"One single implanted GBFC device of 0.24 mL volume (2.4 mL for the whole implant) produced the power required to operate, using a specially designed electronic circuit to charge a capacitor, two types of electronic devices: a LED and a digital thermometer."
I'm waiting for someone to invent the implantable chip that converts blood sugar into heat/light purely with the intention of wasting that energy.
Grab enough power to monitor blood sugar, to make sure you aren't putting someone into a coma, but otherwise just try to burn an extra few hundred calories a day.
You're thinking too fancy - with our technology today, we could install a bypass valve at the pyloric sphincter that just dumps chyme into a stoma appliance/bag.
That's interesting. Seems like a low tech solution would be to give blood every day. I wonder if somebody has already invented the blood donation diet.
The real question is can that conversion be done in an efficient enough way with materials that are safe to put inside someone and in a small enough package.
https://www.nature.com/articles/srep01516