tattooing

Abstract

A system and method of tattooing skin comprising creating voids extending from a surface of the epidermis into the dermis; introducing a dye through the voids into the dermis; and fixing the dye in the dermis. There is provided a system of needleless tattooing comprising a sensor for sensing a location of the surface of a region of skin of a subject, a dermal penetration device for penetrating into the skin, a controller responsive to the sensor to control the dermal penetration device to penetrate into but not through the dermis in the region of skin of the subject.

Description

[0001] Tattooing

[0002] FIELD OF INVENTION

[0003] The present invention relates to a method and system of tattooing.

[0004] BACKGROUND TO THE INVENTION

[0005] Tattooing is the practice of marking skin. Conventional tattooing methods use a needle, often in combination with an electric motor, to pierce the skin repeatedly. Conventional tattoo ink comprises pigments, especially inorganic pigments. Such pigments are especially challenging to remove in a tattoo removal process, often requiring many sessions of laser tattoo removal. There is a need for a method of producing tattoos that may be removed more simply and effectively than conventional tattoos. There is also a need to create tattoos by alternative methods that do not rely on standard tattoo machines.

[0006] Conventional tattoos are applied by a person, known as a tattoo artist. Often the most significant cost involved in tattooing is the labour cost of the tattoo artist. Tattoo artists have limited capacity to tattoo skin in a given period of time and may have a limited ability to create a tattoo as desired by a customer. There is a need for tattooing without the involvement of a tattoo artist. It is desirable to have a tattooing process that is faster and / or more accurately represents a planned tattoo design than the conventional tattooing performed by a tattoo artist.

[0007] The use of dyes in tattooing has previously been unsuitable for producing permanent or long-lasting tattoos. Soluble dyes in particular are broken down in the body by natural processes such as an immune response. It would be desirable to utilise dyes as tattoo ink in such a way that lasting tattoos may be made.

[0008] The methods of tattooing described herein avoid the use of conventional pigment inks and instead use dye to produce the tattoo. The methods are particularly advantageous as the dye is made to fix in the dermis, thus a long-lasting tattoo is made. SUMMARY OF INVENTION

[0009] According to a first aspect there is provided a method of tattooing skin comprising creating voids extending from a surface of the epidermis into the dermis, introducing a dye through the voids into the dermis, and fixing the dye in the dermis.

[0010] Preferably the dye is fixed in the dermis by reaction of the dye with the dermis.

[0011] Preferably the voids do not extend through the dermis into the hypodermis.

[0012] The dye may be soluble in a solution comprising water. The dye may be soluble in oil.

[0013] The dye may comprise a reactive molecule. The reactive molecule may comprise a vinyl sulfone group. The reactive molecule may comprise a triazine group.

[0014] The method may further comprise, prior to creating voids, preparing the dye by dissolving a dry dye and sodium chloride in water. The dry dye may be in powder form. ‘Dry’ may be defined as a solvent content of less than about 5 wt%, preferably less than about 1 wt%, preferably less than 0.1 wt%, preferably substantially dry.

[0015] Each void may have a diameter at the surface of the epidermis of around 10 pm to around 500 pm. Preferably each void has a diameter of around 100 pm. Preferably the diameter relates to the largest dimension across the void.

[0016] Respective voids may be spaced apart by a distance of at least about 50 pm, preferably at least about 100 pm.

[0017] The voids may extend into the dermis by about 10 pm to about 100 pm, preferably about 50 pm.

[0018] The voids may be created using a laser. The voids may be created by laser ablation. The method may further comprise, once the dye has been introduced through the voids into the dermis, observing a waiting period of 5 to 15 minutes. The waiting period may be about 5 minutes to about 10 minutes, preferably about 10 minutes. The method may further comprise washing off excess dye.

[0019] The method may further comprise applying an alkali solution to the voids. The method may further comprise washing off the alkali solution. Preferably washing off means washing the alkali solution from the skin, especially the surface of the skin.

[0020] Creating voids may comprise at least partially removing a basement membrane, the basement membrane being between the epidermis and the dermis. Creating voids may comprise removing a basement membrane.

[0021] The method may further comprise applying a mixture to promote healing, the mixture comprising a steroid, an antibiotic and an antimycotic. The method may further comprise applying a mixture comprising at least one of a steroid, an antibiotic and an antimycotic. Preferably the mixture promotes healing. Preferably the mixture improves the cosmetic appearance of the tattoo.

[0022] The method may further comprise, prior to creating voids, applying a disinfectant to the surface of the epidermis.

[0023] Preferably the dye comprises a reactive species capable of forming a bond with a component of the dermis. Preferably the reactive species comprises one or more of a halo-heterocyclic group, an activated double bond, an epoxide-type system, a carbonyl-based electrophile, a sulfonyl group, a phosphoryl group, an aziridine, a photoreactive group, a click-chemistry group, a metal-coordination group, or a combination of two or more thereof.

[0024] The dye may comprise a reactive molecule. The dye may be covalently bonded to a reactive molecule. Preferably the reactive molecule contains one or more reactive functional groups capable of forming bonds with components of the dermis. Preferably the dye is caused to fix in the dermis by reaction with a dermal component, wherein the dermal component comprises collagen, elastin, fibronectin, laminin, proteoglycans, glycosaminoglycans, or a combination of two or more thereof.

