniaxially, a plate intended to be scanned in two dimensions (e.g. a rectangular plate), a rotatable drum (e.g. a cylindrical drum), and a rotatable disc (e.g. a circular disc). Moreover, the substance may be provided on one side of the substrate or on both sides. Specifically, the carrier may have a physical format selected from the group: an elongate strip, a rectangular plate, a rotatable drum and a rotatable disc. The physical format may be such that the support defines first and second surfaces on both of which are present the at least one substance. The physical format may be such that the support defines at least a first surface on which is present a plurality of different ones of the at least one substance, the substances being arranged on the first surface such that they form a plurality of separate surface regions, each with a different substance or combination of substances.

[0027] The proposed design approach can be used in a wide variety of use cases, including by way of example only:

• Halogens such as iodine are of interest for disinfecting enclosed spaces or specific target objects or surfaces.

• Metal particulate aerosols such as silver are of interest for disinfecting enclosed spaces or specific target objects or surfaces.

• Aroma compounds are of interest for releasing a fragrance and also for releasing as an odorizer when released from the carrier in combination with an odorless trace gas or particulate type. Example aroma compounds include: (R)-Limonene - orange scent; geranial - lemon scent; (E)-beta-ocimene = Lilac; Eucalyptol (Eucalyptus); lavender spike oil (Lavender scent); Citronella oil; Geraniol (Rose scent, also works as a mosquito repellent).

Pheromones are of interest for controlling insect behavior, e.g. for beekeeping. • DEET (N,N-diethyl-m-toluamide), ethyl butylacetylaminopropionate and dimethyl carbate are of interest as insect repellants.

• Natural oils are of interest as insect repellants, e.g. citronella oil or the essential oil of lemon eucalyptus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In the following, the present invention will further be described by way of example only with reference to exemplary embodiments illustrated in the figures.

Figures 1 to 11 are schematic views of different example carriers together with associated electromagnetic radiation sources.

Figure 12 is a schematic plan view of an example apparatus loaded with a rectangular carrier as shown in Figure 7.

Figures 13a and 13b are schematic plan and side section views of an example apparatus loaded with a circular disc carrier as shown in Figures 9a & 9b. Figure 14 shows an example electromagnetic radiation beam emitting unit.

Figure 15 is a schematic plan view of an example apparatus loaded with a circular disc carrier as shown in Figures 9a & 9b.

DETAILED DESCRIPTION

[0029] In the following detailed description, for purposes of explanation and not limitation, specific details are set forth in order to provide a better understanding of the present disclosure. It will be apparent to one skilled in the art that the present disclosure may be practiced in other embodiments that depart from these specific details.

[0030] Certain terms used in this disclosure are defined as follows:

[0031] Ambient Conditions: Normal ranges of temperature and pressure that exist in a range of climatic conditions which vary with latitude and season, including temperatures which may be as high as 40°C, 50°C or 55°C.

[0032] Aroma Compound: A chemical compound that in gaseous form can be sensed by the sense of smell, in particular in the context of the present disclosure a chemical compound that can be emitted as the trace gas to provide an aroma. The aroma may be pleasant, i.e. a fragrance and/or may also serve as an odorizer to add a detectable odor to an odorless substance also emitted into the transport gas as a further trace gas or as particulates.

[0033] Complex: A reversible association of molecules, atoms, or ions, in particular in the context of the present disclosure for the purpose of binding one or more atomic species to a larger molecule in a manner that allows the complex to dissociate and emit the one or more atomic species to produce a gas or particulates.

[0034] Confined Space: A volume with restricted exchange of air, as produced by limited access through doors, open doorways, passageways or windows, such as: a room, stairwell or atrium of a building or the interior of a domestic trailer (residential static caravan); the passenger space of a vehicle such as a car, a recreational vehicle (motorhome), a bus, a train or an airplane; a hothouse (greenhouse, glasshouse) for growing plants; a cargo space such as a ship cargo hold, the interior of a shipping container, the storage box of a truck or van; the interior of a tent.

[0035] Particulates: Particles released from the carrier when the substance or substances are irradiated.

[0036] Spiral: A continuous and widening (or tightening) curve, including a curve of increasing diameter from a central point in 2D and a helix about an axis in 3D. In the context of the present disclosure, a spiral in 2D includes one with stepwise increases (or decreases) in diameter. [0037] Substance: A single substance or combination of substances which are bound to a carrier stably in ambient conditions and which, singly or in combination, cause release of a gas (the trace gas) or of particulates from the carrier when the carrier is irradiated with an electromagnetic radiation beam. The chemical or physical mechanism by which the substance or substances cause release of the gas or particulates include: sublimation, evaporation, ablation, chemical reaction, dissociation (e.g. photodissociation) and chemical decomposition.

[0038] Trace Gas: The gas released from the carrier when the carrier is irradiated.

[0039] Transport Gas: The gas that flows past the carrier in use and takes up the trace gas or the particulates to form either a gas mixture of the transport gas and trace gas, or an aerosol of the transport gas respectively. The transport gas may, for example, be air (ambient air or synthetic air) or an inert gas such as nitrogen, helium or argon.

[0040] In the following detailed description, 'substance' is generally referred to in the singular for linguistic simplicity unless we are specifically discussing examples which require multiple substances, such as when two or more substances are precursors which combine in a chemical reaction to produce the trace gas as a reaction product.

