GB2405013A - Identification micro-tags whose largest area is no more than 0.25mm - Google Patents

Abstract

Objects are marked with identification tags, which are either permanently attached by being applied with paint or laquer or are removably attached by means of a mechanical attachment such as hooks or spikes or chemical attachment such as hydrophobic or hydrophilic attraction. The tags have a body whose largest area is no more than 0.25mm<2>. Attachment is aided by manufacturing the tags to have a non-planar surface. The tags may be applied by aerosol or as dust or in a solution. The tags can be made from SiO2. The tags can fluoresce and carry an identification code.

Description

240501 3 A Security Marker and Security Marking Method The present

invention relates to the field of security markers and security marking methods. More specifically, the present invention relates to a security marker which has a unique code and which allows an object, such as a consignment of narcotics or other illegal goods, to be tracked.

Currently, intelligence and law enforcement agencies such as Customs and Excise, the Police and MT6 use Jensen Violet or the like to track stolen or illegal goods or money.

Jensen Violet is a chemical dye which upon contact with perspiration or moisture discolours the skin of the person handling the goods.

Although this method is highly effective it has many disadvantages. For example, the suspect may wear gloves to stop him getting the dye on his hands and the dye is not effective on hair or clothing. Also, the dye will fade and wash off with time, so detection at a later date is not possible. The dye must be applied in the correct dosage.

Too little dye may not be sufficient to mark objects such that they may be tracked, too much dye may be result in a large cleaning operation. The dye may also absorb moisture from other sources and become discoloured. Finally, if two objects are marked with the dye, it is impossible to determine which one of the objects was handled by the suspect.

Recently, a product called Alpha Dote has been developed for marking luxury goods, Alphadot is a microdot with a I mm diameter and a code. The dots are generally used in luxury vehicles such as cars, motorbikes and boats and are generally distributed over the vehicle so that if it is stolen, the vehicle can be identified from the code on the microdots even if the vehicle has been modified in some way.

The microdots are intended to be permanently attached to the vehicle and not to be removed when a person touches the vehicle. Thus, they do not represent a replacement for Jensen Violet.

Tags or "carriers" marked with a code have been proposed for use in Combinatorial chemistry in GB 2 306 484. This patent application proposes the use of a solid support particle which has a first phase with a machine readable code and a second phase where synthesis is performed. The first phase may be attached to the second phase via a hook or barb provided on the first phase.

Figure 2 of the patent application indicates the typical length for the coded first phase is about I OOpm. Harpoons or hooks provided on the first phase are configured to pierce the polymer bead second phase.

In a first aspect, the present invention provides a method of marking an object, the method comprising providing a plurality of carriers attached to said object, said carriers comprising a body, the largest area of said body being equal to or less than 0.25mm2,and a code provided on said carrier body identifying said object.

Thus, the object may be uniquely identified by reading the code provided on the carriers attached to the body. For example, if the object is a consignment of drugs, illegal money etc. the object or a substitute object may be marked by using the carriers. The object or substitute may then be placed under surveillance as it passes through illegal or other transactions. The object or substitute may then be uniquely identified at the end of the transaction by reading the code on the carriers.

In a preferred embodiment, the carriers are only loosely attached to the object such that the carriers may become detached and attach themselves to a second object or person.

Therefore, for example, in the case of drugs, the carriers may attach themselves to anybody who handles or deals with the drugs. The carriers may also become attached to the possessions of people who handle the drugs such as their cars, bags, clothes etc. The carriers have a largest area which is equal to or less than 0.25mm2, for example O.Smm x O.Smm Thus, the carriers are not readily noticeable by the naked human eye.

The carriers are generally planar with either a flat or a curved main planar surface. The area of this main surface will typically be the largest area of the carrier. Preferably, the length of the carrier body will be 0.5mm or less, more preferably 0.3mm or less, even more preferably 0.1mm or less.

By making the carriers so small, anyone handling the object will not notice the carriers and will not be alarmed and should carry on about their normal business with the object.

By making the carrier so small, a problem is encountered in that the police or other law enforcement agency apprehending a suspect who handled the package may have difficulty in actually locating the carrier to read the code.

Thus, preferably, the carriers comprise means to emit an output signal. The output signal may be emitted in response to external excitation, for example, the carriers may be configured to output the predetermined type of optical radiation in response to optical excitation. One possible method to achieve this is if the carriers comprise a fluorescent material which fluoresces at a predetermined wavelength in response to optical excitation. Alternately, the carriers may comprise a tinted material, such a tinted glass which allows radiation of a specific wavelength to be outputted from said carrier.

Preferably, the carrier comprises a reflective layer which allows the signal emitted by said carrier in response to external excitation to be reflected towards a detector or the like.

The carriers may comprise a radioactive material.

The carriers may be provided in the form of a dry powder and sprinkled over the object.

This method may be, for example, used for the object as a consignment of drugs.

