Manufacturing Bits: Sept. 29

Turning the nano-wrench; 4D printed folding structures.

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Turning the nano-wrench
The University of Vermont has developed a wrench that has linewidth geometries at 1.7nm. The so-called nano-wrench is an atomic-level tool, which could one day be used to create tiny structures and molecules.

The nano-wrench has been devised using a technology called chirality-assisted synthesis (CAS). Chirality is derived from the Greek word for hand. If one holds up their hands, they are identical in structure, but are mirror opposites.

The same is true for molecules. If a molecule is chiral, then the molecule has two enantiomeric forms. They are identical, but are actually different molecules.

Meanwhile, the CAS technology from the University of Vermont enables enantiomerically building blocks. Fully shaped structures can thus be created, even linear chains, according to researchers. Researchers started with a substance found in coal, dubbed anthracene. Then, they assembled C-shaped strips of chiral molecules. The C-shaped strips can join to each other, but in only one geometric orientation.

A blue wrench of molecules adjusts a green bolt (a pillarene ring) that binds a yellow chemical guest. (Image courtesy of Severin Schneebeli)

A blue wrench of molecules adjusts a green bolt (a pillarene ring) that binds a yellow chemical guest. (Image courtesy of Severin Schneebeli)

In effect, the structure is a nano-wrench. The wrench can bind to molecules called pillarene macrocycles. These rings of pillarene can modify other guest chemicals in the middle, according to researchers. As a result, the technology could be used for controlled drug delivery, organic light-emitting substances and other applications. “It’s like a real wrench,” said Severin Schneebeli, a chemist at the University of Vermont, on the university’s Web site.

“Because this kind of molecule is rigid, we can model it in the computer and project how it looks before we synthesize it in the lab,” said theoretical chemist Jianing Li.

“This is a revolutionary idea,” Li said. “We have 100 percent control of the shape, which gives great atomic economy — and lets us know what will happen before we start synthesizing in the lab.”

4D printed folding structures
Georgia Institute of Technology and the Singapore University of Technology and Design have developed a four-dimensional printing technology that creates self-folding structures.

The technology could be used to create structures from specialized materials, based on smart-shape memory polymers (SMP). These materials can respond to temperature, moisture or light.

The technology could one day be used to make space structures, medical devices, robots and toys.

This image shows a folded box, which is intended to simulate a postal mailer. It was made using a 4D printing technology. (Credit: Qi Laboratory)

This image shows a folded box, which is intended to simulate a postal mailer. It was made using a 4D printing technology. (Credit: Qi Laboratory)

Researchers developed digital shape memory polymers. The materials have different shape memory behaviors. The behavior of each polymer activates when the structure is subjected to a temperature. And carefully timing these changes, the structures can be programmed to self-assemble.

“Previous efforts to create sequential shape changing components involved placing multiple heaters at specific regions in a component and then controlling the on-and-off time of individual heaters,” said Jerry Qi, a professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech, on the university’s Web site. “This earlier approach essentially requires controlling the heat applied throughout the component in both space and time and is complicated. We turned this approach around and used a spatially uniform temperature which is easier to apply and then exploited the ability of different materials to internally control their rate of shape change through their molecular design.”

Martin Dunn, a professor at Singapore University of Technology and Design, added: “We have exploited the ability to 3-D print smart polymers and integrate as many as ten different materials precisely into a 3-D structure. We are now extending this concept of digital SMPs to enable printing of SMPs with dynamic mechanical properties that vary continuously in 3-D space.”