YOUNG, energetic and clean-shaven, looks the very antithesis of Santa Claus. Just as well: he makes toys disappear.
The Western world’s festive consumer frenzy contributes to a global crisis that has left the planet up to its neck in long-lasting plastic tat, and its oceans, according to a recent estimate, awash with some 250 million tonnes of the stuff. What we wouldn’t give for plastics that could transform into something else, fall apart or even vanish altogether. In his lab at Penn State University, Phillips is on the case. “We make plastic objects disappear all the time,” he says. Perhaps it won’t be too long before the season’s must-have toy comes equipped with a self-destruct button.
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But today’s plastics are not just for Christmas. Indeed, their durability and low cost mean that many everyday objects are destined to hang around for decades. We can only guess at how long some plastics survive in landfill, but in many cases it extends beyond the 50 years or so we’ve been producing and discarding them on a grand scale. If we recycle plastic instead, melting it down takes a lot of energy and can release toxic components. And even then, the resulting mix of hard plastics that usually enters a recycling stream creates a polymer soup peppered with various dyes and solvents, so we end up with a hunk of junk plastic fit only for a single, final use, like a park bench.
It was that end-of-life problem, rather than any Scrooge-like tendencies, that prompted Phillips to try to design self-destructing toys. “It’s a nice place to start minimising the accumulation of plastic waste,” he says.
The first step is some basic chemistry. Research in the past few years has produced new sorts of polymers, the long, chain-like molecules that make up plastics. These polymers are just as durable as conventional ones in normal use, but contain chemical units at points within them, or at their ends, that when it meets a particular stimulus. Phillips’s lab has been developing plastics that break down in ultraviolet light – not ideal for toys, but good for components not exposed to sunlight, for example on the inside of electronic devices. He has also been looking at plastics that disintegrate on contact with chemicals they don’t encounter in daily use, such as fluoride or hydrogen peroxide.
Destruction trigger
One challenge is ensuring that the self-destruct signal spreads from a plastic’s surface right through the material. Here, Phillips and his colleagues were inspired by plants such as the Venus flytrap, where a fleeting touch to a leaf causes a change in the whole plant. “We are building self-propagating reactions into our materials,” says Phillips. , one molecular component of a water-repelling polymer film reacts to a specific wavelength of light, starting a chemical reaction that spreads through the whole polymer and turns it hydrophilic.
Phillips has also been building plastic objects from layers that react to different triggers, so that applying a sequence of them makes the objects change shape. These morphing materials might not quite make a real-life Transformer toy, but Phillips thinks they could be useful for creating adaptive tools: think bolts and washers that shrink to fit a range of screws or that change from rigid to rubbery. Other plastics can be engineered as they break down, with potential applications in medicine. Another innovative byproduct is a propulsion system: one of Phillips’s plastics springs forward because it releases carbon dioxide as it decomposes.
Phillips is not alone in trying to make plastics vanish. At the University of the West of England in Bristol, UK, and his colleagues want for the robots they are developing. Instead, they plan to build them from soft, biodegradable polymers such as latex or collagen, with microbial fuel cells that extract energy from waste liquids such as urine. “The materials we choose and their properties indicate the lifetime of the whole thing,” says Ieropoulos. The team hopes to develop tricks to change the expiry date of such plastics, perhaps by embedding substances that will ooze out or self-destruct in response to a signal if the robot gets lost.
“The toilet might eventually be the ideal garbage disposal unit for plastic”
Meanwhile, from IBM Research in San Jose, California, and his team were looking for new materials to use in computer hardware when they developed a gentler chemical process to break down both PET plastics, commonly used in drink bottles, and the hard plastics used in smartphones and CDs that usually end up in landfill. Catalysts used in existing recycling processes leave heavy metals in the plastic that have to be removed since they are toxic and affect its structure. The new process creates a pure product, allowing the resulting molecules to be turned into even higher value polymers, for use in composites and in medical applications like drug delivery. “Now when I look at a bottle I don’t see garbage, I see a feedstock for all types of new materials,” says Hedrick. The team is speaking to potential partners about commercialising the process.
With Phillips’s plastics, mass production is still a long way off: they are slightly toxic and too expensive. But he thinks his materials could be put to immediate use as self-destructing adhesives. Small amounts of the polymers can double as glue on a range of materials like glass, metal and plastic, and they are just as strong as conventional adhesive. “What’s neat is that ours can also be reversed,” says Phillips. “By applying a signal, the object you’ve glued together will fall apart.” at the Catholic University of Leuven in Belgium has also developed that can bond the components of a television, and falls apart only when a particular amount of force is applied. Such materials might soon have a ready market: European Union laws being drafted could mean gadgets must be designed to disintegrate at the end of their lives.
Phillips imagines a further, perhaps unexpected boon from his particular plastics. While his ultimate goal is to create a vanishing plastic that emits nothing but inert gases when it decays, many of those developed so far decompose in liquids – meaning the toilet might be an ideal general garbage disposal unit. Imagine plastics that respond to a signal from sewer-dwelling bacteria, or even components in urine, so parents can take unusual vengeance on an annoying toy by peeing on it. Not that Phillips wants to make a splash with that particular idea. “It often creeps people out when I mention it,” he says.
This article appeared in print under the headline “Toy story”