Alternatively, the carriers may be sprayed onto the object by an aerosol. The carriers may also be provided to the object in a liquid suspension. The carriers may be permanently attached to the object, for example, they may be provided in a paint, lacquer or ink which is applied to the object. This may be particularly of use where it is desired to mark a luxury item such as a car etc. When cars are stolen, they are often re- sprayed. Therefore, the carriers will be present in an undercoat of paint. Even if the thieves attempt to remove the coat of paint which contains the carrier, it is unlikely that they will be able to remove all of the carriers. Artwork such as fine art paintings may be protected by applying the carriers in a lacquer to either the frame or a small part of the artwork itself. Carriers may also be applied to an object by printing them onto an object in an ink. For example, carriers may be provided in an ink for printing banknotes or originals of important documents. The carriers may even be attached to gemstones.

The carriers may also comprise attachment means for attaching themselves to the object. These attachment means may be mechanical attachment means, for example, the carrier may be provided with hooks or a similar projection which may hook around fibres in coats or on hair etc. The hooks are designed and sized such that they may be able to hook around the hair shaft or around the shaft of a typical fibre.

Alternatively, the attachment means may physical attachment means may be provided by a material within the carrier. For example, a hydrophilic or hydrophobic material may be used, for example, gold. Other physical attachments means may be used, for example, the carriers may be magnetic or attracted by a magnetic material. They may also be charged with static electricity so that they stick to the intended object.

Preferably, the carrier is also not flat. By adopting a carrier with a raised or curved profile, the carrier can more easily catch in fibres, hair etc. Where a carrier is provided with hooks, a raised or curved carrier means that the hooks will stand slightly proud of the body of the carrier and will hence attach themselves more easily to the suspect or the clothes of the suspect.

In a second aspect, the present invention provides a security marked object, comprising an object with a plurality of carriers attached to said object, said carriers comprising a body, the largest area of said body being equal to or less than 0.25mm2, and a code provided on said carrier body which identifies said object.

The object is preferably one selected from drugs, luxury goods, cars, money, firearms, contraband goods, artwork or gemstones. The object may also be a substitute for one of the above as often, the security services will substitute drugs or the like with a legal substance for tracking purposes. The carrier may be of any of the type previously described and may be provided with attachment means.

In a third aspect, the present invention provides a carrier for security marking an object, the said carrier comprising a carrier body, the largest area of said body being equal to or less than 0.25mm2, a code provided on said carrier body for identifying said object, wherein the carrier body is not flat in profile and comprises attachment means for attaching to the object.

In a fourth aspect, the present invention provides a carrier for security marking an object, the said carrier comprising a carrier body, a code provided on said carrier body for identifying said object and means for producing an output signal in response to excitation.

The carrier of either of the third and fourth aspect of the invention may be configured as described above. For example, the carrier of the third or fourth aspect of the invention may be able to output a signal as previously described. The carrier may further comprise attachment means, the attachment means may be mechanical attachment means, chemical attachment means or physical attachment means.

Mechanical attachment means may be provided by hooks which are used to hook around hair or fibres. The hooks will be sized in order to achieve this task and will typically be from 50 lam to 100 Am Thus, the largest dimension of the carrier body and hooks will preferably be less than 400pm, more preferably less than 300 m.

The projections may be provided on one or more edges of the carrier. Preferably, the projections are provided on all edges of the carrier to allow the carrier the maximum probability of attaching itself to a suspect or the object. The carrier is preferably non- planar for the reasons described above.

Chemical attachment means maybe used to attach the carrier to an object. For example, the carriers may be embedded in paint, ink, lacquer etc. Physical attachment means may also be used. The carriers may comprise a hydrophobic or hydrophilic material. Alternatively, the carriers may comprise a magnetic material, a material which is attracted by a magnet or material which may be charged using static electricity.

The carriers will be relatively small. If the carriers are too small, then they may be inhaled and cause problems for a user's respiratory system. Therefore, typically, the minimum largest dimension of the carrier body will be 4,um and preferably 1 0pm.

The carrier body may be made from a number of different materials. Preferably the carrier comprises SiO2. If the carrier is to fluoresce, the carrier may comprise SiO2 doped with a rare earth metal such as Erbium, Neodymium and Ytterbium.

In a fifth aspect, the present invention provides a method of fabricating a carrier for security marking an object, said carrier comprising a carrier body, the largest area of said body being equal to or less than 0. 25mm2, a code provided on said carrier body for identifying said object, wherein the carrier body is non-planar and comprises attachment means for attaching to the object, said method comprising: providing a substrate having a raised pattern formed on a surface of said substrate, said raised pattern comprising at least one material which forms said surface and defining said carrier body and attachment means; depositing material over said raised pattern; dissolving said substrate to release said deposited material to form said carrier from said released deposited material; and allowing said carrier to curl to form a non-planar carrier.

The carrier may be made to curl by introducing thermal stresses during fabrication.

