There are lots and lots of products that expire, and have either hard to read expiration dates (canned goods, milk), or no expiration dates (leftovers from restaurants).

By building a little chemical dot, filled with a slow-decaying dye, it will be obvious when something is close to going bad. When the spot turns red, the product has expired. (For spoiling products, the fact that refrigeration will slow the decay reaction is a feature.)

A small dispensing machine would accept the desired timing parameters (and expected ambient temperature) and "print" the dot. If this could be done cheaply enough, it could be printed onto reminder cards of oil changes, haircuts, etc. (Get your oil changed before the dot turns red.)

A more deluxe implementation could have a series of dots that expire in order, creating a "progress bar"
-- tspyz, Apr 30 2002

Self Expiring Badges http://www.imagesal...mTec/TimeBadge.html
Google: self expiring badge [half, Apr 30 2002, last modified Oct 17 2004]

I think the link pretty well bakes this idea. But, if I hadn't seen the technology in use on security badges I don't think I would have been able to find this reference.
-- half, Apr 30 2002


While I appreciate the intent, asking the manufacturer to print expiration dates in larger print might be easier. As for the doggy bags, carry a pen.

[half_crazy] That's an interesting link. I wonder if the 'expired' coloration is as subjective as it appears to be.
-- phoenix, Apr 30 2002


I, too, find the self-expiring badges to be clever.  The concept would have probably done well here at the HB.
-- bristolz, May 01 2002


Having once been the guy that wrote the software to print labels at a meat processing plant, I agree with [Phoenix]'s assessment.
-- half, May 01 2002



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