Patent ID: 8880139

Claim:
An eye-mountable device comprising: a polymeric material having a concave surface and a convex surface, wherein the concave surface is configured to be removably mounted over a corneal surface and the convex surface is configured to be compatible with eyelid motion when the concave surface is so mounted; a substrate at least partially embedded within the polymeric material; an antenna disposed on the substrate; an electrochemical sensor disposed on the substrate and including (i) a working electrode having a first side edge and a second side edge, and (ii) a reference electrode situated such that at least a portion of the first and second side edges of the working electrode are adjacent respective sections of the reference electrode; and a controller electrically connected to the electrochemical sensor and the antenna, wherein the controller is configured to: (i) apply a voltage between the working electrode and the reference electrode sufficient to generate an amperometric current related to the concentration of an analyte in a fluid to which the eye-mountable device is exposed; (ii) measure the amperometric current; and (iii) use the antenna to indicate the measured amperometric current, wherein the substrate is a ring-like structure having a mounting surface that extends between an inner edge and an outer edge that are substantially concentric rings, wherein the working electrode and the reference electrode each include a plurality of interdigitated extensions that are curved such that the first and second side edges of the working electrode are approximately locally parallel to the inner and outer edges of the ring-like structure of the substrate.