San Diego, United States - July 31, 2024

Engineers at the University of California San Diego have unveiled a groundbreaking 3D printing technique that could revolutionize materials manufacturing. Published in Nature Communications, their method utilizes a minimalistic approach, employing a polymer ink and a salt water solution to create solid structures with remarkable ease.

The key to this innovative process lies in a liquid polymer solution known as poly(N-isopropylacrylamide), or PNIPAM. When extruded through a needle into a calcium chloride salt solution, the PNIPAM ink undergoes rapid solidification upon contact with the salt water. This phenomenon, driven by the salting-out effect, results from salt ions drawing water molecules out of the polymer solution, causing the ink's polymer chains to densely aggregate into a solid form.

Professor Jinhye Bae, senior author of the study from UC San Diego's Jacobs School of Engineering, highlighted the simplicity and environmental benefits of their approach: "This is all done under ambient conditions, without the need for specialized equipment, toxic chemicals, or energy-intensive processes."

Unlike traditional polymer solidification methods that require heat, pressure, or harsh chemicals, this new technique operates at room temperature and is entirely reversible. The solid structures can be dissolved in fresh water, allowing for the reuse of PNIPAM ink, thereby promoting a sustainable cycle of material reuse and recycling.

The researchers demonstrated the versatility of their method by printing structures using PNIPAM inks infused with other materials. For instance, they successfully printed an electrical circuit incorporating carbon nanotubes, capable of powering a light bulb. This water-soluble circuit underscores the potential for creating recyclable electronic components.

The team's work, supported by the National Science Foundation and the National Research Foundation of Korea, marks a significant step towards environmentally friendly polymer manufacturing technologies.

For further details, the paper titled "Sustainable 3D printing by reversible salting-out effects with aqueous salt solutions" can be accessed in Nature Communications.