The introduction of a fourth dimension into 3D-printed materials, producing dynamic structures that can change shape in response to their environment, is described in Scientific Reports this week. This technique may prove to be useful for medical applications based on soft robotics. The materials can stretch, fold and bend into predetermined shapes when submerged in water, thereby altering property and function of the material post-fabrication, in contrast to conventional 3D printing, where the outcome remains static.
Dan Raviv and colleagues introduce a fourth dimension - time - by using materials that can change shape after they have been printed. Their approach prints 3D structures using materials with different properties: one that remains rigid and another that expands up to 200% of the original volume. The expanding materials can be placed strategically on the main structure to produce joints that can stretch and fold like a bendy straw when activated by water to produce a broad range of shapes with complex geometries. For example, a 3D-printed shape that resembles the initials “MIT” is shown to evolve into another formation that looks like the initials “SAL”. They further designed several new structures that can bend and stretch to form complex geometry deformations in time. Several 2D grids were printed and tested for different pre-programmed deformations, forming curved shapes when placed in water.
The transformations can be reproduced over a few wetting and drying cycles, but repeated folding and unfolding can lead to degradation of the materials. Further testing is required to fully understand the lifespan of these dynamic materials, and the authors note that other activating stimuli, such as heat and light, could also be used to achieve similar effects.