[0041] Figure 1 is a schematic perspective view of an example substance carrier 101 which stores one or more substances which singly or in combination when irradiated cause emission of a trace gas or a particulate aerosol. The carrier 101 is intended for use in combination with an electromagnetic radiation source 111 (hereinafter EM source) with suitable focusing optics. The EM source I l l is shown being electrically driven by a suitable drive current via electrical leads 113 and outputs a beam 115 as would be the case for a semiconductor laser. The EM source 111 may emit at any desired wavelength or wavelength range, e.g. in the ultraviolet, visible or infrared regions of the EM spectrum from 200 nm to 2 pm. A convenient EM source is a laser, such as a solid-state laser. A suitable laser is a semiconductor laser, such as an edge-emitting semiconductor laser or a vertical cavity surface emitting semiconductor laser. An alternative to a laser is a superluminescent light emitting diode. The EM source may be adjustable to tailor for carriers that bear different substances, for example by changing its output wavelength or wavelength range or changing its output power. The EM source may also be adjustable to modulate the rate at which the substance is activated, for example by changing the steady state output power using analog current control, and/or via duty cycle control. Pulsed laser operation may be of particular interest for particle ablation. The carrier 101 contains one substance, or a combination of substances, in a layer 105 formed as an elongate strip on an upper surface of a substrate 103 with a rectilinear shape. The substance or substances are retained bound to the carrier 101 in ambient conditions, but cause emission of the trace gas or the particulate aerosol when locally irradiated with the beam 115. The beam 115 when directed onto any particular position on the substance layer 105 transforms the substance locally around a spot 109 formed by the beam 115 to cause the trace gas or particulate aerosol to be emitted in a plume 117. In use, the beam 115 is scanned to follow a path over the carrier 101, specifically over the carrier's substance layer 105; here a linear path from one end of the strip-shaped substance layer 105 to the other, thereby to emit the trace gas or particulate aerosol at a controlled rate. In the illustration, the path has a direction of travel 119 in the x-direction and the beam 115 has already travelled over a portion 107 of the path, where the substance is depleted as schematically illustrated. A transport gas 121, such as ambient air, is caused to flow past the carrier 101 so that, when the trace gas or particulate aerosol are emitted in the plume 117, they are conveyed away with the transport gas.

[0042] Figure 2 shows cross-sections of an example carrier 101 lengthways in an xz-plane and crosswise in a yz-plane through section AA of the carrier 101. An EM source 111 emitting a beam 115 is also shown. An optional protective layer 201 is shown arranged over the substance layer 105 extending as a blanket to the rim portion of the upper surface of the substrate 103 that is not covered by the substance layer 105, so that the protective layer 201 and substrate 103 collectively encapsulate the substance layer 105. The purpose of the protective layer 201 is to provide a barrier between the substance and the environment. A protective layer is useful for avoiding touching contact with the substance when the carrier is handled by a person. A protective layer is also useful to prevent exposure of the substance to ambient air prior to use. The protective layer can therefore serve to limit or prevent premature loss of the substance during storage of the carrier, e.g. through spontaneous oxidation, deterioration due to moisture ingress, decomposition, evaporation or sublimation. The protective layer may be provided as a coating on top of those areas of the carrier where the substance is present. The protective layer may for example be selected from the following materials: paraffin wax or other waxes; low, medium or high density polyethylenes; poly(ethylene oxides); ethylene vinyl alcohol and polyvinylpyrrolidone (PVP); and combinations thereof. The composition and thickness of the protective layer may be selected to increase retention of the substance in the carrier when the substance layer is not being irradiated, while also allowing for rapid and efficient emission of the trace gas or particulates when the carrier is irradiated with the beam. The protective layer may also incorporate inert microscopic particles or flakes, such as of mica, glass, ceramic, or metal oxides to increase diffusion path length and thus decrease the diffusion rate of gas attempting to escape through to the outer environment. The protective layer may be applied as a film via spin coating, spray coating, or thermal press film application.

[0043] In the inset, a variant for the substance layer 105 is shown. The substance layer 105 is arranged on a substrate 103 and covered with a protective layer 201. In this variant, the substance layer 105 comprises a large number of microcapsules which may all contain the same substance or which may contain two or more different substances with the microcapsules containing the different substances being mixed in close juxtaposition. Microencapsulation can be used to contain the substance or substances as solid particles or liquid droplets. The microencapsulation is effected with a continuous film of material that envelopes the particles or droplets. The film material may for example be ethyl cellulose, polyvinyl alcohol, gelatin or sodium alginate. An advantage of microencapsulation is the ability to isolate two or more substances from each other on the carrier during manufacture, transport and storage so that they do not cross-react with each other until use. At the time of use, the local irradiation with the beam ruptures or otherwise disrupts the thin film coating of the microcapsules, e.g. by heating, so that the different substances are released. For example, the different substances may be precursors in a chemical reaction that generates the trace gas as a reaction product. The precursors are thus kept apart from each other by the encapsulation until irradiated. In this case, with the use of microencapsulation to isolate the precursors from each other prior to use, heat produced by the local irradiation may simply serve to rupture the capsules and not necessarily also be needed to drive the chemical reaction, i.e. the chemical reaction need not be endothermic. Microcapsules can also reduce unwanted material loss prior to the time of use by providing an extra barrier to evaporation or sublimation. Microcapsules can also permit the use of a liquid substance, such as a liquid form of the compound that is the trace gas compound. An example is holding iodine in liquid form e.g. dissolved in a solvent for later release. Another example using microencapsulation would be to have two microencapsulated substances, one being a liquid form of a trace gas with disinfecting or another functional property, such as diatomic iodine, and the other a liquid fragrance so that the trace gas is a mixture of the functional trace gas and the aromatic trace gas. This would ensure that people would be able to associate smelling the fragrance of the aromatic trace gas with the emission of the functional trace gas into the ambient air, e.g. of a room or other confined space. Since the aromatic trace gas and functional trace gas would be emitted in a fixed quantity ratio, the aromatic trace gas may serve as an odorizer in that the strength of the smell of the aromatic trace gas would be an indication of the concentration of the functional trace gas. The microcapsules may be embedded in an inert bedding compound or material for example cellulose, more specifically fibrous cellulose such as porous filter paper, the paper being bonded to a substrate. Microcapsules can also be incorporated into a laminated sandwich structure, e.g. deposited in a layer above a substrate and underneath a layer of porous material such as filter paper, or between two layers of such porous material.

[0044] Figure 3 shows orthogonal cross-sections of another example carrier 101, the crosssections being the same ones as in Figure 2. An EM source 111 with beam 115 is also shown. In this example carrier 101, the substance layer 105 is countersunk in the substrate 103, i.e. the substrate 103 has a recessed portion in its upper surface for accommodating the substance layer 105 flush with the planar, non-recessed rim portion of the upper surface. An optional protective layer 201 is also shown.

