Determining pH of Human Skin

Abstract

A device suitable for assisting in determining the pH of the surface of human skin, comprises a body 12 having an upper surface 14 and a lower contact face 16. The lower contact face includes at least

Description

DETERMINING PH OF HUMAN SKIN FIELD AND BACKGROUND OF THE INVENTION The invention, in some embodiments, relates to the field of skin care, toiletries and cosmetics and, more particularly but not exclusively, to methods and devices for determining the pH of human skin, for example, to assist in characterizing the skin as a prelude to providing and / or recommending customized / personalized skin-care regime and / or cosmetic & care products. Different people have different skin characteristics including: skin moisture (dry skin to hydrated skin), oiliness (sebum production: normal, dry, oily and combination skin types), pH value, scaliness / desquamation and sensitivity. Most cosmetics are formulated for what is considered normal skin. A typical person samples multiple cosmetic formulations until finding one that is compatible with their skin and then continues using that formulations. Some cosmetics are formulated for and marketed as special for unusual skin, for example, formulated for dry skin, formulated for oily skin, formulated for acidic skin or formulated for non-acidic skin. A person who believes that their skin is unusual, e.g., after failing to find a suitable formulation for normal skin, may sample such special formulations and may find one that is suitable. To assist in marketing special cosmetic formulation, there exist skin-testing devices for determining skin characteristics. USP Indicator Solutions (Klagenfurt am Worthersee, Austria) markets a kit for determining the pH value of the skin, the kit comprising an indicator strip with two colorimetric indicator patches and a sachet of activation liquid. A user cuts the top of the sachet open with a pair of scissors, dips the indicator patches of the strip in the liquid, shakes- off any excess moisture, and presses the indicator patches against the skin at the inside of the forearm (just below the wrist) for about 20 seconds during which time the indicator patches interact with the skin and change color. The user then compares the color of the two indicator patches to a reference color scale and finds the pH value of the skin as being one of 4, 4.5, 5, 5.5,6,6.5 7and 7.5. It would be useful to have methods and devices to assist in determining the pH of human skin that have at least some advantage over what is known in the art. SUMMARY OF THE INVENTION Some embodiments of the invention herein relate to methods and devices that, in some embodiments, assist in determining the pH of human skin. According to aspect of some embodiments of the teachings herein, there is provided a device suitable for assisting in determining the pH of the surface of human skin, comprising: a body having an upper surface and a lower contact face, the lower contact face including at least a portion of a pH indicator patch; and inside the body, a volume containing an activation liquid so that when the activation liquid wets the surface of human skin and a surface of the pH indicator patch while the lower contact face makes intimate contact with the surface of the skin, the activation liquid allows material from the surface of the skin to interact with a pH indicator component present in the pH indicator patch, thereby allowing the pH indicator patch to indicate a pH of the surface of the skin. In some embodiments, the pH indicator patch is a colorometric indicator patch comprising at least one colorimetric pH indicator component. In some embodiments, the lower contact face includes at least one additional pH indicator patch. In some embodiments, the lower contact face has a surface area of not less than about 1 em? and not more than about 25 cm?. In some embodiments, the thickness of the device from the lower contact face to a top of the upper surface is not less than about 2 mm and not more than about 1.5 cm. In some embodiments, the activation liquid comprises at least 99% w / w water. In some embodiments, the lower contact face is rigid. Alternatively, in some embodiments, the lower contact face is flexible. In some embodiments, the lower contact face is conformable. In some embodiments, the lower contact face comprises an adhesive portion configured to reversibly adhere to dry human skin for at least 10 seconds subsequent to application to the skin, which adhering is sufficient to maintain the indicator patch in intimate contact with the human skin. In some embodiments, adhesive portion at least partially surrounds the indicator patch and, in some such embodiments, completely surrounds the indicator patch. In some embodiments, the device further comprises a user-removable protective cover on at least a portion of the lower contact face. Such a protective cover is removed prior to use. In some such embodiments, the protective cover is removably-secured to the lower contact face with an adhesive. In some such embodiments, the adhesive is the same adhesive portion that is configured to reversibly adhere to dry human skin, mentioned above. In some embodiments, the device is provided enclosed in a user-openable package. In some embodiments, the pH indicator patch is provided wet, that is to say, the volume containing the activation liquid comprises the pH indicator patch. In some such embodiments, the volume containing the activation liquid consists of the pH indicator patch. Alternatively, in some such embodiments, the volume containing the activation liquid further comprises a liquid reservoir different from the pH indicator patch. In some embodiments, the liquid reservoir is in physical contact with the pH indicator patch. Alternatively, in some embodiments, the liquid reservoir is devoid of physical contact with the pH indicator patch. In some embodiments, the lower contact face includes at least a portion of the liquid reservoir. Alternatively, in some embodiments no portion of the liquid reservoir is apparent on the lower contact face. In