A manufacturing method of an electrochemical sensor comprises forming a graphene layer on a donor substrate, laminating a film of dry photoresist on the graphene layer, removing the donor substrate to obtain an intermediate structure comprising the film of dry photoresist and the graphene layer, and laminating the intermediate structure onto a final substrate with the graphene layer in electrical contact with first and second electrodes positioned on the final substrate. The film of dry photoresist is then patterned to form a microfluidic structure on the graphene layer and an additional dry photoresist layer is laminated over the structure. In one type of sensor manufactured by this process, the graphene layer acts as a channel region of a field-effect transistor, whose conductive properties vary according to characteristics of an analyte introduced into the microfluidic structure.