Nanorobots versus bacteria

Question

Future scientists have developed amazing nanorobots. They use 18 simple chemical reactions to move small metal pieces a few atoms long, and are controlled by a micro antenna that can intercept radio wavesx-rays, cause them to vibrate an atom, and use that vibrating atom to send mechanical controls to a series of electromagnetic nanoscale pulleys and levers. These x-ray signals are carefully directed using a tiny x-ray beam. However, what would happen if (and when) one comes across a bacterium? What would a metal rod, about 20 atoms long and 2 thick, do against a bacterium, and could bacteria harm the nanobot?

Answer 1

So, an important thing to remember is that on these scales, chemistry is more important than "structural strength."

What you are talking about is very similar to how bacteriophages penetrate a cel. This link has some interesting images from modeling and electron microscopes. The T2 Phage for example chemically bonds with the cell membrane and "snips" the proteins creating a gap for the viral RNA to enter. Remember, a bacterium is just a cell.

Many bacteria also have a bacterial capsule providing additional defense. These tend to be about .2 microns thick, which is like 200 nanometers. Iron has an atomic radius of about .1 nanometers (though there is a bit of a gap between atoms). Your weapon is probably 3-4 nanometers long.

So say your metal rod creates a hole in the cell (the thickness is really not very big, it would be smaller than that made by a virus (no proteins could fit through)). If it is so small, there is a good chance you won't have cytoplasm leaking out.

But say, your rod chemically tears the membrane. Cells are surprisingly robust. They are pretty fragile and so have developed many techniques for dealing with what might seem like catastrophic damage. This link gives a very detailed account about how cells deal with this type of damage. It gets kinda technical at points, but I would recommend looking over it.

The short answer is that many cells can easily recover from the type of damage that this weapon would cause.

The bacteria probably would not do much actively against your nanobot. It might engulf and eat the bacteria or produce / excrete chemicals that would be damaging to your nanobot. However, the fact is that something so small is typically beyond the "notice" of a cell. This is why nanomaterials can have such large health impacts and why your immune system can struggle dealing with viruses.

You may want to scale up your nanobots a bit. We are still a long ways off from a practical nanobot, but the stuff I have seen is a bit larger in size (you seem to be looking sub-viral in size).

Also, it would be difficult for the antenna to resonate with radio waves. Radiowaves are kinda big.