Biosensor and method for determining dimension of counter electrode and prolonging usage lifetime of the same

A method for determining a dimension of a counter electrode of a biosensor and for prolonging a usage lifetime of the biosensor, wherein the counter electrode comprises a silver and a silver halide, the dimension is quantified based on an initial amount of the silver halide being sufficient to measure a physiological signal representative of a physiological parameter associated with an analyte in a living body, the biosensor is implanted subcutaneously into the living body and further includes a working electrode and an auxiliary electrode, and the silver halide is consumed during a measurement period and replenished during a replenishment period, the method comprising the following steps of:

• a. defining a required consumption range of the silver halide during at least one of multiple measurement periods performed by the biosensor, wherein the required consumption range is defined based on a predetermined consumption current and a predetermined length of the measurement period;
• b. determining the initial amount based on a sum of an upper limit of the required consumption range and a buffer amount, so that a required replenishment amount of the silver halide during the replenishment period is safeguarded to be sufficient to maintain an amount of the silver halide within a safe storage range, for ensuring a successful retrieval of and a correct correlation between a next physiological signal and a next physiological parameter in a next measurement period;
• c. converting the initial amount into the dimension of the counter electrode;
• d. providing the counter electrode with at least the initial amount of the silver halide;
• e. measuring the physiological signal and calculating a consumption amount of the silver halide during the measurement period;
• f. replenishing the silver halide with a replenishment amount during the replenishment period;
• g. during the measurement period, applying a measurement voltage between the working electrode and the counter electrode to drive the working electrode to measure the physiological signal to obtain the physiological parameter;
• h. stopping applying the measurement voltage, before which the silver halide is consumed;
• i. during the replenishment period, applying a replenishment voltage between the counter electrode and the working electrode, thereby the silver halide gaining the replenishment amount;
• j. during a second measurement period, applying the measurement voltage between the working electrode and the counter electrode to drive the working electrode to measure the physiological signal to obtain the physiological parameter;
• k. stopping applying the measurement voltage, wherein when the measurement voltage is applied, the silver halide is consumed;
• and
• l. during a second replenishment period, applying a replenishment voltage between the counter electrode and the auxiliary electrode, thereby the silver halide gaining the replenishment amount, wherein the step d is implemented before the step e after the biosensor is implanted,
• wherein the step d is implemented before the step e after the biosensor is implanted.

A physiological signal measurement device for measuring a physiological signal representative of a physiological parameter associated with an analyte, comprising:

• a biosensor, comprising:
• a working electrode configured to be driven for measuring the physiological signal during a first measurement period;
• a counter electrode including a silver and a silver halide having an initial amount, wherein the counter electrode is configured to consume the silver halide in a consumption amount during the first measurement period, and during a first replenishment period, the counter electrode and the working electrode are configured to be driven to replenish the silver halide;
• an auxiliary electrode configured to replace the working electrode to be driven to replenish the silver halide during the first replenishment period;
• and
• a circuit configured to drive the working electrode and the counter electrode during the first replenishment period and control a required replenishment amount range of the silver halide within a safe storage range, wherein the safe storage range is defined by a sum of an upper limit of a required consumption range and a buffer amount, and the required consumption range of the silver halide is defined based on a predetermined consumption current and a predetermined length of a specific measurement period performed by the physiological signal measurement device.