[0025] The dye may be capable of binding to tissue in the dermis. Preferably the dye is capable of reacting with collagen, elastin, fibronectin, laminin, proteoglycans, glycosaminoglycans, or two or more thereof. Preferably the dye reacts with one or more components of the dermis, wherein the components comprise collagen, elastin, fibronectin, laminin, proteoglycans, glycosaminoglycans, or a combination of two or more thereof.

[0026] The method may further comprise, after introducing the dye, introducing a fixing solution to the dermis so as to promote fixation of the dye. The fixing solution may promote the better binding of the dye with tissue in the dermis. Preferably the fixing solution comprises an alkali.

[0027] According to a second aspect there is provided a system of needleless tattooing comprising a sensor for sensing a location of the surface of a region of skin of a subject, a dermal penetration device for penetrating into the skin, a controller responsive to the sensor to control the dermal penetration device to penetrate into but not through the dermis in the region of skin of the subject.

[0028] The dermal penetration device may comprise a laser.

[0029] The controller may be configured to cause the laser to ablate voids in the dermis.

[0030] The controller may be responsive to the sensor to control the dermal penetration device to produce a plurality of voids into but not through the dermis in the region of skin.

[0031] The system may further comprise a dye for application to the region of skin. Preferably the dye is a dermis-resident dye. The dye may be a reactive dye. The dermis-resident dye may comprise a reactive molecule. The reactive molecule may comprise a vinyl sulfone group and / or a triazine group.

[0032] The dye may comprise a reactive molecule. The dye may be covalently bonded to a reactive molecule. Preferably the reactive molecule contains one or more reactive functional groups capable of forming bonds with components of the dermis.

[0033] Preferably the dye is caused to fix in the dermis by reaction with a dermal component, wherein the dermal component comprises collagen, elastin, fibronectin, laminin, proteoglycans, glycosaminoglycans, or a combination of two or more thereof.

[0034] The system may further comprise a mixture for promoting healing. The mixture may comprise a steroid, an antibiotic, an antimycotic, or a combination of two or more thereof. The system may further comprise a mixture for improving the appearance of a tattoo. The mixture preferably comprises at least one of a steroid, an antibiotic and an antimycotic.

[0035] The system may further comprise a probe for applying ultrasound and / or vibrations to the region of skin.

[0036] The present invention will now be described by way of example with reference to the accompanying drawings. In the drawings:

[0037] BRIEF DESCRIPTION OF THE FIGURES

[0038] Figure 1 shows a schematic cross section of skin.

[0039] Figure 2 shows a scheme of making a dye tattoo.

[0040] Figure 3 shows healing stages of making a dye tattoo.

[0041] Figure 4 shows an arrangement for making voids in skin.

[0042] Figure 5 shows a top-down view of a region of skin. DETAILED DESCRIPTION

[0043] The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art.

[0044] The general principles defined herein may be applied to other embodiments and applications without departing from the present invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

[0045] There is provided a method of tattooing skin comprising creating voids extending from a surface of the epidermis into the dermis; introducing a dye through the voids into the dermis; and fixing the dye in the dermis. The depth that the dye is able to penetrate affects the extent that the dye can remain in the skin. The dye may be fixed in the dermis by chemical means.

[0046] Figure 1 shows a schematic cross section of skin 100. The skin 100 has an upper layer, the epidermis 101 , a dermis layer 102 and a hypodermis layer 103. In undamaged skin, the epidermis is the outer layer of the skin, and the dermis is a layer between the epidermis and the hypodermis. The epidermis 101 has an upper surface exposed, e.g. to air, at the outer surface of the skin. On the opposing side of the epidermis, the epidermis has an inner boundary at its interface 104 with the dermis 102. The interface 104 comprises a basement membrane, also called a basal membrane. The dermis 102 comprises connective tissue, such as collagen, reticular and elastic fibres. The dermis 102 comprises a papillary layer, proximal to the epidermis, and a reticular layer, proximal to the hypodermis. The papillary layer is composed of looser connective tissue; that is to say connective tissue that is looser than the general density of the reticular layer. The reticular layer is composed of denser connective tissue; that is to say connective tissue that is denser than the general density of the papillary layer. The papillary and reticular layers may not be clearly distinguishable from one another, there is a gradient of transition from papillary to reticular as the depth from the surface of the skin increases.

[0047] Dye introduced only to the epidermis 101 will be removed by the natural exfoliation of epidermal cells over time. It is not believed to be possible to produce a lasting tattoo by superficial application of a dye. It is necessary to expose a deeper level of skin to allow the dye to enter the dermis 102. It may be that at least partial removal of the basement membrane permits dye to enter the dermis. Various methods may be employed to expose a region of skin below the epidermis, such as chemical or mechanical peeling. Preferably, only a proportion of the dermis is exposed to reduce the trauma to a region of skin being tattooed. Preferably the proportion is less than about 50% of the total skin area, preferably less than about 40%, preferably less than about 30%.

