Nanorobot Propulsion Using Helical Elastic Filaments at Low Reynolds Numbers

Abstract

Swimming in micro/nano domains is a challenge and involves a departure from standard methods of propulsion, which are effective at macrodomains. Flagella based propulsion is seen extensively in nature and has been proposed as a means of propelling nanorobots. Natural flagella actively consume energy in order to generate bending moments that sustain constant or increasing amplitude along their length. However, for man-made applications fabricating passive elastic filaments to function as flagella is more feasible. Of the two methods of flagellar propulsion, namely, planar wave and helical wave, the former has been studied from a passive filament point of view, whereas the latter is largely unexplored. In the present work an elastohydrodynamic model of the filament has been created and the same is used to obtain the steady state shape of an elastic filament driven in a Stokes flow regime. A modified resistive force theory, which is very effective in predicting propulsion parameters for a given shape, is used to study the propulsive dynamics of such a filament. The effect of boundary conditions of the filament on determining its final shape and propulsive characteristics are investigated. Optimization of physical parameters is carried out for each of the boundary conditions considered. The same are compared with the planar wave model.