Researchers from Singapore's A*STAR Institute developed a new graphene ribbons (GNRs) based magnetic field-effect transistor (it responds to changes in a magnetic field).
The basic idea is to use two armchair-edged GNRs joined end to end. One of the ribbons acts as a metallic conductor while the other one (which is wider) acts as a semiconductor. The existence of a magnetic field makes this device conductive.
The researchers did not actually make this device, they currently ony used theoretical models to predict how this transistor would work.