Rotational Brownian Motion of Magnetically Clamped Silicon Nanoneedle: Towards Nano-Motors Fueled by Brownian Motion

This paper presents the rotation of a silicon nanoneedle fueled by Brownian motion which may lead to a new class of thermo-mechanical nano-motors. A nanoneedle with a magnetic bead at one end is immobilized at the end by a permanent magnet in the water and its rotational Brownian motion is observed. DRIE of a silicon substrate with magnetic nanobeads as the etching mask results in 3.5 μm long needles with aspect ratios close to 10. They are ultrasonicated and centrifuged to obtain needle suspension. The suspension is introduced onto the magnet and sealed by a cover glass. A magnetic field clamps the needle at the magnetic bead end to constrain 3D random motion into the observation plane. Similar to biomolecular motors, Brownian motion is exploited to rotate the needle at the free end.