In a sixth aspect, the present invention provides a method of fabricating a carrier for security marking an object, said carrier comprising a carrier body, a code provided on said carrier body for identifying said object and means for producing an output signal in response to excitation, said method comprising: providing a substrate having a raised pattern formed on a surface of said substrate, said raised pattern comprising at least one material which forms said surface and defining said carrier body; depositing material over said raised pattern, said material comprising a component which will emit an output signal in response to excitation; and dissolving said substrate to release said deposited material to form said carrier from said released deposited material.

In the methods of the fifth and sixth aspect of the invention, the substrate may be supplicated by using an injection moulding technique, or may be pressed to produce the required pattern.

The pattern may be a planar pattern comprising an upper plane and a lower plane, alternatively, the pattern may be a three dimensional pattern comprising V-shaped ridges and grooves in order to aid fabrication of a non-flat carrier.

The present invention will now be described with reference as following preferred non- limiting embodiments in which: Figure I illustrates a carrier in accordance with an embodiment of the present invention; Figure 2 illustrates a carrier in accordance with a further embodiment of the present invention; Figure 3 illustrates a carrier in accordance with a yet further embodiment of the present invention; Figure 4 illustrates a carrier in accordance with a further embodiment of the present invention; Figure 5 illustrates a carrier in accordance with a further embodiment of the present invention where crescent shaped hooks are provided; Figure 6 illustrates a carrier in accordance with a yet further embodiment of the present invention where hooks are provided at the corners; Figure 7 is a schematic of a sensor assembly for detecting the presence of carriers in accordance with an embodiment of the present invention; Figure 8 is a schematic cross section of a carrier in accordance with an embodiment of the present invention having a reflective layer.

Figure 9 is a flow diagram illustrating how the carriers in accordance with an embodiment of the present invention may be used in tracking narcotics; Figure 10 is a secondary electron image of a carrier with an elementary barcode; Figure 11 is a fluorescence image of the carrier of Figure 10; Figure 12 is an image of a carrier without a code attached to human hair; Figure 13 is an image of a carrier in accordance with an embodiment of the present invention attached to cotton twill fibres; Figure 14 is an image of a carrier in accordance with an embodiment of the present invention; Figure 15 is an image of a carrier in accordance with an embodiment of the present invention; Figure 1 6A is a schematic cross section illustrating a fabrication step for making an encoded carrier in accordance with an embodiment of the present invention; Figure 1 6B is a schematic cross section of a subsequent fabrication step to that shown in Figure 1 6A for making a carrier in accordance with an embodiment of the present invention; Figure 17A is a cross section illustrating a schematic fabrication step for making a carrier in accordance with an embodiment of the present invention; and Figure 17B is a schematic cross section illustrating a subsequent fabrication step to that shown in Figure 17A.

Figure I schematically illustrates a carrier in accordance with an embodiment of the present invention. The carrier I comprises a carrier body 3 upon which is located an alpha-numeric code 5. Alpha-nun1eric code 5 is provided along an edge of carrier body 3 and the characters of the code are open to the edge of the carrier. The code is provided open to the edge for fabrication reasons and these will be described with reference to Figures 16 and 17.

Anchor shaped hooks 7a, 7b, 7c and 7d are provided at each corner of the carrier body 3. Each hook 7a, 7b, 7c and 7d comprises an elongate shaft 9a, 9b, 9c and 9d and a crescent shaped hook member 11a, lib, tic, lid provided et the end of said shaft9a, 9b, 9c and 9d. The shafts 9a, 9b, 9c and 9d are connected to the mid- points of crescents 11a, Fib, tic, lid.

In addition to anchor shaped hooks, 7a, 7b, 7c and 7d, spike projections 13a, 13b, 13c and 13d extend from the centre of each edge of the carrier body 3. The arrangement between spike projections 13a, lab, 13c and 13d and anchor shaped hooks 7a, 7b, 7c and 7d is such that fibres touching said carrier 1 will become trapped between opposing projections 13a-d and hooks 7a-d.

In the figure, the carrier appears to be planar. However, the carrier is actually curled which causes the hooks 7a, 7b, 7c and 7d and projections 13a, 13b, 13c and 13d to stand slightly proud of any surface which the carrier 1 is provided on. This curling of the carrier 1 allows the carrier to catch more easily in fibres etc. The carrier 1 is designed to hook and catch on hair, clothes fibres, etc. Body hair has a diameter of 50 lam upwards and clothes fibres generally have a diameter of 40,um upwards. The carrier I and especially the projections 13a-d and hooks 7a- d are sized so as to engage hair and fibres. In this particular example, the length of the carrier body is 10O'lm and the length of the arms is between 50 1lm and 100pm. Thus the overall maximum dimension of the carrier will be between 20O'lm and 3001lm.

The carrier may be made from a number of different materials. In this preferred embodiment, the carrier is made from a fluorescent material. The reasons for this will be described with reference to Figure 7. As the carrier is fairly small, it can be made from a fairly brittle material such as SiO2 as this material will remain flexible due to the absence of surface microcracks. In this particular example, SiO2 is doped with a rare earth metal such as Erbium, Neodymium or Ytterbium.

