Nanotechnology is the technology of objects whose dimensions are in the range $0.1$ to $100$ nanometre (nm), ie. $0.1\times 10^{-9}$ to $100\times 10^{-9}$ metres. Try these preliminary questions to help you get some idea just how small that is and how it relates to other units of length:

1. An average human hair has a diameter of about 50 microns. How many nanometres is this?
2. Measure the height of a new pack of printer paper. Packs come in reams which contain 500 sheets of paper: estimate the thickness of one piece of paper. What is this in nanometres? What is it in microns?

Do you think that it will be possible in principle to make a robot camera using nanotechnology which could be injected into a person's arteries in order to see if they are becoming blocked? You will need to consider what size a robot would need to be to move along an artery in the blood stream.

Here is some information to get you started:

• the interior diameter of the coronary arteries is about 1-2 mm
• blood contains red and white blood cells and platelets
• red blood cells (erythrocytes) are about 6-8 microns in diameter
• white blood cells (leukocytes) are about 15 microns in diameter
• platelets (thrombocytes) are about 2-3 microns in diameter

Here is an image of blood components taken from http://en.wikipedia.org/wiki/File:Red_White_Blood_cells.jpg