Far-field wireless charging of medical devices

1. A medical device comprising:

a rechargeable battery;

a receiving antenna configured to wirelessly receive electrical power from a transmission antenna;

charging circuitry configured to recharge the rechargeable battery using the electrical power received by the receiving antenna; and

one or more processors configured to:

determine a relative proximity of the medical device to a body of a patient;

determine a power-transfer efficiency based on the relative proximity of the medical device to the body of the patient;

determine, based at least in part on the relative proximity and the power-transfer efficiency, a tuning for the receiving antenna that is safe for the patient; and

cause the receiving antenna to be tuned according to the determined tuning.

2. The medical device of claim 1 , wherein the medical device comprises a continuous glucose monitor (CGM) or an insulin pump.

3. The medical device of claim 1 , wherein the receiving antenna is configured to receive the electrical power from the transmission antenna via far-field microwave-spectrum electromagnetic waves.

4. The medical device of claim 1 , further comprising tuning circuitry configured to modify a resonant frequency of the receiving antenna, wherein causing the receiving antenna to be tuned comprises causing the tuning circuitry to modify the resonant frequency of the receiving antenna according to the determined tuning.

5. The medical device of claim 1 , wherein determining the relative proximity of the medical to the body of the patient comprises determining a physical contact between the medical device and the body of the patient.

6. The medical device of claim 5 , further comprising a flex sensor, wherein determining the physical contact between the medical device and the body of the patient comprises:

receiving an indication of an amount of flex in the flex sensor; and

determining the physical contact based at least in part on the indication of the amount of flex in the flex sensor.

7. The medical device of claim 5 , further comprising an optical sensor, wherein determining the physical contact between the medical device and the body of the patient comprises:

receiving a signal from the optical sensor; and

determining the physical contact based at least in part on the signal from the optical sensor.

8. The medical device of claim 5 , further comprising a skin impedance sensor positioned on an exterior housing of the medical device, wherein determining the physical contact between the medical device and the body of the patient comprises:

receiving, from the skin impedance sensor, an indication of an electrical impedance of a skin of the patient; and

determining the physical contact based at least in part on the indication of the electrical impedance of the skin of the patient.

9. The medical device of claim 1 , further comprising an antenna impedance sensor, wherein determining the relative proximity of the medical device to the body of the patient comprises:

receiving, from the antenna impedance sensor, an indication of an impedance of the receiving antenna, wherein the impedance of the receiving antenna is based on the relative proximity of the relative proximity of the receiving antenna to the body of the patient; and

determining the relative proximity based at least in part on the indication of the impedance of the receiving antenna.

10. The medical device of claim 1 , further comprising a user-input mechanism, wherein determining the relative proximity of the medical device to body of the patient comprises receiving, via the user input mechanism, user input indicative of the relative proximity, and wherein determining the tuning for the receiving antenna comprises determining the tuning based at least in part on the user input.

11. The medical device of claim 1 :

wherein determining the relative proximity of the medical device to the body of the patient comprises determining that the medical device is within a threshold distance from the body of the patient; and

wherein causing the receiving antenna to be tuned according to the determined tuning comprises causing the receiving antenna to be tuned in order to reduce a power-transfer efficiency of the receiving antenna.

12. The medical device of claim 1 :

wherein determining the relative proximity of the medical device to the body of the patient comprises determining that the medical device is not within a threshold distance from the body of the patient; and

wherein causing the receiving antenna to be tuned according to the determined tuning comprises tuning the receiving antenna in order to increase a power-transfer efficiency of the receiving antenna.

13. The medical device of claim 1 , wherein the one or more processors are further configured to maintain a predetermined minimum threshold of electrical charge in the rechargeable battery by:

determining that a current level of electrical charge in the rechargeable battery is below the minimum threshold; and

causing the charging circuitry to charge the rechargeable battery via the receiving antenna in response to determining that the current level is below the minimum threshold.

14. The medical device of claim 1 , wherein the receiving antenna is detachable from the medical device.

15. The medical device of claim 1 , wherein the receiving antenna is integrated within a housing of the medical device.

16. The medical device of claim 1 , wherein the one or more processors are further configured to periodically alternate between causing the charging circuitry to charge the rechargeable battery and enabling an operation of the medical device.

17. A system for wirelessly charging a medical device, the system comprising:

a wireless-power-transfer device comprising a transmission antenna; and

the medical device comprising:

a rechargeable battery;

a receiving antenna configured to wirelessly receive electrical power from the transmission antenna;

charging circuitry configured to recharge the rechargeable battery using the electrical power received by the receiving antenna; and

one or more processors configured to:

determine a relative proximity of the medical device to a body of a patient;

determine a power-transfer efficiency based on the relative proximity of the medical device to the body of the patient;

determine, based at least in part on the relative proximity and the power-transfer efficiency, a tuning for the receiving antenna that is safe for the patient; and

cause the receiving antenna to be tuned according to the determined tuning.

18. The system of claim 17 , wherein the wireless-power-transfer device is configured to transmit the electrical power from the transmission antenna via far-field microwave-spectrum electromagnetic waves.

19. The system of claim 17 , wherein determining the relative proximity of the medical device to the body of the patient comprises determining that the medical device is within a threshold distance from the body of the patient, and wherein causing the receiving antenna to be tuned according to the determined tuning comprises tuning the receiving antenna in order to reduce a power-transfer efficiency of the receiving antenna.

20. One or more non-transitory processor-readable storage media storing instructions that, when executed by one or more processors, cause performance of:

determining a relative proximity of a medical device to a body of a patient, wherein determining the relative proximity comprises determining whether the medical device is being worn by the patient;

determining, based at least in part on the relative proximity and power-transfer efficiency, a tuning for a receiving antenna of the medical device that is safe for the patient; and

causing the receiving antenna to be tuned according to the determined tuning.