[0048] The process of making a dye tattoo will be discussed with reference to Figure 2. The process steps are represented in sequence, viewing the figure from left to right. Figure 2 shows a region of skin 200 having a void 201 extending through the epidermis layer and into the dermis. The void may be made by any suitable means, for example by using a light beam, e.g. from a laser. The void may have a columnar profile, the void may be substantially cylindrical. The cross-section of the void may be substantially constant over the majority of the length of the void. A dye 202 is introduced through the void into the dermis. The dye may be applied manually, for example by pouring or by using a mechanical applicator such as a brush or squeegee, or for example by spraying the dye on the skin surface. Once applied to the surface of the skin, the dye may move into the voids. The dye may be drawn into the voids by capillary action. The way in which the dye is applied to the skin may encourage the dye to penetrate the voids. For example, the action of drawing a blade or other tool over the skin may urge the dye to enter the voids. A period of time between applying the dye 202 and applying subsequent treatments, for example the application of other products (e.g. liquids) to the skin may be observed. For example, a waiting period of between 5 minutes and 20 minutes may be observed. This may allow the dye to adequately move into the dermis, where it may then remain. Preferably a period of between 8 and 12 minutes from introducing the dye is elapsed before further steps are performed. The dye 204 is shown as having moved from the void into the dermis. Without being bound by theory, it is thought that at least partial removal of the basement membrane is needed in order for the dye to move into the dermis. The voids may penetrate the basement membrane.

[0049] Some of the voids may penetrate the skin deeper than other voids. Not all of the voids need to permit the dye to reach a site where it can undergo processes that permit it to dwell in the skin over an extended period of time.

[0050] Advantageously, there is no need to retain the dye in a polymer shell as the dye is delivered via the voids formed into the dermis. The methods of tattooing described herein enable a dye which would otherwise dissolve or dissipate in the skin to be fixed in the skin. Without being bound by theory, it is thought that reaction of the dye with the extracellular matrix causes the dye to be durably fixed in the skin.

[0051] Figure 2 shows a next step in the process. Excess dye is washed off by a suitable liquid 203. The liquid 203 may comprise water. Excess dye is removed so that the resultant tattoo is not blurry. The dye may be hydrolysed by reaction with fluid in the dermis and / or with the introduced liquid 203. Hydrolysed dye may not bind to or remain in the skin. It can be seen in figure 2 that the dye 206 has moved from within the void into the dermis around the void. In a next step, a fixing solution 205 is introduced into the void. The fixing solution may promote the better binding of the dye with tissue in the dermis. The fixing solution may be an alkali solution. The fixing solution may be applied for a short period of time, for example between 30 seconds and 5 minutes. The fixing solution is then washed off with distilled water. The short application time and washing off of the fixing solution is chosen to reduce trauma to the skin caused by reaction with the alkali.

[0052] Put another way, the process described above involves the following steps in order:

[0053] 1 . Voids are made from the surface of the skin into the dermis, or at least through the basement membrane.

[0054] 2. A dye is applied to the skin over the region of the voids. Optionally, the dye may be urged mechanically to enter the voids. Otherwise, it may enter the voids by capillary action. The step of applying the dye is performed when the voids remain open, before they have begun to heal such that migration of dye into the voids may be inhibited. Ideally, the dye is applied immediately after they voids have been formed.

[0055] 3. Excess dye is removed, e.g. by washing, wiping or bathing the region of skin. Washing the skin may involve applying water to the skin. The excess dye is dye remaining on the surface of the skin, and that has not entered the voids. This step may be omitted, but the resulting tattoo may appear to be less sharp as a result.

[0056] 4. A fixing solution is applied to the skin in the region of the voids. The fixing solution may react with the dye and / or components of the dermis such as collagen to help the dye to bond in the dermis and as a result reside in the dermis over an extended period. Preferably the fixing solution is an alkali, preferably the fixing solution is an alkali solution.

[0057] The healing and aftercare of a dye tattoo will now be described with reference to figure 3 which shows a schematic representation of the healing stages of a region of skin 300. The region of skin 300 is depicted as a cross-sectional view. A void 301 extending through the epidermis and into the dermis is shown. The region of skin where the dye has been introduced is washed with a cleaning solution 302. The cleaning solution also functions as a healing solution, the terms will be used interchangeably. The cleaning solution may improve the appearance of the healed tattoo. The cleaning solution preferably comprises one or more of an antiseptic, an antibiotic, an antimycotic, and a steroid. The antiseptic, antibiotic and antimycotic reduce the risk of infection. The steroid reduces inflammation and may promote retention of the dye in the dermis. Retention of the dye may be promoted by the accelerated and / or improved healing of tissue subjected to the tattooing process. An example of a suitable group of steroids is glucocorticoids.

[0058] In figure 3, a partially healed void 303 is shown. The profile of the void is reduced in depth and extent from the void 301 . The skin heals over time by a biological healing process involving platelets, macrophages and fibroblasts. The natural healing process is supported and may be accelerated by the application of the healing solution 302 to the voids after the dye is applied and fixed. To further promote healing a patch may be applied to the surface of the skin. The patch may be a sterile bandage. The patch may be applied to the skin for several days following the tattoo application. The patch may contain or be using in combination with soothing agents such as pantothenic acid and ceramides. An anti-pigmentation agent may be topically applied to the tattooed region to reduce the risk of pigmentation. For example, the anti-pigmentation agent may be applied to the epidermis. The anti-pigmentation agent may be a retinoid.

