ACCURATE ENZYMATIC SENSING OF SWEAT ANALYTES

1 . A device for sensing a biofluid that is adapted to be placed on skin, comprising:

at least one analyte-consuming sensor for measuring at least a first analyte concentration of an analyte in a first biofluid sample having a first biofluid sample flow rate; and

at least one additional component that maintains analyte-consuming sensor measurements within 20% of the first concentration measurement when a biofluid sample flow rate is less than or equal to 2 times the first biofluid sample flow rate.

2 . The device of claim 1 , where the additional component is a concentration regulating component located between the biofluid and said analyte-consuming sensor, wherein said concentration regulating component is adapted to be in contact with an advective flow of the biofluid.

3 . The device of claim 2 , wherein said concentration regulating component is a diffusion limiting material.

4 . The device of claim 3 , wherein said diffusion limiting material is adapted to allow passage of the first analyte and prevent passage of the biofluid.

5 . The device of claim 1 , further comprising:

at least one secondary sensor.

6 . The device of claim 5 , wherein the at least one secondary sensor is at least one of the following: a second analyte-specific sensor for sensing the first analyte; a pH sensor; a galvanic skin response (GSR) sensor; a sample generation rate sensor; a micro-thermal flow sensor; a sweat conductivity sensor; a skin impedance sensor; or an ion selective electrode sensor.

7 . The device of claim 5 , wherein the at least one secondary sensor is adapted to be in contact with an advective flow of biofluid.

8 . The device of claim 1 , wherein the device uses an algorithm to correlate at least one of the following measurements of the biofluid sample with an analyte concentration: a measurement by the analyte-consuming sensor; a pH measurement; a flow rate measurement; or a salinity measurement.

9 . The device of claim 1 , wherein the device uses a data table to correlate at least one of the following measurements of the biofluid sample with an analyte concentration: a measurement by the analyte-consuming sensor; a pH measurement; a flow rate measurement; or a salinity measurement.

10 . The device of claim 1 , further comprising:

an analyte-sensing channel; and

a plurality of analyte-consuming sensors arranged along said analyte-sensing channel, wherein the device is configured to determine a biofluid sample flow rate based on a comparison of outputs from the plurality of analyte-consuming sensors.

11 . The device of claim 1 , further comprising a catalyst region containing a catalyst, where the catalyst region is in fluid communication with the analyte-consuming sensor.

12 . The device of claim 11 , wherein the catalyst region is a coating on the analyte-consuming sensor.

13 . The device of claim 11 , wherein the catalyst is an enzyme.

14 . The device of claim 13 , wherein the enzyme is one of the following: a dehydrogenase; an oxidase; a deglycosylated enzyme; an RNAzyme; a DNAzyme; or a polymeric matrix.

15 . The device of claim 1 , wherein the analyte-consuming sensor is configured to indirectly measure pH by measuring a redox of protons.

16 . The device of claim 1 , wherein the analyte-consuming sensor is configured to measure a redox active metabolite.

17 . The device of claim 1 , wherein the analyte-consuming sensor is configured to indirectly measure a redox active metabolite.

18 . The device of claim 1 , further comprising:

an analyte-sensing channel having a known fluid volume;

a plurality of analyte-consuming sensors; and

at least one catalyst region.

19 . The device of claim 18 , where at least one catalyst region is located upstream of each of the plurality of analyte-consuming sensors relative to a flow direction of the biofluid.

20 . The device of claim 18 , wherein a plurality of paired catalyst regions and sensors are arranged along the analyte-sensing channel in the flow direction of the biofluid.

21 . The device of claim 18 , wherein there are a plurality of catalyst regions each of which is co-located with one of the plurality of analyte-consuming sensors, so that the biofluid must first react with one of the catalyst regions before reaching one of the analyte-consuming sensors.

22 . The device of claim 21 , wherein each of the catalyst regions are in one of the following arrangements: coating a surface of each of the analyte-consuming sensors or suspended in an immobilization matrix.

23 . A method for sensing a biofluid using a device adapted to be placed on skin, comprising:

measuring a first analyte concentration of an analyte in a first biofluid sample having a first biofluid sample flow rate using an analyte-consuming sensor;

measuring the first biofluid sample flow rate; and

maintaining a subsequent analyte concentration within 20% of the first analyte concentration when a subsequently measured biofluid flow rate is less than or equal to 2 times the first biofluid sample flow rate.

24 . The method of claim 23 , wherein maintaining the subsequent analyte concentration includes using a concentration regulating component between the biofluid and said analyte-consuming sensor, the concentration regulating component being in contact with an advective flow of the biofluid.

25 . The method of claim 23 , further comprising:

correlating at least one of the following measurements of the biofluid sample with the first analyte concentration or a subsequently measured analyte concentration: a measurement by the analyte-consuming sensor; a pH measurement; a flow rate measurement; and or a salinity measurement.

26 . The method of claim 23 , wherein the device comprises an analyte-sensing channel and a plurality of analyte-consuming sensors arranged along said analyte-sensing channel, the method further comprising:

determining a biofluid sample flow rate based on a comparison of outputs from the plurality of analyte-consuming sensors.

27 . The method of claim 23 , further comprising:

converting the analyte in the biofluid to a component that is measurable by the analyte-consuming sensor using a catalyst.

28 . The method of claim 23 , wherein measuring the first analyte concentration includes applying electrical pulses to the analyte-consuming sensor.

29 . The method of claim 28 , further comprising:

adjusting a duration of the electrical pulses based on changes in the biofluid flow rate.

30 . The method of claim 23 , further comprising:

delivering the first biofluid sample and subsequent biofluid samples to the analyte-consuming sensor, each biofluid sample having a discrete volume.

31 . The method of claim 30 , further comprising:

forming the first biofluid sample and subsequent biofluid samples based at least in part on capillary forces.