We all think 3D printing is pretty cool, right? But the ability to print three dimensional objects from a digital file has become increasingly accessible as a manufacturing method; it’s becoming so commonplace we can do it at home. So scientists at Harvard have decided the ability to print across three spatial dimensions is too restrictive and they’re bringing in the fourth: time.
When I first read about this, a wise warning from Hermione Granger came into my head: “Awful things happen to wizards who meddle with time, Harry (or Harvard).” Fortunately, though, the team of scientists at the Wyss Institute for Biologically Inspired Engineering at Harvard University and the Harvard John A. Paulson School of Engineering and Applied Sciences are integrating time into the printing process in a way that’s natural rather than manipulative. Inspired by the biological structures and natural movements of plants which can change their form over time in response to changes in their environment, the team has created 4D-printed hydrogel composite flowers that change shape when they’re immersed in water.
You can see the printing process and the flowers themselves changing in the video below. It’s pretty mesmerising.
The hydrogel composite used for printing is almost like liquid in its structure and contains very small fibres called cellulose fibrils which are also present in the cell walls of plants and contribute to their rigid structure. The fact that hydrogels are able to absorb large amounts of water in combination with the rigidity of the cellulose allows the printed object to achieve intricate shape changes.
Of course, it’s not all about the materials – the printing method is essential too. A very intricate and precise printing pattern is used to ensure that the hydrogel swells just the right amount at specific sections of the flower when it absorbs the water to allow it to fold when immersed. As the material absorbs more water over time, its shape continues to change until it becomes fully saturated.
The ability to print transformable objects is an exciting development and the scientists behind the projects say it opens up new applications for 4D printing technology, enabling “the design of almost any arbitrary, transformable shape from a wide range of available materials with different properties and potential applications” including smart textiles, soft electronics, biomedical devices, and tissue engineering. Different shape changes can be achieved simply by altering the printing path, and using different composites for ink could allow for the creation of transformable structures that are conductive or fit for use in a living body. It’s a real step towards being able to design nature’s solutions into engineered structures.
Main Image: Wyss Institute at Harvard University