Powering Devices within the Body



  • It appears that TI chip is for LF (134kHz). Any leads on similar chips operating at 13.56MHz?
  • it appears that there are chips operating at that frequency, providing a high output power. but they don't include any useable communication channels and from what i see, most of them have a standby current i'd rather avoid. if we go for higher frequency power transmittion, my guess would be we'd need a 2-antenna sollution. one for charging, one for communication.
  • Yeah, a few of the datasheets I've come across use separate chips and coils for high-frequency communication.

    Is there a particular reason you're interested in high-frequency solutions?  It seems to me that that would be a bit more challenging to implement.

    When looking for chips, I would suggest searching sites like TI and Atmel for immobilizer solutions; designed for wireless car keys, these typically have small footprints, low power consumption and often come with cryptographic features onboard (which is to me a strict requirement for anything implanted that has a wireless interface.)
  • flexible capacitors that can be made at home


    and an over view of the paper:

    I can't really think of how to use these, but I thought I'd post them because someone might think of a good use case.

  • Amal, are you looking at 13.56 MHz because it is the frequency used for NFC in Android cell phones?  I would be interested in this if it would also work with Windows Phone 8.  The problem is that cell phone manufacturers are extremely power-conscious regarding NFC in order to minimize battery drain on the phone.  I'm not sure they'd look too kindly at increasing the duty-cycle of NFC polling.  It might be more viable to use an external NFC device attached to a PC or Mac.  I could research that if you'd like.
  • Kinetic energy sources have been discussed before, but this is the smallest one I've seen. Although I am a bit worried that the flesh around it could dampen the vibrations too much.

  • Hi @mkabala, yes the idea is to be able to use NFC interrogation cycles (particularly peer to peer mode) to top-up subdermals using your phone, possibly only for emergencies. The primary charging method would be a dedicated power induction system you'd plug into USB or the wall socket.
  • thread-necro time!

    Adding to the discussion. One practical for harvesting mechanical energy from a pendulum motion could be tiny stepper motors. Adding a free-wheeling angle bigger than the full-step angle of the motor allows the pendulum to snap the stepper from one step to the next. It's a bit jerky in motion so probably not the most comfortable choice. On the pro side there are no gears, slip contacts or other mechanically or electrically frail structures. The output voltage is pretty much spikes. But the voltage of the spikes is high enough to simply rectify them and charge a capacitor.
  • Steppers don't do anything better than brushless motors would, other than taking a higher torque to step. If you have that much torque a sliding weight would be better.
  • steppers do better in one regard. they "snap" between steps, causing a quick change in magnetic flux in their driver coils. Which means you can get usable voltage even from nearly zero rpm. torque is a different matter, you can get steppers with different reluctance torque.
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