Chemists Create Playdough/Lego-Like Particles to Make Miniature Building Blocks

Legos and Playdough are two very popular childhood building blocks. But what could one use to create something extremely small—a structure measuring lesser than the width of a human hair?

Computer renderings illustrating the design of micro-structured patchy particles. These tiny objects (1/4th of the size a red blood cell) are first created inside a computer using simulations and then fabricated in the laboratory.( Image courtesy of Theodore Hueckel).

A team of Chemists from New York University have discovered that this can be accomplished by developing particles that possess both playdough and Lego traits.

These “patchy particles” are 1/200th the width of a human hair and can form infinite architectures from a few basic pieces. And in contrast to their larger counterparts, these particles can self-assemble. Details about “patchy particles” can be found in the latest issue of the journal Nature.

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. These smart particles represent an important step forward for the realization of self-assembling new materials and micro-machinery.

Stefano Sacanna, One of the Creators and Assistant Professor, Department of Chemistry, New York University

This process of self-assembling pre-determined micro-architectures is similar to the way atomic crystals self-assemble from a specific combination of atomic building blocks.

“In nature, extremely precise architectures, such as crystals, seamlessly grow from random soups of atoms,” explains Sacanna. “By using similar principles, we can fabricate extremely precise micro-architecture without human intervention.”

Colloidal self-assembly has the potential to revolutionize 3D printing. 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 millimetre and that could someday actually run!

Stefano Sacanna, One of the Creators and Assistant Professor, Department of Chemistry, New York University

For Researchers, however, miniaturization presently poses a daunting challenge.

The direct handling of “construction bricks” which are 10 or even 100 times smaller than a human cell is hard. A more efficient method is to replicate what Sacanna refers to as nature’s “manufacturing technology”: self-assembly. This, however, requires the capability to design and manufacture building blocks that know where to go and what to do.

The technology created in Sacanna's lab enables the formation of such microscopic building blocks and impart them with an on-board instruction manual that informs them how to connect with adjacent particles.

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.

Stefano Sacanna, One of the Creators and Assistant Professor, Department of Chemistry, New York University

Sacanna and his colleague Gi-Ra Yi, a Professor in the School of Chemical Engineering at Sungkyunkwan University (SKKU) in Suwon, South Korea, along with NYU Graduate Students Zhe Gong and Theodore Hueckel, developed these patchy particles via a new artificial methodology termed as “colloidal fusion,” which is not unlike how various pieces of playdough are pieced together.

While playdough requires squeezing together various colors of clay, colloidal fusion combines diverse chemical functionalities to form multi-functional—as opposed to multi-colored—particles that also possess instructions for self-assembly. This process is accomplished by deploying software—called “Surface Evolver”—that is a simulation package similar to the ones used by software engineers to design buildings.

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

The research team was supported by a CAREER Award from the National Science Foundation.

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