Indicating Devices Based onEtching of Metals

Abstract

Compositions, devices and processes related to etching of a very thin layer or fine particles of a metal are disclosed for monitoring a variety of parameters, such as time, temperature, time-temperature, thawing, freezing, microwave, humidity, ionizing radiation, sterilization and chemicals. These devices have capabilities of producing a long and sharp induction period of an irreversible visual change. The devices are composed of an indicator comprising a very thin layer of a metal and an activator, e.g., a reactant, such as water, water vapor, an acid, a base, oxidizing agent or their precursors, which is capable of reacting with the said indicator. Ink formulations composed of a metal powder and a proper activator can be used for monitoring several sterilization processes, such as sterilization with steam. When water is used as an activator, a thin layer of metals, such as that of aluminum can be used as steam sterilization or humidity indicator.

1 . A sterilization indicating device comprising a substrate having a metal layer on its surface wherein the metal layer is capable of being destroyed when exposed to a sterilant, causing an irreversible change in opacity, reflectivity or electrical conductivity of the metal layer. 
     
     
         2 . The sterilization indicating device of  claim 1  wherein the metal layer is composed of a metal or its alloy, with or without an oxide layer. 
     
     
         3 . The sterilization indicating device of  claim 2  wherein the metal layer is composed of 1) a continuous layer of the metal or the metal alloy, with or without its respective oxide or 2) particles of the metal or the metal alloy or with or without its respective oxide dispersed in a binder permeable to the sterilant. 
     
     
         4 . The sterilization indicating device of  claim 3  further having from 1 to 3 layers selected from the group of an activator in a binder layer, a precursor for an activator in a binder layer and a protective binder layer; wherein each layer containing a binder is permeable to the sterilant. 
     
     
         5 . The sterilization indicating device of  claim 4  wherein the metal layer is capable of being destroyed by a reaction of the metal layer with the sterilant, the activator, the activator produced by a reaction of the sterilant with the precursor for the activator or with a combination of the sterilant and the activator. 
     
     
         6 . The sterilization indicating device of  claim 5  wherein one or more sterilants are selected from the group consisting of humidity, water, steam, ethylene oxide, aldehydes, oxidizing agents, plasmas of vapors or gases, dry heat and ionizing radiation. 
     
     
         7 . The sterilization indicating device of  claim 6  wherein the sterilant is UV, X-ray, gamma ray, electrons, ozone, or a vapor, liquid or solution of formaldehyde, glutaraldehyde, hydrogen peroxide, or peracetic acid with or without water. 
     
     
         8 . The sterilization indicating device of  claim 6  which meets the protocols of different classes of chemical sterilization indicators, including class 1 through class 6 of International Organization for Standardization (ISO), European Standards (EN) and American Association of Medical Instrumentation (AAMI). 
     
     
         9 . The sterilization indicating device of  claim 6  wherein the metal is selected from the group consisting of alkali metals, alkaline earth metals, transition metals, post transition metals, lanthanides and actinides metals and their alloys. 
     
     
         10 . The sterilization indicating device of  claim 9  wherein the metal is selected from the group consisting of aluminum, tin, zinc, copper, manganese, magnesium, nickel, cobalt, iron, sodium, potassium, lithium, calcium, gallium, cesium, germanium, indium, silver and their alloys. 
     
     
         11 . The sterilization indicating device of  claim 6  wherein the metal is a continuous layer of thickness of from about 10 to about 10,000 Angstroms on the substrate. 
     
     
         12 . The sterilization indicating device of  claim 5  wherein the metal is round or flat, leafing or nonleafing particles having thickness of from about 10 nm to about 15 microns. 
     
     
         13 . The sterilization indicating device of  claim 12  wherein the concentration of the metal particles is in a range of about 2 wt. % to about 30 wt. %. 
     
     
         14 . The sterilization indicating device of  claim 13  wherein the concentration of the metal particles is in a range of about 5 wt. % to about 10 wt. %. 
     
     
         15 . The sterilization indicating device of  claim 5  wherein the activator is selected from the group consisting of a base, acid, salt, chelate, organometallic, halide, oxide, nitrate, nitrite, phosphate, phosphite, phosphonate, silicate, sulfate, bisulfate, sulfite, sulfide, bisulfide, sulfonate, cyanate, cyanide, thiocyanate, acetylacetonate, carboxylate, percarboxylate, carbonate or bicarbonate, a mono, di and trivalent cation of a metal, cation of nitrogen, sulfur, alcohol, amide, amine, carbamate, ester, halocarbon, ketone, nitro, nitroso, oxime, phenol, urea, urethane and a mixture thereof. 
     
