Magnetic-based closed-loop control of paramagnetic microparticles using ultrasound feedback

Abstract

Controlling the motion of microrobots based on feedback provided using an imaging modality is essential to make them clinically viable. In this study, we demonstrate the wireless magnetic-based motion control of paramagnetic microparticles using ultrasound feedback. This control is accomplished by pulling the microparticles using the magnetic field gradients towards the reference position through feedback provided by an ultrasound system. First, position of the microparticles is determined using the ultrasound images. Second, calibration of the ultrasound-based tracking of microparticles is achieved and verified using a calibrated microscopic system. Third, the feedback provided by the ultrasound system is used in the implementation of a proportional-derivative magneticbased control system. This control system allows us to achieve point-to-point control of microparticles with an average position tracking error of 48±59 µm, whereas a control system based on a microscopic system achieves an average position tracking error of 21±26 µm. The positioning accuracy accomplished using our ultrasound magnetic-based control system demonstrates the ability to control microrobotic systems in situations where visual feedback cannot be provided via microscopic systems.

Magnetic control of self-propelled microjets under ultrasound image guidance

“…Results on closed-loop position control of paramagnetic microparticles under ultrasound guidance have also been previously reported [9]. Nonetheless, a significantly more challenging type of microrobotic agent is investigated herein, i.e.…”

“…Both, previous and current images are available at the blob analysis block in order to estimate the velocity of the jet. This tracking algorithm mainly differs from previous work with paramagnetic microparticles [9], in which the position of the jet has to be corrected by setting it at the border of the blob. To that end, an intersection point is calculated by exploring the blob image, starting at its centroid, and going along the direction of the velocity vector.…”

“…In the specific case of jets, propulsion is due to the continuous ejection of oxygen bubbles originated from a catalytic reaction on their inner platinum surface (as it will be further detailed in Section II). This mechanism imposes additional constraints to our vision system, with respect to previous work [9]. For example, having to accurately determine the position of the constantly moving jets within the trails of bubbles, and also to robustly handle occlusions due to other jets and/or objects in the ROI.…”

“…1. On average, jets present smaller dimensions than the microparticles employed in [9] (i.e. the former consisting of micro-tubes of about 50 μm L × 5 μm dia., while the latter are micro-spheres of about 100 μm dia.).…”

Precise Localization and Control of Catalytic Janus Micromotors Using Weak Magnetic Fields

“…However, there exist at least three challenges that must be overcome before utilization can be made of Janus micromotors in biomedical applications. These challenges are the precise localization and motion control of the Janus micromotors in 2D and 3D spaces [9], the visualization of these micromotors using a clinical imaging modality [10,11], and their biocompatibility for in vivo applications [12].…”