Credit: © 2009 WILEY

Many chemists are aware of the 'chemical garden' demonstration, in which structures that look similar to plants grow from solution. The growths are millimetre-scale hollow tubes that form through a precipitation reaction, which occurs on the addition of crystals of soluble metal salts to solutions of anions such as silicates, borates or carbonates. Now, Oliver Steinbock and colleagues at Florida State University have modified this approach to gain greater control and understanding of the tubular growths, which could eventually lead to applications in microfluidic devices (Angew. Chem. Int. Ed. 48, 8752–8756; 2009).

They use agarose beads that are loaded with copper sulfate solution as reactant vessels that seed the precipitation growth of micrometre-scale tubes (orange in the picture). The beads are exposed to a sodium silicate solution and microtubes grow out from a bubble on their surface. The bubble is attached to the end of the growing microtube and either the bubble or the bead moves as the tube grows. Nodular objects (shown in pink) that have a completely different morphology to the tubes are also seen to grow from the beads.