Design and control of in-vivo magnetic microrobots

Versatile microrobotics using simple modular subunits

The realization of reconfigurable modular microrobots could aid drug delivery and microsurgery by allowing a single system to navigate diverse environments and perform multiple tasks. So far, microrobotic systems are limited by insufficient versatility; for instance, helical shapes commonly used for magnetic swimmers cannot effectively assemble and disassemble into different size and shapes. Here by using microswimmers with simple geometries constructed of spherical particles, we show how magnetohydrodynamics can be used to assemble and disassemble modular microrobots with different physical characteristics. We develop a mechanistic physical model that we use to improve assembly strategies. Furthermore, we experimentally demonstrate the feasibility of dynamically changing the physical properties of microswimmers through assembly and disassembly in a controlled fluidic environment. Finally, we show that different configurations have different swimming properties by examining swimming speed dependence on configuration size.

Small Medical Robot

This chapter describes the development of a small medical robot that remains in the abdominal cavity to monitor sites of medical interest and discusses robot travel operations and specifications. A long, narrow piece of ferromagnetic material was placed inside the robot, and an external magnetic field was used to set the robot in motion. The author developed a prototype robot and conducted experiments in order to verify the proposed concept and the principle of steering the robot. In vivo experiments in rabbits demonstrated that solenoids produce sufficient magnetic force to enable the robot to travel through the abdominal cavity, verifying the motion principles. The experiments also confirmed the appropriate shape of the robot, and friction between the robot and the organs and abdominal wall was measured. A modified prototype of the robot was then used to conduct clinical experiments in the rabbit model; a surgeon operated the XYZ axis stages in order to adjust the position of the subject for the experiment and moved the robot to the liver. Robot travel from the insertion point to the liver was verified on X-rays. The long distance was possible due to the improved shape and the use of accurate magnetic field imaging.

Medical and technical protocol for automatic navigation of a wireless device in the carotid artery of a living swine using a standard clinical MRI system

A 1.5 mm magnetic sphere was navigated automatically inside the carotid artery of a living swine. The propulsion force, tracking and real-time capabilities of a Magnetic Resonance Imaging (MRI) system were integrated into a closed loop control platform. The sphere was released using an endovascular catheter approach. Specially developed software is responsible for the tracking, propulsion, event timing and closed loop position control in order to follow a 10 roundtrips preplanned trajectory on a distance of 5 cm inside the right carotid artery of the animal. Experimental protocol linking the technical aspects of this in vivo assay is presented. In the context of this demonstration, many challenges which provide insights about concrete issues of future nanomedical interventions and interventional platforms have been identified and addressed.