some embodiments, the body of the device is collapsible by manual pressure applied to the upper surface where, when the body is manually collapsed while the lower contact face contacts a skin surface, the collapsing leads to expulsion of the activation liquid from the liquid reservoir, thereby wetting the skin surface and a surface of the pH indicator patch. In some embodiments, the pH indicator patch is provided dry, that is to say, the volume containing the activation liquid is in a sealed reservoir separate from the pH indicator patch. In some embodiments, the device further comprises a user-removable protective cover on at least a portion of the lower contact face, configured that, when the protective cover is removed, the sealed reservoir is unsealed so that activation liquid can exit the reservoir. In some embodiments, the body of the device is collapsible by manual pressure applied to the upper surface where, when the body is manually collapsed while the lower contact face contacts a skin surface, the collapsing leads to opening of the sealed reservoir, allowing release of the activation liquid from the liquid reservoir, thereby wetting the skin surface and a surface of the pH indicator patch. In some such embodiments, the opening of the reservoir is breaking of at least a portion of the reservoir. BRIEF DESCRIPTION OF THE FIGURES Some embodiments of the invention are described herein with reference to the accompanying figures. The description, together with the figures, makes apparent to a person having ordinary skill in the art how some embodiments of the invention may be practiced. The figures are for the purpose of illustrative discussion and no attempt is made to show structural details of an embodiment in more detail than is necessary for a fundamental understanding of the invention. For the sake of clarity, some objects depicted in the figures are not to scale. In the Figures: Figures 1A and 1B schematically depict an embodiment of a device according to the teachings herein in side cross section (Figure 1A) and in bottom view (Figure 1B); Figures 2A, 2B and 2C schematically depict an embodiment of a device according to the teachings herein in side cross section (Figure 2A), bottom view without a protective cover (Figure 2B) and and in bottom view with a protective cover partially removed (Figure 2C); Figure 3 schematically depicts an embodiment of a device according to the teachings in bottom view without a protective cover; Figures 4A, 4B and 4C schematically depicts an embodiment of a device according to the teachings in bottom view without a protective cover (Figure 4A), in enlarged partial bottom view without a protective cover (Figure 4B) and in partial side cross section (Figure 4C); Figure 5 schematically depicts an embodiment of a device according to the teachings in side cross section; Figure 6 schematically depicts an embodiment of a device according to the teachings in side cross section; and Figures 7A and 7B schematically depicts an embodiment of a device according to the teachings in side cross section (Figure 7A) and bottom view without a protective cover (Figure 7B); and Figures 8A and 8B schematically depicts an embodiment of a device according to the teachings in side cross section (Figure 8A) and bottom view without a protective cover (Figure 8B). DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION Some embodiments of the invention herein relate to methods and devices that, in some embodiments, assist in determining the pH of human skin. The principles, uses and implementations of the teachings of the invention may be better understood with reference to the accompanying description and figures. Upon perusal of the description and figures present herein, one skilled in the art is able to implement the teachings of the invention without undue effort or experimentation. In the figures, like reference numerals refer to like parts throughout. Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and / or methods set forth herein. The invention is capable of other embodiments or of being practiced or carried out in various ways. The phraseology and terminology employed herein are for descriptive purpose and should not be regarded as limiting. According to an aspect of some embodiments of the teachings herein there is provided a device suitable for assisting in determining the pH of the surface of human skin, the device comprising: a body having an upper surface and a lower contact face, the lower contact face including at least a portion of a pH indicator patch; and inside the body, a volume containing an activation liquid, so that when the activation liquid wets the surface of human skin and a surface of the pH indicator patch while the lower contact face makes intimate contact with the surface of the skin, the activation liquid allows material from the surface of the skin to interact with a pH indicator component present in the pH indicator patch, thereby allowing the pH indicator patch to indicate a pH of the surface of the skin. For use, the device is contacted with bare human skin (for example, on the face or inside of the arm) so that the lower contact face, and particularly the pH indicator patch, makes intimate contact with the skin. The activation liquid wets both the skin surface and the pH indicator patch, thereby allowing material from the surface of the skin to interact with a pH indicator component present in the pH indicator patch, thereby allowing the pH indicator patch to indicate a pH of the surface of the skin. pH indicator patch and pH indicator component The pH indicator patch is any suitable pH indicator patch as known in the art, a patch that includes a pH indicator component that interacts with materials on the surface of human skin, where the results of the interaction, typically a change in the appearance of the pH indicator patch, indicate the pH of the surface of the skin. In some embodiments, the pH indicator patch is a colorometric indicator patch comprising at least one colorimetric pH indicator component. Colorimetric pH indicator components and the uses thereof