Someday soon, your refrigerator or even the bottles in your wine collection may inform you when its contents have gone bad. It's the preferable method when you're dealing with food or pharmaceuticals, rather than tossing everything out based on an arbitrary best-if-ingested-by date. The packaging will know what's rotten the same way you do: by taking a whiff to see if it stinks.
MAJOR INNOVATION Cheap printed polymers will detect food spoilage and dangerous odors.
WHY IT MATTERS Sniffing out true rot could eliminate product waste.
ESTIMATED ARRIVAL Minimum of five years for consumer and pharmaceutical packaging, maybe earlier for expensive, single-use products.
Hard to believe, but such electronic-nose (e-nose) technology has been around for several years, and the general idea goes back decades. Commercial e-noses today check for dangerous gases we can't sense. They're used by hospitals, the military, and NASA. So what big breakthrough is the next generation of digital sniffers poised to make? First, they're going to use printed organic polymers made with modified ink jet printers. Second, those polymers are going to make e-noses incredibly cheap compared to today's, which cost several hundred or even thousands of dollars.
Vivek Subramanian, associate professor in the Department of Electrical Engineering and Computer Sciences at University of California, Berkeley, says his team of Ph.D. candidates—most of whom are involved in interdisciplinary studies across fields of chemistry, material science, and electrical engineering—build the polymer printers themselves and print with them all the time.
Just don't expect to buy an e-nose that can smell all 10,000 odors the human nose can sense any time soon. The trick is to teach it what to detect. "I know what I want to smell. I want to smell spoilage. So I have a specific e-nose for that spoilage," says Subramanian. It's all about recognizing a rotten-smelling pattern. He cautions that we're a long way off from e-noses sniffing out specifics, like drugs—or worse. "For bomb sniffing," he says, "you need parts-per-trillion detection. That's really hard." So Homeland Security should probably keep training dogs.
Subramanian guesses that a large amount of food is tossed every day that is not even close to bad, because expiration dates are, by necessity, very conservative. That kind of waste could go away for good with the right e-noses in place.
His vision for a commercial e-nose is a piece of plastic made of a low-cost polymer with circuits printed on it. It would connect to a little signal processor, probably running off a printable battery, on the outside of the food container. The output signal indicating whether the food inside is spoiled could be sent via radio frequency. Naturally, e-noses used in warehouses would have RFID tags. A change of color in the plastic polymer would indicate the contents' status.
Other researchers are working on using nanoparticles to print even more sensitive polymers. Subramanian thinks the best e-noses will someday combine several different methods to make individual sensors that respond to different smells by mixing and matching different types of scent pattern recognition. Those sensors will eclipse what's available today.
"The e-nose is a wonderful match for printing," he says. "You print multiple materials everyday at home to get colors in photos. Now we'll just replace colors with sensors."