In FIG. 3F mouldable polymer 27 is provided overlaying the layer of graphene, the electrodes 25, the dielectric 35 and the second release layer 37. The mouldable polymer 27 is deposited on the first release layer 33 overlaying the layer of graphene, the electrodes 25, the dielectric 35 and the second release layer 37. The mouldable polymer 27 comprises any polymer which will embed the components of the apparatus 21. The mouldable polymer 27 may form a planar surface against the surface of the first release layer 33.

The second release layer 37 may be positioned so as to prevent the mouldable polymer 27 from contacting the layer of graphene. In the example of FIGS. 3A to 3I the second release layer 37 prevents the mouldable polymer 27 from coming into contact with the dielectric 35. The second release layer 37 may provide a barrier between the mouldable polymer 27 and the layer of graphene and/or the dielectric 35. The second release layer 37 may be positioned so that the mouldable polymer 27 forms different portions 24, 26, 28 of different thicknesses. The different portions 24, 26, 28 of different thicknesses may be as described above.

In some examples the mouldable polymer 27 may comprise a liquid polymer which may be deposited onto the first release layer 33 via spin coating, spray coating or any other suitable process. In other examples the mouldable polymer 27 may comprise a polymer foil which may be deposited by hot embossing or any other suitable process.