Breakthrough: Physicists Take Particle Self-Assembly to New Level by Mimicking Biology

A group of physicists have developed a brand-new technique for self-assembling particles. This development offers fresh hope for creating intricate and cutting-edge materials at the tiny scale.

Self-assembly, which was developed in the early 2000s, provides scientists with a way to "pre-program" particles, enabling the creation of materials without additional human involvement. This is essentially the smallest version of self-assembling Ikea furniture.

The discovery, which was published today, September 28, in the journal Nature, focuses on emulsions—oil droplets dissolved in water—and how they might be used to help foldamers self-assemble. The sequence of droplet interactions can possibly be used to anticipate these particular shapes.

Through interactions between blue-blue, blue-yellow, and eventually yellow-yellow droplets, which are all mediated by sticky DNA strands, a chain of alternating blue and yellow droplets folds into a crown shape in microscopy images. The image above demonstrates how sticky DNA strands instruct microscopic droplets to interact with one another and fold into specific shapes. Credit: Photograph from the Brujic Lab

The self-assembly procedure borrows from biology by utilizing colloids to simulate the folding of proteins and RNA. In their study published in Nature, the researchers produced tiny, oil-based droplets in water that contained a variety of DNA sequences that acted as "instructions" for assembly. These droplets initially form pliable chains, which are then successively folded by DNA molecules. Twelve different forms of foldamers result from this folding, and with more specificity, more than half of the 600 conceivable geometric shapes might be encoded.

Jasna Brujic says, "Being able to pre-program colloidal frameworks provides us the ability to develop materials with complicated and novel features. She is a researcher on the study and a professor in the department of physics at New York University. Our research opens us new avenues for developing the materials of the future by demonstrating how hundreds of self-assembled shapes can be made uniquely.

Researchers on the project included Maitane Muoz Basagoiti and Zorana Zeravcic of ESPCI Paris, as well as Angus McMullen, a postdoctoral associate in the Department of Physics at NYU.

Scientists underline the method's paradoxical and ground-breaking feature: because each building block can take on a variety of configurations according to its folding methodology, only a small number of building blocks are required to encode accurate shapes.

According to Brujic, "our approach uses only two types of particles, which considerably minimizes the diversity of building blocks needed to encode a given shape, unlike a jigsaw puzzle in which every piece is unique. The key to the breakthrough is employing folding on a scale 1,000 times larger than that of proteins—roughly one-tenth the width of a hair strand. These particles initially unite to form a chain, which folds in accordance with predetermined interactions that direct the chain via intricate paths to create a certain geometry.

To further assemble into bigger scale materials, she explains, "the capacity to obtain a lexicon of morphologies opens the route, just as proteins hierarchically aggregate to build cellular compartments in biology."

By NEW YORK UNIVERSITY