The days of wondering whether milk has spoiled or eggs are rotten could be coming to a merciful end. Biomedical engineers at Tufts University crafted tiny spoilage indicators out of gold and silk that can even be eaten.

A team led by Tufts biomedical engineering professor Fiorenzo Omenetto and postdoc Hu Tao embedded gold antennae in a film made from a purified silk substrate they first developed in 2010. When food spoils, it changes chemically. These naturally sticky sensors work by detecting those subtle changes and emitting a unique electromagnetic signal that can be picked up by an external reader, according to Fast Company's Co.Exist contributor Nidhi Subbaraman.

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The engineers' goal for these sensors, Subbaraman reported, is to be able to wave a smart phone over a sensor and learn instantly whether the food has gone bad. Their work was published in a recent issue of the journal Advanced Materials (abstract).


Gee, why not just smell it? Or peel it? Or crack that egg open? Well, imagine you've lost your sense of smell due to a medical condition and no one else is around. Or maybe you'd rather not find out about those eggs the hard way. These sensors could be helpful.

To those who say that tech like this is a waste, consider that such indicators might be adopted for prepared foods. That would make inventory management much easier — and potentially more efficient since fresh food wouldn't have to be tossed simply because of its sell-by date.

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Granted, I doubt anyone wants to throw even tiny amounts of gold away. Plus, it's not clear whether the sensors could be mechanically composted although the components are biodegradable. Perhaps the engineers could make effective antennae from a different material.

If the food is still good, these sensors are designed to be edible. Subbaraman reported that the gold amounts are comparable to the gold leaf in fancy schmancy desserts, and the silk substrate is essentially pure protein. Yum?