The rotational propulsion characteristics of scaled-up helical microswimmers with different heads and magnetic positioning

Micro and nanorobots capable of controlled propulsion at low Reynolds number are foreseen to change many aspects of medicine by enabling targeted diagnosis and therapy, and minimally invasive surgery. Several kinds of helical swimmers with different heads actuated by a rotating magnetic field have been proposed in prior works. Beyond these proofs of concepts, this paper aims to study behaviours of helical swimmers with different head and magnetic positing adapted to low Reynolds number liquids. For this, we designed an experimental setup and scaled-up helical nanobelt swimmers with different heads and tail coatings to compare their rotational propulsion characteristics. We found in this paper that the head shape of a helical swimmer does not influence on the shape of the rotational propulsion characteristics curve, but it influences on the values of the cut-off frequency. The rotational propulsion characteristics of helical swimmers with a magnetic head or a magnetic tail are much different. The helical swimmer with uniformly coated magnetic tail does not show a cut-off frequency but a saturation of frequency.