[0045] Figure 4 shows orthogonal cross-sections of another example carrier 101, the crosssections being the same ones as in Figure 2 and Figure 3. An EM source 111 with beam 115 is also shown. A porous layer 405 is arranged on the upper surface of the substrate 103, whose pores are filled with the substance, either directly or by the pores being filled with microcapsules containing the substance as depicted in Figure 3. A depleted portion of the porous layer 407 is also shown. Storage of the substance in pores may provide a stable binding of the substance to the carrier. Trace gas emission from the pores may be by any one of ablation, sublimation, evaporation, dissociation, chemical reaction or chemical decomposition. The porous material is preferably capable of withstanding any elevated temperatures that result from the local irradiation during use. Example porous materials include some ceramics as well as polymers that remain inert even at relatively high temperatures. An example high temperature inert polymer is microporous or expanded PTFE, such as microporous PTFE available from POREX™ under the trademark Virtek™, such as Virtek™ MD10, e.g. having nominal thickness of 0.13mm and a pore volume of approximately 50%. Other example porous materials are aerogels and porous sintered materials. Aerogels are materials that can absorb extremely large fractions of a substance, to over 99% by volume, while withstanding high temperatures. Aerogels can be fabricated, for example, from silica or alumina. A porous sintered material can, for example, be produced from a ceramic or a glass.

[0046] Figure 5 shows in lengthways cross-section another example carrier 101 which is essentially a two-sided version of Figure 4. An EM source 111 emitting a beam 115 is also shown. The features corresponding to 111, 115, 117, 119, 121, 201, 405 and 407 on the upper surface are labeled as 511, 515, 517, 519, 521, 501, 505 and 507 respectively on the lower surface. The carrier 101 is intended for use with first and second EM sources 111 and 511 for directing first and second beams 115 and 515 to respective sides of the carrier 101. It is thus possible to effect liberation of a trace gas or a particulate aerosol from either side of the carrier 101 as desired.

[0047] Figure 6 shows in lengthways cross-section another example carrier 101 together with an EM source 111 configured and arranged to output a beam 115 onto the carrier 101. The substance is held in pores of a self-supporting porous structure 601. An optional protective layer 603 is provided that extends completely as a surface wrap over the porous structure 601, so that the volume occupied by the substance is fully encapsulated. A variant to the illustrated use of separate EM sources 111, 511 arranged to direct their respective beams onto the upper and lower surfaces of the carrier 101 would be to have only one such source. [0048] Figure 7 is a schematic perspective view of another example carrier 101. An EM source 111 emitting a beam 115 is also shown. Compared with the elongate rectangular carrier 101 of Figure 1, the carrier 101 of Figure 7 has a rectangular substrate 703 of smaller aspect ratio. The beam path over the substance layer 105 is a meandering serpentine path 705 going to and fro in the positive and negative y-directions as illustrated, instead of being a straight line in the x-direction as in Figure 1. The direction switching portions of the serpentine path 705 are shown as straight lines extending in the x-direction; alternatively, these could be semicircular. The X and Y axis may be interchanged, and that other patterns of paths both continuous and discontinuous may also be employed to comparable effect. It may be useful to embed an identification tag, such as an RFID (radio frequency identification) tag into the carrier. Figure 7 has an RFID tag 707 arranged on the substrate 703. An identification tag can be useful for inventory and tracking, product certification and authentication against counterfeiting, and for conveying product details to the apparatus designed to employ the carrier as well as storing information related to usage history. For example, the identification tag may hold readable information which conveys a serial number, manufacturing date for expiry purposes, contents, content density, and coordinate or path location of last use in case the carrier is removed from an apparatus and later reinserted, so that use may resume from the last used location along the path. These pieces of information may also be used by the apparatus controller to set beam power and path speed according to the type of substance contained in the carrier. The identification tag may contain formulae or data to be used by the apparatus controller for the aforementioned power and speed control purposes, which would give the apparatus carrier-specific information to optimize the controlled emission of the trace gas or particulates for any given carrier. An identification tag may be employed in all carrier implementations disclosed herein. The apparatus may also incorporate an identification tag reader (or reader/writer) operable to read the identification tag of a carrier loaded into the apparatus (and optionally also to write to it). Information that it may be useful to write to the identification tag includes a log of the carrier's use, e.g. what parts of the carrier have been depleted, or identification information of the apparatus or apparatuses which the carrier has been loaded into.

[0049] Figure 8 is a schematic perspective view of another example carrier 101. An EM source 111 emitting a beam 115 is also shown. The carrier 101 has the form of a cylindrical drum based on a substrate 803 in the shape of a cylinder. The beam path 105 taken over the substance layer 105 formed on the cylindrical surface of the drum is a helix 701, i.e. helical spiral. The carrier 101 is therefore generally best described in terms of cylindrical polar coordinates rOz rather than Cartesian coordinates. The beam 115 is directed along the radial axis of the cylindrical polar coordinates of the carrier 101 so as to meet the cylindrical drum surface orthogonal to its tangent. In use, the carrier 101 is rotated about its principal axis 805 with an example direction of rotation being shown with arrow 807. While the use of a helical pattern is quite intuitive, it is also possible to employ the orthogonal scanning pattern of Figure 7 by scanning the beam 115 first from an origin at one end along the Z-axis while holding the drum in constant 9 position, then rotating the drum by approximately one path width at its circumference and then retracing the path of the beam linearly back to the origin. Other patterns of paths, both continuous and discontinuous, may also be employed to comparable effect. The EM source 111 is arranged relative to the drum so that its beam 115 is incident from outside on the drum surface. In variants, the beam could be routed to be directed to scan over the drum surface from the inside, e.g. using a rotatable mirror mounted on the principal axis 805 that is movable axially, or there could be respective beams for inside and outside beam scanning. In further variants, the transport gas 121 is routed over the inside surface of the cylinder, or both the inside and outside surfaces. In further variants, the substance may be arranged on the inside of the cylindrical surface, on both the inside and outside of the cylindrical surface as respective substance layers (see Figure 5) or right through the cylindrical surface (see Figure 6).

[0050] Figures 9a and 9b are schematic perspective views of the front and back sides of another example carrier 101. An EM source 111 emitting a beam 115 is also shown. The carrier 101 has the form of circular disc which is rotated about an axis 905 in an example rotational direction 907. The beam scanning is therefore generally based on polar coordinates r0 rather than Cartesian coordinates xy. The carrier 101 comprises a disc-shaped substrate 901. A substance layer 105 extends to close to, but not right up to, the outer rim of the substrate 901 of the substance, leaving a rim portion 903 free of the substance layer 105. A fiducial mark 913, 914, 917 and a barcode 909, 911, 915 are arranged on the rim portion 903. The barcode 909 gives product information which can be read by an optical sensor that may be integrated in an apparatus. As illustrated, the fiducial mark 913, 914, 917 and barcode 909, 911, 915 may be arranged on one or more of the disc's upper surface, radial outer surface and/or lower surface. The fiducial mark 913, 914, 917 is provided to allow an apparatus to measure the rotational alignment of the disc carrier 101. In use, the disc format carrier 101 is rotated about its axis in direction 907 while the beam is moved along its beam path 705 over the substance layer 105, which has a spiral pattern. The depicted spiral pattern is of major arcs of concentric circles with an angle slightly less than for a circle, e.g. 5° or 10° less than 360°, interconnected by radially extending step portions of a length equal to the difference in radius between adjacent concentric circles. In this document, this spiral pattern is referred to as a stepped spiral pattern. A stepped spiral pattern for the path is optimized for efficient use of the substance compared with a true spiral (in 2D). While the use of a true spiral or stepped spiral pattern is quite intuitive, it is also possible to employ the orthogonal scanning pattern of Figure 7 by moving the beam 115 in linear segments across the surface of disc 101; this may readily be accomplished under algorithmic control of the position of the beam 115 and rotation of disc 901. Other patterns of paths, both continuous and discontinuous, may also be employed to comparable effect. In a variant of this embodiment which is generally suitable for any rotatable disc format of carrier, the carrier may have a through hole arranged at least approximately centrally in the manner of a CD/DVD or gramophone record to allow the carrier to be centered on a spindle for rotation with a spindle drive.

[0051] Figure 10 is a schematic plan view of the front side of an example disc-format carrier 101. The carrier 101 is intended for use with an apparatus that scans the beam with a path 1013 that conforms to a plurality of sectors 1001. By way of example, four sector regions A, B, C and D are shown with reference numerals 1003, 1005, 1007 and 1009 respectively. Region D is a circular region with a radius equal to a fraction of the radius of the circular area covered with the substance. Regions A, B and C are arranged radially outside Region A, with Regions A and B occupying quadrants and Region D a semicircle. Each region may host a different substance or mix of substances. The disc-format carrier 101 may be controlled to rotate clockwise and counterclockwise as schematically indicated by the bidirectional arrow 1011. With the sector arrangement of the paths, the beam spot 109 will traverse the carrier 101 in a relatively large number of relatively short discontinuous path fragments. It is noted that beam spot is schematically illustrated as having a substantially rectangular cross-section as may be produced by suitable beam-shaping optics as discussed further below. The controller of the apparatus is operable to move the scan beam to traverse a path segment in a chosen sector in accordance with the trace gas or particulates that it is desired to emit. The scan beam may be moved between sectors, e.g. back and forth between sectors, to cause multiple trace gas or particulate types to be emitted successively over a short time period to create trace gas mixtures or mixed component aerosols in a target volume such as a room or other confined space. The scan beam may also be moved between sectors to cause emission of one trace gas or another as desired, so that a single carrier can selectively be used to emit different trace gases at different time periods, thereby giving the flexibility to emit different trace gases without having to switch carriers in the apparatus. It will be understood that having a single carrier with multiple spatially separated regions that hold different substances is not limited to any particular carrier format or any particular geometric definition of the paths.

[0052] Figures I la, 11b and 11c are different views of another example carrier 101. An EM source 111 emitting a beam 115 is also shown. It is noted that beam spot is schematically illustrated as having an elongate elliptical cross-section with a major axis and a minor axis, the major axis being aligned transverse to the scan direction, i.e. tangentially to the arcuate path of the spiral. Figure 1 la is a plan view of the carrier 101 and is illustrated with the beam path 705 following a helical spiral. Variants could use a stepped spiral (Figure 9a) or arcuate or circular paths (Figure 10). Figure 1 lb is a side view showing a barcode 911 and a fiducial mark 914. Figure 11c is a section view through section AA of Figure I la showing how the substance is contained in a porous structure 1103 that is fixedly attached by, for example, bonding (e.g. ultrasonic, adhesive, heat fusion) or clamping, to a ring frame 1101 over a fixing area 1105. Since the ring frame 1101 provides structural rigidity, the porous structure 1103 need not be self-supporting, e.g. it could be made of a flexible and/or resilient material. In the case of a resilient porous structure it can be stretched across the supporting perimeter of the ring frame 1101 and fixedly attached thereto to provide a taut surface as may be the case when using e.g. a porous PTFE film as the porous structure. A frame construction such as shown in Figures 1 la to 11c may also be used with other designs, such as the plate-like carrier formats, e.g. Figure 7, and three dimensional cylindrical drum format of Figure 8 via the use of an open cylindrical frame, possibly with the addition of an internal supporting latticework.

[0053] Figure 12 shows in plan view details of an example emission unit 1200 that may be used in a set-up as already described with reference to Figure 7, i.e. with a 2D carrier 101 with a substance layer 105 on top of a rectangular substrate 703. The substance layer 105 is shown partly depleted with a depleted portion 107. The substance layer 105 is scanned over by the beam along a serpentine path 705. The carrier 101 is held stationary against a base and an orthogonal pen-plotter style mechanism moves the beam so that it follows the serpentine path 705. The emission unit 1200 comprises a bed 1225 on which a carrier 101 can be removably held. The EM source 111 is moved above the bed with an XY-drive mechanism which is shown implemented with leadscrews and stepper motors and is supported to lie above the bed with appropriate mounting flanges. The XY-drive mechanism is as follows. A Y-axis stepper motor 1219 is in driving engagement to rotate a Y-axis leadscrew 1221. An X-axis stepper motor 1205 is in driving engagement to rotate an X-axis driven leadscrew 1201. An X-axis slave leadscrew 1203 is arranged parallel to the X-axis driven leadscrew 1201. Leadscrew 1203 is arranged to follow the driven (master) leadscrew 1201 by means of a belt drive, comprising a belt drive sprocket 1207 on the driven lead screw 1201 and a belt sprocket 1211 on the slave lead screw 1203 with an associated drive belt 1209 wrapped around both sprockets. The directed EM source I l l is mounted on a scan head in the form of the Y-axis leadscrew traveler car 1223 so that the EM source 111 can be positioned at any desired XY- coordinate location over the carrier 101. The Y-axis motion is cumulative to the X-axis motion in that the Y-axis mechanism is carried by the master and slave X-axis leadscrews 1201 and 1203 with respective X-axis leadscrew traveler cars 1213 and 1215, which also serve as bearings for each end of the Y-axis leadscrew 1221. The X-axis motion is shown with arrows 1217.

