Reconfigurable Vortex-like Paramagnetic Nanoparticle Swarm with Upstream Motility and High Body-length Ratio Velocity

Abstract

Drug delivery systems with high-targeted doses can minimize excipients, reduce side effects, and improve efficacy. Human blood circulation is a complex circulatory system, and the motion control of microrobots in the static flow field in vitro is completely different from in vivo. How to achieve precise counterflow motion for targeted drug delivery without vascular blockage and immune rejection is the biggest challenge for micro-nano robots. Here, we propose a control method that enables vortex-like paramagnetic nanoparticle swarm (VPNS) to move upstream against the flow. By mimicking the clustering motion of wild herring schools and the rolling of leukocytes, VPNS are incredibly stable even when subjected to high-intensity jet impacts in the blood environment, can travel upstream, anchor at the target location, and dissipate when the magnetic field is withdrawn, which greatly reduces the risk of thrombosis. VPNS can also upstream along the vessel wall without an additional energy source and has a marked targeted therapeutic effect on subcutaneous tumors.

Programming structural and magnetic anisotropy for tailored interaction and control of soft microrobots

“…In larger vessels such as arteries, where flow rates are typically high, it is essential for microrobots to exhibit robust locomotion capabilities. Formation of clusters can enhance their ability to travel upstream and facilitate targeted delivery of higher doses of therapeutic agents 13,40 . On the other hand, in smaller capillaries, microrobots should ideally disperse into individual entities to fit through the narrow vessels, and it is critical that they do not form irreversible clusters that can cause microvascular obstruction.…”

Micro/Nanorobotic Swarms: From Fundamentals to Functionalities

“…In magnetic fields, magnetic agents interact with each other through dipole–dipole interactions and may assemble into chainlike clusters [Figure A­(i)]. By rotating or oscillating the magnetic fields, the chains perform rotation or oscillation and they may undergo fragmentation because of viscous torque. − The magnetic interaction between the chains changes with the time-varying fields, and compact swarms are generated when the overall magnetic interaction is attractive, e.g., wheel-like particles swarm in out-of-plane rotating fields. − The generation of a ribbonlike paramagnetic nanoparticle swarm by using an in-plane dual-axis oscillating magnetic field has been demonstrated (Figure B). , The particles initially formed oscillating chains. As the strength of the magnetic field changed with time, the chains broke because of viscous torque when the dipole–dipole interaction was weak, while they attracted each other to reform chains when the interaction was sufficiently strong.…”

Droplet Rolling Transport on Hydrophobic Surfaces Under Rotating Electric Fields: A Molecular Dynamics Study

“…For instance, the rotating magnetic field enables magnetic microrobots to capture and transport microorganisms, and moon-shaped magnetic microrobots spinning at high speed under the rotating magnetic field can be used to generate microscale vortex . In addition, a vortex-like paramagnetic nanoparticle swarm can roll upstream near the walls of the microchannel . Electric field driven droplets have the advantage of flexibility, precision, programmability, and no pollution. , Droplet transport driven by electric fields is achieved mainly by controlling droplet wettability, and the major principles are electrowetting on dielectric, dielectrowetting, and the mixing of the two. ,, Ionic-surfactant-mediated electro-dewetting is a reliable, stable, and widely applicable method because it does not require a dielectric layer and a hydrophobic topcoat .…”