Monitoring system based on etching of metals

A process to monitor the status of medical products, food, or biological waste which comprises placing an indicating system comprising:

• a zero-valent metal or metal alloy indicator layer;
• and
• a layer of an activator or a precursor of said activator on a packaging of said medical products, food, or biological waste.

A process to monitor the presence or absence of a toxic chemical, an agent or water which comprises:

• placing an indicating system comprising a zero-valent metal or metal alloy indicator layer, a layer of an activator or a precursor of said activator, and a metal oxide layer between the metal or metal alloy indicator layer and the layer of said activator or said precursor of said activator in the area to be monitored;
• and
• monitoring the indicating system for a physical change in said indicator layer.

A process to monitor the status of a perishable item which comprises:

• placing an indicating system comprising a zero-valent metal or metal alloy indicator, a layer of an activator or a precursor of said activator and a metal oxide layer between the metal or metal alloy indicator layer and the layer of said activator or said precursor of said activator on or near the perishable item wherein the perishable item is a food item, or a nonfood item;
• and
• monitoring physical change in a physical property of said indicator layer.

A process to monitor a limited time consumer use for items that have been opened or in use and should be used within a certain period comprising:

• placing an indicating system comprising a zero-valent opaque metal or metal alloy indicator and a layer of an activator or a precursor of said activator, near an item to be monitored, wherein the item is selected from the group consisting of drinks, food items, health, personal and family care products wherein when said indicator becomes transparent said certain period has expired.

A process to make an indicating system comprising a zero-valent metal or metal alloy indicator layer and a layer of an activator or a precursor of said activator comprising:

• laminating an activator tape comprising said layer of said activator or said precursor of said activator on said metal or metal alloy indicator layer.

A process to make an indicating system comprising a zero-valent metal or metal alloy indicator layer and a layer of an activator or a precursor of said activator comprising:

• coating said layer of activator or precursor of said activator on said metal or metal alloy indicator layer wherein said metal or metal alloy indicator is on a support;
• coating onto said support at least one additional layer selected from the group consisting of a permeable layer, a wedge shaped permeable layer, a barrier layer, a reactive, destroyable or degradable barrier layer, an expiration indicating layer, a tamper indicating layer, an activation indicating layer, a message or image creating layer, separating layer, removable layer, naturally formed oxide layer, a disappearing layer, activatable layer, a microencapsulated layer and a thermally printable layer.

A process to determine the concentration of an agent comprising:

• monitoring a change in conductivity, or opacity of an indicator layer of an indicating system comprising a zero-valent metal or metal alloy indicator layer and a layer of an activator or a precursor of said activator.

A process to monitor a change in a material or a process comprising:

• measuring a change in the material or the process with an indicating system comprising a zero-valent metal or metal alloy indicator layer and a layer of an activator or a precursor of said activator.

An indicating system comprising:

• a zero-valent opaque metal or metal alloy indicator layer wherein said metal is selected from the group consisting of aluminum, zinc and copper;
• and
• a layer of an activator or a precursor of said activator wherein said activator or said precursor renders said indicator transparent upon reaction with said activator.