A while back I came up with the idea of an ultra-miniature quadro copter with asynchronous outrunner motors who's stators would most likely be sintered (with or without a ferromagnetic matrix) to handle the power density, and a simple tube-shaped rotor (though a squirrel cage style might be better).
I'm thinking 5-20 mm rotor diameter (3M-750k rpm transonic limit), or maybe even smaller.
The interesting part would be an analogue ASIC that decodes an external control signal modulated onto the microwave (via rectenna) or optical (solar cell/photodiode) "wireless power" beam.
Demodulation would first do naive rectenna-based AM demodulation, followed by a bandpass and FM demodulation, revealing 12 carriers corresponding to the 4 3-phase motors, which are just FM-demodulated to yield the H-bridge control signals.
These would primarily be one xx MHz PLL and 12 lower-frequency ones spaced 50-200 kHz (the FM subcarrier's bandwith (assuming narrow-band FM) is twice the maximum motor field frequency), starting as low as feasible while still being able to use AC-coupling liberally.
Also either some amplifiers for (potentially-overdriven) "linear" H-bridge operation or (NE555-like?) PWM chopper drivers to exploit the winding inductance for less-wasteful H-bridge operation.
Far too much to realize in discrete circuitry, but nothing really fancy beyond a parametric PLL design. And not really realistic for a μC, either, because of brown-out resilience and overall latency.
At least the polyphase induction motors are very easy to drive, compared to the typical 3-phase permanent magnet outrunner motors used in most multicopters.
Depending on how predictable the effects of some tuning parameters are, maskless litho could allow for chips to be tuned to measured electro-mechanical properties of these sintered motors, reaching optimal drive waveforms. And for digital circuits, hard-wired ROM (security/shelf life/radiation-hardness) for individual chips or even doping-controlled ROM for anti-readout private/secret key storage.
I expect a maskless double-patterning ArF+immersion process allowing NDA-free-usage to be "the" thing that would enable true state-of-the-art experimentation and true ASICs (where the prototype needs an ASIC to be more than a paperweight after some photoshoots and staged interactions).
Feel free to contact me/let me know if you'd like further discussion(s).