second material the second mask having an opening over a portion of the second material that is over the offset region application_number US 70963507 A description the invention is directed toward using a flex circuit to create an active electrode the flex circuit has a copper trace that is masked and imaged onto a polyimide substrate flex circuits with copper traces have a low manufacturing cost the end of the copper trace may be plated with a first material of interest e g gold a first mask is used to create an opening for an active electrode a second material of interest e g graphite and or platinum may be deposited or screen printed into the opening and on an offset region a second mask is used to cover the second material of interest that is over the opening a membrane may be placed over the offset region to form the active electrode the second material of interest over the offset region acts as a diffusion barrier to prevent for example electrolytes from coming into contact with the copper trace the offset region prevents the copper trace from oxidizing at a positive potential such as would be the case for a glucose electrode measuring peroxide vs silver silver chloride for example fig1 is a cross section view of an active electrode 10 that is created using a flex circuit 100 according to an embodiment of the invention the flex circuit 100 may include a.