Okay, so you want to put electrodes in the brain. How do you power them if there are no wires? Simple. You use nanoparticles that self-assemble into antennas and circuits capable of harvesting RF and outputting a mild electric current.
How do you titrate the dosage to each person's brain? Simple. You use a source that can steer different beams of different dosages to different people's brains. 5G base stations are phased-array antennas with beamforming and MIMO. Problem solved.
Antenna size is directly correlated to wavelength. Minimum antenna size for 5G signal is ~3mm. AFAIK there are some tricks to reduce that slightly, perhaps to 2mm. That's still 4-5
orders of magnitude beyond what is considered nanotechnology. Not gonna fit through the needle either.
None of this stuff is technologically infeasible. At all.
Yeah... it is technologically infeasible. The fact that you talk a lot about remote mind control via nanoparticles but provide links to much more limited experiments with electrodes should be a hint that you're not exactly honest with that statement.
Then there is another huge leap between technological feasibility and the ability to do it covertly at scale.