there is disclosed a biosensor comprising a conducting surface , a layer of dielectric material overlying the conducting surface , a plurality of micro electrodes constituted by a plurality of pores extending through the thickness of said dielectric layer , a biopolymer positioned on the conducting surface in said pores , and a counter electrode arranged such that electrical connection can be made between it and at least part of said conducting surface by a fluid to be assessed . such a device can be made using a method comprising the steps of providing a conducting surface ; providing a layer of dielectric material adjacent to said conducting surface , said dielectric material comprising a plurality of pores extending through the thickness of the dielectric layer ; providing a biopolymer on the conducting surface in said pores ; and providing a counter electrode insulated from said conducting surface .