[0059] After several days, the void will have healed to a greater extent, as shown at 304. The healing void 304 extends only slightly into the dermis and has a reduced diameter. After a further period of time, for example a few weeks, the void in the skin will have substantially healed and a scab 305 may have formed. Without being bound by theory, it is understood that the dye is made to remain in the dermis by being introduced at a particular depth into the dermis and the reaction with tissue in the dermis. The dye may bind to proteins in the dermis. Dye molecules may agglomerate with each other in the dermis. Agglomeration of the dye will be described in more detail below.

[0060] As used herein, ‘fix’ or ‘fixation’ in the dermis may describe binding of the dye to one or more components of the extracellular matrix. Such components include fibrous proteins (e.g. collagen, elastin), cell-adhesive glycoproteins (e.g. fibronectin, laminin), proteoglycans and glycosaminoglycans (e.g. hyaluronic acid, chondroitin sulfate, dermatan sulfate, heparan sulfate), constituents of the basement membrane, and constituents of the papillary dermis.

[0061] Conventional tattoo ink comprises pigments, especially inorganic pigments. These pigments may be solid particles having a size between 200 nm - 200 pm. The presently-described method of tattooing avoids the use of conventional pigment inks and instead uses a dye to produce the colour of the tattoo. In certain embodiments of the present invention, the term ‘dye’ is used to mean a colouring agent in which the chromophores are in solution in a solvent. As used herein ‘dye’ preferably means any substance or combination of substances capable of producing a visible colour in the dermis when applied according to the disclosed methods. Preferably the term ‘dye’ includes materials which are colourless or weakly coloured prior to fixation in the skin but which develop or reveal colour when situated in the skin. Such dyes may develop colour as a result of a chemical and / or physical reaction, for example by a change in pH, by oxidation or reduction, a photochemical activation, covalent bonding to constituents of the skin, or a combination of two or more thereof. Examples of suitable dyes include pro-dyes, leuco-dyes, photochromic dyes, thermochromic dyes, solvatochromic dyes, coordination systems, soluble metal salts, or a combination of two or more thereof. The term ‘dye’ as used herein may encompass a colouring agent together with any solvent, carrier, or auxiliary substances forming a solution, dispersion, or mixture.

[0062] The dye may be provided in particulate form, for example as an organic or inorganic pigment, optionally a carbon-based pigment, optionally dispersed or suspended in a carrier. The dye may comprise particles. Such particulate colourants may be delivered via the voids according to the methods described herein. Particulate colourants are preferably retained or fixed within the dermis. Pigments may function as dyes to colour the skin when applied according to the methods described herein. Particulate dyes may be suitable for use in the methods and systems of tattooing described.

[0063] The term “dye” may be used to refer to the combination of colouring agent and solvent. The solvent may be an aqueous solvent or a non-aqueous solvent. It is preferred that the solvent is an aqueous solvent since an aqueous solvent may have better biocompatibility.

[0064] The dye may comprise or be covalently bonded to a reactive molecule containing one or more reactive functional groups capable of forming bonds with nucleophilic or electrophilic sites in dermal tissue, for example amino, hydroxyl, thiol, or carboxyl groups. Examples of reactive functional groups include: halo-heterocyclic groups, activated double bond systems (Michael acceptors), epoxide-type systems (ringopening alkylation), carbonyl-based electrophiles, sulfonyl or phosphoryl groups, leaving-group-activated systems, aziridines, photoreactive groups, click-chemistry groups (for in-situ activation), and metal-coordination groups.

[0065] The dye may fix in the dermis through covalent interactions, non-covalent interactions, or a combination of the two. Non-covalent interactions include ionic or electrostatic forces, hydrogen bonding, hydrophobic and n - n stacking interactions. Fixation of the dye may occur by coordination or chelation with metal ions present in tissue. The binding or interaction of the dye may involve chemical and / or physicochemical bonding. Such bonding may include covalent bonding, for example formation of new ff or 7i bonds between reactive groups of the dye (e.g., vinyl sulfone, triazine, isocyanate, aldehyde, carboxyl, amino, hydroxyl groups) and functional groups of components of the dermis and / or extracellular matrix (e.g., -NH2, -OH, -COOH, -SH groups).

[0066] The dye may fix in the dermis by ionic bonding. For example, cationic dyes can ionically bond to anionic sulfate or carboxylate groups of glycosaminoglycans.

[0067] The dye may fix in the dermis by hydrogen bonding, such as by donor and acceptor atoms (e.g., N-H- 0 or O-H- O) linking dye molecules and polar moieties in the dermis. The dye may fix in the dermis by Van der Waals interactions, such as dipoledipole, dipole-induced dipole, and London dispersion forces. The dye may fix in the dermis by hydrophobic interactions, for example non-polar association between aromatic or aliphatic groups of the dye and hydrophobic domains of proteins or lipids. Ti - Ti stacking and Tr-cation interactions may occur between aromatic rings of dye chromophores and aromatic amino acids or cationic residues.

