In this modern world we’re continually bathed in a sea of electromagnetic energy. Radio frequency fields can be harvested for (small amounts of) power, effectively for free.

A lovely array of helium-filled balloons bobbles across your ceiling, lighting your room. They comprise an LED light source, a helium-filled envelope with a conductive printed parasitic coil, and a tiny remote control receiver.

No battery required, no wires, no worries.
-- Frankx, Sep 18 2019

Hydrogen would be cheaper [+] but slightly more dangerous [++]
-- 8th of 7, Sep 19 2019


Nice, different levels of buoyancy could map the spectrum in a volume. Biodegradable life span needed though.
-- wjt, Sep 20 2019


Helium, being so small, is difficult to contain, and leaks out of any small balloon I'm familiar with within days.
-- notexactly, Sep 24 2019



random, halfbakery