Smart 3D Printing Ink Allows Structures to Change Shape and Color

3D printers create everything from prosthetic limbs to houses and even food. However, a new type of ink could expand those capabilities even more. Researchers from Dartmouth College created a new type of smart ink that could lead to an entirely new style of 3D printed materials. 

The ink allows structures to change shape and color, promising to add more functionality to an already functional style of craftsmanship. The team at Dartmouth wanted to branch into the emerging technology of form-changing intelligent printing -- aka 4D printing. Fans of 3D printing hope that 4D printing could offer a low-cost option for critical parts in areas like energy to biomechanics.  

"This technique gives life to 3D-printed objects," said Chenfeng Ke, an assistant professor of chemistry at Dartmouth. "While many 3D-printed structures are just shapes that don't reflect the molecular properties of the material, these inks bring functional molecules to the 3D printing world. We can now print smart objects for a variety of uses."

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Most common 3D printing inks use photo-curing resins that create hard, plastic objects or rigid structures. The researchers noted these structures often have random molecular architectures. The Dartmouth team developed a new process that allows for designers to keep their ideal molecular alignments and its functions. The process combines new techniques in both pre-printing and post-printing. The researchers could even shrink printed objects to 1 percent of their original size and with 10 times the resolution, the study reported. Using fluorescent trackers, the printed objects could even change color in response to stimuli such as light. 

According to Ke, the smart ink could save researchers looking to leverage the technology for other disciplines time, money, and other resources. 

"This process can use a $1,000 printer to print what used to require a $100,000 printer," said Ke. "This technique is scalable, widely adaptable and can dramatically reduce costs."

The smart ink comes from a polymer-based vehicle that combines molecular systems into the printing gel. This allows the molecules to quickly shift their functions from the nanoscale to the macroscale. 

In a statement, the team said "We believe this new approach will initiate the development of small molecule-based 3D printing materials and greatly accelerate the development of smart materials and devices beyond our current grasp that are capable of doing complex tasks in response to environmental stimuli."

The researchers hope their new smart ink could help alleviate some frustrations of current printing -- particularly for materials chemists, printing engineers, bioengineers, and other researchers looking for more functional and adjustable printing features. 

"This is something we've never seen before. Not only can we 3D print objects, we can tell the molecules in those objects to rearrange themselves at a level that is viewable by the naked eye after printing. This development could unleash the great potential for the development of smart materials," Ke said.

Ke and his team did note that they're still far from intelligent 3D systems that could dynamically change shape. However, current uses could create a new type of macroscale 3D objects for things like bone replacements or medicine delivery.