Color changing expiration indicator

A printer system comprising:

• a memory;
• an interface configured to receive an expiration date;
• a processor in communication with the memory and the interface, wherein the processor is configured to:
• determine a number of transmission layers to use in a color changing expiration indicator based at least in part on a time period between a print date of the color changing expiration indicator and the received expiration date;
• determine a thickness for each of the transmission layers based at least in part on the time period;
• determine a number of barrier layers to use in the color changing expiration indicator based at least in part on the time period;
• determine a thickness for each of the barrier layers based at least in part on the time period;
• determine a porosity for each of the barrier layers;
• and
• determine a thickness of a reactive layer based at least in part on the determined number of transmission layers and the determined number of barrier layers;
• and
• one or more printer heads configured to:
• print the reactive layer onto print media, wherein at least a portion of the reactive layer is configured to migrate through the transmission layers;
• print the determined number of transmission layers and the determined number of barrier layers in alternation with one another;
• and
• print a reactant layer that is configured to change color responsive to a reaction that occurs between the reactant layer and the reactive layer upon migration of the reactive layer through the determined number of transmission layers, wherein the reaction is configured to occur on the received expiration date.