Engineers at Princeton University have developed an exciting 3D printing technique to create soft plastics that are stretchy, flexible, recyclable, and affordable—all at the same time.
These qualities, rarely combined in commercial materials, could revolutionize industries ranging from healthcare to consumer products.
The research, led by Professor Emily Davidson and published in Advanced Functional Materials, uses a type of polymer called a thermoplastic elastomer to produce 3D-printed structures with tunable flexibility and stiffness.
The technique could lead to a wide range of applications, such as soft robots, prosthetics, lightweight helmets, custom shoe soles, and even wearable electronics.
What makes this plastic special?
The magic lies in the material’s tiny internal structure.
The team used a special type of polymer called a block copolymer, which naturally forms stiff, cylinder-like structures about 5-7 nanometers thick (for comparison, a human hair is 90,000 nanometers wide) within a stretchy matrix.
By aligning these nanoscale cylinders using 3D printing, the researchers were able to create a material that is hard in one direction but soft and stretchy in others.
This unique property allows engineers to design objects with tailored flexibility and strength in specific regions. For instance, a device could bend easily in one direction while staying rigid in another.
A key part of the process is thermal annealing, which involves carefully heating and cooling the material.
Graduate student Alice Fergerson, the study’s lead author, explained, “Thermal annealing drastically improves the material’s properties after printing. It also allows the printed objects to be reused many times and even self-heal if they’re damaged or broken.”
For example, the researchers cut a flexible piece of their plastic, reattached it through annealing, and found that it performed just as well as the original.
One of the biggest advantages of this technique is its affordability. The thermoplastic elastomers used in the study cost only about a cent per gram and can be printed using a commercial 3D printer.
This makes the technology much more accessible compared to alternatives like liquid crystal elastomers, which cost upwards of $2.50 per gram and require complicated processing steps.
Davidson emphasized that their goal was to create soft materials with customizable properties in a way that is both affordable and scalable for industrial use.
The team also demonstrated that their materials can incorporate functional additives. In one experiment, they added an organic molecule that made the plastic glow red under ultraviolet light, showcasing the potential for creative and functional designs.
The researchers used their technique to print complex, multi-layered objects, such as a tiny plastic vase and intricate text spelling out “PRINCETON.”
This breakthrough opens the door to a range of possibilities. The team plans to explore new 3D-printable designs that could be used in wearable electronics, biomedical devices, and other cutting-edge applications.
Davidson believes this approach has the potential to transform how we manufacture and use soft materials. “We can create materials with tailored properties in different directions, making them ideal for a wide variety of applications,” she said.
By combining stretchability, recyclability, and affordability, this innovative 3D printing technique could lead to smarter, more sustainable designs in industries that rely on soft, flexible materials.
Source: Princeton University.
