Building Technologies

New 3D Printing Smart Ink Creates Shape and Color Shifting Objects

04 April 2018

Dartmouth College researchers created a smart ink that is going to change the 3D-printing game. The new ink turns 3D-printed structures into color and shape-shifting objects. This new development adds a whole new level of innovation and functionality to the 3D printing industry.

An example from the research shows how a 3-D-printed object composed of hydrogel (G1) can change size after printing. Source: Chenfeng KeAn example from the research shows how a 3-D-printed object composed of hydrogel (G1) can change size after printing. Source: Chenfeng Ke

Form-challenging intelligent printing (otherwise known as 4D printing) has been the focus of many researchers as the next step after 3D printing. 4D printing costs less than printing precision parts for industries like biomedicine or energy.

"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."

Typical protocols for 3D printing uses photo-curing resins that create hard plastic objects that have random molecular architectures. The 4D printing process with the newly developed ink allows creators to maintain precise molecular alignments and functions while working with 3D printing.

The researchers used a combination of the new techniques during the pre- and post-printing processes. By doing this the objects were reduced to one percent of the original size with 10 times the resolution. The objects could be animated to expand and contract with their supramolecular pillars. The objects can change color with fluorescent trackers when exposed to a stimulus.

Printing preserving functional features while also increasing resolution means that an inexpensive printer can be used to print high-resolution objects has only been possible in the past with incredibly sophisticated printers.

The smart ink can print at a rough, 300-micron resolution. The end product features a finer line with a width of 30 microns.

"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 was created with a polymer-based “vehicle” that uses intelligent molecular systems so the end result of the object can transform under light or heat from nanoscale to macroscale.

Most 3D-printed material is hardened throughout the printing process. The newly developed process involves post-printing reactions that lock inactive ingredients to maintain the molecular structure through the entire printing process.

"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.

This tech still has a far way to go in development but the current stage can be used in items like 3D printed precision filters, storage devices, material chemists or 3D printing engineers. The team believes that once the process is fully refined, it will create a new class of macroscale 3D printed objects to deliver medicine or create bone replacements.

"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,” said the researchers.

The paper on this research was published in Angewandte Chemie.

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