Achieving high-speed rotations with a semi-flexible rotor driven by ultralow-frequency vibrations

Rotational motions are generally enabled by the flow energy for generating electricity or by the electric energy to drive various mechanical motions. Here, we report a fundamentally different approach (which we name "semi-flexible rotor") that uses omnipresent ultralow-frequency (<5 Hz) vibrations as the energy source to achieve high-speed rotational motions. The semi-flexible rotor comprises mainly a turntable, an elastic support, a lid, and a piece of rope, in which the periodically tensioned and released rope under external excitations provides the torque for spinning the turntable. The feasibility of the proposed approach is confirmed by both experimental measurements and theoretical simulations. As excited by a quasi-harmonic vibration with an amplitude of 10 mm, the rotor achieves a high rotational speed of up to 250 rad/s (2400 rpm) at around 2 Hz, and can provide an average rotational speed higher than 50 rad/s within a frequency range from 0.5 Hz to 5 Hz. The semi-flexible rotor is thus an option for realizing some rotation-based devices (e.g., miniature centrifuges) that work in scenarios without electricity supply or for designing efficient energy harvesters that exploit ubiquitous ultralow-frequency vibrations to generate electricity.