A multifunctional magnetic catheter robot (MCR) is proposed in this paper to treat occlusive vascular disease by generating steering, tunneling, and stent delivery motions. Using external magnetic fields generated by a closed-loop magnetic navigation system, the MCR can be manipulated remotely and can generate each motion by magnetic manipulation methods. The MCR has novel structures with a magnetic joint and tension springs for selective stent delivery. Constraints and a dynamic model were derived to specify the manipulation conditions for the selective treatment motions and design parameters of the MCR. Then, the MCR was prototyped, and the steering, tunneling, and stent delivery motions were verified by several experiments. Finally, an in vitro experiment with a pseudo blood clot was conducted to demonstrate the effectiveness of the MCR and its motions for the treatment of occlusive vascular disease.

Magnetic milli/microrobots and magnetic navigation systems have been widely investigated for medical applications due to their advantages of generating torque and force remotely and the simple mechanical structure of magnetic robots. However, there are very few cases that have been commercialized because of the limitations of conventional magnetic navigation systems (e.g., heavy weight, bulky structures, and limited compatibility with other medical devices). In this article, we propose a novel concept of a robotically adjustable magnetic navigation (RAMAN) system, which can adjust the size and position of its workspace using a robotic stage. We developed the concept and structure of the system to overcome the conventional limitations and then developed an optimization method to maximize the magnetic performance of the system. Several experiments were conducted to evaluate the performance of the RAMAN system and verify the control methods. According to the results, the RAMAN system, weight of just 910 kg, can generate a magnetic field within its workspace from 13.5 to 120 mT and adjust the height of the workspace from 200 to 400 mm. Finally, the effectiveness of the system was validated by manipulating the tethered magnetic robot in a planar open space and an artificial vascular environment.

We developed an integrated magnetic robot (IMR) that can selectively separate and assemble tethered and untethered magnetic robots. The proposed IMR is composed of a flexible-legged untethered magnetic robot (FLUMR) and a delivery catheter. Assembled magnets (AMs) with zero net magnetic moment are placed at the distal tip of the catheter and the rear part of the FLUMR. A selective separating and assembling (SSA) mechanism was proposed that can control the separating and assembling motion by an external magnetic field (EMF) to generate relative rotational movements between the catheter and FLUMR by selectively producing the attractive and repulsive forces between AMs. Finally, the IMR was prototyped to verify the SSA mechanism, and the separation, mobility, drilling, and retrieval of the developed IMR using SSA mechanism was verified in in vitro experiments.

We have proposed a novel image-based feedback control method to enhance the path-following capability for position and orientation of a magnetic catheter at its distal part. The proposed control method uses only a navigation status of the magnetic catheter for manipulation without utilizing complex analytical models. By comparing the positions of two markers of the magnetic catheter relative to a predefined path, we classify the navigation status of the magnetic catheter into four cases and determine the external magnetic field and feeding velocity according to a proposed control algorithm. Finally, we conduct a path-following experiment in an environment with multiple branches to verify the improved position and minimization of the orientation error regarding the path-following capability of the proposed control method.

We developed a magnetic catheter with enhanced steering ability of the distal end by utilizing magnets with optimized magnetization directions. The proposed magnetic catheter is composed of a flexible tube and three-ring magnets that enable the magnetic catheter to be steered by controlling external magnetic fields. We analyzed the curvature of the magnetic catheter’s distal end and the vertical displacement of the magnetic catheter’s proximal end with a mathematical model using the Euler-Bernoulli beam theory, and then determined the optimal magnetization direction of each magnet. Finally, we prototyped the magnetic catheter with optimized magnetization directions and conducted several experiments to verify its effectiveness.

We developed a crawling magnetic robot (CMR), which can stably navigate and perform biopsies remotely in tubular environments by controlling a magnetic field. The CMR is composed of a crawling part and a biopsy part. The crawling part allows the CMR to crawl forward and backward via an asymmetric friction force generated by an external precessional magnetic field. The biopsy part closes or opens the cover of a needle to use the biopsy needle selectively with the control of the external precessional magnetic field. The cover of the biopsy part prevents damage to the tubular environments because the biopsy needle is inside the cover while the CMR is navigating. We developed the design of the proposed CMR using magnetic torque constraints and a magnetic force constraint, and then we fabricated the CMR with three-dimensional printing technology. Finally, we conducted an experiment to measure the CMR’s puncturing force with a load cell and conducted an experiment in a Y-shaped watery glass tube with pseudo-tissue to verify the crawling motion, the uncovering and covering motion of the biopsy needle, and the CMR’s ability to extract tissue with the biopsy needle.