4D Printing: A Revolution of Smart Objects

3D printing is a process for constructing three-dimensional solid objects from a digital model by successively adding or stacking layers of material.  3D printing differs from conventional manufacturing methods which typically create objects by removing material through cutting and drilling.

In 2013, Skylar Tibbits, director of the Massachusetts Institute of Technology Self-Assembly Lab, proposed a concept called 4D printing that takes the 3D printing process to another level.  ‘4D printing’ refers to the creation of objects built from materials that are programmed to be able to transform their shape over time and to even ‘self-assemble’.  The fourth dimension refers to the ability to change over time.

Tibbits described the origin of the idea to the New Scientist, saying that  “at first, the name was a bit of a joke. When you 3-D-print an object, it’s a fixed, static thing. If you want something more complex, you need to print it as parts and then assemble it. We thought, instead of assembling intelligence into it afterwards, why not print intelligence into it?”

Tibbits said that with 4D printing “we are looking at the ability to program physical and biological materials to change shape, change properties and even compute outside of silicon-based matter…  Imagine if water pipes could expand or contract to change capacity or change flow rate; or maybe undulate like peristalsis to move the water themselves.”

One approach to 4D printing is to construct objects out of shape-memory materials.  A team led by H Jerry Qi at the University of Colorado used shape-memory polymer fibers with a 3D printing device.  Martin L Dunn, a collaborator on the project, described their research saying that  “in this work, the initial configuration is created by 3D printing, and then the programmed action of the shape-memory fibers creates time dependence of the configuration, the 4D aspect.  We advanced this concept by creating composite materials that can morph into several different, complicated shapes based on a different physical mechanism.  The secret of using shape memory polymer fibres to generate desired shape changes of the composite material is how the architecture of the fibres is designed, including their location, orientation and other factors.”

Anna C. Balazs, leading another group of researchers at University of Pittsburgh’s Swanson School of Engineering, described their research by saying that “rather than construct a static material or one that simply changes its shape, we’re proposing the development of adaptive, biomimetic composites that reprogram their shape, properties, or functionality on demand, based upon external stimuli.  By integrating our abilities to print precise, three-dimensional, hierarchically-structured materials; synthesize stimuli-responsive components; and predict the temporal behavior of the system, we expect to build the foundation for the new field of 4D printing.”