WASHINGTON — The latest revolutionary robot isn’t the metallic, costly machine you’d expect: It’s squishy like Silly Putty, wireless, battery-less and made for pennies by a 3-D printer. Meet Octobot. It looks like a tiny octopus and is designed to mimic that slithery creature to get through cracks and tight places, making it ideal as a rescue robot. A team at Harvard University has created a robot — actually about 300 of them, since they are so cheap to make — that is opposite of the common view of a robot.