are well known in the art of chemistry as components that react with materials in solution and adopt a color indicative of the pH of the solution as a result of the reaction. In some embodiments, the pH indicator component(s) and / or the pH indicator patch are the same as used in the commercially-available indicator kit by USP Indicator Solutions discussed in the introduction. In some embodiments where the pH indicator component changes appearance as a result of interaction with material from the surface of the skin, a user looks at the pH indicator component (for example, by lifting the device from contact with the scan to look at the lower contact face) to get an indication what the pH of the skin is. Additionally or alternatively, in some embodiments a user uses a camera, such as found in a cellular telephone or a smartphone, to capture an image of the pH indicator patch and a computer (local or remote) analyzes the image to get an indication of what the pH of the skin is. In some such embodiments, the lower contact face has a property (shape of the contact face and / or color of at least part of the contact face and / or patterns on at least part of the contact face) that assists in image-processing, for example, allows determining which of multiple pH indicator patches is which, allows determining the orientation of an acquired image, allows identification of a user and / or assists in providing color correction of an acquired image that may be required due to lighting conditions when the image was acquired. Dimensions of the device In some embodiments, the lower contact face has a surface area of not less than about 1 cm? and not more than about 25 cm? In some preferred embodiments, the lower contact face has a surface area of not less than about 4 cm?. Additionally or alternatively, in some preferred embodiments the lower contact face has a surface area of not more than about 16 cm? Such dimensions are large enough to allow a person to easily manipulate the device and easily see the pH indicator patch, and small enough to be able to make intimate contact with the surface of a human skin, for example, on the face of a human. In some embodiments, the thickness of the device from the lower contact face to a top of the upper surface is not less than about 2 mm and not more than about 1.5 cm. Activation liquid The activation liquid is any suitable activation liquid. Without wishing to be held to any one theory, it is believed that the activation liquid serves to wet the pH indicator patch and the skin surface, thereby providing fluid communication for materials from the surface of the skin to migrate to the pH indicator patch and to interact with a pH indicator component present in the pH indicator patch. The exact nature and composition of the activation liquid is, in part, dependent on the pH indicator component. In some embodiments, the activation liquid comprises at least 99% w / w water, in some embodiments, double-distilled or triple- distilled water. An exemplary embodiment of the device according to the teachings herein, device 10, is schematically depicted in Figure 1A (side cross section during use) Figure 1B (bottom view). Device 10 includes a body 12 having an upper surface 14 and a lower contact face 16, lower contact face 16 including a surface 26 of a pH indicator patch 18; and inside body 12, a volume 20 containing an activation liquid. Body 12 of device 10 comprises a rigid polycarbonate frame holding a polyethyelene strip bearing pH indicator patch 18.. The polyethylene strip is kept in place in the polycarbonate frame with adhesive. pH indicator patch 18 is kept flat by protrusions inside the polycarbonate frame. ‘When the activation liquid wets the surface of human skin 24 and surface 26 of pH indicator patch 18 while lower contact face 16 makes intimate contact with skin surface 24, the activation liquid allows material from skin surface 24 to interact with a pH indicator component present in pH indicator patch 18, thereby allowing pH indicator patch 18 to indicate a pH of skin surface 24. Number of pH indicator patches In some embodiments, the lower contact face of a device includes a single pH indicator patch. Lower contact face 16 of device 10 depicted in Figures 1 includes a single pH indicator patch 18. Alternatively, in some embodiments, the lower contact face includes at least one additional pH indicator patch, i.e., the lower contact face includes at least two pH indicator patches. In some embodiments, at least two pH indicator patches on a lower contact face of a single device include the same indicator chemistry. In preferred embodiments, two pH indicators on a lower contact face of a single device have different indicator chemistry, analogous to the two different indicator patches found on the commercially-available indicator kit by USP Indicator Solutions discussed in the introduction. In Figure 2, a second exemplary embodiment of a device according to the teachings herein, device 28 is schematically depicted in Figure 2A (side cross section during use), Figure 2B (bottom view without protective cover) and Figure 2C (bottom view with a protective cover 30 partially removed). Lower contact face 16 of device 28 depicted in Figures 2 has two pH indicator patches 18a and 18b. Body 12 of device 28 is a 0.5 mm thick ‘water vapor-impermeable polyethylene sheet. Flexibility of lower contact face In some embodiments, the lower contact face is rigid, that is to say, the lower face deforms by not more than 1% when pressed against the forehead of a human adult with a force of about 5 N. Lower contact face 16 of device 10 depicted in Figure 1 is rigid, inter alia, as a consequence of a periphery 32 of body 12 being of 1 mm thick polycarbonate. In some embodiments, the lower contact face is flexible, that is to say, the lower contact face conforms to the curvature of the forehead of a human adult when pressed against the forehead of a human adult with a force of less than about 5 N and even less than about 3 N. In some such embodiments, the lower contact face is confrmable, that is to say, the lower contact face conforms to the curvature of the forehead of a human adult without the application of force. In some embodiments, both the body of the device as well as the lower contact face are conformable, in a manner analogous to an adhesive bandage Lower contact face 16 of device 28 depicted in Figures 2 is conformable, inter alia as a consequence of body 12, including a periphery 32 thereof, being of 0.5 mm thick water vapor-impermeable polyethylene sheet so that body 12 is conformable. Adhesive It is currently believed that for use the lower contact face should preferably make intimate contact with a skin surface for a period of at least about 10 seconds so that the activation liquid can wet the skin surface and so that material from the skin surface can interact sufficiently with a pH indicator component of the pH indicator patch. In some embodiments, the lower contact face of the device is devoid of an adhesive. Typically, such devices are configured to be manually pressed against the skin for a sufficient period of time. Lower contact face 16 of device 10 depicted in Figure 1 is devoid of an adhesive. Alternatively, in some embodiments, the lower contact face comprises an adhesive portion configured to reversibly adhere to dry human skin for at least 10 seconds subsequent to application to the skin, which adhering is sufficient to maintain the indicator patch in intimate contact with the human skin. The adhesive is configured to reversibly adhere to human skin, allowing a person to manually separate the lower contact face from skin without pain and discomfort, as is known in the art of adhesive bandages. Any suitable adhesive may be used, for example, adhesives known in the art of adhesive bandages (e.g, BAND-AID® by Johnson & Johnson, New Brunswick, New Jersey, USA) such as rubber adhesives and acrylates, including methacrylates and epoxy diacrylates. In some embodiments, the adhesion of the adhesive as measured by the loop tack testing method (Finat Test Method No. 9) is at least about 16 N / 25mm (e.g., like the MED 6000 double-coated conformable polyethylene film with acrylic adhesive by Avery Dennison, Glendale, CA, USA) and not more than about 75 N / 25 mm (e.g., like the MED 6323 double-coated conformable polyester film with rubber adhesive by Avery Dennison). In some embodiments the adhesion of the adhesive is at least about 20 N / 25 mm. In some embodiments the adhesion of the adhesive is not more than about 60 N / 25 mm and even not more than about 50 N / 25 mm. It is currently believed that a particularly suitable adhesive is MED 1832 a single-coated pliable polyurethane film with an acrylic adhesive having adhesion of 23 N / 25 mm. In some embodiments, the adhesive portion at least partially surrounds the indicator patch, in some preferred embodiments, the adhesive portion completely surrounds the indicator patch. In preferred such embodiments, during use at least a portion of the adhesive portion that adheres the lower contact face to the skin also serves as a barrier that keeps activation liquid localized near the pH indicator patch or patches, trapped between the skin at the bottom, the lower contact face at the top and by the border of the adhesive portion at the sides. Lower contact face 16 of device 28 depicted in Figures 2 comprises an adhesive portion 34 (light grey portion) that completely surrounds indicator patches 18a and 18b. For use of some embodiments of devices including such an adhesive portion, the lower contact surface is pressed against a skin surface so that the adhesive keeps the indicator patch in intimate contact with the skin for a sufficient time. When sufficient time has passed, the device is manually removed from the skin. In this context, "dry human skin" refers to a skin surface without water thereupon, which, if required, can be achieved by blotting the skin surface with a towel, as known in the art of adhesive bandages. Protective cover In some embodiments, a device further comprises a user-removable protective cover covering at least a portion of the lower contact face. In some embodiments, such a protective cover covers the pH indicator patch. Additionally or alternatively, in some embodiments such a cover covers an adhesive portion of the lower contact surface. . The protective cover is removed prior to use, exposing the lower contact face. In some embodiments, the protective cover is configured to prevent one or more components of the activation liquid (e.g., water or other solvent) from escaping from the volume containing the activation liquid, for example, as a result of evaporation during storage. In some embodiments, the protective cover is removably-secured to the lower contact face with an adhesive. In some embodiments, the protective cover is removeably-secured to an adhesive portion on the lower contact face which is configured to reversibly adhere to dry human skin as described above. Such protective covers are well known, for example, in the field of adhesive bandages. Device 28 depicted in Figures 2 comprises a protective cover 30 that is removeably- secured to lower contact face 16 with adhesive portion 34. As seen in Figure 2C, protective cover 30 is a two-part 0.3 mm thick water vapor-impermeable polyethylene sheet as known in the art of adhesive bandages. Package Additionally or alternatively to a protective cover on at least a portion of the lower contact face, in some embodiments, a single device is enclosed in a user-openable package. In some embodiments, the protective cover is configured to prevent one or more components of the activation liquid (e.g., water) from escaping from the volume containing the activation liquid, for example, as a result of evaporation during storage. Such protective covers are well known, for example, in the field of adhesive bandages. Wet pH indicator patch In some embodiments, the device is provided with a wet pH indicator patch, that is to say, that the volume containing the activation liquid comprises the pH indicator patch, in which the activation liquid is absorbed. In some embodiments, the volume containing the activation