Navigation and Control of Motion Modes with Soft Microrobots at Low Reynolds Numbers

Abstract

This study investigates the motion characteristics of soft alginate microrobots in complex fluidic environments utilizing wireless magnetic fields for actuation. The aim is to explore the diverse motion modes that arise due to shear forces in viscoelastic fluids by employing snowman-shaped microrobots. Polyacrylamide (PAA), a water-soluble polymer, is used to create a dynamic environment with non-Newtonian fluid properties. Microrobots are fabricated via an extrusion-based microcentrifugal droplet method, successfully demonstrating the feasibility of both wiggling and tumbling motions. Specifically, the wiggling motion primarily results from the interplay between the viscoelastic fluid environment and the microrobots’ non-uniform magnetization. Furthermore, it is discovered that the viscoelasticity properties of the fluid influence the motion behavior of the microrobots, leading to non-uniform behavior in complex environments for microrobot swarms. Through velocity analysis, valuable insights into the relationship between applied magnetic fields and motion characteristics are obtained, facilitating a more realistic understanding of surface locomotion for targeted drug delivery purposes while accounting for swarm dynamics and non-uniform behavior.

How the Magnetization Angle of a Linear Halbach Array Influences Particle Steering in Magnetic Drug Targeting—A Systematic Evaluation and Optimization

“…For particle steering, most Halbach arrangements are linear and consist entirely of PMs (e.g., [43,47,49,51,52,54]). However, there are also 3D Halbach arrays consisting of EMs [86], which are combined with a core to focus SPIONs at a desired location (usually the tumor), or 3D constructs [37,87], which enclose the vessel and can precisely steer SPIONs here. However, since it is impossible to place the magnets around the blood vessel in reality, this paper focuses on linear arrays placed sideways to a vessel.…”

Magnetic Microrobots for In Vivo Cargo Delivery: A Review

“…However, its effectiveness is often limited by the inherent rigidity of the pre-established models, which struggle to adapt to the complexities of the in vivo environment. This limitation becomes particularly evident in extreme or unforeseen conditions, where the predefined models cannot accurately predict or respond to the dynamic changes [135].…”

“…The second category, dynamics model-based navigation, is noted for its precision and interpretability. It relies on fixed physical and mathematical models, limiting adaptability in dynamic environments [135,136]. To overcome those limitations, integrating the two approaches could be a promising strategy.…”

Selective Locomotion Control of Magnetic Torque-Driven Magnetic Robots Within Confined Channels

“…The channels were filled with a mixture of water and glycerin with a dynamic viscosity of 45.38 mPa•s. As in most research regarding magnetic milli/microrobots, the fluid's viscosity was tuned to the referred value so that the Reynolds number approached a low value (between 10 -2 to 10 -3 ) similar to that of microorganisms [27], [28].…”