Simple Flagellated Soft Robot for Locomotion near Air-Fluid Interface

TL;DR

This paper presents a simple, soft flagellated robot capable of complex 2D locomotion near air-fluid interfaces, utilizing viscosity variations and a binary control signal, with experimental fabrication and simulation-based control development.

Contribution

It introduces the simplest soft robot with a binary control for complex trajectory following near fluid interfaces, combining experimental and simulation methods.

Findings

Robot successfully follows arbitrary 2D trajectories.

Simulation validated against experimental results.

Single binary control signal enables complex movement.

Abstract

A wide range of microorganisms, e.g. bacteria, propel themselves by rotation of soft helical tails, also known as flagella. Due to the small size of these organisms, viscous forces overwhelm inertial effects and the flow is at low Reynolds number. In this fluid-structure problem, a competition between elastic forces and hydrodynamic (viscous) forces leads to a net propulsive force forward. A thorough understanding of this highly coupled fluid-structure interaction problem can not only help us better understand biological propulsion but also help us design bio-inspired functional robots with applications in oil spill cleanup, water quality monitoring, and infrastructure inspection. Here, we introduce arguably the simplest soft robot with a single binary control signal, which is capable of moving along an arbitrary 2D trajectory near air-fluid interface and at the interface between two fluids. The robot exploits the variation in viscosity to move along the prescribed trajectory. Our analysis of this newly introduced soft robot consists of three main components. First, we fabricate this simple robot and use it as an experimental testbed. Second, a discrete differential geometry-based modeling framework is used for simulation of the robot. Upon validation of the simulation tool, the third part of this study employs the simulations to develop a control scheme with a single binary input to make the robot follow any prescribed path.