liquid consists of the pH indicator patch. In such embodiments, the amount of activation liquid absorbed in the pH indicator component is such that is sufficient to also wet the skin during use of the device. In device 10 depicted in Figures 1, pH indicator patch 18 is a water-absorbant fibrous material (paper or cloth, for example of cotton) to which a pH indicator component is bonded and in which the activation liquid is absorbed. In some embodiments, the volume containing the activation liquid further comprises a liquid reservoir different from the pH indicator patch. In some embodiments, the liquid reservoir is in physical contact with the pH indicator patch. In some embodiments, the liquid reservoir is devoid of physical contact with the pH indicator patch. In some embodiments, the lower contact face includes at least a portion of the liquid reservoir. In some embodiments, no portion of the liquid reservoir is apparent on the lower contact face. In some embodiments, the body of the device is collapsible by manual pressure applied to the upper surface where, when the body is manually collapsed while the lower contact face contacts a skin surface, the collapsing leads to expulsion of the activation liquid from the liquid reservoir, thereby wetting the skin surface and a surface of the pH indicator patch. Device 28 depicted in Figures 2, comprises a liquid reservoir 36 (a water-absorbant fibrous material having about three times the volume of the combined volume of pH indicator patches 18a and 18b). Liquid reservoir 36 and pH indicator patches 18a and 18b together constitute activation liquid-containing volume 20 of device 28. Liquid reservoir 36 is in physical contact with pH indicator patches 18a and 18b and no portion thereof is apparent on lower contact face 16. During use, after device 28 is adhered to skin surface 24 with adhesive portion 34, a user presses upper surface 14 with a finger. The applied pressure leads to inwards collapse of body 12 which expels activation liquid from reservoir 36 and pH indicator patches 18a and 18b. The expelled activation liquid wets skin surface 24 and ensures that respective surfaces 26 of indicator patches 18a and 18b are sufficiently wet. When the finger is moved so that pressure is no longer applied to device 28, excess activation liquid is be absorbed back into reservoir 36 through pH indicator patches 18a and 18b. In device 28 depicted in Figure 2, no portion of liquid reservoir 36 is apparent on lower contact face 36. In some variants similar to device 28, a portion of a liquid reservoir 36 extends downwards to be apparent on lower contact face 36, for example, between pH indicator patches 18a and 18b and / or between adhesive portion 34 and pH indicator patches 18a and 18b. Such an embodiment is not depicted for brevity. In Figure 3, an exemplary embodiment of a device according to the teachings herein that is provided with a wet pH indicator patch, device 38 is depicted in bottom view. Device 38 is ordinarily provided with a protective cover which is removed prior to use. For brevity, the protective cover is not depicted in the Figures. Device 38 is similar to device 28 depicted in Figures 2, with a few notable differences. A lower contact face 16 of a device 38 comprises a rectangular ring-shaped liquid reservoir 36 of an absorbant material. Reservoir 36 encircles an empty space 40. Space 40 has the shape of a rectangular ring that surrounds pH indicator patch 18. As a result, reservoir 36 is devoid of physical contact with pH indicator patch 18. Reservoir 36 is apparent on a lower contact face 16 of device 38 so that when lower contact face 16 of device 28 contacts a skin surface, both reservoir 36 and pH indicator 18 also make contact with the skin surface. Liquid reservoir 36 and pH indicator patches 18 together constitute activation liquid containing volume 20 of device 38. During use, after device 38 is adhered to a skin surface 24 with an adhesive portion 34, a user presses an upper surface 14 with a finger. The applied pressure leads to inwards collapse of body 12 which expels activation liquid from reservoir 36. The expelled activation liquid wets skin surface 24 and ensures that surface 26 of indicator patch 18 is sufficiently wet. When the finger is moved so that pressure is no longer applied to device 38, excess activation liquid is be absorbed back into reservoir 36, so that the skin surface remains pleasantly dry. In device 38 depicted in Figure 3, liquid reservoir 36 is devoid of physical contact with pH indicator patch 18. In some variants of device 38, liquid reservoir 36 is in physical contact with pH indicator patch 18, specifically, reservoir 36 extends inwards to contact pH indicator patch 18 in the region occupied by empty space 40. Such an embodiment is not depicted for brevity. Dry pH indicator patch In some embodiments, the device is provided with a dry pH indicator patch, that is to say, that the pH indicator patch is not part of the volume containing the activation liquid. For use of such a device, the activation liquid is released from the volume to wet a skin surface and the pH indicator patch. Accordingly, in some embodiments, the volume containing the activation liquid is in a sealed reservoir separate from the pH indicator patch. In some such embodiments, the device further comprises a user-removable protective cover on at least a portion of the lower contact face, configured that, when the protective cover is removed, the reservoir is unsealed so that activation liquid can exit the reservoir. Such a device is device 42 depicted in Figure 4A (bottom view with the protective cover removed), Figure 4B (partial bottom view without the protective cover, depicted at 3x scale relative to Figure 4A) and in Figure 4C (side cross section with the protective cover, depicted at 2x scale relative to Figure 4A). In device 42, a pH indicator patch 18 is provided dry and a volume 20 containing the activation liquid is a sealed liquid reservoir 36. Body 12 of device 42 is a flat strip of molded silicone rubber about the size of an adhesive bandage having a