MINIATURIZED NONINVASIVE GLUCOSE SENSOR AND CONTINUOUS GLUCOSE MONITORING SYSTEM
Systems and methods are described herein for utilizing a photoacoustic sensor for estimating analyte concentration levels. Also described here are calibration and training methods for calibrating and/or training an analyte sensor to more accurately estimate an analyte concentration level on the basis of a received acoustic signal.
1 . An analyte monitor comprising:
a first light emitter configured to emit light of a first wavelength towards a surface of a target;
a resonance chamber positioned to receive acoustic waves generated by the target in response to the light emitted by the first light emitter, the resonance chamber sized to form a standing acoustic wave in the resonance chamber;
an acoustic sensor configured to sense acoustic waves in the resonance chamber, wherein the acoustic sensor and the first light emitter are positioned side-by-side and face a same direction towards the surface of the target; and
a processor configured to estimate an analyte concentration level in the target based on at least the acoustic waves sensed by the acoustic sensor.
2 . The analyte monitor of claim 1 , wherein the acoustic sensor is positioned proximate to an anti-node of the standing acoustic wave.
3 . The analyte monitor of claim 1 , further comprising a case enclosing the first light emitter, the resonance chamber, the acoustic sensor, and the processor, wherein the case has a length below 50 mm.
4 . The analyte monitor of claim 3 , wherein the case includes a case cover having an electronic transmitter incorporated therein, the case cover configured to be positioned on the surface of the target.
5 . The analyte monitor of claim 1 , wherein the processor is configured to determine whether the estimated analyte concentration level falls within one of two or more pre-determined ranges.
6 . The analyte monitor of claim 1 , further comprising a circuit configured to measure an impedance of the surface of the target, wherein the processor is configured to estimate the analyte concentration level in the target based on the acoustic waves sensed by the acoustic sensor and the measured impedance of the surface of the target.
7 . The analyte monitor of claim 6 , wherein the circuit includes a first electrode and a second electrode configured to be in direct or indirect contact with the surface of the target.
8 . The analyte monitor of claim 7 , wherein each of the first electrode and the second electrode includes a hydrogel pad configured to directly contact the surface of the target.
9 . The analyte monitor of claim 7 , wherein the circuit includes an electrical impedance spectroscopy (EIS) circuit configured to apply electrical signals of one or more frequencies to the first electrode and the second electrode, and measure the impedance between the first electrode and the second electrode at each of the one or more frequencies.
10 . The analyte monitor of claim 1 , further comprising:
a heating element configured to apply heat to the surface of the target; and
a thermal sensor configured to measure a thermal response of the surface of the target to the applied heat,
wherein the processor is configured to estimate the analyte concentration level in the target based on the acoustic waves sensed by the acoustic sensor and the measured thermal response.
11 . The analyte monitor of claim 1 , further comprising:
a second light emitter configured to emit light of a second wavelength towards the surface of the target,
wherein the acoustic sensor is configured to sense secondary acoustic waves generated by the target in response to the light of the second wavelength, and
wherein the processor is configured to estimate the analyte concentration level in the target based on the acoustic waves and the secondary acoustic waves sensed by the acoustic sensor.
12 . The analyte monitor of claim 11 , wherein the processor is configured to:
estimate, based on the secondary acoustic waves sensed by the acoustic sensor, a background light absorption level; and
estimate the analyte concentration level in the target based on the estimated background light absorption level and the acoustic waves sensed by the acoustic sensor.
13 . The analyte monitor of claim 11 , wherein:
the first light emitter and the second light emitter are configured to emit the light of the first wavelength and the light of the second wavelength at different time or at different pulse frequencies.
14 . The analyte monitor of claim 1 , further comprising:
a cathode and an anode configured to be in contact with the surface of the target, wherein an area of the surface of the target irradiated by the light emitted by the first light emitter is closer to the cathode than to the anode; and
a voltage controller coupled to the cathode and the anode to bias the cathode and the anode.
15 . A method of estimating an analyte concentration level in a target, the method comprising:
emitting, by a light emitter, light of a first wavelength towards a surface of the target;
receiving, in a resonance chamber, acoustic waves generated by the target in response to the light emitted by the light emitter, the resonance chamber sized to form a standing acoustic wave in the resonance chamber;
sensing, by an acoustic sensor positioned side-by-side with the light emitter and facing a same direction towards the surface of the target as the light emitter, the acoustic waves in the resonance chamber; and
estimating, by a processor, the analyte concentration level in the target based on at least the acoustic waves sensed by the acoustic sensor.
16 . The method of claim 15 , further comprising:
measuring an impedance of the target via electrical impedance spectroscopy,
wherein estimating the analyte concentration level in the target includes estimating the analyte concentration level in the target based additionally on the measured impedance of the target.
17 . The method of claim 15 , further comprising:
applying heat to the target; and
measuring a thermal response of the target to the applied heat,
wherein estimating the analyte concentration level in the target comprises estimating the analyte concentration level in the target based additionally on the measured thermal response.
18 . The method of claim 15 , further comprising:
emitting light of a second wavelength towards the surface of the target;
sensing, with the acoustic sensor, secondary acoustic waves generated by the target in response to the light of the second wavelength; and
estimating, based on the sensed secondary acoustic waves, a background light absorption level,
wherein estimating the analyte concentration level in the target comprises estimating the analyte concentration level in the target based additionally on the estimated background light absorption level.
19 . The method of claim 18 , wherein emitting the light of the first wavelength and emitting the light of the second wavelength occur at different time or at different pulse frequencies.
20 . The method of claim 15 , further comprising:
applying, using an anode and a cathode, a potential bias across an area on the surface of the target irradiated by the light emitted by the light emitter to draw analyte molecules towards the cathode, wherein the cathode is positioned closer to the area than the anode.