Doping the carrier with a rare earth metal forms a carrier with an output signal which forms a sharp emission peak. The same effect may also be achieved if the carrier comprises a tinted layer, for example a tinted glass layer which will allow transmission or reflection of incident radiation over a narrow band of frequencies. Glass may be tinted with a wide range of dopants including Cr. Cu. Au.

Figure 2 is a schematic of a simpler type of carrier than that shown in Figure 1. The carrier 21 of Figure 2 comprises a carrier body 23 and an alpha-numeric code 25 located on the edge of said carrier body 23 exactly as described with reference to Figure 1. Two spike projections 27 and 29 are provided on one edge of carrier body 23. The spikes 27 and 29 are intended to pierce fibres thus attaching the carrier 21 to the fibres.

In this particular example, the length of the carrier body is 10O'lm and the length of the arms is between 50 Am and 10O'lm. Thus the overall maximum dimension ofthe carrier will be between 150pm and 200pm. If the arms were provided on both sides of the carrier body, the overall maximum dimension of the carrier will be between 20OIlm and 300pm. As described with reference to the carrier of Figure 1, the spikes 27 and 29 will stand slightly proud of any surface on which carrier 21 is placed due to the curling of the carrier. This curling of the spikes allows them to more easily engage fibres or hair. The carrier 21 is made out of the same material as described with reference to Figure 1.

Figure 3 shows a variation on the carrier of Figure 2. The carrier 31 of Figure 3 has a carrier body 33 and a code 35 provided along the edge of carrier body 33. The code 35 is identical to that described with reference to Figures 1 and 2. Two arrow projections 37 and 39 are provided along one edge of carrier body 33. The arrow projections 37 and 39 each comprise an arrow head 41 and 43 which are respectively provided at the end of tapering shafts 45 and 47.

The arrow projections 37 and 39 are configured to both pierce fibres or material and hook around fibres since fibres may be caught between the two shafts 45 and 47 and arrow heads 41 and 43.

The carrier 31 will be non-planar for the reasons described with reference to Figures 1 and 2. In this particular example, the length of the carrier body is 1 OO'lm and the length of the arms is between 50,um and lOO,um. Thus the overall maximum dimension of the carrier will be between 15OIlm and 2001lm. If the arms were provided on both sides of the carrier body, the overall maximum dimension of the carrier will be between 200pm and 300pm. The carrier will be made out of the material described with reference to Figure 1.

Figure 4 schematically illustrates a further type of carrier 51. The carrier comprises a carrier body 53 and a code 55 provided along the edge of the carrier body 53. The code is identical to that described with reference to Figures 1 to 3. A single projection 56 is provided on one side of carrier body 53. The single projection 56 has a tapering shaft 57 and a single barb 59 is provided along the tapering shaft 57. The shaft 57 tapers to a point 61 at its end. The projection 56 is again configured to primarily pierce fibres and then lock into position with barb 59.

In this particular example, the length of the carrier body is l OOpm and the length of the arms is between 50 1lm and] OO'um. Thus the overall maximum dimension of the carrier will be between 15Olm and 200pm. If the arms were provided on both sides of the carrier body, the overall maximum dimension of the carrier will be between 200pm and 300pm. The carrier 51 will curl as described with reference to Figures 1 to 3 such that projection 56 stands proud of any surface which carrier 51 is laid upon. The carrier 51 wild be made out of a similar material to that described with reference to Figures 1 to Figure 5 schematically illustrates a further carrier 71 in accordance with an embodiment of the present invention. As described in relation to the carriers with reference to Figures I to 4, the carrier 71 has a carrier body 73. A code 75 is provided in the centre of carrier body 73. Code 75 is an alpha-numeric code and, contrary to the codes described with reference to Figures 1 to 4 is provided in the centre of carrier body 73 as opposed to the edge of a carrier body.

Mechanical attachment means comprise four crescent shaped hooks. A first pair of crescent shaped hooks 77 and 79 are provided on opposing sides of carrier body 73.

Crescent hooks 77 and 79 each comprise a crescent which spans more than 180 . The width of the hook tapers towards its distal end such that points 81 and 83 are formed at the distal ends of hook 77. The hook 77 is not perfectly circular and is flattened such that points 81 and 83 point towards each other. Hook 79 is configured in a similar manner to hook 77 but is a mirror image of hook 77. Smaller crescent hooks 85 and 87 are formed on the remaining two edges of carrier body 73. Crescent hooks 85 and 87 are smaller than crescent hooks 77 and 79, but are configured in the same manner.

As described with reference to Figures 1 to 4, the carrier 71 will curl slightly, thus hooks 77, 79, 85 and 87 will stand slightly proud of the carrier body 73 when the carrier is provided on a surface. The hooks are configured to wrap around fibres or human hair. In this particular example, the length of the carrier body is I OOIlm and the length of the arms is between 50,um and l OOpm. Thus the overall maximum dimension of the carrier will be between 200'um and 300pm.

The characters of the code 75 are typically approximately 30,um high and 80 rim wide in total. The line width of the characters of the code 75 is 6 sum.