rectangular inset on the bottom surface thereof. Protruding from the bottom of the rectangular inset is an integrally-formed silicone rectangular ring 44. The dimensions of pH indicator patch 18 are such that pH indicator patch 18 fits snugly inside and resting against the walls of rectangular ring 44, pH indictaor patch 18 is secured to the lower face of the rectangular inset with adhesive. Reservoir 36 is of an absorbant material and is shaped like a rectangular plate with a rectangular hole in the center. The dimensions of reservoir 36 are such that reservoir 36 fits snugly inside and resting against the walls of the rectangular inset. Reservoir 36 is secured to the lower face of the rectangular inset with adhesive. The rectangular hole in the center of reservoir 36 is sufficiently large so that there is a rectangular space 40 separating the inside of the rectangular hole in the center of reservoir 36 and the outside of silicone rectangular ring 44. Device 42 is provided with a protective cover 30 that covers the entirety of lower contact face 16 of device 42. Protective cover 30, depicted in Figure 4C, is a flat strip of molded silicone rubber about the size of body 12. Protective cover 30 is secured to lower contact face 16 by adhesive portion 34 (light grey area in Figure 4A) the covers most of the surface of lower contact face 16. Protruding from the upper face of protective cover 30 is an integrally-formed rectangular ring 46. The outer dimensions of rectangular ring 46 of protective cover 30 are such that the inner hole in the center of reservoir 36 fits snugly around and rests against the walls of rectangular ring 46 (see Figure 4C). The inner dimensions of rectangular ring 46 of protective cover 30 are slightly larger than the outer dimensions of rectangular ring 44 of body 12 so, when protective cover 30 is covering lower contact face 16, rectangular ring 46 of protective cover 30 is inside rectangular space 40 of body 12 and rectangular ring 44 of body 12 is nested inside rectangular ring 46 of protective cover 30. As a result, rectangular rings 44 and 46 form a water-tight seal separating reservoir 36 from pH indicator patch 18 so that activation liquid in reservoir 36 cannot leak to pH indicator patch 18 as long as protective cover 30 is associated with and covering lower contact surface 16. In some embodiments, during manufacture of device 42, after the other components are assembled and protective cover 30 is already associated with and covering lower contact face 16, a hollow needle is passed through body 12 into reservoir 36 and activation liquid is injected through the needle into reservoir 36. After reservoir 36 is filled with sufficient activation liquid, the needle is withdrawn, leaving a puncture 48 that does not leak due to the sealing properties of silicone rubber. As long as protective cover 30 is associated with lower contact face 16, the seal formed between rectangular rings 44 and 46 ensures that activation liquid from reservoir 36 and leak to pH indicator patch 18 and cannot evaporate. For use of device 42, a user grasps protective cover 30 and body 12 at an end 50 devoid of adhesive and separates the two, breaking the seal formed between rectangular rings 44 and 46. Lower contact face 16 is then placed against a skin surface so that adhesive portion 34 of lower contact face 16 holds lower contact face 16, including a surface 26 of pH indicator patch 18 and a surface of liquid reservoir 36, in intimate contact with the skin. A user presses upper surface 14 with a finger, the applied pressure leads to inwards collapse of body 12 which expels activation liquid from reservoir 36. The expelled activation liquid wets the skin surface and surface 26 of indicator patch 18. Release of the applied pressure allows any excess activation liquid to be absorbed back into reservoir 36 so that the skin surface remains pleasantly dry. In some embodiments where the device is provided with a dry pH indicator patch, the body is collapsible by manual pressure to the upper surface where, when the body is manually collapsed while the lower contact face contacts a skin surface, the collapsing leads to opening of the sealed reservoir, allowing release of the activation liquid from the reservoir, thereby wetting the skin surface and a surface of the pH indicator patch. In some such embodiments, the opening of the reservoir is the breaking of at least a portion of the reservoir. In Figure 5, an exemplary embodiment of a device, device 52, is schematically depicted in side cross section. In device 52, a body 12 comprises a hollow shell 54 of 2 mm thick silicone rubber. A lower contact face 16 is the lower surface of a 2 mm thick flat sheet 56 of silicone rubber that is sealingly secured to the bottom rim of hollow shell 54. A window 58 in sheet 56 hold pH indicator patch 18. Inside shell 54 as a reservoir 36 is a 0.5 mm thick rubber sealed ballon which inner volume is a volume 20 containing an activation liquid. Reservoir 36 is held away from a needle 60 that protrudes from pH indicator patch 18 by four springs 62 (two springs 62 are seen in Figure 5). For use of device 52, lower contact face 16 is pressed against a skin surface and the user applies pressure to upper surface 14. The applied pressure compresses springs 62 until the point of needle 60 pierces reservoir 36, releasing activation liquid inside shell 54. The activation liquid is wicked into and through pH indicator patch 18, wetting skin surface 24 and surface 26 of pH indicator patch 18. In Figure 6, an exemplary embodiment of a device, device 64, is schematically depicted in side cross section. In device 64, a body 12 comprises a hollow shell 54 of 2 mm thick silicone rubber. A lower contact face 16 is the lower surface of a 2 mm thick flat sheet 56 of silicone rubber that is sealingly secured to the bottom rim of hollow shell 54. A window 58 in sheet 56 holds pH indicator patch 18. Inside shell 54 as a reservoir 36 is a frangible ampoule made of a frangible material such as glass or frangible plastix which inner volume is a volume 20 containing an activation liquid. For