Additive Manufacturing’s Next Frontiers – 4D Printing and Self-Assembly

Today, 3D printing is relatively well established, with an ever-increasing selection of printers available, ranging from low-cost personal/desktop 3D units for home to the larger and much more capable industrial-strength printers.

The technology itself has also evolved and is now being implemented in a wide range of industries from automotive to aerospace, construction, health, food, and many others.

By now most of us are familiar with 3D, but for the past couple of years there has been increasing chatter about 4D printing. So what is 4D printing?

A couple of years ago 4D-printing was introduced at a TED Conference in 2013 by Skylar Tibbits, director of MIT’s Self-Assembly Lab.

The Emergence of 4D Printing

He described 4D printed objects as 3D-printed objects that reshape themselves or self-assemble over time, depending on the environment they’re in. In other words, the 4th dimension is time and/or environmental conditions.

Tibbits is said to be working with GEOSyntec to design 4D printed water pipes. As the scale and reach of the technology increases, applications in the military (no surprise here) and construction industries are likely to materialize.

Shapeshifting: 3D printed materials that change shape over time.

Dr Dan Raviv, postdoctoral fellow at MIT, believes that 4D printing may be used in a wide range of applications such as home appliances, childcare products, or even clothes and footwear that optimize their form and function by reacting to changes in the environment.

New York’s Museum of Modern Art (MoMA) recently acquired a 4D-printed dress which designers were able to print using a powder-based nylon material, and made the dress out of thousands of interlocking pieces.

The pace at which 3D printing has evolved in various industries is impressive, but the technology is still too slow for mass manufacturing, and precision and repeatability must still improve for fabrication of structural components.

The power to offer customized products that are manufactured closer to their point of consumption certainly makes the technology appealing to both providers and consumers. It’s a growing market, but there’s still a lot work to be done – particularly around process speed, product size, and the variety of materials that can be used with the technology.

In the near future, 4D printing could be used in space. For example, an improved 3D printing process using materials that could self-assemble (the next topic below) was used to fabricate components on-site and on-demand for astronauts during a space mission.

Self-Assembling 3D Printing

A recent study reported in The Conversation has shown that high frequency vibrations can cause bricks to self-assemble into a larger 3D object, a finding that may one day help reduce the need for factory assembly lines.

The findings, published recently in the journal, Scientific Reports, signal a key advancement in programmable self-assembly, which was previously thought to only be possible using one-dimensional or two-dimensional objects.

Self-Assembly Demonstration

The research team, led by Dr Ido Bachelet from the Institute for Nanotechnology and Advanced Materials at Bar-Ilan University in Israel, used an algorithm from the Computational Geometry Algorithm Library (CGAL) as part of a design that allowed 18 tetrahedral bricks to self-assemble into a larger 3D cylinder.

The following video shows blocks in the self-assembly process. Two sets of the object (36 bricks) were inserted in the chamber and after 2.5 hours in a constant speed of 320 rpm one set was assembled. The video doesn’t contain the whole, but portions of it.

The Basic Self-Assembly Process

“Assembly rules are encoded by topographic cues imprinted on brick faces while attraction between bricks is provided by embedded magnets,” the researchers said in their paper. “The bricks can then be mixed in a container and agitated, leading to properly assembled objects at high yields and zero errors.

“Improved designs inspired by our system could lead to successful implementation of self-assembly at the macro-scale, allowing rapid, on-demand fabrication of objects without the need for assembly lines.”

The ability for life to self-assemble is something that continues to puzzle scientists. For example, proteins, viruses, living cells and multi-cellular organisms are all examples of systems in which parts are bonded to each other through attraction to form a structure or pattern.

Hamza Bendemra, a Research Engineer at the Australian National University, who was not involved in the study, said the research of 3D printed assemblies is remarkable.

“The algorithm was inspired by the molecular assembly of the DNA,” he said. But he added that more research was needed to address challenges of time, space and safety for the model to be more efficient at forming and remaining together.

“In the study, a two-brick assembly took less than a minute to self-assemble. However, an 18-piece assembly required over two hours to perform the same feat.”

“The components are subject to high vibrations and collide over and over again until they fit in the right combination. It would be a challenge to implement such a method with materials with low strength and poor impact tolerance without causing damage.”

The next step in developing this concept for construction and manufacturing industries is to use both magnetic forces and adhesives to ensure the assembly stays in place.

Bendemra agreed, saying that “the researchers did a great job at adding topographic cues to ensure a unique combination only would lead to the pieces locking in. Their footage clearly shows that pieces that collide in a non-desired formation detach until they lock-in as planned.”

“The number of pieces involved in the assembly and the nature of the materials being used (including the magnet) in more complex assemblies could limit the use of such a method.”

This self-assembly effort is not entirely unique, as the Self-Assembly Lab is collaborating with Autodesk and Stratasys for 4D printing.

So, there you have it: 4D printing and self-assembly. There is certainly a long way to go to commercial viability, but these demonstrations point the way to some fascinating possibilities.

Tags: 3D printing, 4D printing, additive manufacturing, AM, self-assembly

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