Time is the key
Scientists at Wyss Institute for Biologically Inspired Engineering at Harvard University have developed together with their colleagues at the Harvard John A. Paulson School of Engineering and Applied Sciences a microscale 3D printing technology which uses the fourth dimension: time. Plants gave the original idea that an artificial structure should be able to change its form throughout time – like a flower moving its blossom to face the sun. Now the results have been published in a new study.
The senior author of the study, Jennifer Lewis, Sc.D., describes the outcomes as an “elegant advance in programmable materials assembly”. 4D-printed hydrogel composites mimic microstructures that can be seen in all kinds of flowers or plants. Through exact swellings caused by external influences like temperature or humidity, the scientists were able to program specific movements in printed structures.
Printed cellulose fibrils
The hydrogel composites contain cellulose fibrils – an important component to enable 4D printing. By stringing the fibrils in a specific order, the scientists were able to take advantage of the natural capabilities of cellulose: swelling and stiffness. Putting the structure into water, the cellulose fibril ink reacts in preset swellings which change the shape of the structure. Complex mathematical calculations were used to precisely forecast the movement of the prints and to plan the printing patterns.
The composite ink itself has liquid features when printed through a regular 3D printer but immediately becomes solid once printed. Through changing different components within the ink different mechanisms can be realized and different behaviors can be triggered. The combination of biological knowledge, mathematical modeling, and state-of-the-art 3D printing techniques make this project so unique and opens up great possibilities in smart textiles, soft electronics, biomedical devices or many more.
For more information on 4D biomimetic printing, visit Prof. Jennifer A. Lewis’ profile on Harvard’s website.