Revision as of 23:55, 18 August 2018

This is an introduction to the character of robotic work in the nanocosm.
It should deliver some intuitive feeling of how things work down there.

How big is an atom?

False claim? "Atoms are unimaginably small."
That's commonly assumed. And whenever some comparison is brought up one usually feels confirmed on hat assumption. Turns out that there is a "best way" to get an inuitive feel for their size that is rarely (or never) used.
Here are the details: "Magnification theme-park". – Judge yourself.

How does it feel when you grab two atoms and rub them against each other?

Moved to: "The feel of atoms"

How do atoms work and what shape do they have ?

Moved to: "The basics of atoms"

At which speeds do Atoms usually move

As we all know being hit by a bullet from a handgun is not good for health. But what if you split the bullet into many many small pieces and let them hit you with the same speed but now evenly distributed from all sides (assuming no breaking through air resistance)? Would you dare to try this? What if I tell you that you already did this for your whole life.

When we assume that:

• the bullet is split up into all its individual atoms such that there now is plenty of space between them
• the bullet is converted into a spherical shell of dispersed atoms
  (a shell with of about a thousandfold volume and a thousandth of the density of the original bullet)
• the shell is concentically coming at you and hittig you with the original non-reduced speed

then you probably would not even notice being hit.
Baffling?

What the split up atoms of the bullet bullet would do to you is actually very similar to what the molecules of the air do to you.

If one looks at free flying atoms (or very small molecules) like the ones one finds in air, then their speed of motion lies around the speed of sound. That is the main constituents of our earth's atmosphere (dinitrogen N₂ and dioxygen O₂ zip around with speeds that average out at about 340m/s (at normal conditions). This is about the speed of a bullet of a hand gun.

In contrast to the bullet air molecules do hit you permanently and relentlessly instead of just for roughly 30 microsceconds. 30 microseconds is the time it takes for a 1cm long (hopefully atomically dispersed) bullet to hit you tip to tail. Well since this "impact" would be atop normal air pressure you would experiences doubled air pressure for these 30 microseconds. But 30 microseconds are so short that due to the inertia of mass of your skin there will barely be any effect.

The speed of sound is pretty fast even for macroscale objects. Being smaller makes motions with same speeds seem to be faster. Driving an 1:10 RC car with FPV (first person view) remote vision at about 10m/s=36km/h feels like driving with 100m/s=360km/h but in reality it is still the 10m/s=36km/h. What we actually experience as "speed" is the frequency with which we are passing some stuff in the environment.

Scaling up just size by the aforementioned ideal scaling factor of 500.000 and leaving time unchanged as-is leads to a scaleup of speeds too The speeds of real size air molecules go from only ~340m/s at 1:1 scale to an experienced pseudo-speed of scaled up air molecules of about 170.000.000 m/s at 500.000:1 scale. This is a bit more than halve the speed of light. There is absolutely no way to intuitively ascertain that.

Now add all the inter-atomic collisions and you end up with a ridiculous pinball motion.

This has pretty wild consequences. Among others is provides the explanation why life could emerge just by accident. Why evolution works.

To have a more natural feel for the speeds at the nanoscale, speeds must be scaled in the opposite direction. One wants to scaling ... time to keep operation frequencies natural when transferred to the model scaled up in size Using this approach still leaves us with hair diameter model air molecules bouncing around at the speed of sound ~340m/s while now for every real second to pass we need to wait 500.000 seconds (almost 6 days) in the model for the real second to pass.

So a we have a model-molecule (scaled up to hair diameter) bouncing around with the speed of sound in a densely populated molecular environment (scaled up a heap of beard stubbles) for about six days that is thereby emulating just one real second. Just one. Let that sink.

Ok, this is not very intuitive. Now we have distributed one totally and utterly unintuitive and unimaginably big quantity (halve the speed of light) into two still quite unintuitive and unimaginably large quantities (speed of sound and a quite big stretching of time). This is not much better than before, if even, isn't it? Well yes.

Where this scaling method that also scales time not only space will become more useful for an attainment of an inuitive feel is when it comes to parts that are just a slightly bit bigger than molecules (nanomachinery crystolecules). Such parts already move quite a bit slower than single molecules. In fact usually slow enough that they can convebiently be traced around by eye. With our intuitivity preserving "magnification factor" of 500.000 typical nanomachinery operation frequencies e.g. 1MHz will get downscaled to just 2Hz.

Speeds of motion in nanorobotics

Today it's general education that temperature is equivalent to the speed of motion of particles at the atomic scale. If you unfamiliar with this "thermal motion" also known as "brownian motion" I suggest you read up on this elsewhere (e.g. wikipedia) before continuing here.

The incredible rate things zap past their surroundings (just driven by temperature)

Thermal motion at the nanoscale is pretty incredible.
Small single molecules zip around at thermal speeds of a few hundred meters per second. That's about the speed of sound. When we scale up size by our usual magnification factor of 500.000 to make model atoms (say water molecules) have the diameter of a human hair and when we keep the flow of time unchanged then those hair sized molecules zip around with more than half the speed of light.

But since those water molecules are densely packed they do not move in long straight lines.

• In liquid phase (e.g. water) they move in twisty paths with curve radii of about their own size.
• In one atmosphere gas phase (e.g. air) they move about 250 times their size (the mean free path length) before colliding and making a more or less U turn. In the 500,000 times scaled up model those U-turns are executed at near the speed of light every 2.5 centimeters (250 x 0.1mm).

Note that molecules in a liquid or gas that are not bond to a crystal run apart quantum-blurrily quite quickly (more on that later). So a "soup" of a superposition of all possible collision-histories is a better picture for fluids and gasses.

Assembly by mindlessly throwing parts together at ridiculous rates

Given this situation it becomes very obvious that in a liquid environment that is densely packed with other solvent molecules (e.g. water) solvated molecules meet a lot of other solvated molecules in a very short amount of time. Bigger more massive molecules like proteins ("puzzle piece molecules") move slower but collision rates are still very very high.

This is why puzzle piece shaped proteins molecules in biological systems can "assemble themselves" into their intended products. Via their random collisions they just mindlessly try all possible places they could bond to in very very fast succession. It's mindless trying like having toddlers that do not yet grasp that cubes do not fit through round holes do the assembly job but since it's done so fast (like brute force computer algorithms) useful things can be assembled nonetheless.

The technical term for this method of assembly is "self assembly" but here we'll call it "thermally driven assembly" which captures the meaning better. On the day to day macroscale this method of assembly is usually not applied for practical purposes due to its ridiculous slowness and requirement of parts fitting together like a sticky puzzle. Fully grasping the process how it happens at the nanoscale at an intuitive level may be impossible due to the vast number of trials until the final successful bonding reaction. (TODO: investigate better visualization methods) There are beautiful CG videos of molecular biology that use fake motions mo make it comprehensible (TODO: add link).

Use of thermally driven assembly to get away from thermally driven assembly ASAP

Thermally driven assembly is the predominant form of assembly in biological systems. Thermally driven assembly of increasingly artificial molecules will be (and already is!!) a very useful tool for walking the initial steps of the path to advanced nanofactories. But as it turns out in an advanced nanofactory (the far term goal) it makes much more sense to actually constrain / suppress thermal vibrations and take care of the transport oneself in a fully controlled and less mindless fashion.

The idea of working towards a point where we deny the help of thermal motion (shunning the teachings of nature) but doing assembly tightly controlled and guided instead has received harsh criticism in the past. It was and still is often misunderstood as a misunderstading of the real nature of the nanocosm.

But there actually is an example where we already succeeded with the suppression of thermal noise. Nanoelectronics. In microchips we've already learned to suppress thermally caused electrical noise without even noticing it since it just gradually got more difficult.

The two necessary requirements for thermal noise suppression are the same that we used to get away from analog technology namely:

• error margins and
• error correction

Now we use mostly digital electronics.

