4-D Printing Could Make Replacement Organs

A group of Harvard University researchers may have brought 4-D printing closer for use in making medical devices and replacement organs.

Nancy Crotti

Harvard researchers took inspiration from nature in developing 4-D printed
architectures. Image courtesy Wyss Institute at Harvard University.

Inspired by the way that plants change shape over time in response to environmental stimuli, the researchers devised a mathematical model that determines how a 4-D object must be printed to achieve prescribed, changeable shapes, according to a statement from the university.

They used hydrogel composite ink containing aligned cellulose fibrils that swell lengthwise along the printing path. The researchers applied the mathematical model to print the fibrils in patterns that would allow them to curve in the predetermined ways when immersed in water, according to an article in New Scientist.

The new method has potential for applications in medical devices, tissue engineering, smart textiles, and soft electronics, according to the university.

"We have now gone beyond integrating form and function to create transformable architectures," Jennifer Lewis, senior author on the study, said in a statement. Lewis is a core faculty member at Harvard's Wyss Institute for Biologically Inspired Engineering and an engineering professor at the university's John A. Paulson School of Engineering and Applied Sciences. L. Mahadevan, professor of physics, applied mathematics, and evolutionary biology at Harvard, co-authored the study with chemistry professor Ralph Nuzzo from the University of Illinois at Urbana-Champaign. It was published in Nature Materials.

4D Printing: Shapeshifting Architectures from Wyss Institute on Vimeo.

Mahadevan's studies of how botanical tendrils coil, how flowers bloom, and how pinecones open and close helped inform the work. Elsewhere, others are working on 4-D printing of neurovascular coils and shape-shifting thiolene/acrylates that could enable self-coiling cochlear implants inside the ear, electrodes that coil around a nerve, and a host of cardiovascular implants.

3-D printing equipment manufacturer Stratasys joined forced in 2014 with MIT research scientist Skylar Tibbits to study how 3-D printed materials might change shape on their own. Stratasys' Connex multi-material technology also relies on the water-absorbing properties of different materials to activate the shape-shifting process.

Lewis told New Scientist that she and her colleagues wanted to simplify the process by using a single material. Now they're studying how this technology could be used to grow new organs.