Dumbbell micro-robot driven by flow oscillations

TL;DR

This paper analyzes the self-propulsion mechanisms of a dumbbell-shaped micro-robot in viscous fluid driven by flow oscillations, deriving analytical expressions for its movement and rotation.

Contribution

It introduces a novel model of a micro-robot with oscillating link length and provides analytical formulas for its propulsion and rotation velocities.

Findings

The micro-robot exhibits both translational and rotational motion.

Analytical expressions for average velocities are derived.

Zero angular velocity case results in straight-line propulsion.

Abstract

In this paper we study the self-propulsion of a dumbbell micro-robot submerged in a viscous fluid. The micro-robot consists of two rigid spherical beads connected by a rod or a spring; the rod's/spring's length is changing periodically. The constant density of each sphere differs from the density of a fluid, while the whole micro-robot has neutral buoyancy. An effective oscillating gravity field is created via rigid-body oscillations of the fluid. Our calculations show that the micro-robot undertakes both translational and rotational motion. Using an asymptotic procedure containing a two-timing method and a distinguished limit, we obtain analytic expressions for the averaged self-propulsion velocity and averaged angular velocity. The important special case of zero angular velocity represents rectilinear self-propulsion with constant velocity.