[0068] The dye may fix in the dermis by coordinate bonding (chelation). The dye may form a complex with metal ions present in tissue (e.g. calcium, iron, copper, zinc ions. Dipole and induced-dipole interactions, halogen bonds, or other weak non-covalent forces may contribute to the stabilization of the dye in the extracellular matrix. Fixation of the dye may result from one or more interactions as described above. Reaction of the dye may form a network that immobilizes dye molecules within the dermis. Preferably, the network containing the dye molecules forms in the extracellular matrix of the dermis.

[0069] The dye is preferably soluble. The solubility of the dye at 37°C and at a pH in the range 6.5 - 8.0 is preferably in the range from 1 m^lmd to where mSv is the mass of solvent required to dissolve one unit of mass ma of dye (as a solute). The dye may be selected so as to be suitable for at least partially dissolving in interstitial fluid and / or blood. The dye may be soluble in interstitial fluid and / or blood. Preferably the dye is water soluble. Preferably the dye is at least partly soluble in oil. The dye may be soluble in fatty tissue.

[0070] Preferably, the dye comprises a reactive molecule or a functional group which reacts with a moiety in the dermis. The dye may comprise an azo dye. The dye may comprise sulfur. The reactive molecule may comprise a vinyl sulfone and / or a triazine group. The reactive molecule may comprise a chloro-triazine group. The dye may comprise Reactive Black 5, also known as Remazol Black B. The dye may comprise Reactive Orange 16, also known as Remazol Brilliant Orange 3R. A tattoo ink which appears black once applied by the method described herein may comprise both Reactive Black 5 and Reactive Orange 16. The dye may be prepared prior to application by dissolving a powder dye in water. Preferably the dye is prepared immediately prior to application, for example not longer than 1 hour before application. Additionally, salt (NaCI) may be added to the dye.

[0071] The dye may comprise or be covalently bonded to a reactive species. The reactive species may be a reactive molecule. The reactive species preferably contains one or more reactive functional groups capable of forming bonds with constituents of the dermis and / or extracellular matrix. Preferably the dye reacts with nucleophilic or electrophilic sites in dermal tissue, for example amino, hydroxyl, thiol, or carboxyl groups.

[0072] Examples of reactive functional groups include: halo-heterocyclic groups, activated double bond systems (Michael acceptors), epoxide-type systems (ring-opening alkylation), carbonyl-based electrophiles, sulfonyl or phosphoryl groups, leaving- group-activated systems, aziridines, photoreactive groups, click-chemistry groups (for in-situ activation), and metal-coordination groups.

[0073] Halo-heterocyclic groups bond by nucleophilic substitution. Examples of dyes having a halo-heterocyclic group include: monochlorotriazine, monofluorochlorotriazine, dichlorotriazine, difluorochloropyrimidine, trichloropyrimidine, dichloroquinoxaline, monofluorotriazine and mixed halotriazines. Activated double-bond groups (known as Michael acceptors) form bonds by donating an electron pair. Examples of activated double-bond systems include vinyl sulfone (- SO2-CH=CH2), vinyl amide (-CH=CH-CONH-), acrylamide, acryloyl, crotonyl, maleimide derivatives, and haloacrylamido groups (such as a-bromo- or a-chloro- acrylamides).

[0074] Epoxide-type systems react by ring-opening alkylation. Examples of epoxide-type groups include glycidyl, epoxy groups, epichlorohydrin, 3-chloro-2-hydroxypropyl, and oxirane derivatives.

[0075] Examples of carbonyl-based electrophiles include acyl halides (-COCI, -COBr), acid anhydrides (-CO-O-CO-), isocyanates (-N=C=O), isothiocyanates (-N=C=S), aldehydes and activated ketones (which may be used for Schiff base formation)

[0076] Examples of sulfonyl and phosphoryl groups include sulfonyl halides (-SO2CI), sulfonic anhydrides, sulfates, phosphoryl chlorides and phosphoram idates.

[0077] Examples of leaving-group-activated systems include tosylates, mesylates, triflates, sulfonate esters, activated esters (e.g., N-hydroxysuccinimide esters).

[0078] The reactive functional group aziridines react by nucleophilic ring-opening. Other strained ring structures similar to aziridines which are capable of nucleophilic ringopening may also provide the reactive molecule.

[0079] Photoreactive and click-chemistry groups may provide the reactive molecule for in-situ activation. Examples of photoreactive and / or click-chemistry groups include aryl azides (-N3), diazirines, alkynes and azides for 1 ,3-dipolar cycloaddition (“click” reaction), tetrazoles (photo-activated nitrile imine sources).

[0080] Examples of metal-coordination groups include carboxylate, catechol, and imidazole moieties. Without being bound by theory, such moieties are thought to form coordinate bonds with metal ions naturally present in skin tissue. An optional additional step of the method of tattooing will now be described. After introducing the dye into the dermis, a treatment solution may be applied. The treatment solution comprises one or more components which promote fixation of the dye to components of the dermis or the extracellular matrix. Preferably the treatment solution comprises soluble components in aqueous solution. The treatment solution may contain activators which react with reactive groups to enhance covalent or coordination bonding between dye functional groups and tissue constituents. In this way, the treatment solution is applied to promote fixation of the dye. The treatment solution may enhance the reaction of reactive groups of the dye with components of the extracellular matrix.

