A nonstick chewing gum could reduce litter and household messes.
Taking the stick out of a stick of gum. I'm Bob Hirshon and this is Science Update.
A chewing gum that won't stick to shoes, hair, or pavement may soon be coming to a store near you. It's made by a British company called Revolymer, spun off from the University of Bristol. CEO Roger Pettman says they've replaced sticky ingredients found in regular gum with a polymer that easily detaches from surfaces. They've field-tested it on a number of surfaces, including real city sidewalks.
As soon as it rains, our chewing gum is simply washed away. And in three out of four cases, the commercial gums just remained there.
They also found that the gum actually dissolves in water over several weeks—which may curb the impact of chewing gum litter. Pending government approval, they hope to start selling the gum in Europe and the United States within a year. I'm Bob Hirshon, for AAAS, the science society.
Making Sense of the Research
Nonstick gum might not sound like a very important invention to you, but it may have a bigger impact than you realize. According to Pettman, over 660 million tons of chewing gum are manufactured every year worldwide—and much of it gets spit out on sidewalks, stuck under desks, or otherwise disposed of irresponsibly.
Who pays to get it removed? The taxpayers. In 2005, some of London's city assembly representatives reported that it cost about four million dollars per year just to remove used gum from subway trains and stations. Add in all the sidewalks, statues, park benches, and other public places with gum litter, and the price tag gets much higher.
What's more, even if it's successfully washed away into the sewer system, regular chewing gum takes a very long time to degrade. So the fact that this gum not only washes away easily, but actually dissolves over time, could solve a major urban environmental headache.
Regular gum sticks to surfaces because several of its base materials are hydrophobic: in other words, “water-hating.” Simply put, it means the chemical surfaces of these materials repel water. On the other hand, they're attracted to oil, which means that when they come in contact with an oily surface—and sidewalks, human hair, and clothing all have oily components—they form a strong bond that makes it stick.
In contrast, the nonstick gum uses a polymer that has a hydrophilic (“water-loving”) surface surrounding a hydrophobic base. If you drop the gum, it will still stick to the sidewalk at first. But when you rinse it with water, the hydrophilic component of the gum attracts water molecules, allowing them to squeeze in between the gum and the sidewalk. The result? The gum loosens and detaches easily, and washes away. Better yet, as Pettman mentions, the gum actually dissolves in water over time. This means that if it's washed into the sewers, it will break down over the course of several weeks.
In addition to the trials on sidewalks, the gum also was tested informally on one of the researchers' daughter's hair. The results were also reportedly positive. Furthermore, a blind taste test indicated that the gum tastes as good as regular gum. It remains to be seen whether this gum will be a hit with consumers, but it's likely to at least be a hit with sanitation workers.
Now try and answer these questions:
- How does the nonstick gum differ from regular gum?
- What is the difference between “hydrophobic” and “hydrophilic"? What does that have to do with the gum?
- What other kinds of litter might be a bigger problem than most people realize?
You may want to check out the October 26, 2007, Science Update Podcast to hear further information about this Science Update and the other programs for that week. This podcast's topics include: Chewing gum that's not sticky, worms and bacteria that team up, some very hairy genetics, and more.
The Exploratorium's feature on Soap Bubbles explains hydrophobic and hydrophilic properties as they relate to soap and water.
The Access Excellence lesson plan, Using Bubbles to Explore Membranes, is a hands-on activity that simulates cell membrane structure and function, including an introduction to phospholipid bilayers, which have both hydrophobic and hydrophilic components.