Prey by Michael Crichton

In the Nevada desert, a handful of scientists are battling to retrieve a swarm of rogue micro-bots that has escaped from the lab. The swarm is self-sustaining, self-reproducing and capable of learning from experience. It is, to all intents and purposes, alive. And very, very deadly. Because it has been programmed as a ruthless predator, a predator that becomes more dangerous with every passing hour...

And we are the prey.