[0081] Examples of treatment solutions include alkaline solutions, acidic solutions, solutions containing metal salts, organic or inorganic catalysts, buffers, high-pH activators (pH 8-11 ), and low-pH activators (pH 3-5). Examples of each type of treatment solution will now be given.

[0082] Alkaline solutions may include sodium carbonate, sodium hydroxide, potassium carbonate, or two or more thereof. Alkaline solutions may provide hydroxide ions which promote activation of vinyl sulfone, triazine, or epoxide reactive groups.

[0083] Acidic solutions may include citric acid, acetic acid, lactic acid, or two or more thereof. Acidic solutions may provide protonic activation for carbonyl-based or amide-based reactive systems.

[0084] Metal salts may including chlorides, sulfates, or acetates of Na+, K+, Ca2+, Mg2+, Zn2+, Cu2+, Fe2+ / Fe3+, Al3+, capable of forming coordination complexes with dye molecules and tissue ligands, thereby improving fixation.

[0085] Organic or inorganic catalysts and buffers may include ammonium salts, phosphate buffers, borates, imidazoles, amines (e.g., triethanolamine, morpholine), or two or more thereof. Such substances in the treatment solution may be used to adjust reaction kinetics and / or pH of the solution. High-pH activators (pH 8-11 ) are suitable for nucleophilic substitution, for example with triazine, vinyl sulfone, and epoxide groups.

[0086] Low-pH activators (pH 3-5) are suitable for condensation or Schiff-base reactions of aldehyde and carbonyl groups with amino-containing biomolecules.

[0087] The solution may also contain ionic salts (NaCI, KCI, CaCl2, MgCl2, ZnCl2) to modulate electrostatic interactions between the dye and tissue and to minimize charge-based repulsion.

[0088] Fixing the dye in the dermis may comprise forming water-insoluble precipitates, polymers, or coordination complexes of the dye within the dermis. Following formation of voids into the dermis and at least partial removal of the basement membrane, one or more reagent solutions may be applied to the skin. The reagent solutions may be applied sequentially. The reagents may diffuse into the dermis. The reagents preferably react with each other and / or with components of the extracellular matrix (e.g., collagen, elastin, fibronectin, glycoproteins, proteoglycans, hyaluronic acid, integrins), to produce water-insoluble species. In this way, the dye is durably fixed in the dermis. Advantageously, a water-soluble dye can be delivered to the dermis via the voids and fixed in the dermis such that a substantially water-insoluble species remains. The insoluble species may form in the papillary dermis and / or in the reticular dermis.

[0089] Examples of combinations of reagents and an overview of the reactions will be provided. In each example, voids are formed in a region of skin using a CO2 laser prior to application of a reagent solution. Optionally, after application of a first reagent, the region of skin may be rinsed with deionised water. Optionally, after application of the reagents, a neutralising solution is applied to the region of skin to dilute and / or remove residual reactants. The neutralising solution may contain buffers to restore the pH of the region of skin to around 5.5 (typical skin pH).

[0090] In a first example, a first solution of aqueous p-phenylenediamine (PPD) was applied to the skin. A waiting period of between about 1 to about 10 minutes was observed. A second solution comprising hydrogen peroxide (H2O2) was applied to the skin. Optionally, tannic acid and / or a solution containing iron (III) ions may be applied to catalyse the reaction between PPD and hydrogen peroxide. The formation of dark (brown-black) oligomers was observed. It is theorised that dye species are retained by covalent bonding within the dermis. It is understood that oxidative polymerisation of the PPD occurs.

[0091] In a second example, an iron-gall type dye was fixed in the dermis. A first solution of tannic acid was applied to the skin. A second solution of ferric chloride (FeCh) was applied to the skin. A dark bluish-black precipitate was observed. Similarly, a first solution of gallic acid may be reacted with ferric chloride to produce a dark precipitate in the dermis. Similarly, either gallic or tannic acid may be reacted with ferric sulfate (Fe2(SO4)s) to produce a dark precipitate in the dermis.

[0092] In a third example, a first solution containing ferric nitrate (Fe(NOs)3) and ferrous sulfate (FeSC ) in a molar ratio of about 2:1 Fe3+:Fe2+was applied to the skin. A second solution containing ammonium hydroxide was applied to the skin. Preferably the ammonium hydroxide is dilute in solution, having a pH of about 8 to about 9. A black species was observed. The reaction is understood to produce iron oxide, known as magnetite (FesO4).

[0093] In a fourth example, a Prussian blue dye was made to fix in the dermis. A first solution of potassium ferrocyanide (K4[Fe(CN)e] ■ 3H2O) was applied to the skin. A second solution comprising iron (III) ions was applied. The second solution may contain one or more of ferrous chloride and ferrous nitrate. The resulting dye contained the insoluble complex Fe4[Fe(CN)e]3 which appeared dark blue. The Prussian blue dye may be produced by reacting sodium ferrocyanide with Fe3+ions.

