by Carl Bugeja @ hackaday.io designed a brushless motor using a 3D printer and a 4-layer PCB. He writes:
The PCB motor is my solution for trying to design a smaller, cheaper and easier to assemble brushless motor.
The motor’s stator is a 6 spiral PCB coil in a star configuration. Although it has less torque compared to an iron core stator, it still suitable for high-speed applications.
The current prototype has a 3d printed rotor with a 16mm diameter.
PCB Motor – A smaller and cheaper brushless motor – [Link]