Nanomachines Could Revolutionize Technology
Imagine: spinach plants that “sniff” explosives and warn authorities via smartphone; ethanol fuel derived directly from CO2 waste; an injectable nano-scale semiconductor that uses “cold light” to target and kill cancer cells; lab photosynthesis that converts water into hydrogen fuel; smart textiles that sense and respond like muscle.
That’s not sci-fi, but rather a list of the dramatic breakthroughs molecular machines, or nanomachines, could make possible.
Molecular machines are microscopic agents that perform specific, controllable tasks. They use biological, chemical, mechanical, electrical, optical or magnetic means to create or enhance new processes and materials in any number of different environments. They’re an important next step in the application of nanoscience, the precise design and control of materials of 1–100 nanometers in size.
A Long, Fantastic Voyage
Scientists and engineers have spent decades dreaming about how microscopic machines — 100,000 times thinner than a human hair — might revolutionize agriculture, medicine, security and other fields. New energy sources, treatments, sensors, drug-delivery, materials and computing and storage systems — all could be possible with the right nanomachines.
Now, those dreams are turning into waking reality. Advances in visualization, fabrication, measurement, simulations and control have been helped along by powerful public-private partnerships, and molecular machines are rolling closer to commercialization. A little tiny industrial revolution is taking shape, and it will have an enormous impact.
Or so the Nobel committee believes. They called the work of three nanomachine pioneers who won the 2016 Nobel Prize in Chemistry1 “the dawn of a new industrial revolution.”
Copying Nature’s Machines
Steam engines or electrical motors are easy to understand. After all, their inner workings are visible to the naked eye. But things aren’t quite so clear-cut for nanomachines and molecular machines. In fact, they are not really machines at all, at least not in the usual sense. They may do the same tasks as macro-machines like lasers, vacuum cleaners, or winches, but that’s where the similarity ends. Nanomachines are built of collected molecules, which are assembled like building blocks into devices that perform useful tasks at a cellular level.
Scientists divide these nanomachines into two categories: biological and synthetic machines. Biological nanomachines use chemistry to emulate the vast array of tools and tricks developed in nature over billions of years, such as flagella — the corkscrew-like locomotive tail on some microbes. Another example is the two-pronged proteins called kinesins, which put one “foot” in front of the other as they carry molecular cargo along a cell’s stiff scaffolding of microtubules.
Synthetic machines attempt to artificially create similar, but original, tools out of nature’s building blocks — artificial forms like elevators, pumps, sensors, etc. The latter are of special interest to nanoengineers looking to create miniature fabrication lines.
Small Machines, Big Challenges
Chemists have been able to design and synthesize simple molecular machines since the early 1990s. Many tended to be “cute” proof-of-concept devices such as nano racing cars2 or molecular Pac Man games. But aside from a self-healing auto finish and a smartphone screen protector, commercially available molecular machines remain rare.
It’s surprising to some. After all, nano-tech materials such as DuPont™ Nomex® Nano are common in our daily lives. The materials include: metal oxides, ceramics, graphenes, nanotubes, liposomes and others that are widely used in agriculture, pharmaceuticals, electronics, protective clothing, paints and coatings, and personal care. Yet these tiny machines that employ energized natural and nanotech materials largely remain in labs.
There are three reasons why. First, nanomachines, like every other machine, require engines and parts. Much work over the last 20 years has focused on creating switches, propellers, rings, rods, pulleys, etc. Progress is quickening, some say, thanks to improved analytical chemistry tools and reactions that make it easier to build big organic molecules.
The second difficulty: seeing the parts being assembled. Molecular machine components are so small they require an electron microscope. But even that does not provide the 3D view needed for complex assembly.
Fortunately, new breakthroughs3 using X-rays, crystals and computers make visualization easier and more powerful. For example, a University of Tsukuba research group has established a three-dimensional probe that can depict the switching of a single molecule between two different conformations induced by a mechanical force.
The third challenge is nanomanufacturing, something DuPont and The University of Delaware are tackling. Together, they’re working to develop a radical new approach4 that uses self-assembly of block copolymers to create “templates” that can produce everything from digital information storage devices to medical bio-sensing arrays. “Nanomanufacturing presents a new set of challenges and opportunities for chemists and engineers to design polymers and processes to build functional nanostructures cost-effectively,” notes Kai Qi of DuPont Performance Materials.
What’s on the Horizon?
While there’s no commercially available tiny machines yet, many believe the commercial era is near. The U.S. National Nanotechnology Initiative (NNI), a public-private partnership, has made commercialization of nano-materials and nano-technology-abled devices a priority for 2017.5
Debate continues whether molecular machines will be most effective in the molecular world, scaled to handle macroscopic tasks, or both. Regardless, there’s widespread belief development is on the right track.
“Biology has found through evolution that molecular machines are the best way to get things done,”6 says David Leigh of the University of Manchester, UK, in Chemistry World. “I’m sure that’s going to be true for mankind as well.”