Next, they placed a sheet of graphene on top of the aligned bacteria and cooked the lot in a vacuum chamber heated to 250°C. This caused the bacteria to dehydrate and shrink, dragging the graphene sheet with them so that it took on the wrinkle patterns of the cells underneath it.

Crucially, bacteria do not wrinkle at random. Bacillus subtilis cells form wrinkles about 33 nanometres (billionths of a metre) apart—so that was the separation of the ridges imposed on the graphene. Unfortunately, this is too far apart to create a significant bandgap. The ridges do not disrupt graphene’s electronic structure enough. To do that, they would have to be less than five nanometres apart. But Dr Berry thinks such distances might be achieved by using another species of bacterium, one with stronger cell walls—or, perhaps, different sorts of cells altogether.

Even the 33-nanometre wrinkles, though, give graphene some interesting properties. Instead of zipping randomly across it, electrons traversing a sheet of wrinkly graphene are channelled between the ridges. This suggests that, if the bandgap problem can be resolved, then placing bacteria in preset arrays to create complex channel patterns would be the equivalent of etching a silicon chip. Components like the logic gates which form the basis of computing could thus be created.

Before that happens, though, two other problems need to be resolved. One is removing the bacteria and releasing the wrinkled graphene. That will mean finding the right chemical to do the loosening. The other is reproducibility. Individual bacteria differ slightly, not least because they are often of different ages, so any product that used unsorted cells as templates would be unreliable. This might be dealt with by cell-sorting techniques, or even by synthesising artificial scaffolds that behave similarly to cells. These, though, are details. The important thing is that Dr Berry has managed to push graphene towards semiconductivity in a novel and intriguing manner. The search for an application for the stuff has taken a step forward.