5+1 Weird Chemicals

In case you missed the stuff of dreams article in the New Scientist Technology Blog here’s a quick overview, with one addition.

  • Dilatants are fluids that get more solid under stress. There are videos of people running across it and even dancing! This video shows sound waves at 80Hz producing interesting shapes using Cornstarch.
  • Auxetic materials get thicker when stretched. Pull them in one direction and they expand in another. A video demonstration from Bolton University.
  • Superfluids are made by cooling Helium down to a couple of degrees above absolute zero and can flow endlessly without friction. This article has an audio example of nano-whistles as helium-4 is pushed through nanometer-sized holes.

    In the case of superfluids, a pressure difference across a tiny hole would cause a vibration in the superfluid at a frequency – the Josephson frequency – that increases as the pressure increases. The fact that the fluid oscillates back and forth through the hole rather than flows from the high-pressure side to the low-pressure side, as a normal liquid would, is one of the many weird aspects of quantum systems like superfluids.

  • Ferrofluids are made from nanoscale magnetic particles suspended in a liquid. Sachiko Kodama‘s Protrude Flow sculpture uses ferrorfluids with electromagnets.
  • Dry ice is Carbon Dioxide in its solidic form (frozen at -78.5 °C). A video showing patterns produced when dry ice is dropped into water.
  • Aerogel a low density solid, semi-transparent in appearance and feels like Styrofoam. Used by NASA to trap spacedust particles aboard the Stardust spacecraft.