The Smallest Factory


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On the nano assembly line, tiny biological tubes called microtubules serve as transporters for the assembly of several molecular objects. Image: Samuel Hertig / ETH Zurich

Let’s not give too much credit to old Henry Ford. Yes, it’s true that the invention of the internal combustion engine, our touch screens, our Roombas, and our Fitbits would all have come to nothing without the invention of the assembly line. But in the macro world, cobbling products together part by part, rather than all at once, is a bit of a no-brainer. There’s little doubt that we would have figured it out sooner or later, with or without Ford.

But putting the assembly line concept to use at the nanoscale is something else altogether. That’s just what Viola Vogel, a professor in the Department of Applied Mechanobiology at the ETH Zurich, has done. Her process takes place on a tiny chip, and has all the elements of larger assembly lines: a main body, motors to move things along, parts to attach to a main body, and a finished product.

“The idea was we push our nanoshuttles from one reaction chamber to the next to the next,” says Vogel. The nanoshuttle she speaks of travels down a canal that’s just a third of a hair wide. Perpendicular to that canal are other, smaller canals from which come the cargo that will attach to the tube.

Researchers are attempting to build a nanoscale transport device, where proteins are transported by kinesin. Image: Christian Brunner / ETH Zurich

The shuttle is marched across a microtube by the protein kinesin. The tiny factory exploits this nanoscale protein’s natural biological function to move much larger cellular elements to their proper destination (conveniently, their tails stick to glass). “In order to use these biological motors in the device, we have to design conditions to allow them to survive,” says Vogel. “They’re so fragile. They need the right water, temperature, and solid concentrations to be functional.”

Unlike other nano creations, where elements are mixed together to make a new material, the tiny assembly line is truly a sequential process. “If we want to build a crane, we don’t put the parts in a beaker, shake them, and hope the product jumps out,” says Vogel. "You build it step by step by step.”

Once the kinesin is pumped through the system, the shuttle is placed in the first compartment. Then the cargo is loaded in the reaction chambers. The shuttle is walked through one reaction chamber after another, so that the cargo is sequentially loaded onto it. Dye molecules are attached to the cargo, so the success of the assembly can be measured by a change of color in the solution at the finish line

Vogel and her team analyzed some 200 molecules to find the perfect cargo for nano manufacturing. But keeping the process moving forward, from start to finish, was the trickier challenge. “So far, the biggest sticking point was to have the larger fraction of our molecular shuttles pass from one reaction chamber to the next to the next. We don’t want them to walk backward,” says Vogel.

As the new technology moves forward, it may some day work to build or alter proteins, DNA, polymers, or nanotubes. But Vogel is quick to point out that, at this stage, the assembly line is a proof of concept first and foremost. “Think back to the very first descriptions of steam engines,” she says. “How long did it take to make something commercial with a steam engine? We were not focused on making something really elegant or really complicated. We just wanted to show that such an idea is possible. Then, hopefully, people will have all kinds of crazy ideas of what to do with this technology.”

Michael Abrams is an independent writer.

If we want to build a crane, we don’t put the parts in a beaker, shake them, and hope the product jumps out.

Prof. Viola Vogel, ETH Zurich

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November 2014

by Michael Abrams, ASME.org