Itty-bitty Living Space

Okay so the power in question isn't really "phenomenal" or "cosmic".

But anyway I was thinking. Can you beam power to nano-bots? They're smaller than the wavelength of microwave-power transmission; a dipole antenna is about half a wavelength long, so even if you made the entire length of a 500-nanometer bot into an antenna, it'd still only be able to receive wavelengths of up to one micrometer (can you beam power in the near-infrared?). Fractal antennas, maybe?

The frequency recommended for microwave power-transmission is 24 GHz, 12.5 millimeters wavelength. Apparently an "electrically small" antenna is one whose maximum dimension is less than the wavelength λ (specifically the "free space" i.e. "propagating in vacuum" wavelength but "wavelength" simpliciter, for our purposes) divided by 2π. 12.5 millimeters over 2π is 1.989 millimeters, which is to say "almost exactly 2"; the maximum dimension of a 500 nanometer bot is λ/25,000. Is that feasible in an antenna? I doubt it; you'd probably have to pack it pretty tight.

Another option might be ultrasonic power transmission. You can use that for all kinds of things; it might some day replace microwaves not only for wireless power but for at least some data, though of course it's totally worthless for a spacefaring civilization. (It's apparently subject to jamming just as EM is, which is fortunate.) And in air at room temperature, the frequencies at which ultrasonic power-transmission works (45-75 kHz) have much shorter wavelengths than those used for microwaves—4.576 millimeters to 7.627 millimeters. That means much less space is required for the receiver (though I wonder if there might be "noise" issues—literal and figurative noise, given we're talking sound waves—at the nanometer scale).

I guess I'll go with ultrasonic power-beaming, for my weaponized nano-bots. It occurs to me that since zledo can hear sounds up to 65 kHz (same as tigers), this choice gives me plot options. (It also gives me an excuse to keep the humans using EM for power transmission on one of the planets—that the sunspots of a BY Draconis variable play hell with EM transmission is an important facet of one of my characters' backstory. Then again ultrasonics, in the frequency-range and decibel-levels (145-155 dB) involved in wireless power, don't seem to be much use for transmission beyond about 1 meter per decibel—at room temperature, and depending somewhat on humidity and air-pressure.)

Medical nano-bots, of course, can be powered from their host's body in various ways, e.g. by heat, blood-flow, borrowing some of the body's electrolytes, etc. (Maybe while undergoing nano-bot treatment you have to drink lots of Gatorade.) So I probably don't have to worry about that.