Researchers at MIT and Delft University of Technology have developed a method of 3D printing that uses heat-responsive materials to print multi-colour and multi-textured objects in one step.
The method, which came out of a project exploring the potential for multi-property single material printing, is called speed-modulated ironing. It uses two print nozzles, whereby a heat-responsive filament is printed using one nozzle, followed by a second empty nozzle, which passes over the material to activate colour, shade or roughness changes, using heat.
“Today, we have desktop printers that use a smart combination of a few inks to generate a range of shades and textures. We want to be able to do the same thing with a 3D printer — use a limited set of materials to create a much more diverse set of characteristics for 3D-printed objects,” says Mustafa Doğa Doğan PhD ’24, co-author of a paper on speed-modulated ironing.
The researchers are able to control the speed of the second nozzle to heat the filament to specific temperatures, and have developed a model that predicts the amount of heat the second nozzle will transfer based on its speed – the temperature of the second nozzle itself remains constant. The method is said to not require any hardware modifications.
“As we modulate the speed, that allows the printed layer we are ironing to reach different temperatures. It is similar to what happens if you move your finger over a flame. If you move it quickly, you might not be burned, but if you drag it across the flame slowly, your finger will reach a higher temperature,” AlAlawi says.
The MIT team collaborated with TU Delft researchers to develop the theoretical model that predicts how fast the second nozzle must move to heat the material to a specific temperature. The model has also been used to create a user interface that automatically generates printing instructions for colour, shade, and texture specifications.
The method has so far been tested using three heat-responsive filaments including a foaming polymer with particles that expand as they are heated, and wood and cork fibre-filled filaments. The team tested the foaming polymer by printing partially translucent water bottles, ironing at low speeds to create opaque regions and higher speeds to create translucent ones. The plan is to continue testing with other thermally responsive materials, such as plastics.
The project is a collaboration between the research groups of Zjenja Doubrovski, assistant professor at TU Delft, and Stefanie Mueller, the TIBCO Career Development Professor in the Department of Electrical Engineering and Computer Science (EECS) at MIT and a member of the MIT Computer Science and Artificial Intelligence Laboratory (CSAIL). Doğan worked closely with lead author Mehmet Ozdemir of TU Delft; Marwa AlAlawi, a mechanical engineering graduate student at MIT; and Jose Martinez Castro of TU Delft.
