| 摘要 |
A device and method for monitoring the expiration of goods includes a substrate, a coating of polydiacetylene, said coating having properties of (1) changing from a first color irreversibly to a second color immediately upon being subjected to a specified temperature and (2), upon activation upon contact by an activating agent, changing from said first color to said second color at a temperature lower than said specified temperature after a time delay of at least one hour and an activating agent on a portion but not all of said coating.
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