Here is a precautionary principle two-for-one special.  

Though we have been momentarily sidetracked in recent years by the LHC Ragnarok Supermoons Biblical numerology dead Mayan astrologers fracking in science-media-hyped scare journalism (when they aren't helping us with new miracle vegetable claims) we never really forget about robots.  We're always wondering when that Roomba is going to achieve sentience and overthrow us (if it happens, blame Science 2.0 scribe Sam Kenyon, since he writes code for that little fifth columnist in your closet) and nanotechnology is so scary that anti-science hippies can't even figure out what to protest.

Causing no end to confusion among the types of people who like to protest everything is the fact that our new robotic nanotech overlord will run on wholesome renewable energy. And it's cute. Robojelly is a robotic jellyfish now powered by hydrogen and oxygen found in water. All it produces as waste is more water.  If it takes 140 liters of water to create one cup of coffee, as virtual water voodoo environmentalists claim, we can only make about 9,600,000,000,000,000 cups of coffee before all the water is gone (unless water recycles, that is), so we need to act now.  And a cool robot jellyfish is a perfect way to go. 

Robojelly has two 'bells' made of silicone that fold like an umbrella and are connected by 'muscles' made of a nickel-titanium alloy wrapped in carbon nanotubes, coated with platinum and housed in a pipe, that contract to move. 

Robojelly. Credit: University of Texas, Dallas.

The platinum interacts with the hydrogen and oxygen, creating heat and water vapor that causes the contraction that moves the nanotube muscles of Robojelly, pumping out the water and starting the cycle again. It's pretty slick. Take a look.

Cool, right??? But this one ran on electricity and the new one runs on hydrogen. Credit: University of Texas, Dallas

It sounds awesome for future robotic jellyfish applications but also pretty scary. Didn't carbon nanotubes kill Steve McQueen or something?  How will Jason Statham or whoever will have to save us in whatever upcoming movie focuses on new, scary science save us?  Right now these little critters can only move one way. All he has to do is flip them over and they would try to jelly walk to China. But of course, we'd have to think about what might happen if they did starting digging to China.  They might reach the Earth's core.  If you think fracking is bad, wait until Robojelly is causing liquid hot magma to spew forth.

Citation: Yonas Tadesse, Alex Villanueva, Carter Haines, David Novitski, Ray Baughman and Shashank Priya, 'Hydrogen-fuel-powered bell segments of biomimetic jellyfish', Smart Materials and Structures Volume 21 Number 4, doi:10.1088/0964-1726/21/4/045013 (FREE TO READ)