[0054] Figures 13a and 13b show details of an example emission unit 1300 reminiscent of a CD/DVD player that may be used with a circular disc format carrier 101. Here the disc format carrier 101 is rotatable about its central axis (the axis out of the paper in the drawing) while the beam 115 is moved along a stepped spiral pattern path 705 over the carrier surface (either from the inside out or from the outside in). The EM source I l l is mounted on a stepper-motor driven leadscrew car 1223 which in conjunction with a stepper motor-driven turntable as shown (or alternatively a spindle drive, not shown) creates the stepped spiral path 705. The uniaxial lead screw arrangement with stepper motor 1219, leadscrew 1221, leadscrew car 1223 and lead-screw end bearing block 1303 for moving the EM source 111 in the radial direction 1305 is substantially the same as the Y-drive arrangement in Figure 12. Reference numeral 907 indicates an example direction of rotation of the circular carrier 101 as driven by a stepper motor 1307 via a coupling shaft 1309 that connects the stepper motor 1307 to a traylike carrier holder 1301 for removably receiving and holding the carrier 101. The emission unit 1300 is provided with a suitable reader 1311 (Figure 13b) to read the fiducial mark 913 and barcode 909, such as an optical reader. The fiducial mark 913 could alternatively be a magnetic mark readable with a magnetic sensor. The fiducial mark and its reader allow a controller to locate physical reference point on the carrier as the carrier is rotated, so that the apparatus can, through the use of digitally controlled motors such as stepper motors, know the position of the EM source 111 with respect to the carrier 101. By this means, the controller knows where on the path the beam is directed or should be directed even if the carrier 101 were removed from the apparatus and reinserted at a later time.

[0055] Figure 14 shows one example of a beam emitting unit comprising a laser diode 1401 and a beam focusing lens ensemble 1405 comprising a group of lenses including a group of at least one Powell lens 1407, which creates a desired beam profile 1409 or 1411 at beam exit 1413 which, when directed at a carrier surface, may serve to more fully, precisely, and/or evenly emit the trace gas or a particulate aerosol from the carrier than would be possible with the direct use of a simply focused unshaped beam profile 1403 emitted from the laser diode 1401. The Powell lens group may be used to shape the beam into a top hat function on one or both axes. Clipping of the beam may also be performed using an aperture, such as an iris. The spot size may also be adjustable, e.g. by adjusting optical elements used for collimating and/or focusing the beam. This may be useful if the apparatus is designed to operate with carriers that bear different substances that have different heating requirements. The beam as incident on the carrier may be a focused or a collimated beam. The beam and hence the beam's spot on the carrier may to a good approximation have a Gaussian intensity distribution. In the case of an elongate beam cross-section, as would be provided by cylindrical lens optics, there would be an elliptical beam cross-section with respective approximately Gaussian distributions along each of the major and minor axes of the ellipse. In the case of an elongate, line-like beam spot, the major axis may advantageously be aligned transverse, preferably orthogonally, to the beam scan direction (or the predominate beam scanning direction in the case of a zig zag scan path). In the case of a spiral path with a rotating carrier, the major axis would be aligned transversely, preferably orthogonally, to a tangent of the arcuate path. For beam-shaping, optical components, such as a microlens array or a holographic grating may be provided to modify the beam cross-section, e.g. to provide an intensity distribution that is more like a top hat function.

[0056] Figure 15 shows an apparatus 1501, many features of which will be understood from the foregoing descriptions, especially of Figure 1, Figure 10, Figure 12, Figures 13a and 13b, or variations thereof (for example also featuring double-sided carriers). The apparatus 1501 comprises an emission unit 1300 as described above accommodated in a housing 1503. While we show by way of example the emission unit 1300 of Figures 13a and 13b, in variants the apparatus 1501 could be adapted to use with any of the other above-described emission units and carrier formats. The housing 1503 defines an inlet passage 1507 and an outlet passage 1513. The inlet passage 1507 serves to bring the transport gas into the housing's interior volume. A flow generator 1509 such as a fan is arranged in or adjacent to the transport gas inlet 1505 to promote flow of the transport gas into the housing 1503 and over a carrier that is removably arranged in the housing 1503. The housing 1503 further comprises an outlet passage 1513 for emitting the transport gas mixed with the trace gas or carrying the particulates as an aerosol as indicated with reference numeral 1511. In a variant, the fan could be placed in the outlet passage 1513 to suck the transport gas through the apparatus. A controller 1515, such as a digital controller, is provided. An interface 1517 is also provided for interfacing the controller 1515 with external components such as a computer to allow external human and/or machine control of the unit 1501. The digital controller 1515 is responsive to the multiple inputs including inputs from a computer or other components connected via the interface 1517, a signal 1529 indicating flow speed generated by the flow generator 1509, a signal from a temperature sensor 1527 arranged inside the housing adjacent the carrier holder, signals from an electrooptical unit 1311 configured to read bar codes and fiducial markings, and a signal measuring the concentration of trace gas or particulates in the outlet passage as measured by the trace gas or particulates concentration sensor 1531. An RFID module 1533 is provided that is configured to read and/or write application data such as manufacturing related information, encrypted codes to prevent counterfeiting, and to store information related to carrier usage history. The flow generator 1509 is preferably adjustable to vary the transport gas flow speed. To this end, if the flow generator 1509 is a fan, the flow speed signal 1529 may be from a tachometer output of the fan. The digital controller 1515 also has various outputs for controlling components including motor drivers 1519 and 1521 respectively for the radial and rotational actuation (leadscrew and spindle), a motor driver 1523 for the fan 1509, and a laser diode driver 1525 for the laser diode beam source 111. For many applications, it will be desired to emit the trace gas or the particulates at a constant target rate. A feedback loop may be used to achieve this based on measuring the emitted concentration of trace gas or particulates with a sensor 1531 arranged in the outlet passage 1513. The rate of emission can then be incremented or decremented under suitable control, e.g. a PID (proportional-integral-derivative) control loop to vary one or more relevant parameters such as output power of the laser (or other EM source) or beam scan speed.

