Multiple layer gel
A multiple layer gel and method for forming a multiple layer gel are provided. The multiple layer gel includes an isolation layer and an electrolyte layer. The isolation layer provides a molecular weight screen, to prevent proteins or other molecules from contacting a reference cell covered by the isolation layer. The electrolyte layer covers the isolation layer, and provides a source of ions that place the reference cell in ionic and/or electrical contact with a fluid sample. The multiple layer gel can be used to maintain a reliable reference voltage from an associated reference cell while an electrical potential or other electrical characteristic of a sample fluid is being determined.
1. A method for forming a multiple layer gel on a test strip, comprising:
providing a test strip, wherein the test strip includes:
a substrate at least partially defining a sample chamber, and the substrate having a readout region;
a reference cell positioned on the substrate outside of the sample chamber;
a working electrode extending from the readout region of the substrate to the sample chamber;
a counter electrode extending from the readout region of the substrate to the sample chamber;
a reference electrode extending from the readout region of the substrate to the reference cell;
applying an isolation layer over the reference cell, wherein the isolation layer covers portions of the reference cell not in contact with a surface of the substrate or the reference electrode;
applying an electrolyte layer over the isolation layer; and
providing a bridge extending between the electrolyte layer and the sample chamber.
2. The method of claim 1 , wherein applying an isolation layer includes applying a gel containing agarose and hydroxyethyl cellulose (HEC) over the reference cell.
3. The method of claim 2 , wherein the isolation layer is applied using a heat block technique.
4. The method of claim 3 , wherein applying an electrolyte layer includes applying a gel containing 3% HEC in 3M KCl over the isolation layer.
5. The method of claim 3 , wherein after applying the isolation layer the test strip is allowed to dry at ambient temperature, and wherein after applying the electrolyte layer the test strip is placed in a pre-heated vacuum oven at 0.02 MPa below atmospheric pressure.
6. The method of claim 1 , wherein applying an isolation layer includes applying a molecular screening layer.
7. The method of claim 1 , wherein applying the electrolyte layer includes applying a source of chloride ions.
8. The method of claim 1 , wherein applying the isolation layer includes applying an agarose and hydroxyethyl cellulose layer, and applying the electrolyte layer comprises applying an agarose and KCl layer.
9. The method of claim 1 , wherein applying the isolation layer includes applying a water based gel containing about 4% agarose and about 1% hydroxyethyl cellulose, and applying the electrolyte layer comprises applying a water based gel containing about 4% agarose and about a 3M concentration of KCl.
10. The method of claim 1 , wherein the isolation layer covers all portions of the reference cell that are not in contact with the surface of the substrate or the reference electrode.
11. A method for forming a multiple layer gel, comprising:
providing a test strip substrate that includes a plurality of test leads and a reference cell;
applying an isolation layer over the reference cell, wherein applying an isolation layer includes applying a gel containing agarose and hydroxyethyl cellulose (HEC) over the reference cell, and wherein the isolation layer is applied using a heat block technique; and
applying an electrolyte layer over the isolation layer, wherein applying an electrolyte layer includes applying a gel containing 3% HEC in 3M KCl over the isolation layer.
12. A method for forming a multiple layer gel, comprising:
providing a test strip substrate that includes a plurality of test leads and a reference cell;
applying an isolation layer over the reference cell, wherein applying the isolation layer includes applying a water based gel containing about 4% agarose and about 1% hydroxyethyl cellulose; and
applying an electrolyte layer over the isolation layer, wherein applying the electrolyte layer comprises applying a water based gel containing about 4% agarose and about a 3M concentration of KCl.