The carrier 71 is fabricated from the same material as described with reference to Figures 1 to 4.

Figure 6 shows a further carrier 91 in accordance with an embodiment of the present invention. The carrier 91 comprises a carrier body 93 and a code 95 provided in the centre of said carrier body 93. The code is configured in a similar manner to that described with reference to Figure 5.

The carrier body 93 is generally rectangular. Doubled-headed projection groups 97, 99, 101 and 103 are provided extending from each corner of the carrier body 93. Each of the carrier projection groups 97, 99, 101 and 103 are largely identical and only one of the groups 97 will be described here. Carrier projection group 97 comprises two projections 105, 107. Each projection 105, 107 is generally T-shaped and comprises a shaft 109, 111 and a head 113, 115 which is provided generally at right angles to shaft 109, 111. Shafts 109, 111 are provided away from the ends of heads 113, 115 so that heads 113, 115 extend out beyond shafts 109, 111. Shaft 109 extends generally at right angles to the long edge of carrier body 93 and shaft 111 extends generally at right angles to the short edge of carrier body 93.

The group of projections 97 is repeated for each corner of the carrier body 93. Thus, there are adjacent projections, for example projection 105 of projection group 97 and projection 119 of projection group 103. The projections 119 and 105 are configured such that fibres or hair may become caught between the projections 105, 119 and trapped by the heads of adjacent projections 105 and 119. Hair and fibres may also be caught between projections at right angles within the same projection group 97. The heads 113, 115 are thus sized to allow hair or fibres to be caught between adjacent projections regardless of whether they are adjacent projections in the same projection group or not. The projections may be symmetric T-shapes or non-symmetric T-shapes where shaft 111 does not meet head 115 in its centre.

As explained with reference to Figures 1 to 5, the carrier 91 will curl slightly, thus projection groups 97, 99, 101 and 103 will stand slightly proud of carrier body 93. The carrier 91 is formed from a similar material as the carriers described with reference to Figures I to 5.

In this particular example, the length of the carrier body is 10OIlm and the length of the arms is between 50 rim and 100pm. Thus the overall maximum dimension of the carrier will be between 20Olm and 300'um.

Previously, it has been explained that the carriers of Figures 1 to 6 are formed from a fluorescent material. The carriers of Figures 1 to 6 are designed to be so small that they are not noticeable by the human eye. Therefore, if a person has some carriers on his hand or caught in his clothes, in his hair, etc., the carriers will not be seen. However, it is desirable to have a quick way to check for the presence of the carriers on a person or object. This may be achieved by measuring the fluorescence of the carriers.

Figure 7 schematically illustrates how the presence of carriers may be detected. A carrier 121 which may be any of the carriers described with reference to Figures 1 to 6 has been caught on surface 123. Laser 125 provides a beam of radiation 127 which illuminates carrier 121. In response to the excitation from illumination 127, the carrier 121 fluoresces due to the fluorescent material provided within the carrier 121.

In the carriers described with reference to Figures 1 to 6, the fluorescent material is SiO2 doped with a rare earth metal. The carrier 121 fluoresces with radiation of a particular frequency. Radiation coming from carrier 121, i.e. that is radiation which has either been reflected by carrier 121 or fluoresced by carrier 121 is passed through filter 129.

Filter 129 is configured to block all frequencies except for the frequency of the fluorescent material. This allows photons 131 arising from carrier 121 fluorescence to be separated from other photons reflected from the carrier or from other sources in the vicinity ofthe carrier 121. The photons 131 which arise due to fluorescence are then detected by detector133. When detector 133 indicates the presence of photons with a correct energy, there is very high probability that they have arisen from carrier 121.

The composition ofthe carrier 121 is configured such that the emitted fluorescent radiation is of a wavelength which is not generally present in day-to-day background radiation to minimize the chances of the detector 133 mistaking background radiation for fluorescence from carrier 121.

Although laser 125 and detector 133 and filter 129 are shown as separate components, they may be provided within a single unit to provide a handheld scanner for easy detection of the carriers 121.

In the apparatus of figure 7, a laser is used as the light source. Any high intensity light source may be used. For example, a high intensity white light source of the type commonly used in forensic science. If a polychromatic source is used, the light may be filtered in order to block photons which may interfere with the emitted signal from the carriers. An example of a high intensity white light source is a halogen lamp.

Figure 8 is a schematic of a cross section of a carrier. The carrier may be any of the types described with reference to figures 1 to 6.

The carrier comprises a first SiO2 layer 151 which is doped with the rare earth metal Erblum 153. A reflective layer 155 comprising Au is provided overlying and in contact with said first SiO2 layer 151.

A second sio2 layer 157 is provided overlying and in contact with said reflective layer 155. The second SiO2 layer is also doped with Erbium 153.

Incoming radiation 159 enters said carrier and impinges on the Erbium particles causing them to fluoresce. Some of the photons emitted by the fluorescent particles 153 will exit the carrier through top surface 161. Some photons will propagate further into the structure of the carrier towards first layer 151. As the detector of figure 7 will usually collect output from one side of the carrier, photons propagating deeper into the structure will not be detected in the absence of reflective layer 155. Reflective layer 155 reflects photons propagating away from surface 161 back towards surface 161 hence increasing the number of photons which may be detected.