[0057] The controller is responsible for beam control and other control functions of the apparatus. The controller may be under software control and may be configured to act in accordance with settings input by a human or machine operator, for example as part of a process control feedback loop. The overall control of the EM source and its beam can provide near-instantaneous start/stop operation (via direct beam control) as well as real time control over the rate of gas or particulate emission. This can be accomplished by controlling the various relevant parameters as listed above. An important function of the controller is to control the path of the beam as it is scanned over a carrier held in the holder. The controller may be configured to track sections of the path already traveled by the spot over any given carrier that is loaded into the apparatus. This is helpful in the case that a given carrier is used in multiple instances, so that for each new instance the scan can be restarted at a position on the path that is at, or an incremental distance from, the end position of the previous use. The controller can then record how much of the carrier has been used up, i.e. what proportion of the path has already been covered. The controller can be configured to output a signal to cause removal of a carrier held in the apparatus when the path has been covered completely or nearly completely. In other words, if the carrier is completely used up or nearly used up, where ‘nearly used up’ can be defined for the apparatus by the apparatus manufacturer, then a signal to that effect is output by the controller. For example, ‘nearly used up’ may be defined as when less than a fixed amount of the path remains used, or a fixed percentage of the path, he output signal may be transmitted by a warning light, e.g. a red light or equivalent indication on a display; a sound emitter and/or a data transmitter. In addition, an additional early warning of nearing the end of the carrier life may also be provided at an earlier stage, e.g. an amber warning light or equivalent indication on a display. The apparatus may include a fail-safe which prevents a new use when the carrier is sensed to have been used up or nearly used up and which also stops an existing use when the carrier is sensed to be used up or nearly used up.

[0058] The apparatus is designed to be operated in combination with a specific carrier format. The beam scanning mechanism may: steer the beam, e.g. with tiltable mirrors in a galvanometric-type mirror assembly, move the EM source; and/or move the carrier (e.g. translationally and/or rotationally) as needed to scan the beam over the carrier along a desired path. The size and shape of the spot formed by the beam on the carrier is defined by the crosssection that the beam makes with the carrier. Generally, the beam will be directed such that it intersects the surface of the carrier orthogonally or close to orthogonally, but this need not be the case. If the mode of action for emitting the trace gas or particulates is local heating, then the local area of the carrier over which the substance is heated by the beam sufficiently to emit the trace gas or particulates may be somewhat larger or smaller than the beam spot. The mode of action of the beam on the carrier may be purely absorption to generate heat and locally elevate the temperature of the carrier to above a threshold for gas or particulate emission from the substance.

[0059] The rate at which the trace gas or particulates are emitted can be well defined and controlled by the controller. Firstly, the form and quantity of substance per unit area on the carrier is at time of manufacture. Secondly, the rate at which the substance is depleted, and so the rate of trace gas or particulate release, can also be controlled by controlling the speed of travel of the beam over the carrier along with the power density of the beam as it follows its path. The beam scan speed is selected to ensure the substance is evenly depleted along the path, i.e. a relatively constant fraction of the substance is depleted per unit of time. In this regard, it may be difficult and also not necessary to ensure the substance is completely depleted. However, it is beneficial if the substance is substantially evenly depleted, i.e. that the percentage of the substance that is depleted remains relatively constant along the path taken by the beam as it traverses the carrier. The density of loading of the substance and the physical volume occupied by the substance determine the capacity of the carrier in terms of the maximum amount of the trace gas or particulates that it is possible for the carrier to emit. For the scan beam of a defined cross-sectional area, this places an upper limit of the total amount of trace gas or particulates that the beam can cause to be emitted. In addition, the percentage conversion of substance and its variation in use can be calibrated to give a closer estimate of the likely amount and rate of emitted trace gas or particulates. For example, with a given set-up of the apparatus and a given type of carrier, it may be known that say 60±10% of the total exposed substance will be depleted, from which the amount and rate of trace gas or particulate emission can be estimated. The rate of trace gas or particulate emission through activation with the beam will depend on many factors. These factors may include one or more of the following:

• the intensity and wavelength emitted by the EM source

• the cross-sectional energy distribution function, i.e. beam profile, of the beam, e.g. Gaussian, top hat

• the size and shape of the beam spot on the carrier

• the scan speed of the beam spot over the carrier

• the thermal conductivity of the carrier parts (e.g. the substrate and porous structure)

• the physio-chemical characteristics of the substance(s), in particular the ‘heat and time’ response profiles of the substance(s) diffusion rate of the trace gas through the substance layer (and the protective layer if present) given the temperature profile of the irradiated zone

• the flow speed, density, temperature and composition of the transport gas into which the trace gas or particulates are emitted

• ambient temperature, since a lower ambient temperature may reduce the effect of the local irradiation and thus require one or more forms of compensation in order to achieve the same rate of trace gas or particulate emission as would have been achieved at a higher ambient temperature.

[0060] It will be understood that the apparatus is also provided with a suitable power supply (not shown), which may be a mains power supply or a battery-operated power supply. Not all of these functions are necessary; for example the temperature sensor, a concentration sensor and a fan speed sensor are not needed for basic functionality.

[0061] Having described various specific embodiments, it will be understood that features described in detail in connection with one embodiment may be applied in other embodiments, for example in respect of materials options, microencapsulation, inclusion of a protective layer, including identification tags, fiducial marks and barcodes on the carrier with associated reader or reader/writer in the apparatus, apparatus control, and options for the EM source and scan optics. Furthermore, some additional general features applicable to any of the above embodiments are now discussed in more detail.

[0062] Regarding the transport gas, example use cases are air or an inert gas such as nitrogen, helium or argon. A significant use-case is one in which the transport gas is ambient air. Ambient air may be taken from the environment around the apparatus and forced to flow past the carrier by a suitable flow arrangement, e.g. based on a fan. In the case of another gas being used for the transport gas, e.g. nitrogen, helium, argon or synthetic air, this may be provided from a gas bottle or from a plumbing system from which it is piped into the apparatus. Trace gas or particulates emitted from the carrier may mix with the transport gas in very small ratios, e.g. the trace gas or particulates may only be desired to provide ppm (parts per million) or ppb (parts per billion) concentrations in the transport gas, or in the air of a room or other confined space into which the transport gas is distributed. The exiting transport gas mixed with the trace gas or containing the particulates as an aerosol may be directed at an object, surface or anatomical part of the human or animal body instead of a volume of space, for example in order to provide a direct disinfection function. The transport gas is directed to flow over the carrier on the side where the substance is bound, preferably with laminar flow, and to convey the trace gas or particulates away from the carrier to the intended target environment or object. [0063] Regarding the mode of action of the electromagnetic radiation on the carrier, in some embodiments, the wavelength or wavelength range of the EM source is selected to match a particular molecular or atomic transition in one or more of the substances. This may assist in driving certain chemical reactions in the case of gas emission caused by a chemical reaction or dissociation of a complex. In other embodiments, the emission is produced purely by heating effects by means of ablation, sublimation, decomposition, dissociation or evaporation. In some embodiments, the electromagnetic radiation induces a gas-generating chemical reaction, for example between two substances or one substance and oxygen, or by chemical decomposition.

