Researchers at the University of Colorado Boulder have developed and tested a method for 4D printing, opening up exciting possibilities for the creation and use of adaptive, composite materials in manufacturing, packaging and biomedical applications.
The team led by H. Jerry Qi, associate professor of mechanical engineering at CU-Boulder, and his collaborator Martin L. Dunn of the Singapore University of Technology and Design has successfully added a fourth dimension to their printing technology by incorporating ‘shape memory’ polymer fibres into the composite materials used in traditional 3D printing, which results in the production of an object fixed in one shape that can later be changed to take on a new shape.
Dunn explains that the initial configuration is created by 3D printing, followed by the programmed action of the shape memory fibres creating time dependence of the configuration – the 4D aspect. Dunn is a former CU-Boulder mechanical engineering faculty member who has studied the mechanics and physics of composite materials for more than two decades.
The 4D printing concept, which allows materials to ‘self-assemble’ into 3D structures, was initially proposed by Massachusetts Institute of Technology faculty member Skylar Tibbits in April of this year. Tibbits and his team combined a strand of plastic with a layer made out of ‘smart’ material that could self-assemble in water.
This concept was advanced by the CU-Boulder team by creating composite materials that could morph into several different, complicated shapes based on a different physical mechanism.
The CU-Boulder team’s findings were published last month in the journal Applied Physics Letters in a paper co-authored by Qi ‘Kevin’ Ge, who joined MIT as a postdoctoral research associate in September.
The CU-Boulder team demonstrated that the orientation and location of the fibres within the composite determines the degree of shape memory effects such as folding, curling, stretching or twisting. The researchers also showed the ability to control those effects by heating or cooling the composite material.
Qi says 3D printing technology, which has existed for about three decades, has only recently advanced to the point that active fibres can be incorporated into the composites so their behaviour can be predictably controlled when the object is subjected to thermal and mechanical forces.
The technology promises exciting new possibilities for a variety of applications. As 3D printing technology matures with more printable materials and higher resolution at larger scales, the research should help provide a new approach to creating reversible or tuneable 3D surfaces and solids in engineering such as the composite shells of complex shapes used in automobiles, aircraft and antennas.