Pattern generation and motion control of a vortex-like paramagnetic nanoparticle swarm

Abstract

Controlling a swarm of microrobots with external fields is one of the major challenges for untethered microrobots. In this work, we present a new method to generate a vortex-like paramagnetic nanoparticle swarm (VPNS) from dispersed nanoparticles with a diameter of 500 nm, using rotating magnetic fields. The VPNS exhibits a dynamic-equilibrium structure, in which the nanoparticles perform synchronized motions. The mechanisms of the pattern-generation process are analyzed, simulated, and validated by experiments. By tuning the rotating frequency of the input magnetic field, the pattern of a VPNS changes accordingly. Analytical models for estimating the areal change of the pattern are proposed, and they have good agreement with the experimental data. Moreover, reversible merging and splitting of vortex-like swarms are demonstrated and investigated. Serving as a mobile robotic end-effector, a VPNS is capable of making locomotion by tuning the pitch angle of the actuating rotating field. With a small pitch angle, e.g. 2 • , the whole swarm moves as an entity, and the shape of the pattern remains intact. In addition, the trapping forces of VPNSs are verified, showing the critical input parameters of the magnetic field that affect the morphology of the swarm. Finally, we demonstrate that VPNSs pass through curved and branched channels with high positioning precision, and the access rates for targeted delivery are over 90%, which are significantly higher than those in the cases of particle swarms moving with tumbling motions.

A Magnetically-Triggered Soft Capsule for On-Demand Mucus Collection

“…When combines with bacteria sensing technologies [28], the capsule may achieve in-vivo mucus analysis in further prototypes. Cargo delivery function may also be designed for releasing swarming microrobots in specific location [29]- [31] for targeted therapy or other biomedical applications.…”

Closed-Loop Control for Trajectory Tracking of a Microparticle Based on Input-to-State Stability Through an Electromagnetic Manipulation System

“…The magnetically driven microparticles are made of either ferromagnetic materials [28] or superparamagnetic materials [29], [30]. Ferromagnetic materials exhibit high susceptibility and saturation magnetization, thus requiring small magnetic field and field gradient of the manipulation system.…”

Magnetic Navigation of a Rotating Colloidal Swarm Using Ultrasound Images

“…Then the tank is put into the workspace of the Helmholtz coil for further actuation. We use the previously reported method from our group to generate a swarm [23], [24]. After turning on the rotating field, rotating particle chains will be formed firstly due to the induced magnetic dipole-dipole interaction among particles.…”