[0064] Regarding the provision of a carrier which is designed to be removable from an emission apparatus, this is convenient, since it allows the carrier to be used as a consumable item and exchanged for a fresh carrier when the old carrier is depleted. Another advantage of the above-defined design approach of using a carrier that can be removably held in an apparatus is that there is the potential to provide a range of different carriers that can be used in a universal apparatus design. There may be different carriers for generating different gases and/or different types of particulates and/or different concentrations of the same gas or particulate and/or different mixtures. The same apparatus can therefore potentially be used for emitting different trace gases, particulates etc. by swapping out the carrier.

[0065] Regarding embodiments that use a substrate, suitable materials choices are those materials that will remain inert under irradiation from the beam are those with relatively low thermal conductivities, e.g. less than 5 W/(m K) at 300 K to limit heat dissipation where heating is the principle mode of gas generation, for example by means of a laser beam. Further, it is desirable to limit the reactivity of the substrate material by preventing its degradation with heat or exposure to EM radiation. Suitable materials therefore are those that can withstand relatively high temperatures e.g. up to a few hundred degrees Celsius without changing phase; certain ceramics, glasses and heat-resistant polymers have these properties. Heat-resistant polymers include some fluorinated polymers such as a perfluorinated polymer e.g. polytetrafluoroethylene (PTFE) and its several variants, and others such as poly(methyl methacrylate) (PMMA), and polyether ether ketone (PEEK). The substrate may comprise synthetic materials such as nanofibers that do not contaminate the emitted trace gas and that do not deteriorate from a chemical or physical degradation process such as oxidation. The same discussion of materials choices also applies to any other materials used in the carrier that may be exposed to the beam, or be otherwise subject to effects caused by the beam, such as porous materials used in embodiments that have a support with a porous structure.

[0066] Comparing the example paths shown in the different embodiments, it is apparent that some show a path that can be traversed by the scan beam in a continuous manner from start to finish, such as the spiral and serpentine path embodiments. With such paths, there is no need for any interruption in the emission until the whole path has been traversed. On the other hand, other example paths are possible in which the beam will scan separate path segments in a discontinuous manner, e.g. as shown in Figure 10. This is acceptable in any applications that are insensitive to brief interruptions in trace gas or particulate emission, for example in the case of filling room air with a scent or disinfectant. In such cases, discontinuous emissions may be acceptable, even with interruptions with no emission of minutes, allowing for the use of paths on the carrier which may be more efficient or more flexible in terms of operational control. [0067] It will be clear to one skilled in the art that many improvements and modifications can be made to the foregoing exemplary embodiment without departing from the scope of the present disclosure.

The following numbered clauses give further definitions of carriers according to the disclosure:

1. A carrier for storing at least one substance capable of producing a trace gas or particulates, the carrier comprising a support to which is bound at least one substance for producing a gas or particulates, wherein the at least one substance is retained bound to the support in ambient conditions and in response to being exposed to an electromagnetic radiation beam to locally irradiate a location on the carrier emits the trace gas or the particulates.

2. The carrier of clause 1, wherein the at least one substance comprises a halogen selected from the group iodine, chlorine and bromine for emitting halogen gas as the trace gas.

3. The carrier of clause 1, wherein the at least one substance comprises iodine for emitting iodine gas as the trace gas.

4. The carrier of clause 3, wherein the iodine is present as molecular iodine.

5. The carrier of clause 4, wherein the molecular iodine is present releasably dissolved in a host or as crystalline molecular iodine covered with a protective barrier.

6. The carrier of clause 3, wherein the iodine is present as a dissociable part of a complex.

7. The carrier of clause 6, wherein the complex is one of: an iodophor, diiodomethane, amylose-iodine and cellulose-iodine.

8. The carrier of clause 1, wherein the at least one substance comprises a metal for emitting metal particulates as the particulates.

9. The carrier of clause 8, wherein the metal is one of: silver, zinc, copper and bismuth.

10. The carrier of clause 1, wherein the at least one substance emits an aroma compound as the trace gas.

11. The carrier of clause 1, wherein there are at least two of said substances which are precursors of a chemical reaction which has the trace gas as a reaction product.

12. The carrier of any preceding clause, wherein the at least one substance is bound to the support in that the support comprises a substrate and the at least one substance is present in a layer arranged on the substrate. 13. The carrier of any preceding clause, wherein the at least one substance is bound to the support in that the support has a porous structure providing pores that are filled with the at least one substance.

14. The carrier of clause 13, wherein the porous structure is selected from the group: a polymer, a ceramic, a glass, a sintered material and an aerogel.

15. The carrier of any preceding clause, wherein the at least one substance is present as solid particles or liquid droplets microencapsulated in microcapsules that are configured to release the at least one substance when irradiated by the electromagnetic radiation beam.

16. The carrier of any preceding clause, further comprising a frame arranged to hold the support.

17. The carrier of any preceding clause, wherein the carrier further comprises a protective layer arranged to provide a barrier between the at least one substance and the surroundings of the carrier.

18. The carrier of any preceding clause having a physical format selected from the group: an elongate strip, a rectangular plate, a rotatable drum and a rotatable disc.

19. The carrier of any preceding clause having a physical format in which the support defines first and second surfaces on both of which are present the at least one substance.

20. The carrier of any preceding clause having a physical format in which the support defines at least a first surface on which is present a plurality of different ones of the at least one substance, the substances being arranged on the first surface such that they form a plurality of separate surface regions, each with a different substance or combination of substances.

The following numbered clauses give further definitions of apparatus, methods and carriers according to the disclosure:

1. An apparatus for emitting a gas or particulates, the apparatus comprising: a holder configured to removably hold a carrier containing at least one substance, which responsive to the carrier being locally irradiated with an electromagnetic radiation beam causes the carrier to emit a trace gas or particulates; an electromagnetic radiation source operable to output an electromagnetic radiation beam; a scanning mechanism operable to direct the electromagnetic radiation beam onto a carrier held in the holder and thereby locally irradiate a location on the carrier sufficiently to emit the trace gas or the particulates; a flow generator operable to cause a transport gas to flow past a carrier held in the holder so that when the trace gas or particulates are emitted from the carrier they are conveyed away in the transport gas as a mixture of the transport gas and the trace gas or as an aerosol in which the particulates are in suspension in the transport gas; and a controller configured to control the electromagnetic radiation source and the scanning mechanism so that the beam is scanned to follow a path over the carrier, thereby to emit the trace gas or particulates into the transport gas at a controlled rate.

