Analysis: you could fit over 1,000 of these machines across the width of a single hair, but these nanomachines can carry out a huge number of tasks

By Rob Elmes, Maynooth University and Sarah Hayes, University of Limerick

Machines are all around us, from the coffee machine that ensures you can function in the morning to the rockets that bring astronauts to the moon. Machines transform our world by helping us do tasks that make life easier. How do they do it? Put simply, a machine takes energy and transforms that energy in to motion to carry out a specific function, just like your car burns fuel to make its wheels rotate which gets you from A to B.

But what if we could replace our traditional machines with nanomachines, machines which are too small to see but help us to perform tasks in our everyday lives? Actually, that's exactly what happens already because our bodies are full of them. Nanomachines are the workhorses that power our cells, they are the builders that create proteins in our body and they are the eco warriors that harvest energy from the sun to allow plants to thrive. We call them machines because, just like your toaster and your bicycle, they produce motion in response to an input that allows them to perform a task.

Biology has been tweaking its own designs for millennia and the result is nanomachines that carry out an unimaginable number of very specific tasks. The protein kinesin is a a motor protein that supports cell regeneration in our bodies. It uses the reaction of adenosine triphosphate (ATP) with water as a fuel to allow it to "walk" along microtubule filaments carrying all types of cargo to where they need to be in our cells, making it a delivery machine of sorts.

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Reactions looks at how the tiny chemistry of nanomachines can have some big results

The study of nature's machines has provided researchers with ample inspiration and new insights into how to construct their own man-made nanomachines. While biological machinery is incredibly complex, typically consisting of thousands upon thousands of atoms, synthetic nanomachines or molecular machines consist of just hundreds of atoms to create molecular components that resemble large-scale machinery. Things that are familiar to us all - wheels, rotors, axles, pistons, chains, cars, and elevators - have considerable potential as the components required to design our very own molecular machinery.

How small is small?

We're talking unimaginably tiny here, so small you could fit over 1,000 of them across the width of a single hair. It's all thanks to chemists who have made breakthroughs in making mechanically bonded molecules, which are molecules that are interlocked with physical attachments rather than chemical bonds. Think about how chains are put together: they are interlocked without being stuck to each other. It is exactly this ability to interlock molecules that allow us to realise the smallest machines on the nanoscale range.

The mechanical bond

This allows the components of the machine to move freely around each other. Crucially, this movement can be controlled by external forces such as light, heat or changing chemical conditions such as pH, for example making the environment the machine is situated in more acidic or basic.

Molecular machines are no longer ideas of science fiction

One of the first major breakthroughs in the development of molecular machines took place in the early 1980s when French chemist Jean-Pierre Sauvage made a mechanically interlocked molecule known as a [2]catenane. His design consisted of two molecular rings that were inseparable without breaking a covalent bond. This design also meant that one ring could rotate around the other when energy was supplied, a first generation of molecular machinery.

In the 1990s, James Fraser Stoddart developed a molecule called a rotaxane in a landmark paper that cracked open the world of molecular machines. The rotaxane represented the first molecular shuttle and was constructed from a molecular axle threaded through a molecular ring. Again, by supplying energy, the ring could be made to slide along the length of the rod providing movement in response to an energy input.

Later in the 1990s, Dutch chemist Bernard Feringa synthesised the first molecular motor. His design allowed the control of molecular motion in response to light and heat. The rotary structure used light as a power source to spin continuously in a particular direction. Feringa went one further and used his molecular motor to create one of the world’s first nanocars. Although, at just a few nanometers long and with an operating temperature of -266°C you are unlikely to see it in your local used car showroom anytime soon! The three scientists shared the 2016 Nobel Prize in Chemistry for their work and the Nobel committee described the tools developed by these chemists as the "world’s smallest machines."

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Reactions looks at how Jean-Pierre Sauvage, Sir Fraser Stoddart, and Ben Feringa won the 2016 Nobel Prize in Chemistry for molecular machines

Molecular machines and modern technology

So where do we go from here? How will these tiny machines impact on our daily lives? The unique features of catenanes, rotaxanes and molecular motors, combined with the remarkable expertise of chemists who can build almost any molecule, give molecular machines unimaginable potential in the future of modern technology. Recent advances show promise of using nanomachines in biomedical applications from working to detect diseases or drug delivery to specific sites in the human body such as hard-to-reach tumours. 

Molecular machines are no longer ideas of science fiction. They will revolutionise many aspects of technology and medicine where their potential impact has been likened to that of the computer microchip, which revolutionised computing through its miniaturisation. Without microchips, the world as we know it would not exist. But chemists in their quest to produce nanomachines have only just begun. Where they are going gives us all a reason to believe those science fiction books and movies that portray armies of tiny robots taking over the world may be closer than you think (not really)!

Dr Rob Elmes is a Lecturer in the Department of Chemistry, a researcher at the Kathleen Lonsdale Institute for Human Health Research and a funded investigator at the Synthesis and Solid State Pharmaceutical Centre, a Science Foundation Ireland (SFI) funded research centre, at Maynooth University. He is a former Irish Research Council awardee. Dr Sarah Hayes is the Education, Outreach and Training Officer at the SSPC at the University of Limerick

The views expressed here are those of the author and do not represent or reflect the views of RTÉ