Whilst I was researching for the last video about inertial guidance, I came across the miniaturization of what were basically large spinning flywheels down to parts that could be fabricated on a silicon chip just millimeters in size and yet did the same overall function.
But how small can we go with machines that actually do something?, and is the age of nanobots from science fiction just around the corner?
For centuries the size of the things we could make was limited to our ability to physically handle the objects and tools and to see what we were doing.
For example the fine watches built by Jagger- LeCoultre still are the smallest mechanical watches ever built. The Calibre 101 first made in 1929 and still made today is just 14 mm long by 4.8 mm wide by 3.4mm high and weighs about 1 gram.
Each of the 98 components is custom-made by hand and weighs in the milligrams range. But they are so time-consuming to make and so few of the watchmakers have the requisite skills to make them, that just a few dozen examples are made each year.
Beyond this level, the parts must be made by other processes, our hands are just too large, and their movement is larger than the components themselves. Clearly, new methods had to be used.
It would be Physicist Richard Feynman who would set the wheels in Motion when he gave a lecture at Caltech on the 29th of December 1959 titled “There’s Plenty of Room at the Bottom: An Invitation to Enter a New Field of Physics”
In the unscripted talk, he laid out the idea of manipulating individual atoms one by one and that in principle, it would be possible to make nanoscale machines that “arrange the atoms the way we want” and do chemical synthesis by mechanical manipulation to create new materials not found in nature.
The only problem was that we lacked the technology to do this. Feynman put forward an idea that by using machines to build machines and each generation would make the next generation of even smaller machines and smaller and in greater numbers until you reached the molecular level and you had billions of machines to create massively parallel operations. Of course now we will do this by chemical engineering but in a way these new machines will probably build the machines of tomorrow.
He also pointed out that when making these nano-sized objects that the force gravity would be much less of a problem but other forces like surface tension, and at the molecular and atomic scales, as the distance between atoms decreases, the van der Waals force starts to make atoms repel each other such as with varying electron density from one side of a nucleus to the other.
Feynman also mentioned that glass or plastic would have better uniformity at the very small scale than metal, because metals have a lattice structure of the atoms.
Although his lecture didn’t get much traction or have much of an impact for the next 20-odd, years it did resonate a lot more in 1990s as the term nanotechnology gained serious attention.
In the 1960s with the advent of integrated circuits, the possibility of making tiny electromechanical devices on the chips themselves was first raised.
The first of these was the resonant-gate transistor, basically like a tiny tuning fork made of tiny gold beams 0.1 mm in length that would resonate a given frequency and act like a bandpass filter that could have a Q factor of up 500 and a gain 10db. This proved that it could be done and in the 1970s to early 80s several MOSFET microsensors were developed for measuring physical, chemical, biological and environmental parameters.
Today, this technology is known as MEMS or micro-electromechanical systems, sensors such as accelerometers are in your phone and smart watches that pickup movement. Silicon sensors can do the same as a rotating gyroscope by using resonating or vibrating silicon ring suspended on spokes.
When stationary it vibrates in a regular way and the fixing point stays stationary but when an angular force is applied, the Coriolis force causes the ring to bend in one direction which moves the fixing points and this movement is picked up and the direction and amount of movement can be calculated.
The scale of these devices can be in the micrometer range with the movement of this microcantilever resonating at 17 micrometers. Biological sensors like this one for measuring glucose levels in the body and not externally have some parts like the Tintiam oxide sensing beam which are just 600nm thick and detect viscosity changes in the sample.
These are all forms of surface technology, in other words they are built on a surface of a material , the most common being silicon chips along side the data acquisition electronics and CPU.
But we have also entered the world of truly independent nano-machines, devices that are not fixed down to a surface like in the MEMS devices, these are independent and some can move around.
The field of science dealing with nanoscale machines powered by tiny motors draws inspiration from natural systems. In 1973, a significant discovery revealed that the flagella responsible for the mobility of numerous microorganisms operates through a rotary motor.
In 1983, French chemist Jean-Pierre Sauvage and his collaborators constructed the first catenane, two interlocking molecular rings, these are unusual as they were not linked by chemical bonds but by physical ones like the links in a chain.
The next step was taken in 1991 when Scottish chemist Fraser Stoddart and his collaborators created a rotaxane, a cyclic molecule like the catenane is threaded onto an “axle” molecule and end-capped by bulky groups to stop it from coming off so now we have a ring with an axle.
In 1999, two groups led by Ross Kelly and Ben Feringa, respectively, built molecular rotors that had blades that moved in only one direction.
Kelly’s device achieved a 120-degree rotation, driven by chemical energy, while Feringa’s completed a full 360-degree turn continuously, using light as its power source.
Then in 2011 came the nanomotor when researchers at Tufts University (USA) produced what was then the smallest electric motor, measuring just one nanometre and consisting of 18 atoms. It consists of a single molecule of butyl methyl sulphide on a copper surface, which can be made to rotate using electrons.
Roll on ten years and researchers at the Swiss Federal Laboratory for Materials Science and Technology successfully miniaturized the 18-atom motor to a more compact 16-atom version. This motor features a four-atom acetylene rotor, and its functioning intersects the realms of classical and quantum physics.
Equally remarkable is the development of a single-atom heat engine at the University of Mainz in Germany. This engine’s central component is a calcium ion, which, as described by its creators, operates akin to a combustion engine, undergoing expansion and cooling, contraction and heating, thereby transforming fluctuations in temperature into mechanical energy.
Now we have all the components for a nanocar and when you have a cars you can have a race, and yes there are now yearly championships at the CNRS or National Centre for Scientific Research in Franch, where teams compete to race their nano cars around a track of gold under a scanning tunneling microscope which not only allow the participants to see the vehicles but also provides the power for them to run.
But that’s not all, one of the dreams of medicine is to have nanomachines that can travel through the blood to places around the body and deliver drugs to fight cancer. These Unimolecular Submersible Nanomachines or nanosubmarines have already been developed and can carry RNA capable of reprogramming or killing diseased cells. One developed by the Rice University, Texas has motors powered by ultraviolet light that rotate at 2-3Mhz and travel at up 25mm per second, which is very fast considering it just 20 odd atoms in size and another nanomotor can carry a payload like a drug across a cell membrane.
And it not just using atoms, DNA has been used to make nanomachines or nubots, or nanobots of nucleic acids. This has already been used to make nano-tweezers to grab molecules and walkers that can travel along strands of DNA.
Now these might seem like slightly pointless exercises in chemical engineering but the winner of the Nobel prize 2016 in chemistry for the design and synthesis of molecular machines, Jean-Pierre Sauvage, and 2 collaborators said that molecular motors now are at the same stage as the electric motor was in the 1830s.
We have a way to go before we see this technology in widespread use but by then we will see ever more sophisticated machines that one day might offer the ability to make or change matter in ways that would have seemed like magic not only to our ancestors but to us today.
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