The reflectiec layer 155 also reflects incoming radiation so that it passes twice through second layer 157 thus increasing the probability of fluorescent particle 153 being excited by the incoming radiation 159.

Figure 9 is a flow diagram schematically illustrating how the carriers of Figures 1 to 6 may be used in order to track a drugs or narcotics consignment.

In step S201, HM Customs & Excise or an equivalent body discover a consignment of illegal narcotics in a packing case at a port. In step S203, the narcotics are substituted with a legal substance and the substitute "narcotics" are marked using carriers as described with reference to Figures 1 to 6. The carriers may simply be provided within the drugs and/or placed on the outside of the packaging of the substitute narcotics. This may be achieved by simply sprinkling the carriers as a dry powder or by spraying the carriers using an aerosol or the like. The carriers are sized such that they will not be noticeable to anyone handling the substitute narcotics. The carriers may be made out of an inert material such as they may be safely ingested. They are sized to avoid any problems if they are ingested. The code on the carriers is unique to this particular narcotics assignment. Therefore, if the carriers are later found, it is highly unlikely that they have come from anywhere except the substitute narcotics.

Customs & Excise then allow the substituted narcotics to continue in step S205. In step S207, the packing case containing the substituted narcotics is opened by the drugs runner. It is likely that this will be done away from the prying eyes of the Customs & Excise surveillance team. The drugs will be handled and possibly transferred to different packages. In step S209, due to the handling of the substituted narcotics, the drug runner's skin, hair and clothing becomes marked with the carriers. The drugs runner then delivers the drugs by car to the main drug dealer in step S211. The drugs runner's car will also become marked with encoded particles in step S2 13. Following on from step S2 1 1, the main drug dealer then handles the substituted narcotics in step S215. Thus, the drug dealer also becomes marked with the encoded particles.

All this time, Customs & Excise have been monitoring the procedure of the consignment of narcotics in step S217. They now apprehend the suspects. However, some suspects may have left the scene before Customs & Excise arrive, some suspects may escape. If these suspects are apprehended away from the scene, Customs and Excise will need proof that the suspects have handled the particular consignment of narcotics. The carriers comprise a fluorescent material as described with reference to Figures 1 to 6 and the suspects and the drug runner's car, etc., can be quickly tested for the presence of the carriers using the system described in Figure 7 for detecting the presence of fluorescence from the carriers. If carriers are detected by fluorescence, the suspects are then arrested in step S219.

Full forensic examination of the suspects' clothing and cars may then be performed as per step 221 back in a laboratory to determine if the fluorescing particles are the carriers which were used to mark the substituted narcotics consignment back in step S203.

Since the narcotics consignment was marked with carriers having a unique code, reading this code proves unequivocally that the suspects have handled the drugs and this gives a high probability of conviction.

The code on the carriers may be easily read using a microscope.

The tags are so small, they would not become immediately obviously to the suspect.

Thus, the suspect is unlikely to curtail his or her activities once they are marked with the carriers. Further, the carriers are very difficult to remove by washing because they are so small. Thus, the suspect may be picked up weeks after the narcotics were initially marked in step S203 and may still have the carriers about their person.

Previously, the carriers described with reference to Figures 1 to 6 have hooks or the like which allow them to hook or pierce fibres or hair. However, the tag may also become attached to a suspect even if it doesn't have the hooks described with reference to Figures 1 to 6.

Figure 10 gives a secondary electron image of a non-planar tag according to an embodiment ofthe present invention. The tag is corrugated and is approximately 10 lam in width and 60 Am in length.

Figure I I illustrates a fluorescent image of the tag of Figure 10. The fluorescence is fairly weak due to a gold coating on the carrier. The gold coating is provided in order to allow the carrier to be more easily imaged in an electron microscope. The fluorescence would be much stronger without the gold.

Figure 12 is a micrograph showing human hair 251 and tag 253 provided on the strand of human hair 251. It can be clearly seen that the carrier 253 attaches itself to the hair 251. The carrier 253 is a representative carrier and does not have a code.

Figure 13 clearly shows how tag 261 embeds itself within cotton twill cloth 263.

The attachment means may also be provided by a layer on the carrier or the composition of the carrier itself. For example, gold is hydrophobic and this may be used in order to encourage the carrier to attach itself to clothes or hair.

Previously, it has been described that the carriers are loosely attached to an object.

However, in some cases, it may be desirable to permanently attach carriers to an object in order to track the whereabouts of that object. For example, the carriers may be provided in a paint or lacquer and applied to a luxury article such as a car, etc. Since the carriers are so small, they would not be seen within the paint. However, if the car was stolen, it should be possible to still identify the car even if it has been repainted.

Generally, cars will be re-sprayed if they have been stolen. This will not prevent the police or similar investigative authorities later acquiring the car and checking for the presence of carriers in an undercoat of paint. Even if the paint is removed, it is unlikely that all the carriers could be removed from the car.