[0094] In a fifth example, a copper (II) sulfate (CuSO4 ■ 5H2O) solution was applied to the skin. A second solution containing a basic sodium compound such as sodium carbonate or sodium bicarbonate solution was applied to the skin. The first and second solutions react to produce basic copper carbonate (CuCO3'Cu(OH)2), an insoluble green solid. The precipitate was observed to develop from a pale green colour to a vivid green. Optionally, a third solution comprising an acid may be added to reduce the copper carbonate and turn the precipitate blue. As described herein, in addition to agglomeration, dye fixation in the dermis may occur by polymerization and / or polycondensation of the dye in the dermis. The dye may be fixed by other mechanisms of immobilization, including ionic complexation, coordination / chelation, supramolecular assembly, photo-activated or enzyme-mediated covalent deposition, and bio-orthogonal reactions.

[0095] Figure 4 shows an exemplary system for making voids in the skin. The system 400 comprises a scanner 401 and a device 402 for marking the skin. The device 402 may be a laser. The laser may comprise a lens 403 and, in operation, a beam 404. The device 402 is connected to a processor 405. The system could be implemented by one or more computer devices which could be co-located or distributed across multiple locations. The processor 405 comprises or is in communication with a memory storing in non-transient form instructions executable by the processor to cause the processor to implement functions of the system as described below. The system 400 comprises a display 406, the display may be configured to receive user-input and to display content to a user of the system. The processor 405 may be in communication with the display 406. Alternatively, the display 406 may be in communication with a different processor.

[0096] The scanner 401 is suitable for imaging a region of skin to be tattooed. For example, the scanner may comprise a camera, binocular imaging hardware, an infrared imaging device, or a LIDAR sensor. It is advantageous to be able to determine the depth and topography of a region of skin to be tattooed prior to patterning the skin. The scanner 401 is preferably configured to send an indication of a scanned region of skin to the processor 405. The processor 405 may determine adjustments to a tattoo pattern in response to the scanner data. For example, in a 10cm by 10cm region scanned at a user’s forearm, the imaged areas at the outer and inner forearm will be detected as curved and further away from the scanner while the centre of the forearm will be detected as relatively planar and closer to the scanner. A tattoo design can be modified to make deeper voids at the regions detected as being further from the scanner. In other words, regions further from the scanner may be designated in the design as requiring a greater depth than regions closer to the scanner. The system is particularly advantageous as it permits the application of a tattoo without the need for a tattoo artist. A human tattoo artist is susceptible to deviation from an intended tattoo design due to the limitations of applying a tattoo by hand, and due to the skill and experience of the artist. Further, the system is advantageous in that a tattoo can be applied in a much shorter time. This is especially beneficial for large tattoos, which may take several hours to be applied by a conventional tattooing process. A shorter duration of tattooing is preferable as the pain experienced by a person being tattooed is minimised.

[0097] The device for marking skin may be an automated device such as a printer or a robotic drawing tool. The device for marking skin may be operational without the input of a tattoo artist, for example an automated device may be configured to tattoo a selected design on a region of skin.

[0098] A method of tattooing will be described using the system as described above, in which the system comprises a laser. The exemplary system provides for needleless tattooing, i.e. without the use of a needle. Dermal penetration is achieved without the use of a needle. A user selects a tattoo design from a library shown on the display 406. A region of skin to be tattooed is positioned proximal to the scanner 401 . The scanner images the region of skin, collecting depth information and sending said information to a processor. A transform or other modification(s) may be made to the selected tattoo design in response to the scanner imaging. The region of skin is moved proximal to the laser 402. The lens 403 may be adjusted to focus the laser about the surface of the region of skin. Preferably, the laser beam is focused at a depth just below the surface of the skin, or at the surface of the skin. The lens 403 may be moved by motors controlled by the processor 405. The laser 402 patterns the region of skin with the selected design. The laser may remove skin by ablation. The laser may be pulsed. The system may be configured such that each laser pulse produces a single void in the skin. The epidermis and part of the dermis is removed by ablation. Once the voids have been formed, a dye is applied to the region of skin. The method then proceeds as described above with reference to figure 2.

[0099] In an alternative embodiment of the system, the device for marking skin 402 comprises a blade. The blade may be configured to penetrate into the skin at an acute angle to the planar surface of the skin. The device for marking skin may further comprise a probe for applying ultrasound and / or vibrations to the skin. The application of the probe at or near the region of skin promotes movement of the dye from the skin surface and epidermis into the dermis.

[0100] Figure 5 shows a top-down view of a region of skin 500. Voids 501 in the skin are made by any suitable method, such as by laser ablation. Each void is seen as a hole in the top-down view of figure 5. Each void may have a diameter of between 10 pm to 500 pm, preferably between 50 pm to 150 pm. Respective voids may have a horizontal spacing 502 of at least 50 pm, preferably at least 100 pm. Respective voids may have a vertical spacing 503 of at least 50 pm, preferably at least 100 pm. The minimum spacing being of this length ensures that there is enough skin surrounding a void to allow good healing of the tattoo. The horizontal spacing 502 and vertical spacing 503 may be equal.

[0101] The total depth of the void will depend on the thickness of the epidermis. The thickness of the epidermis varies for different persons, and at different body parts of the same person (for example, the eyelid epidermis is particularly thin, while the heel epidermis is significantly thicker). Preferably the voids extend from the epidermisdermis interface into the dermis by a depth of 10 pm - 80 pm, preferably about 50 pm. In a typical region of skin to be tattooed, such as the thigh, the total depth of the void is about 150 pm.

