I don't like the portrayal of nanites in current films. Suits are created in seconds because you use Nanotec.
What are nanites? Mini robots that are as small as viruses or bacteria. And what problem do they have? The same thing that viruses or bacteria have: they are very small.
1. No matter how fast you are, 1 cm is an enormous distance for something this small. Covering a person's body would hardly be faster than filling a Petri dish with viruses. So the hero would have to wait weeks for his suit to grow.
2. Energy. Where does it come from? How do you power nanites? The films deliberately say nothing about this because they have no answer. Must be magic.
3, Sometimes the suit that the nanites create has more mass than what they are starting with. Where does the extra mass come from?
I really don't like the portrayal of nanites in films.