The carriers could also be applied in lacquers and inks. For example, artwork could be marked by covering a very small portion of the work with lacquer containing the carriers. Similarly, important documents and money could be marked by providing the carriers in an ink.

Figure 14 is a further image of a carrier in accordance with an embodiment of the present invention. The carrier 231 has a rectangular carrier body 233 and four projections 235a, 235b, 235c and 235d.

A code "TOSHIBA" is provided on carrier body 233.

The four projections 235a, 235b, 235c and 235d arc located at each of the four corners of the carrier body 233 and extend at substantially 45 to the sides of rectangular carrier body 233.

Two projections 235a and 235b which are provided on the same short side of the rectangular body 233 are substantially "L-shaped". Each of the two projections 235a and 235b has a main shaft 237a, 237b extending away from the carrier body 233 and forming an angle of approximately 135 with the short side of the carrier body 233. A cross bar 239a and 239b is provided on each main shaft 237a, 237b at 90 to the main shaft and extending in just one direction from the main shaft 237a, 237b.

The two cross bars 239a and 239b point away from one another. A small projection 241a, 241b is provided on the end of each cross bar 239a, 239b. Two secondary projections 243a, 243b are provided on the main shaft 237a, 237b close to the end of the main shaft 237a, 237b and pointing in the opposite direction to cross bars 239a, 239b.

The two other projections 235c and 235d which are provided on the other short side of the rectangular body 233 to projections 235a and 235b. Projections 235c and 235d are substantially "T-shaped". Each of the two projections 235c and 235d has a main shaft 237c, 237d extending away from the carrier body 233 and forming an angle of approximately 135 with the short side of the carrier body 233. A cross bar 239c and 239d is provided on each main shaft 237c, 237d at 90 to the main shaft and extending in both directions from the main shaft 237c, 237d.

The two cross bars 239c and 239d are not symmetric about main shaft 237c, 237d and the long end of the cross bars 239c, 239d point away from one another. Small projections 245c, 245d and 247c are provided on either end of each cross bar 239c, 239d.

Figure 14 shows two of these carriers which have become linked with each other.

Figure 15 is an image of a carrier of the types described with reference to figure 5.

Figures 16 and 16B are cross sectional views, showing two stages in the production of a carrier according to an embodiment of the invention.

In figure 16A, a soluble substrate 301 has a raised pattern 303 provided on lower substrate level 305. The pattern 303 defines an upper level 307 which is separated from the lower level 305 by substantially vertical side walls 309.

The soluble substrate may be positioned by wet or dry etching techniques such as RIE.

Alternatively, the substrate may be made from a mould.

Figure 16A is a cross section through pattern 303, such that the pattern 303 appears as a plurality of vertical pillars. In reality the pillars are elongated into the plane of the paper and are connected at their ends to form, in this embodiment, a continuous structure as indicated by the dotted lines.

In figure 16A, a doped SiO2 layer is deposited onto the substrate 301 such that there is an upper coating 313 formed on upper level 307 and a lower coating 317 formed on lower level 305. The deposition is directional such that neither of the layers are provided on the side walls 309. The side walls 309 cause the coating 313 to be discontinuous from the lower coating 317. Due to the overall shape of pattern 303, the sections of upper coating 313 are all connected to each other to form an essentially planar structure.

The substrate 301 is dissolved in order to release the upper coating 313 as shown in Figure l 6B. This upper coating forms the encoded carrier. By appropriate patterning of the substrate 301, both the carrier body and any attachment means may be patterned using this technique.

Figure 16B shows the stage of the process after the substrate 301 has been partially dissolved to release the carrier 313. The substrate is dissolved by placing it in a flowing solvent. The flow direction of the solvent is indicated by the arrow.

Figures 17A and 17B show two stages in a method of making a corrugated carrier. A substrate 321, as shown in perspective view in figure 17A, is provided with a three dimensional relief pattern 323 on its surface. The pattern 323 comprises "V" shaped indents 325 and indents with vertical side walls 327.

Figure 17B shows an example of material to form an encoded carrier deposited onto the substrate of Figure l 7A. The material is deposited over the relief of the substrate 321.

Material deposited over the V-shaped indents 325 takes on a corrugated form. Material deposited over the indents with vertical side walls 327 may form part of the code region or may be used to separate adjacent encoded carriers.

The indents with the steep side walls in both Figures 16 and 17 may be used to form holes which are bounded on each side or may be used to form holes which are open to the edge of the carrier. To avoid debris getting caught in the holes, it is preferable if the code is formed from bars or characters which are open to the edge of the carrier.

Also, forming the code from bars or characters which are open to the edge avoids the formation of small debris which later has to be separated from the carriers.

