  We have fabricated suspended metal paddle resonators with carbon nanotubes
functioning as self-detecting torsional springs. We observe gate-tunable
resonances, that either tune to higher or to lower frequencies when increasing
the dc voltage on the back-gate. We attribute the former modes to flexural
vibrations of the paddle resonator, while the latter ones are identified as
torsional vibrations. Compared to top-down silicon fabricated paddle
resonators, nanotube springs have smaller torsional spring constants and
provide a larger frequency tunability.
