The wireless light emitters were fabricated on small circular pieces of circuit board with an LED (OSA Opto Light OCU-440 UE365-X-T or Luminus SST-10-UV-A130-E365-00) and a capacitor (82 nF) on the top and a ferrite core inductor (WE-PD2 4532 10 μH, Würth) on the bottom. These elements were connected all in parallel and form an oscillating circuit with a certain resonance frequency (178 kHz). The electronics are then surrounded by spherical half-shells (10 mm diameter) made from ETFE by injection molding and subsequently sealed using ultrasonic welding.