Scientists at the Wyss Institute for Biologically Inspired Engineering and the Harvard John A. Paulson School of Engineering and Applied Sciences have developed a 4D printing process to create structures that change shape when submerged into water.
The team, including Jennifer A. Lewis who is also part of the Harvard spin-off Voxel8, used a hydrogel composite material containing cellulose fibrils derived from wood. These fibrils are similar to microstructures that enable plants to change shape according to their environments and are programmed to contain precise, localised swelling behaviours. In the study titled Biomimetic 3D Printing the research team combined this material with a proprietary mathematical model that can predict how an object must be printed to achieve prescribed transformable shapes. Mimicking plants, they 4D printed two flowers with individual pre-programmed shapes, that changed into two different forms upon immersion in water.
This new 4D printing method could potentially be used to created smart textiles, soft electronics, biomedical devices or engineered tissue.
A. Sydney Gladman, on of the study’s co-lead authors and graduate research assistant advised by Lewis, explained: “Using one composite ink printed in a single step, we can achieve shape-changing hydrogel geometries containing more complexity than any other technique, and we can do so simply by modifying the print path. What’s more, we can interchange different materials to tune for properties such as conductivity or biocompatibility.”
The research team also 4D printed an orchid shaped hydrogel composite structure, that was later immersed in water to activate its shape transformation: