Researchers from the University of Illinois and Dioxide Materials have showed that randomly stacked graphene flakes can make an effective chemical sensor. The flakes were fabricated by placing bulk graphite in a solution and bombarding it with ultrasonic waves that broke off thin sheets. This solution was filtered to produce a graphene film - made from stacked flakes. The flakes were used as the top layer of a chemical sensor. Movement of electrons through the film produced an electrical signal that flagged the presence of a test chemical.
According to the researchers, this new sensor is more reliable than existing sensors made from carbon nanotubes or graphene crystals. The researchers think that this is due to the fact that defects in the carbon-lattice structure near the edge of the graphene flakes allow electrons to easily "hop" through the film.