I think this article from Ars Technica shows the true power of modern nanotechnology. This isn’t little nano-bots crawling around, this is serious applied science and that fact that these guys can now get amazingly specific items custom made.
This process started with a need to measure the viscosity (thickness) of the fluid in blood samples in order to diagnose health problems. This is complex because blood is a mess of various tiny items that get in the way. Existing approaches involved separating the liquid part from everything else and then testing it on its own and were slow and expensive.
These guys came up with a way to use tiny cork-screw shaped metal particles to selectively reflect light from within the blood sample so they could measure the motion of particles in the liquid. Then they needed to align those particles to get a decent signal out.
Up to this point, this is just applied science and while impressive, this sort of thing is not that out there.
The amazing bit comes when they conclude that they need helical metal particles that are a tiny fraction of the size of a blood cell and made of a gold (for reflecitivity) and iron (so they can align and move them with magnetic fields) alloy. These particles need to be of a particular size and the pitch of the helix needs to match the wavelength of the laser they’re using.
They got these fabricated and on the budget of a research scientist looking to test blood viscosity! The fact that the fabrication of something like this has been commoditized to this degree is stunning (and wonderful).