"the conductor be very thin; its heat capacity must be small, and it must be able to conduct at once to its surface the heat produced in its interior."

The thermal expansion and contraction of the air in the vicinity of the thin film produces sound, not the mechanical movement of the thin film itself.

Ultra small heat capacity per unit area

Wide frequency response range

High sound pressure level

Thin, transparent, flexible, stretchable

No magnets or moving parts

CNT thin film pulled from array and put on two electrodes of a frame to make a loudspeaker.

SEM image showing CNTs are aligned in the drawing direction.