3D Printing to Be Revolutionized by Colloidal Self-Assembly

Play is often referred to as the ‘work’ of children, and sometimes those interests overlap into the research of adult scientists too, gleaning inspiration from popular building blocks and materials like LEGOs and Play-Doh. Of course, in the world of grownup science and 3D printing innovation, the projects are just a tiny bit more complex—and with an emphasis on tiny—no wait, make that microscopic!

Chemists from the New York University Department of Chemistry and the School of Chemical Engineering at Sungkyunkwan University (SKKU) in Suwon, South Korea are creating ways to make structures tinier in width than a piece of your hair. Borrowing from material elements in both LEGOs and Play-Doh, they have been able to create ‘patchy particles.’ Their research, outlined in the paper ‘Patchy particles made by colloidal fusion,’ was published recently in Nature:

“Using coordination dynamics and wetting forces, we engineer hybrid liquid–solid clusters that evolve into particles with a range of patchy surface morphologies on addition of a plasticizer,” state the researchers in their abstract. “We are able to predict and control the evolutionary pathway by considering surface-energy minimization, leading to two main branches of product: first, spherical particles with liquid surface patches, capable of forming curable bonds with neighbouring particles to assemble robust supracolloidal structures; and second, particles with a faceted liquid compartment, which can be cured and purified to yield colloidal polyhedra.

These findings outline a scalable strategy for the synthesis of patchy particles, first by designing their surface patterns by computer simulation, and then by recreating them in the laboratory with high fidelity.”

According to the scientists, they can make an infinite number of architectures with these innovative particles that are able to assemble themselves into place, not unlike atomic crystals moving into place.

“Imagine that you want to build a castle, but instead of handpicking the bricks and patiently connecting them one by one, you simply shake the box of pieces so that they magically connect to one another in forming a full-featured castle,” says Stefano Sacanna, an assistant professor in the New York University Department of Chemistry and one of the creators. “These smart particles represent an important step forward for the realization of self-assembling new materials and micro-machinery.”

The study of crystals and their random growth from atoms inspired the scientists to innovate micro-architectures that can be made without intervention from humans.

“Colloidal self-assembly has the potential to revolutionize 3D printing,” he adds. “This could be achieved by not merely by further reducing the size of the printed architectures, but also by allowing us to ‘print’ functional architectures. Say you want to print a model car–using colloidal self- assembly, you could print a car that is a fraction of a millimeter and that could someday actually run!”

Because the creation of such miniature structures is challenging, Sacanna and the team chose a more efficient route in making them independent with self-assembly, even capable of understanding instruction regarding direction and connection.

“These particles will help us to understand—and allow to mimic—the self-assembling mechanisms that nature uses to generate complexity and functionalities from simple building blocks,” he says.

Sacanna worked on the colloidal fusion concept with Gi-Ra Yi from the School of Chemical Engineering at SKKU, along with two other NYU graduate students: Zhe Gong and Theodore Hueckel.

If you are wondering how Play-Doh came into the equation with this process, just imagine how it looks when you press together a variety of colors. With colloidal fusion, the pieces come together as multi-functional pieces rather than multi-colored. And the particles are made ‘smart’ thanks to Surface Evolver simulation software.

“The software allows us to predict how an initial cluster will evolve when ‘squeezed’ and how the resulting multifunctional patchy particle will look like,” says Sacanna.

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