Electrode with improved signal to noise ratio

A method of measuring the amount or concentration of glucose in a human patient, comprising the steps of:

• contacting the skin of the patient with a first surface of a hydrogel medium through which glucose diffuses, said hydrogel comprising water, electrolyte and glucose oxidase, wherein (i) glucose oxidase catalyzes a reaction resulting in conversion of glucose to gluconic acid, (ii) the thickness of said hydrogel is in the range of 10 μm to 1,000 μm;
• contacting an electrode assembly to a second surface of the hydrogel medium, the assembly comprising a working electrode comprised of a plurality of substantially physically separated working electrode planar surfaces and an electroosmotic electrode, wherein (i) the working electrode surfaces are separated by a gap having a width in a range of 10 μm to 1,000 μm, (ii) an electrically insulating material is positioned in each gap separating the electrode surfaces, (iii) the working electrode is characterized by a substantially planar configuration, and (iv) the working electrode has a thickness in a range of 0.25 μm to 250 μm;
• providing current to the electroosmotic electrode sufficient to draw ions through the skin of the patient along with glucose wherein the working electrode planar surfaces are configured such that the glucose is drawn in a first direction normal to the planar surfaces and in a second direction substantially parallel to the planar surfaces;
• providing a voltage to each of the working electrode surfaces sufficient to drive electrochemical detection of a product of the reaction of glucose and glucose oxidase which generates an electrical current at the working electrode surfaces;
• measuring the electrical current at the working electrode surfaces;
• and
• correlating the measured current to the amount or concentration of glucose in the patient.

A method of measuring the amount or concentration of a chemical signal in a mammalian subject, the method comprising the steps of:

• contacting a first surface of an ionically conductive hydrogel with a skin surface of the mammalian subject, said hydrogel comprising water, electrolyte, and an enzyme, wherein the thickness of said hydrogel is in the range of 10 μm to 1,000 μm;
• contacting an electrode assembly to a second surface of the hydrogel, the assembly comprising an electroosmotic electrode, a working electrode comprised of a plurality of substantially physically separated working electrode planar surfaces, a counter electrode, and a reference electrode, wherein (i) the working electrode surfaces are separated by a gap having a width in a range of 10 μm to 1,000 μm, (ii) an electrically insulating material is positioned in each gap separating the electrode surfaces, (iii) the working electrode is characterized by a substantially planar configuration, and (iv) the working electrode has a thickness in a range of 0.25 μm to 250 μm;
• providing current to the electroosmotic electrode sufficient to draw the chemical signal across the mammalian subject's skin, through the hydrogel and to the working electrode;
• providing a voltage to the working electrode planar surfaces sufficient to drive electrochemical detection of chemical signal which generates an electrical current at the working electrode surfaces, wherein said electrical current is generated at the working electrode surfaces by electrochemical oxidation of hydrogen peroxide producing an electrical signal;
• measuring the electrical current generated at the working electrode;
• and
• correlating the measured current to the amount or concentration of chemical signal in the mammalian subject.

A method of measuring the amount or concentration of glucose in a mammalian subject, the method comprising the steps of:

• contacting a first surface of an ionically conductive hydrogel with a skin surface of the mammalian subject, said hydrogel comprising water, electrolyte and glucose oxidase, wherein (i) glucose oxidase catalyzes a reaction resulting in conversion of glucose to gluconic acid, and (ii) the thickness of said hydrogel is in the range of 10 μm to 1,000 μm;
• contacting an electrode assembly to a second surface of the hydrogel, the assembly comprising an electroosmotic electrode, a working electrode comprised of a plurality of substantially physically separated working electrode planar surfaces, a counter electrode, and a reference electrode, wherein (i) the working electrode surfaces are separated by a gap having a width in a range of 10 μm to 1,000 μm, (ii) an electrically insulating material is positioned in each gap separating the electrode surfaces, (iii) the working electrode is characterized by a substantially planar configuration, and (iv) the working electrode has a thickness in a range of 0.25 μm to 250 μm;
• providing current to the electroosmotic electrode sufficient to draw the glucose across the mammalian subject's skin and into the hydrogel;
• providing a voltage to the working electrode planar surfaces sufficient to drive electrochemical detection of a product of the reaction of glucose and glucose oxidase which generates an electrical current at the working electrode surfaces;
• measuring the electrical current generated at the working electrode;
• and
• correlating the measured current to the amount or concentration of glucose in the mammalian subject.