Shape-changing plastic with a flexible future
With restrictions on space and weight, what would you bring if you were going to Mars? An ideal option could be a single material that can change shape into any object you can imagine.
In the morning you can mold the ingredients into eating utensils. When breakfast is done, you can turn your fork and knife into a hoe to tend your Martian garden. And then when it's happy time on the Red Planet, that spade can become a cup for your Martian beer.
What sounds like science fiction is probably one step closer to reality. Researchers at the University of Chicago Pritzker School of Molecular Engineering have created a new type of plastic that has properties that can be set by heat and then locked by rapid cooling, a process called tempering. Unlike classic plastics, the material retains this stiffness when returned to room temperature.
conclusion, published An article published Thursday in the journal Science says it could someday change the way astronauts pack for space.
“Instead of carrying all the different plastics around, you carry this one plastic around and then give it the properties you need,” said Stuart Rowan, a University of Chicago chemist and author of the new study. ,
But location isn't the only place content can be useful. Dr. Rowan's team also sees its potential in other environments where resources are at risk – such as at sea or on the battlefield. It can also be used to make soft robots and improve plastic recycling.
“We all depend on plastic in our daily lives,” said Shreyash Patel, a chemical engineer at the University of Chicago and author of the new study. But foam cups, trash bags and eyeglass lenses, for example, all require plastics with different properties.
On the other hand, a single material that can be tailored to different needs “simplifies the way you make plastics,” Dr. Patel said. It will also make plastics more sustainable as all items can be processed together during recycling. He explained that plastics should be sorted when recycling only contributes a small fraction to being reused.
Modern plastics are made of chains of molecules that are permanently bonded, making them difficult to break. But the Chicago researchers say their new material is “pluripotent” – a term commonly used to describe a general property of stem cells – or made up of bonds that can be broken using heat and Can be rebuilt.
They were inspired by the way blacksmiths heat steel in a furnace and then cool it rapidly. But unlike metal, plastics are lightweight and can be molded at temperatures achievable with an oven or stovetop.
The researchers heated the red, transparent plastic to temperatures between 140 and 230 degrees Fahrenheit and then placed it in a freezer to cool immediately. When tempered at lower temperatures, more molecular bonds are formed, making the plastic tougher. But at higher temperatures, the material became soft and sticky.
The team molded the plastic into a spoon that was stiff enough to scoop peanut butter from a jar, and a fork that could pick up cheese. He also created an adhesive strong enough to stick two pieces of glass together, and a small claw like you might find in a toy machine.
Julia Callow, a chemist at Northwestern University who was not involved in the study but wrote Perspective Based on the results of science, the idea of a single material that can achieve a variety of unique and exciting properties was found. “Now that we know it can be useful to acquire this property, many other researchers will be inspired to find new ways to accomplish that goal,” she said.
The first generation of pluripotent plastics has some limitations. Although the team has shown that the material can be reprocessed at least seven times, and can hold its shape for at least a month, there is uncertainty about its shelf life.
“They're not going to be a replacement for commodity plastics yet,” said Nicholas Boynton, a University of Chicago graduate student who led the study's experiments. For example, the material cannot yet reach the stiffness of a plastic bag, nor the elasticity of a rubber band.
“We're not there yet, but we're pretty close,” Mr. Boynton said. “I think having content that can reach this huge range is really exciting at this point.”