Nano — Why Making It Small Makes It Different

Divide it and the outside grows

Dissolving happens only where water touches. The cube's inside is shut away and must wait its turn; in powder nearly every grain is already in contact.

There is a pleasing piece of arithmetic here. Dividing changes nothing about the amount, yet the outside grows. Cut one cube in half each way into eight and the surface area doubles. Cut again and it doubles again.

What happens if you keep dividing

Keep cutting and you reach a point where there is no inside left to hide in. Almost every atom ends up on the outside.

That point is the nanoscale: a hair split a hundred thousand ways, a few atoms laid side by side.

An atom on the surface lives differently from one within. The one inside is surrounded by neighbours; the one on the surface has an empty side — a hand still free to grasp with.

So the properties change

Gold is yellow. As nanoparticles it looks red. The red glass of cathedral windows is glass with gold in it; a thousand years ago people took the colour without knowing the reason.

Gold is also a metal that reacts with almost nothing — yet as nanoparticles it makes an excellent catalyst. Even not reacting is a property that size can undo.

So nanotechnology is less the handling of small things than the changing of properties by changing size: not finding a new substance, but turning an old one into a different one.

A little further in

They are drawn, not carved

How do you make something at this size? Not by carving. At that scale a blade is the size of a log.

So it is printed. A round plate called a wafer is coated with a light-sensitive film; a mask carrying the pattern is laid over it; light is shone through; the exposed film is washed away and what lies beneath is etched. Where different properties are wanted, ions are fired in. Repeat a few hundred times, layer on layer.

Why that matters follows from what came before. Parts are not made one by one and joined; tens of billions are drawn at once on a single plate. The meaning of making has moved from assembly to printing.

One speck cuts a circuit

A difficulty arises. The lines are nanometres wide and airborne dust is hundreds of times larger. One speck landing there severs the circuit.

Hence the cleanroom: a room whose air is filtered continuously and made to flow downwards.

Without somewhere to build it, an idea dies

Such a plant costs hundreds of millions to build, and the building is harder than the equipment. It must not vibrate; special gases and chemicals must arrive by pipe; the exhaust must leave safely.

No university laboratory or small firm can own one — and that is where the trouble starts. A good idea with nowhere to be built ends on paper.

So the plant is built and hired out. A graduate student has one device made as a trial; a small company runs off a prototype. That is the work of the National NanoFab Center in Yuseong-gu, Daejeon, alongside the electronics and telecommunications institute nearby.

And then it must be seen

Making it is not the end. At this size neither the eye nor an ordinary microscope can confirm anything. There has to be a way of knowing whether the pattern came out.

So beside the place where things are made stand the instruments that look: microscopes that see with electrons, and machines that weigh to identify. Making and seeing are one body of work. What cannot be seen cannot be known to have been made.

Not only chips

Several things are made the same way.

1. Sensors — your phone knows it is tilted because a very small set of scales sits inside it.
2. Biochips — fine channels cut into a plate the size of a fingernail, tested with one drop of blood.
3. Light devices — tiny emitters and optical communication parts.
4. New materials — the place where the earlier point, that dividing changes properties, is put to work directly.

Small is not only good

One thing should be said plainly. Nanoparticles react readily — which means they also react readily inside a body.

They are small enough to reach deep into the lungs, and a substance harmless as a lump may behave otherwise at this size. So research that makes nanomaterials travels with research that asks whether they are safe. What is newly made must be newly checked.

What you would study to do this

Running a plant like this is shared among many hands.

1. Someone who designs what is to be made — electronic engineering, materials, physics.
2. Someone who sets the process — in what order and how many times to print and etch. Chemical engineering weighs heavily here.
3. Someone who makes the masks — if the original is wrong, hundreds of wafers are wrong.
4. Someone who supplies the gases and chemicals — plant work, moving dangerous material safely in and out by pipe.
5. Someone who measures and verifies what was made — metrology and analysis.
6. Someone who keeps the cleanroom itself — air, temperature, humidity, vibration.

Look at the fourth line. Accidents in a fabrication plant happen at the pipework far more often than in the design office, so the job belongs to people who know plant and safety — and the road to it runs as often through a technical high school as through a university.

The third line likewise. Making the master pattern is a job that is nothing but precision, and steady hands are valued there for a long time.

The question that remainsIf changing only the size changes what a substance does — what is it that we are calling the same substance?