Newly developed “smart” inks could allow 3D printed objects to change both shape and color.

A team from Dartmouth College has created the novel smart ink, which could lead to a new generation of printed materials and provide a low-cost alternative to printing precision parts for uses in biomedicine, energy and other applications. The innovation is known as form-changing intelligent printing, or 4D printing. 

“This technique gives life to 3D-printed objects,” Chenfeng Ke, an assistant professor of chemistry at Dartmouth, said in a statement. “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.”

To create the smart ink, researchers used a polymer-based “vehicle” that integrates intelligent molecular systems into printing gel and allows for the transformation of their functions from the nanosacle to the macroscale and a printed object with a molecular design that is programmed to transform itself.

For example, the printed objects could change shape when provided a chemical fuel, or change color if light is shined on it.

The researchers used a combination of new techniques in the pre-printing and post-printing processes to reduce printed objects to 1 percent of their original size, with 10-times the resolution. The team can also animate the objects to repeatedly expand and contract in size by using supramolecular pillars.

 “This is something we’ve never seen before,” Ke said. “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.”

The new smart ink can print at a rough, 300-micron resolution. However, the final product would feature a much finer line 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.”

3D printing protocols often rely on photo-curing resins that result in hard plastic objects with rigid and random molecular architectures. However, in the new process, designers can retain specific molecular alignments and functions in a material and then convert them for 3D printing.

With fluorescent trackers, the objects can change color in response to an external stimulus such as light.

By reducing the size of an object after printing, researchers can preserve functional features and increase the resolution. The researchers believe that eventually the technology could be used for intelligent 3D systems that can dynamically change their configuration, as well as for a new class of macroscale 3D printed objects that can deliver medicine or produce high-resolution bone replacements.

Currently, the technology can be used to print precision filters and storage devices.

The study was published in Angewandte Chemie.