Given that electrons start to behave strongly quantum-mechanically in the nanoscale (quantum blurriness and thermal motion can often be treated in a common fashion) -- which stands is in stark contrast to nanomechanical nanomachines -- this is even more of a feat. We where not forced to switch some sort of probabilistic electronics (whatever that would be). Since much less quantum mechanical in behavior advanced nanomechanical systems will have even less reason to work in a purely probabilistic fashion.

The smaller the more productive

Main article: "Higher productivity of smaller machinery"

While size goes down speed goes up. A good example in nature is the increasing wing flapping rate seen in birds and insects.

By naively scaling down a current day 3D-printer by a factor of 500.000 (just for illustration - not a serious proposal) it becomes 500.000 times faster. A typically time for 3D printers to print parts that have about the mass of the printer itself is on the order of 10 hours. This shrinks down to just 0.72 seconds.

Now a single shrunk down printer won't produce much but imagine the whole volume of the original non-shrunk printer filled up with shrunk down printers. This would then produce the macroscale printers own mass in less than a second.

In a serious advanced nanofactory design the time to produce the production machinery's own mass can become even smaller due to better materials, lower friction, smaller size steps, to name a few reasons. For a good intuitive feel about the production rate imagine products shooting out like rifle bullets.

I fact the time to produce production machinery's own mass can become so short that the products that can be produced at the nanoscale cannot be fed out fast enough at the macroscale anymore. Getting even remotely near there would require impractical levels of cooling.

Solution: One humbly accepts not to get the full crazy level potential of nanoscale production machinery and is content with just more than practical levels of productivity.

To do this one does not fill up the whole volume with productive nanosystems. One abandons the concept of clouds of molecular assemblers. Instead one integrates everything in a thin chip. A nanofactory. For details check the main article: Macroscale slowness bottleneck

Even in the case when one really wants to push the limits (there's likely military interest here) its likely that a highly advanced fractal nanofactory that is a little thicker is the best solution. For a continuously running device the cooling facilities then are likely much bigger than the productive device itself. The production becomes highly inefficient and turns a lot of energy into heat. Still there is the fundamental specific acceleration limit which cannot be exceeded. This is the point where no known material would not break from the acceleration loads.

Motions in the far term goal of advanced nanofactories

Assembly in an advanced nanofactory will resemble more of a factory assembly line far away from any similarity to biological systems. All the machinery will usually run much slower than the thermal motions (about at least a factor of 1000) but since every try is a hit (for all practical purposes) the production throughput can be the same or higher than the one of natural bio-systems that work with thermally driven assembly.

In rare occasions one might want to let go of molecules or crystolecules in an advanced nanosystem. Thermal motion for bigger crystolecules in a vacuum under gravity are statistically distributed throwing parabolas. Single molecules show significant quantum blurring when released.

• Envelope of throwing trajectories with same speed
• Throwing trajectories with various speed in same direction

What happens when you let go of a building block?

Main article: "The heat-overpowers-gravity size-scale"

Let's consider an somewhat unusual fall experiment. A small gripper let go of a building block. Simple? See if you answer right.

A fall experiment quiz to illustrate the quite unfamiliar mechanical behavior in the nanoscale.

Scaling laws

They describe what changes when one goes down the scale. E.g. that magnetic motors become weak but electrostatic ones strong. More details can be found at the scaling laws main page.

The feel of AP Products

AP products though robotic and gemstone like in the nanocosm are not necessarily cold hard and robot like to the human senses. Emulated elasticity can create any form imaginable with gradients from soft to hard. It isn't an easy to attain property but it is an highly desirable one and will emerge at some point.

Bonding energies - Tensile strengths - Stiffnesses

(TODO: Add the same info table as on VdW force page)
[Todo: Add table - make it visualizable for covalent bonds and VdW bonds]
[Todo: show surface area thats VdW ashesion is energetically equivalent to one covalent bond - related: Form locking]

• Connection method#Van der Waals locking
• Van der Waals force

Further

• Periodic table of elements
• acceleration limits
• jumping building blocks
• Why nanomechanics is barely mechanical quantummechanics
• Video Playlist: The Shape of Atoms and Bonds (By "Learn Hub")
• Distorted visualisation methods for convergent assembly
• Scaling laws