While 3D printing has yet to fully prove itself to some people, that doesn't stop scientists from pushing on with 4D printing -- a similar process that creates objects able to transform themselves over time. Now, a Harvard lab has produced these delicate folding flowers using the approach. While 4D printing isn't new, it usually requires multiple materials be used -- stiffer sections resist folding compared to softer ones, allowing for tuned structures to flex preferentially in certain conditions. But a team of Harvard scientists sought inspiration in nature to create structures from a single material that could also bend and twist by themselves.
To do that, they created an extrudable jelly made from cellulose fibres, from wood pulp, held in an acrylamide hydrogel. When it's pumped though a nozzle, the fibres align with the axis of extrusion, creating materials that have directional properties. In other words, they extend more easily in one direction than the other.
The team used that technique, combined with some maths to work out how they could lay down the material to exploit its properties, to create a series of different flower-like shapes. These structures, due to the way the material is printed out, can not just stretch but bend, twist and curl. Above is an approximation of an orchid, that looks increasingly like the flower as its structure buckles.
The team hopes the material could be doped with live cells, to create interesting living structures in the future -- and potentially even synthetic organs.