     
         16 . The sterilization indicating device of  claim 15  wherein the activator is selected from the group consisting of ammonium bromide, ammonium thiocyanate, calcium chloride, copper chloride, copper ammonia complexes, lithium acetylacetonate, lithium chloride, lithium formate, potassium acetate, potassium benzoate, potassium bromide, potassium chloride, potassium ferrocyanide, potassium ferrocyanide, potassium formate, sodium acetate, sodium bicarbonate, sodium bromide, sodium carbonate, sodium cyanate, sodium diethyldithiocarbamate, sodium iodide, sodium metasilicate, sodium nitrate, sodium sulfite, sodium tetrafluoroborate, sodium tetraborate, sodium thiocyanate, sodium thiosulfate, tetraethylammonium bromide, tetrabutylammonium bromide, zinc chloride and a mixture thereof. 
     
     
         17 . The sterilization indicating device of  claim 6  wherein the precursor of the activator is a monomeric or polymeric acid, base, salt or organometallic compound. 
     
     
         18 . The sterilization indicating device of  claim 17  wherein the precursor of the activator is a cyanate, thiocyanate, halo, halide, halonium, sulfonium or phosphonium compound. 
     
     
         19 . The indicating device of  claim 18  wherein the precursor of the activator is tetraalkylammonium bromide, benzyltributylammonium bromide, benzyldodecyldimethylammonium bromide, dimethyldioctadecylammonium bromide, dodecylethyldimethylammonium bromide, dodecyltrimethylammonium bromide, ethyltriphenylphosphonium bromide, ethylhexadecyldimethylammonium bromide, hexadecyltrimethylammonium bromide, myristyltrimethylammonium bromide, polybrene, poly(benzophenonetetracarboxylic dianhydride-ethidium bromide), tetraheptylammonium bromide, tetrakis(decyl)ammonium bromide, thonzonium bromide, acetyl choline chloride, ammonium bromide, choline chloride, choline iodide, glycidil trimethyl ammonium chloride, potassium bromide, potassium iodide, sodium iodide, tetrabutyl ammonium iodide, tetraethyl ammonium bromide, tetrahexyl ammonium bromide, tetramethyl ammonium chloride, tetrabutyl phosphonium bromide, sodium thiocyanate and potassium thiocyanate. 
     
     
         20 . The sterilization indicating device of  claim 6  which has one or more messages in color, word, number, barcode or symbol on one or both the sides of any one layer of the device. 
     
     
         21 . The sterilization indicating device of  claim 20  which contains at least two messages wherein a first message of said two messages does not start to appear at a same time as a second message of said two messages. 
     
     
         22 . The sterilization indicating device of  claim 21  wherein a first appearing message indicates a status or quality of an item before a sterilization treatment of the item and a second appearing message alone or in combination with the first appearing message indicates a status or a quality of the item after the sterilization treatment. 
     
     
         23 . The sterilization indicating device of  claim 22  wherein the first appearing message indicates un-doneness, not-processed, non-usability, non-acceptability, untreated, unexposed or non-sterile and the second appearing message alone or in combination with the first appearing message indicates doneness, processed, usability, acceptability, treated, exposed or sterile. 
     
     
         24 . The sterilization indicating device of  claim 4  which further comprises an additional one or more layers to the device, wherein the additional layers are selected from the group consisting of a permeable to activator and sterilant layer, a wedge shaped permeable to activator and sterilant layer, a barrier to activator and sterilant layer, a reactive layer, destroyable or degradable barrier layer, a doneness indicating layer, a tamper indicating layer, an activation indicating layer, a message or image appearing layer, a separating layer, a removable layer, a naturally formed oxide layer, a disappearing layer, activatable layer, a microencapsulated layer and a printed layer. 
     
     
         25 . The sterilization indicating device of  claim 6  which further comprises an additional one or more layers to the device, wherein the additional layers are selected from the group consisting of a permeable to activator and sterilant layer, a wedge shaped permeable to activator and sterilant layer, a barrier to activator and sterilant layer, a reactive layer, destroyable or degradable barrier layer, a doneness indicating layer, a tamper indicating layer, an activation indicating layer, a message or image appearing layer, a separating layer, a removable layer, a naturally formed oxide layer, a disappearing layer, activatable layer, a microencapsulated layer and a printed layer. 
     
