Poly-acrylamide polymer crystals are able to absorb up to 200 times their volume of water. 7 small spheres ~4 mm in diameter were immersed in water for 3 hours, after which they were ~23 mm across. The final gel sphere is more than 99.5% water https://t.co/VOSUBSrvRvpic.twitter.com/MPtzRRzF4Z