Optimal structure of particles-based superparamagnetic microrobots: application to MRI guided targeted drug therapy

This paper presents an optimal design strategy for therapeutic magneticmicro carriers (TMMC) guided in real time by a magnetic resonanceimaging (MRI) system. As aggregates of TMMC must be formed to carrythe most amount of drug and magnetic actuation capability, differentclustering agglomerations could be arranged. Nevertheless, its difficultto predict the hydrodynamic behavior of any arbitrary-shaped objectdue to the nonlinear hydrodynamic effects. Indeed, the drag effectis related not only to the properties of the bolus but also to itsinteraction with the fluid viscosity, the free-stream velocity andthe container geometry. In this work, we propose a mathematical frameworkto optimize the TMMC aggregates to improve the steering efficiencyin experimental endovascular conditions. The proposed analysis iscarried out on various sizes and geometries of microcarrier: spherical,ellipsoid-like and chain-like of microsphere structures. We analyzethe magnetophoretic behavior of such designs to exhibit the optimalconfiguration. Based on the optimal design of the boluses, experimentalinvestigations were carried out in mm-sized fluidic artery phantomsto demonstrate the steerability of the magnetic bolus using a proof-of-conceptsetup. The experiments demonstrate the steerability of the magneticbolus under different velocity, shear-stress and trajectory constraintswith a laminar viscous fluidic environment. Preliminary experimentswith a MRI system confirms the feasibility of the steering of theseTMMCs in hepatic artery microchannel phantom.