     
         26 . The sterilization indicating device of  claim 6  which is in the form of a label, strip, card or tape. 
     
     
         27 . The sterilization indicating device of  claim 6  wherein a time, temperature or time-temperature required for a change in opacity or conductivity of the metal layer or an activation energy of the device is varied or adjusted by changing one or more of the parameters selected from the group consisting of: thickness of the activator layer, thickness of the metal or the metal alloy layer, thickness of the metal oxide or the metal alloy oxide layer, thickness of the permeable layer, concentration of the activator, concentration of the precursor, concentration of an additive, nature of a solvent, surfactant and a catalyst, nature of the activator, nature of the metal or the metal alloy, nature of metal oxide or metal alloy oxide, nature of the permeable layer, nature of the additive and nature of a reaction accelerator and retarder. 
     
     
         28 . The sterilization indicating device of  claim 6  wherein the device is capable of providing an induction period caused by the destruction of the metal layer, the metal oxide layer or both the metal and the oxide layers, which destruction is measured by a delay in a visual indication or change in conductivity of the metal or metal alloy layer. 
     
     
         29 . The sterilization indicating device of  claim 6  further comprising at least one electronic chip or an electronic component connected to a conductive path. 
     
     
         30 . The sterilization indicating device of  claim 29  wherein the electronic device is a radio frequency identification device (RFID) or an electronic article surveillance device. 
     
     
         31 . The sterilization indicating device of  claim 6  wherein the continuous metal layer of the metal or its alloy is an antenna of a RFID having at least one readable RFID electronic chip and at least a portion of the antenna or the whole antenna is covered with a layer of an activator or a precursor for an activator. 
     
     
         32 . The sterilization indicating device of  claim 31  wherein the readable RFID chip is made non-readable by destruction of the antenna under the activator or the precursor layer upon sterilization. 
     
     
         33 . A process of monitoring sterilization by reading the RFID of the device of  claim 31 . 
     
     
         34 . A process of monitoring sterilization by reading the RFID of the device of  claim 32 . 
     
     
         35 . The sterilization indicating device of  claim 6  wherein a RFID electronic chip is connected to the continuous layer of a metal or a metal alloy and a barrier mask in form an antenna on the metal or the metal alloy layer. 
     
     
         36 . The sterilization indicating device of  claim 35  wherein the chip is made readable by an antenna created by the destruction of the metal layer except the metal layer under the barrier mask upon sterilization. 
     
     
         37 . The process of monitoring sterilization by reading the RFID device of  claim 35 . 
     
     
         38 . The process of monitoring sterilization by reading the RFID device of  claim 36 . 
     
     
         39 . A sterilization indicating ink composition comprising an ink containing particles of a metal or its alloy, with or without an oxide layer, a binder permeable to a sterilant, and water or an organic solvent; wherein when the particles of the metal or its alloy, with or without an oxide layer are capable of being destroyed when exposed to a sterilant, causing an irreversible change in opacity, reflectivity, or electrical conductivity of the metal or the metal alloy. 
     
     
         40 . The sterilization indicating ink composition of  claim 39  wherein the binder is a polymeric latex, water dispersible or a water soluble polymer. 
     
     
         41 . The sterilization indicating ink composition of  claim 39  wherein the binder is a polymer soluble in an organic solvent. 
     
     
         42 . The sterilization indicating ink composition of  claim 39  wherein the binder is ethyl cellulose, nitro cellulose, cellulose acetate, hydroxypropyl cellulose, polystyrene, polymethacrylates, polyvinyl chloride, polyvinyl acetate; polyvinylidene chloride, polyacrylics, polyethylene, polypropylene, polyurethanes, polyesters, polycarbonates, polybutylene, polyvinylbutyral, polybutadiene and their copolymers. 
     
     
         43 . The sterilization indicator ink composition of  claim 39  wherein the metal or the metal alloy is selected from the group consisting of alkali metals, alkaline earth metals, transition metals, post transition metals, lanthanides and actinides metals and their alloys. 
     
     
         44 . The sterilization indicator ink composition of  claim 43  wherein the metal is selected from the group consisting of aluminum, tin, zinc, copper, manganese, magnesium, nickel, cobalt, iron, sodium, potassium, lithium, calcium, gallium, cesium, germanium, indium, silver and their alloys. 
     
     
         45 . The sterilization indicator ink composition of  claim 39  where the sterilant is one or more selected from the group consisting of ionizing radiation, dry heat, plasmas of vapors of gases, water, humidity, steam and a vapor, liquid or solution of ethylene oxide, aldehydes and oxidizing agents. 
     
     
         46 . The sterilization indicator ink composition of  claim 45  wherein the sterilant is UV, X-ray, gamma ray, electrons, ozone or a vapor, liquid or solution of formaldehyde, glutaraldehyde, hydrogen peroxide, or peracetic acid with or without water. 
     
     
         47 . The sterilization indicating ink composition of  claim 39  wherein the ink composition is coated on a substrate and dried. 
     
     
         48 . The sterilization indicating ink composition of  claim 39  further containing one or more materials selected from the group consisting of an activator, a precursor for an activator and an additive. 
     
     
         49 . A sterilization indicating ink composition comprising an ink containing a binder permeable to a sterilant, and water or an organic solvent and one or more materials selected from the group consisting of an activator, a precursor for an activator and an additive. 
     
     
         50 . The sterilization indicating device of  claim 6  which is a wash indicating device for monitoring washing of an item. 
     
     
         51 . A process of monitoring sterilization comprising
 1) placing, in the same environment as an item to be sterilized, a sterilization indicating device of  claim 1 ;   2) adding a sterilant to the environment; and   3) monitoring an irreversible change in opacity, reflectivity or electrical conductivity of the sterilization indicating device.   
     
     
         52 . A process of monitoring sterilization comprising
 1) placing, in the same environment as an item to be sterilized, a sterilization indicating device of  claim 6 ;   2) adding a sterilant to the environment; and   3) monitoring an irreversible change in opacity, reflectivity or electrical conductivity of the sterilization indicating device.   
     
     
         53 . The method of monitoring sterilization of  claim 52  wherein the sterilant is one or more of the group consisting of ionizing radiation, dry heat, plasmas of vapors of gases, water, humidity, steam and a vapor, liquid or solution of ethylene oxide, aldehydes and oxidizing agents. 
     
     
         54 . The method of  claim 53  wherein the sterilant is UV, X-ray, gamma ray, electrons, ozone or a vapor, liquid or solution of formaldehyde, glutaraldehyde, hydrogen peroxide, or peracetic acid with or without water. 
     
     
         55 . The process of  claim 51  wherein the item is a piece of medical equipment, a medical supply, a medical device, a perishable, a canned food, a pharmaceutical or biological waste. 
     
     
         56 . A process for determining the degree of sterilization which comprises reading the indicating device of  claim 20  with a barcode reader, spectrophotometer, optical densitometer or a charge coupled device (CCD). 
     
     
         57 . A process for making sterilization indicating device comprising applying a coating of the sterilization indicating ink composition of  claim 39  on to a substrate and drying the coating. 
     
     
         58 . A process for making sterilization indicating device comprising applying a coating of the sterilization indicating ink composition of  claim 40  on to a substrate and drying the coating. 
     
     
         59 . A process for making sterilization indicating device comprising applying a coating of the sterilization indicating ink composition of  claim 41  on to a substrate and drying the coating. 
     
     
         60 . The process of making the sterilization indicating device comprising applying the ink formulation of  claim 48  on a substrate having a metal or its alloy layer and drying it. 
     
     
         61 . The sterilization indicating device of  claim 1  wherein the substrate is composed of natural or synthetic paper, metal, polyethylene, polypropylene, polyester, nylon, polyvinyl chloride, polyvinyl acetate, polystyrene, cellulose acetate and their copolymers. 
     
     
         62 . The sterilization indicating device of  claim 28  wherein the induction period is sharp. 
     
     
         63 . The sterilization indicating device of  claim 1  wherein the change in opacity is abrupt. 
     
     
         64 . The sterilization indicating ink composition of  claim 39  wherein the change in opacity is abrupt. 
     
     
         65 . The process of monitoring sterilization of  claim 51  wherein the change in opacity is abrupt. 
     
     
         66 . The process of monitoring sterilization of  claim 52  wherein the change in opacity is abrupt. 
     
     
         67 . The sterilization indicating device of  claim 6 , wherein the device undergoes an abrupt change in the opacity of the metal layer upon sterilization.