Claims (37)

1. CLAIMS: 1. A method of marking an object, the method comprising providing

   a plurality of carriers attached to said object, said carriers comprising a body, the largest area of said body being equal to or less than 0.25mm2, and a code provided on said carrier body identifying said object.
2. 2. A method according to claim 1, wherein the carriers comprise means to output a signal.
3. 3. A method according to claim 2, the carriers further comprising a reflective layer.
4. 4. A method according to either of claims 2 or 3,, wherein the means to output a signal comprises means to output an optical signal in response to optical excitation.
5. 5. A method according to claim 4, wherein the means to output an optical signal comprises a fluorescent material provided on said carrier body.
6. 6. A method according to any preceding claim, wherein the carriers are loosely attached to the object such that they will adhere to a second object coming into contact with the first object.
7. 7. A method according to any preceding claim, wherein the carriers are provided to the object as a dry powder.
8. 8. A method according to any of claims 1 to 6, wherein providing the carriers on the object comprises spraying the carriers onto the object via an aerosol.
9. 9. A method according to any of claims 1 to 6, wherein the carriers are provided to the object in a liquid suspension.
10. 10. A method according to any of claims 1 to 6, wherein providing the carriers on the object comprises printing, painting or spraying the carriers onto the object in a paint, lacquer or ink.
11. 11. A method according to any preceding claim, wherein the carriers comprise attachment means for attaching themselves to the object.
12. 12. A method according to claim l l, wherein said attachments means are mechanical attachment means.
13. 13. A method according to claim l l, wherein said attachment means are physical or chemical attachment means.
14. 14. A method according to claim 13, wherein said attachment means comprise a hydrophobic or hydrophilic material.
15. 15. A method according to any preceding claim, wherein said carrier is non-planar.
16. 16. A security marked object, comprising an object with a plurality of carriers attached to said object, said carriers comprising a body, the largest area of said body being equal to or less than 0.25mm2, and a code provided on said carrier body which identifies said object.
17. l 7. A security marked object according to claim 16, wherein said object is at least one selected from: drugs; luxury goods; cars; money, arms, explosives, contraband goods, art works and gemstones.
18. 18. A security marked object according to either of claims 16 or 17, wherein the carriers are provided with attachment means.
19. l9. A carrier for security marking an object, the said carrier comprising a carrier body, the largest area of said body being equal to or less than 0.25mm2, a code provided on said carrier body for identifying said object, wherein the carrier body is not flat in profile and comprises attachment means for attaching to the object.
20. 20. A carrier according to claim 19, further comprising means for producing an output signal in response to excitation.
21. 21. A carrier for security marking an object, the said carrier comprising a carrier body, a code provided on said carrier body for identifying said object and means for producing an output signal in response to excitation.
22. 22. A carrier according to claim 20, wherein the carrier is non-planar.
23. 23. A carrier according to either of claims 21 or 22, wherein the carrier further comprises attachment means.
24. 24. A carrier according to any of claims 19, 20 or 23, wherein the attachment means comprise projections provided along at least one edge of the carrier body.
25. 25. A carrier according to claim 24, wherein the projections are adapted to hook around fibres of clothing or hair.
26. 26. A carrier according to either of claims 24 or 25, wherein the projections are provided on at least two edges of the carrier.
27. 27. A carrier according to either of claims 20 or 21 or claims 22 to 26 when not dependent on claim 19, wherein the means to output a signal are means which produce an optical signal.
28. 28. A carrier according to claim 27, wherein the means for producing an output signal comprise a fluorescent material.
29. 29. A carrier according to any of claims 19 to 28, wherein said carrier body has a length of between Am to 200,um
30. 30. A carrier according to any of claims 19 to 29, wherein said carrier body comprises SiO2.
31. 31. A method of fabricating a carrier for security marking an object, said carrier comprising a carrier body, the largest area of said body being equal to or less than 0.25mm2, a code provided on said carrier body for identifying said object, wherein the carrier body is non-planar and comprises attachment means for attaching to the object, said method comprising: providing a substrate having a raised pattern formed on a surface of said substrate, said raised pattern comprising at least one material which forms said surface and defining said carrier body and attachment means; depositing material over said raised pattern; dissolving said substrate to release said deposited material to form said carrier from said released deposited material; and allowing said carrier to curl to form a non-planar carrier.
32. 32. A method according to claim 31, wherein said carrier curls due to thermal stresses.
33. 33. A method of fabricating a carrier for security marking an object, said carrier comprising a carrier body, a code provided on said carrier body for identifying said object and means for producing an output signal in response to excitation, said method compnsmg: providing a substrate having a raised pattern formed on a surface of said substrate, said raised pattern comprising at least one material which forms said surface and defining said carrier body; depositing material over said raised pattern, said material comprising a component which will emit an output signal in response to excitation; and dissolving said substrate to release said deposited material to form said carrier from said released deposited material.
34. 34. A method of marking an object as substantially hereinbefore described with reference to any of the accompanying figures.
35. 35. A method of fabricating a carrier as substantially hereinbefore described with reference to any of the accompanying figures.
36. 36. A security marked object as substantially hereinbefore described with reference to any of the accompanying figures.
37. 37. A carrier as substantially hereinbefore described with reference to any of the accompanying figures.