2. The apparatus of clause 1, wherein the controller is configured to record what portion of the path has already been followed over any given carrier that is loaded into the apparatus.

3. The apparatus of clause 1 or 2, wherein the electromagnetic radiation source is a laser.

4. The apparatus of any preceding clause, further comprising beam-shaping optics to bring the electromagnetic radiation beam into an elongate cross-section for irradiating the carrier.

5. The apparatus of clause 4, wherein the elongate cross-section has major axis and a minor axis, the major axis being aligned transverse to at least most of the path.

6. The apparatus of any preceding clause, wherein the scanning mechanism consists of a single linear drive assembly for moving the electromagnetic radiation beam relative to a carrier held in the holder along a linear axis.

7. The apparatus of clause 6, the controller is configured to describe the path as a line.

8. The apparatus of any preceding clause, wherein the scanning mechanism comprises first and second drive assemblies for moving the electromagnetic radiation beam relative to a carrier held in the holder along a linear radial axis and a rotational axis. 9. The apparatus of clause 8, wherein the controller is configured to follow the path as a spiral.

10. The apparatus of any preceding clause, wherein the scanning mechanism comprises first and second drive assemblies for moving the electromagnetic radiation beam relative to a carrier held in the holder along first and second linear axes that are transverse to each other.

11. The apparatus of clause 10, wherein the controller is configured to follow the path as a serpentine.

12. The apparatus of any preceding clause, further comprising a sensor configured and arranged to measure concentration of the trace gas or particulates emitted from the carrier and to supply a sensor signal indicative thereof to the controller, the controller being configured to control at least one of the electromagnetic radiation source and the scanning mechanism responsive to the sensor signal so as to maintain the concentration of the trace gas or particulates at a desired level.

13. A method of emitting a gas or particulates comprising: providing a carrier containing at least one substance, which responsive to the carrier being locally irradiated with an electromagnetic radiation beam causes the carrier to emit a trace gas or particulates; causing a transport gas to flow past the carrier so that when the trace gas or the particulates are emitted from the carrier they are conveyed away in the transport gas as a mixture of the transport gas and the trace gas or as an aerosol in which the particulates are in suspension in the transport gas; directing an electromagnetic beam onto the carrier to locally irradiate a location on the carrier sufficiently to emit the trace gas or the particulates; and scanning the electromagnetic beam to follow a path over the carrier, thereby to emit the trace gas or the particulates into the transport gas at a controlled rate.

14. A carrier for storing at least one substance capable of producing a trace gas or particulates, the carrier comprising a support to which is bound at least one substance for producing a gas or particulates, wherein the at least one substance is retained bound to the support in ambient conditions and in response to being exposed to an electromagnetic radiation beam to locally irradiate a location on the carrier emits the trace gas or the particulates.

15. An apparatus according to any of clauses 1 to 12 adapted for use with a carrier according to any of clause 14.

Claims

29 CLAIMS

1. A carrier for storing at least one substance capable of producing a trace gas, the carrier comprising a support to which is bound at least one substance for producing a gas, wherein the at least one substance is retained bound to the support in ambient conditions and in response to being exposed to an electromagnetic radiation beam to locally irradiate a location on the carrier emits the trace gas.

2. The carrier of claim 1, wherein the at least one substance is bound to the support in that the support has a porous structure providing pores that are filled with the at least one substance.

3. The carrier of claim 2, wherein the porous structure is selected from the group: a polymer, a ceramic, a glass, a sintered material and an aerogel.

4. The carrier of claim 1, 2 or 3, wherein the at least one substance comprises a halogen selected from the group iodine, chlorine and bromine for emitting halogen gas as the trace gas.

5. The carrier of claim 1, 2 or 3, wherein the at least one substance comprises iodine for emitting iodine gas as the trace gas.

6. The carrier of claim 5, wherein the iodine is present as molecular iodine.

7. The carrier of claim 6, wherein the molecular iodine is present releasably dissolved in a host or as crystalline molecular iodine covered with a protective barrier.

8. The carrier of claim 5, wherein the iodine is present as a dissociable part of a complex.

9. The carrier of claim 8, wherein the complex is one of: an iodophor, diiodomethane, amylose-iodine and cellulose-iodine.

10. The carrier of any preceding claim, wherein the at least one substance comprises a substance for emitting an aroma compound as the trace gas.

11. The carrier of any preceding claim, wherein there are at least two of said substances which are precursors of a chemical reaction which has the trace gas as a reaction product.

12. The carrier of any preceding claim, wherein the at least one substance is bound to the support in that the support comprises a substrate and the at least one substance is present in a layer arranged on the substrate.

13. The carrier of any preceding claim, wherein the at least one substance is present as solid particles or liquid droplets microencapsulated in microcapsules that are configured to release the at least one substance when irradiated by the electromagnetic radiation beam. 30

14. A carrier according to any preceding claim in combination with an apparatus adapted for use with the carrier, the apparatus comprising: a holder configured to removably hold the carrier; an electromagnetic radiation source operable to output an electromagnetic radiation beam; a scanning mechanism operable to direct the electromagnetic radiation beam onto the carrier while held in the holder and thereby locally irradiate a location on the carrier sufficiently to emit the trace gas; a flow generator operable to cause a transport gas to flow past a carrier held in the holder so that when the trace gas is emitted from the carrier the trace gas is conveyed away in the transport gas as a mixture of the transport gas and the trace gas; and a controller configured to control the electromagnetic radiation source and the scanning mechanism so that the beam is scanned to follow a path over the carrier, thereby to emit the trace gas into the transport gas at a controlled rate.

15. A method of emitting a gas or particulates comprising: providing a carrier according to any one of claims 1 to 13; causing a transport gas to flow past the carrier so that when the trace gas is emitted from the carrier the trace gas is conveyed away in the transport gas as a mixture of the transport gas and the trace gas; directing an electromagnetic beam onto the carrier to locally irradiate a location on the carrier sufficiently to emit the trace gas; and scanning the electromagnetic beam to follow a path over the carrier, thereby to emit the trace gas into the transport gas at a controlled rate.