A team of researchers at Princeton University has developed a 3D printing technique that can be used to produce soft plastics with programmable stretchability and strength. The materials used are cost-effective, recyclable and scalable – a combination of properties rarely found in commercial manufacturing to date. The results were published in the journal Advanced Functional Materials.
The research focuses on the use of thermoplastic elastomers, a widely used class of polymers. By specifically aligning the internal nanostructures using 3D printing, the scientists were able to create materials that are flexible and stretchable in one direction while remaining rigid in another.
“The elastomer we are using forms nanostructures that we are able to control,” said Emily Davidson, assistant professor of chemical and biological engineering. “We can create materials that have tailored properties in different directions.”
The key technology lies in the structure of the material at nanoscale level. The use of block copolymers creates rigid cylindrical structures with a thickness of just 5 to 7 nanometers within a flexible polymer matrix. The researchers developed a process in which the printing rate and targeted sub-extrusion influence the alignment of these nanostructures. In addition, thermal tempering, i.e. targeted heating and cooling, significantly improves the material properties and even enables self-healing: damaged parts can be repaired by tempering them again without losing functionality.
Alice Fergerson, a graduate student at Princeton and the article’s lead author, noted: “I think one of the coolest parts of this technique is the many roles that thermal annealing plays— it both drastically improves the properties after printing, and it allows the things we print to be reusable many times and even self-heal if the item gets damaged or broken.”
Davidson emphasizes that the advantage of thermoplastic elastomers lies primarily in their cost efficiency. While comparable materials such as liquid crystalline elastomers are expensive and complex to process, the polymer used here costs less than a cent per gram and is compatible with standard 3D printers.
As a next step, the team plans to research new 3D architectures suitable for wearable electronics and biomedical applications. The research was supported by funding from the National Science Foundation and the Princeton Center for Complex Materials.
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