use of device 64, lower contact face 16 is pressed against a skin surface and the user squeezes hollow shell 54 with two fingers, breaking reservoir 36, releasing activation liquid inside shell 54. The activation liquid is wicked into and through pH indicator patch 18, wetting the skin surface and surface 26 of pH indicator patch 18. In Figures 7 an exemplary embodiment of a device, device 66, is schematically depicted in side cross section (Figure 7A) and in bottom view without a protective cover (Figure 7B). Device 66 is ordinarily provided with a protective cover which is removed prior to use. For brevity, the protective cover is not depicted in the Figures. In device 66, a body 12 comprises a hollow shell 54 of 2 mm thick silicone rubber. A lower contact face 16 is the lower surface of a 2 mm thick flat sheet 56 of silicone rubber that is sealingly secured to the bottom rim of hollow shell 54. Window 58a and 58b in sheet 56 hold pH indicator patches 18a and 18b. Inside shell 54 as a reservoir 36 is a rubber balloon which inner volume is a volume 20 containing an activation liquid. Reservoir 36 has rectangular scoring 68 that weakens the walls of reservoir 36 and a pull string 70 of UHMWPE which distal end 72 is secured to reservoir 36 inside rectangular scoring 68, which pull string 70 passes through a hole in shell 54 so that a proximal end 74 of string 70 is accessible from outside of device 64. For use of device 66, lower contact face 16 is pressed against a skin surface so that an adhesive portion 34 on lower contact face 16 holds lower contact face 16, including surfaces 26 of pH indicator patches 18a and 18b in intimate contact with the skin. A user pulls proximal end 74 of pull string 70, tearing reservoir 36 along the scoring 68, so that activation liquid exits reservoir 36, soaking indicator patches 18a and 18b, and wetting the skin surface therethrough. In Figures 8 an exemplary embodiment of a device, device 78, is schematically depicted in side cross section (Figure 8A) and in bottom view without a protective cover (Figure 8B). Device 78 is ordinarily provided with a protective cover which is removed prior to use. For brevity, the protective cover is not depicted in the Figures. In device 78, a body 12 comprises a hollow shell 54 of 2 mm thick silicone rubber. A lower contact face 16 comprises a flat flexible sheet 80 of water-absorbant material such as non-woven felt that is sealingly secured to the bottom rim of hollow shell 54 with adhesive. pH indicator patches 18a and 18b are attached to the bottom face of flexible sheet 80 with adhesive. Inside shell 54 as a reservoir 36 is a rubber balloon which inner volume is a volume 20 containing an activation liquid, substantially identical to the described for device 66 with referenced to Figures 7. For use of device 78, lower contact face 16 is pressed against a skin surface so that an adhesive portion 34 on lower contact face 16 holds lower contact face 16, including surfaces 26 of pH indicator patches 18a and 18b in intimate contact with the skin. A user pulls proximal end 74 of pull string 70, tearing reservoir 36 along the scoring 68, so that activation liquid exits reservoir 36, soaking absorbant sheet 80. Activation liquid passes through absorbant sheet, wetting the skin and indicator patches 18a and 18b. Excess activation liquid is absorbed into absorbant sheet 80 so that the skin surface remains pleasantly dry. Lower contact face 16 of device 78 comprises a calibration card 80. Calibration card 80 is a thin, flexible,water-resistant component that is attached to flexible sheet 80 with adhesive. Calibration card 80 is shaped and positioned relative to pH indicator patches 18a and 18b in such a way that it is trivial for a person having ordinary skill in the art to configure a computer image-processing system to determine which part of an acquired image corresponds to pH indicator patch 18a and which part of the image corresponds to pH indicator patch 18b, and the tilt angle of the lower contact face 16 to the camera that acquired the image. Calibration card 80 has five differently-colored portions: a red-colored portion, a green-colored portion, a blue-colored portion, a yellow-colored portion and a grey-colored portion. A person having ordinary skill in the art can easily configure a computer image- processing system to correct the color and white balance of an acquired image, and particularly, to correct the color of the portion of the image that corresponds to pH indicator patches 18a and 18b. In such a way, a person having ordinary skill in the art can easily configure a computer image-processing system to determine the exact color of pH indicator patches 18a and 18b after interaction with human skin, to determine the pH of the skin. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. In case of conflict, the specification, including definitions, takes precedence. As used herein, the terms “comprising”, “including”, "having" and grammatical variants thereof are to be taken as specifying the stated features, integers, steps or components but do not preclude the addition of one or more additional features, integers, steps, components or groups thereof. As used herein, the indefinite articles "a" and "an" mean "at least one" or "one or more" unless the context clearly dictates otherwise. As used herein, when a numerical value is preceded by the term "about", the term "about" is intended to indicate + / -10%. As used herein, a phrase in the form “A and / or B” means a selection from the group consisting of (A), (B) or (A and B). As used herein, a phrase in the form “at least one of A, B and C” means a selection from the group consisting of (A), (B), (C), (A and B), (A and C), (B and C) or (A and B and C). It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements. Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the scope of the appended claims. Citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the invention. Section headings are used herein to ease understanding of the specification and should not be construed as necessarily limiting.