[0102] The equipment described above may be programmable to form a series of voids in the skin of a subject. The equipment may image the skin to determine its distance from a reference plane. Using that information the equipment may adjust the process of forming the voids so that each void has a desired depth. The desired depth may depend on the depth of the epidermis at the location of the void. The desired depth may depend on the depth of the dermis at the location of the void. The equipment may be pre-programmed to estimate the depth of the dermis based on the scanning of the subject and / or on information provided to it such as the age, height and weight of the subject. The equipment may then adjust the power of an optical beam and / or the distance from the skin of a head from which the beam is generated so as to form voids of the desired depth. The equipment may be programmed with an image that is to be defined as a tattoo. The equipment may then determine a pattern of voids to apply for forming a tattoo of the image.

[0103] The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description, it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.

[0104] Within this specification, the term "about" means plus or minus 20%, more preferably plus or minus 10%, even more preferably plus or minus 5%.

[0105] Within this specification, the term "substantially" means a deviation of plus or minus 20%, more preferably plus or minus 10%, even more preferably plus or minus 5%.

[0106] Within this specification, reference to “substantially” includes reference to “completely” and / or “exactly.” That is, where the word substantially is included, it will be appreciated that this also includes reference to the particular sentence without the word substantially.

[0107] Some implementations may be described using the expressions “one / an embodiment” or “one / an example,” along with their derivatives. These terms mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Moreover, unless otherwise noted the features described above are recognized to be usable together in any combination. Thus, any features discussed separately may be employed in combination with each other unless it is noted that the features are incompatible with each other.

[0108] The foregoing description of example embodiments has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the present disclosure to the precise forms disclosed. Within this specification embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without parting from the invention. Many modifications and variations are possible in light of this disclosure. It is intended that the scope of the present disclosure be limited not by this detailed description, but rather by the claims appended hereto.

Claims

AMENDED CLAIMS received by the International Bureau on April 1st, 2026 (01.04.2026)Claims

1. A method of tattooing skin comprising: creating voids extending from a surface of the epidermis into the dermis, wherein the voids are created by laser ablation; introducing a dye through the voids into the dermis; and fixing the dye in the dermis.

2. A method as claimed in claim 1, wherein the voids do not extend through the dermis into the hypodermis.

3. A method as claimed in claim 1 or 2, wherein the dye is soluble in a solution comprising water.

4. A method as claimed in any preceding claim, wherein the dye is soluble in oil.

5. A method as claimed in any preceding claim, wherein the dye comprises a reactive molecule.

6. A method as claimed in claim 5, wherein the reactive molecule comprises a vinyl sulfone and / or a triazine group.

7. A method as claimed in any preceding claim, further comprising, prior to creating voids, preparing the dye by dissolving a dry dye and sodium chloride in water.

8. A method as claimed in any preceding claim, wherein each void has a diameter at the surface of the epidermis of around 10 pm to around 500 pm, preferably around 100 pm.

9. A method as claimed in any preceding claim, wherein respective voids are spaced apart by a distance of at least about 50 pm, preferably at least about 100 pm.

10. A method as claimed in any preceding claim, wherein the voids extend into the dermis by about 50 pm.

11. A method as claimed in any preceding claim, further comprising: once the dye has been introduced through the voids into the dermis, observing a waiting period of 5 to 15 minutes; washing off excess dye; and applying an alkali solution to the voids and washing off this alkali solution.

12. A method as claimed in any preceding claim, wherein creating voids comprises at least partially removing a basement membrane, the basement membrane being between the epidermis and the dermis.

13. A method as claimed in any preceding claim, further comprising:applying a mixture to promote healing, the mixture comprising a steroid, an antibiotic and an antimycotic.

14. A method as claimed in any preceding claim, further comprising, prior to creating voids, applying a disinfectant to the surface of the epidermis.

15. A method as claimed in any preceding claim, wherein the dye is applied by a mechanical applicator or by spraying the dye on the skin surface.

16. A system of needleless tattooing comprising: a sensor for sensing a location of the surface of a region of skin of a subject; a dermal penetration device for penetrating into the skin, wherein the dermal penetration device comprises a laser; a controller responsive to the sensor to control the dermal penetration device to produce a plurality of voids into but not through the dermis in the region of skin.

17. A system as claimed in claim 16, wherein the controller is configured to cause the laser to ablate voids in the dermis.

18. A system as claimed in claim 16 or 17, further comprising a dermisresident dye for application to the region of skin.

19. A system as claimed in claim 18, wherein the dermis-resident dye comprises a reactive molecule.

20. A system as claimed in claim 19, wherein the reactive molecule comprises a vinyl sulfone and / or a triazine group.

21. A system as claimed in any of claims 16 to 20, further comprising a mixture for promoting healing, the mixture comprising a steroid, an antibiotic and an antimycotic.

22. A system as claimed in any of claims 16 to 21, further comprising a probe for applying ultrasound and / or vibrations to the region of skin.

23. A system as claimed in any of claims 16 to 22, further comprising a display configured to receive user input for selecting a tattoo design, wherein the laser is controlled to pattern the region of skin with a selected tattoo design.

24. A system as claimed in any of claims 16 to 23, wherein the scanner is configured to send an indication of a scanned region to a processor to determine the depth and topography of the scanned region of skin.

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