Potentiometric wearable sweat sensor
A potentiometric sensor that includes a housing and working electrode is provided. The housing includes a reference electrode, a first hydrogel containing hydrogel that contains a reference solution, and a salt bridge. The sensor is wearable and can be used for continuous on-body sweat measurements.
1. A potentiometric sweat sensor comprising:
a substrate which has a through hole;
a working electrode which is in contact with sweat on skin;
a reference electrode, wherein the reference electrode is disposed above an upper surface of the substrate and at least a portion of the working electrode is disposed on a bottom surface of the substrate;
a reference solution hydrogel disposed on the upper surface of the substrate, wherein the reference electrode is disposed at least partially within the reference solution hydrogel; and
a salt bridge which is formed in the through hole, wherein one side of the salt bridge contacts the sweat on the skin and an opposing side of the salt bridge is in physical contact with the reference solution hydrogel, and wherein an ionic path between the reference electrode and the working electrode is formed through the salt bridge via the sweat.
2. The potentiometric sensor of claim 1 , wherein the substrate is a flexible substrate.
3. The potentiometric sensor of claim 1 , wherein the through hole overlaps with the reference hydrogel and does not vertically overlap with the working electrode.
4. The potentiometric sensor of claim 1 , wherein the reference electrode comprises a conductive layer and a AgCl (silver chloride) layer, and wherein the conductive layer is interposed between the substrate and the AgCl layer.
5. The potentiometric sensor of claim 1 , wherein the working electrode comprises a conducting part and a sensing part, and wherein the conducting part is interposed between the substrate and the sensing part.
6. The potentiometric sensor of claim 5 , wherein sweat is in contact with the sensing part and an electrochemical equilibrium is established with a sweat component along the ionic path.
7. The potentiometric sensor of claim 6 , wherein the sensing part detects chloride ions, and wherein the sensing part is a Ag/AgCl layer.
8. The potentiometric sensor of claim 1 , wherein a reference solution in the reference solution hydrogel contains chloride ions.
9. The potentiometric sensor of claim 1 , wherein the salt bridge contains a hydrogel or an ion selective polymer.
10. The potentiometric sensor of claim 1 , wherein the reference solution hydrogel is covered by an encapsulation layer.
11. The potentiometric sensor of claim 10 , wherein the encapsulation layer contains a UV curable resin or polymer.