NTU Research Team Confirms Durability of 4D Printed Objects

The fabrication method. Credit: Materials & Design

The fabrication method. Credit: Materials & Design

Researchers from Nanyang Technological University Singapore have proven the durability of 4D printed structures. 4D printing relates to objects that can adapt over time once they have been 3D printed. These structures rely on shape memory polymers that are able to transform into a certain shape.

​In a new study, the team evaluated the performance of these structures. According to them, high shape fixity, shape recovery, and “prolonged shape memory cycle life” are desirable aspects of 4D printed parts; however, the durability of 4D printed parts is rarely investigated.

The 4D printing process

To test the viability of 4D printed parts, the team tested the process by 3D printing a bucky ball  – a cage-like structure resembling a soccer ball – using an SLA 3D printer.

But first, they had to create a specially formulated resin as resins commonly used in SLA printers are “highly crosslinked thermoset polymers”, which means that the parts produced are typically quite stiff and without desired properties for shape memory effect (SME).

The fourth dimension

Following a number of different tests, the researchers were able to successfully create a resin that had different properties depending on the temperature of the environment it was exposed to. In addition, they also demonstrated how different resins could affect the performance of the 4D objects. Thereby, the team was able to create a 4D printed spherical bucky ball that could be manually deformed to lie flat before then re-forming to its original shape when submerged in warm water.

A 3D printed bucky ball used in the researchers’ evaluation. It  was able to change shape when submerged in 65 ̊C water. Credit: Materials & Design

A 3D printed bucky ball used in the researchers’ evaluation. It was able to change shape when submerged in 65 ̊C water. Credit: Materials & Design

The resulting 4D printed bucky ball performed very well, as an outstanding durability of 22 cycles was demonstrated to show its “prolonged shape memory cycle life”.

Potential of 4D printing

This research could have an impact on the application of 4D printing as a viable manufacturing technique. 4D printing has strong potential for its ability to self-assemble objects, with particular interest in construction or for self-assembling flat-park furniture.

The paper, titled ‘4D printing of high performance shape memory polymer using stereolithography’, has been published in the ‘Materials & Design’ journal. The research was written by Yu Ying Clarrisa Choong, Saeed Maleksaeedi, Hengky Eng, Jun Wei, and Pei-Chen Su from the Singapore Centre for 3D Printing, School of Mechanical & Aerospace Engineering, Nanyang Technological University and the Singapore Institute of Manufacturing Technology.

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