Using material reactions
4D printing is similar to 3D printing except that it changes materials from location to location. The separate material is used because it is reactive to a particular stimulus: water, cold or heat, for instance. Initial printing is done on a flat surface that is then exposed to the stimulus, causing a reaction, and changing the surface shape. The fourth dimension refers to the altered configuration of the once-flat material.
Composite 4D printing is more complex. Rather than using a soft, dough-like substance commonly used by 3D and 4D printers, it relies on a sinewy combination of long, fine filaments held in place by a resin. Each filament is only 10 microns thick — about 1/10th the diameter of a human hair. The 4D composite printer unrolls its filament-resin mixture in ultra-thin layers at 90-degree angles from each other. The layers are then compacted together and cured in an oven at 180˚C, and then cooled down to 0˚C, creating an object that is stiff but not brittle.
As the authors explain in their paper, this allows them to create a section of material with a uniform curvature that is sandwiched in between the wing flap’s upper and lower surfaces. It is flexible and strong enough to support the 20-degree deformation the wing requires for flight maneuverability.
“The idea is to have a wing that can change its shape easily during flight, which would be a great benefit as compared to fixed-wing aircraft,” Hoa explains.
He believes the composite 4D technology has great potential for all manner of applications. Its products’ transportability, he says, is a major draw.
“Because it is flat, it is easy to package to send to remote areas, from Canada’s Far North to outer space.”
Read the cited paper: “Development of a new flexible wing concept for Unmanned Aerial Vehicle using corrugated core made by 4D printing of composites.”