What is the world's smallest robot? First, you need to define what you mean by "robot." If by "robot" you mean "autonomous self-powered robot" then this little guy from Sandia might be a good place to start.
(The latest version of Pico in video)
This is the new 2007 upgraded version of the earlier robot; see the video below for the previous version.
(Pico really can turn on a dime)
Here are the stats:
0.5 inch / 12.5 mm on a side
0.125 cubic inch / 2 cc volume
15 minute run time
0.5 f/s / 0.15 m/s maximum speed
Is Pico really the smallest robot? Here's what it's creators say:
Pico qualifies as the smallest in its category in spite of the existence of a 1 cc class in some Japanese robot competitions because to my knowledge (to date), none of those robots have contained their own power source, and many of them don't even contain any circuitry.
Some people have also pointed out a cool little nano-tech inch-worm from Dartmouth that moves along a mesh of wires. Do I even have to defend pico's place here? "...it reacts to electric changes in the grid of electrodes it moves on. This grid also supplies the microrobot with the power needed to make these movements." While I'm impressed with the (incredibly) micro-bot, it still can't carry around its own juice. I can't compete at a nano-level, so here's hoping they don't make a battery soon that can strap to its back.
Readers might want to compare Pico to these tiny bots: