Wake-up batteries for invasive biosensors
Example biosensor devices having wake-up batteries and associated methods are disclosed. One example device includes a biosensor that has a first electrode for insertion into a subcutaneous layer beneath a patient's skin, and a second electrode coupled to the first electrode for insertion into the subcutaneous layer, and a first battery to apply a voltage across the first and second electrodes, the first battery at least partially electrically decoupled from the electrodes. The device also includes a second battery having an anode material coupled to the first electrode for insertion into the subcutaneous layer, and a portion of the second electrode. The second battery is activatable upon immersion in an electrolytic fluid. The device also includes a wake-up circuit to receive a signal from the second battery and, in response, to electrically couple the first battery to the first and second electrodes to activate the biosensor.
1. A device comprising:
a biosensor comprising:
a first electrode having a distal end configured for insertion into a subcutaneous layer beneath a patient's skin,
a second electrode coupled to the first electrode, a portion of the second electrode for insertion into the subcutaneous layer, and
a first battery to apply a voltage across the first and second electrodes, the first battery electrically decoupled from at least one of the electrodes;
an anode material coupled to a portion of the distal end of the first electrode, the anode material configured for insertion into the subcutaneous layer with the portion of the first electrode, and in combination with the portion of the second electrode, forming a portion of a second battery, wherein the second battery is configured to activate upon immersion in an electrolytic fluid by transmitting a signal; and
a wake-up circuit coupled to the second battery to receive the signal from the second battery and, in response, to electrically couple the first battery to the at least one of the first and second electrodes.
2. The device of claim 1 , further comprising a glucose oxidase material disposed on a portion of the distal end of the first electrode.
3. The device of claim 1 , further comprising a radio frequency (“RF”) transmitter, and wherein:
the first battery is at least partially electrically decoupled from the RF transmitter and is further to apply power to the RF transmitter, and
the wake-up circuit is further to electrically couple the first battery to the RF transmitter in response to receiving the signal from the second battery.
4. The device of claim 1 , wherein:
the first electrode comprises a platinum material;
the second electrode comprises a silver/silver-chloride material coating a portion of the first electrode; and
the anode material comprises zinc, iron, aluminum, or nickel.
5. The device of claim 1 , wherein the anode material comprises approximately 10 to 100 nanograms (“ng”) of zinc, approximately 10 to 100 ng of nickel, approximately 10 to 100 ng of iron, or approximately 3 to 30 ng of aluminum.
6. The device of claim 1 , wherein the wake-up circuit comprises one or more of (1) a voltage threshold detection circuit and a reference voltage source, (2) a current threshold detection circuit and a reference current source, (3) a ring oscillator, (4) a power-on reset circuit, or (5) an NMOS footer switch.
7. The device of claim 1 , wherein the biosensor further comprises a processor, and wherein the wake-up circuit is further to electrically couple the first battery to the processor.
8. The device of claim 7 , wherein the wake-up circuit comprises a ring oscillator electrically coupled to a clock circuit of the processor to activate the clock circuit after receiving the signal from the second battery.
9. A method comprising:
inserting an insertable portion of a biosensor and a second battery into a patient's skin and into the patient's interstitial fluid, the insertable portion comprising:
a distal end of a first electrode and a portion of a second electrode, the first electrode coupled to the second electrode,
the biosensor further comprising a first battery to apply a voltage across the first and second electrodes, the first battery electrically decoupled from at least one of the electrodes,
the second battery comprising an anode material coupled to a portion of the distal end of the first electrode and a portion of the second electrode;
generating a signal by the second battery after the second battery is activated upon inserting the insertable portion of the biosensor into the patient's interstitial fluid;
electrically coupling the first battery to the at least one of the first and second electrodes by a wake-up circuit in response to receiving the signal from the second battery; and
generating sensor information from the biosensor.
10. The method of claim 9 , further comprising transmitting the sensor information to a remote wireless device.
11. The method of claim 10 , wherein the transmitting is performed using a radio frequency identification (“RFID”) or near-field communication (“NFC”) technique.
12. The method of claim 9 , wherein the biosensor comprising a processor, and further comprising activating a clock circuit of the processor by the wake-up circuit.