A device comprising a non-liquid medium which can be arranged to contact and adhere to a patient's skin. The medium comprises a co-polymer of an acrylic moiety and a polyether, together with a hygroscopic electrolyte capable of conducting electrical signals from the patient's skin. The copolymer can be produced by blending together the polyether, acrylic moiety and electrolytic followed by irradiating the blend to initiate copolymerisation of the polyether and acrylic moiety.