Claims

CLAIMS:

1. Adevice (10, 28, 38, 42, 52, 64, 66, 78) suitable for assisting in determining the pH of the surface of human skin, comprising: a body (12) having an upper surface (14) and a lower contact face (16), said lower contact face (16) including at least a portion of a pH indicator patch (18); and inside said body (12), a volume (20) containing an activation liquid so that when said activation liquid wets the surface of human skin and a surface (26) of said pH indicator patch (18) while said lower contact face (16) makes intimate contact with the surface of the skin, said activation liquid allows material from the surface of the skin to interact with a pH indicator component present in said pH indicator patch (18), thereby allowing said pH indicator patch (18) to indicate a pH of the surface of the skin. 2 The device of claim 1, wherein said pH indicator patch (18) is a colorometric indicator patch comprising at least one colorimetric pH indicator component. 3 The device of any one of claims 1 to 2, wherein said lower contact face (16) includes at least one additional pH indicator patch (18).

4. The device of any one of claims 1 to 3, wherein said lower contact face (16) has a surface area of not less than about 1 cm? and not more than about 25 cm?.

3. The device of any one of claims 1 to 4, wherein a thickness of the device from said lower contact face (16) to a top of said upper surface (14) is not less than about 2 mm and not more than about 1.5 cm.

6. The device of any one of claims 1 to 5, wherein said activation liquid comprises at least 99% w / w water.

7. The device of any one of claims 1 to 6, wherein said lower contact face (16) is rigid.

8. The device of any one of claims 1 to 6, wherein said lower contact face (16) is flexible.

9. The device of claim 8, wherein said lower contact face (16) is conformable.

10. The device of any one of claims 1 to 7, said lower contact face (16) comprising an adhesive portion (34) configured to reversibly adhere to dry human skin for at least 10 seconds subsequent to application to the skin, which adhering is sufficient to maintain said indicator patch (18) in intimate contact with said human skin.

11. The device of claim 10, wherein said adhesive portion (34) at least partially surrounds said indicator patch (18).

12. The device of claim 11, wherein said adhesive portion (34) completely surrounds said indicator patch (18).

13. The device of any one of claims 1 to 12, further comprising a user-removable protective cover (30) on at least a portion of said lower contact face (16).

14. The device of claim 13, wherein said protective cover (30) is removably-secured to said lower contact face (16) with an adhesive (34).

15. The device of any one of claims 1 to 14, enclosed in a user-openable package. 16 The device of any one of claims 1 to 15, wherein said volume (20) containing said activation liquid comprises said pH indicator patch (18).

17. The device of claim 16, wherein said volume (20) containing said activation liquid consists of said pH indicator patch (18).

18. The device of claim 16, said volume (20) containing said activation liquid further comprises a liquid reservoir (36) different from said pH indicator patch (18).

19. The device of claim 18, wherein said liquid reservoir (36) is in physical contact with said pH indicator patch (18).

20. The device of claim 18, wherein said liquid reservoir (36) is devoid of physical contact with said pH indicator patch (18).

21. The device of any one of claims 18 to 20, wherein said lower contact face (16) includes at least a portion of said liquid reservoir (36).

22. The device of any one of claims 18 to 20, wherein no portion of said liquid reservoir (36) is apparent on said lower contact face (16).

23. The device of any one of claims 18 to 22, wherein said body (12) is collapsible by manual pressure applied to said upper surface (14) where, when said body (12) is manually collapsed while said lower contact face (16) contacts a skin surface, said collapsing leads to expulsion of said activation liquid from said liquid reservoir (36), thereby wetting the skin surface and a surface (26) of said pH indicator patch (18) that contacts the skin surface.

24. The device of any one of claims 1 to 15, wherein said volume (20) containing said activation liquid is in a sealed reservoir (36) separate from said pH indicator patch (18).

25. The device of claim 24, further comprising a user-removable protective cover (30) on at least a portion of said lower contact face (16), configured that, when said protective cover (30) is removed, said sealed reservoir (36) is unsealed so that activation liquid can exit said reservoir (36).

26. The device of claim 24, wherein said body (12) is collapsible by manual pressure applied to said upper surface (14) where, when said body (12) is manually collapsed while said lower contact face (16) contacts a skin surface, said collapsing leads to opening of said sealed reservoir (36), allowing release of said activation liquid from said liquid reservoir (36), thereby wetting the skin surface and a surface (26) of said pH indicator patch (18) that contacts the skin surface.

27. The device of claim 26, wherein said opening of said sealed reservoir (36) is breaking of at least a portion of said reservoir (36).

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