Kyoungrae Cha

Development of Biomedical Microrobot for Intravascular Therapy

Recently, coronary artery disease such as angina pectoris and myocardial infarction has become the major causes of death. As a method of medical treatment for the disease, the pharmacological approaches and the surgical operations are executed. Especially, percutaneous coronary intervention (PCI) using catheters are the mostly preferred treatment for coronary artery diseases. The PCI technologies are advanced and the various useful devices are developed and utilized. However, some clinical operations such as the treatment of chronic total occlusion (CTO) remain a limitation of PCI and a major challenge. As robot-assisted coronary interventions, this paper proposes the microrobot for the therapy of CTO. The microrobot consists of the functions of position recognition, locomotion and treatment in the blood vessels. The functions of the microrobot can be validated through in-vitro & in-vivo experiments. The innovative technologies and surgical concept using the microrobot are currently being developed.

3-D Locomotive and Drilling Microrobot Using Novel Stationary EMA System

For 3-D locomotion and drilling of a microrobot, we proposed an electromagnetic actuation (EMA) system consisting of three pairs of stationary Helmholtz coils, a pair of stationary Maxwell coils, and a pair of rotating Maxwell coils in the previous research . However, this system could have limited medical applications because of the pair of rotational Maxwell coils. In this paper, we propose a new EMA system with three pairs of stationary Helmholtz coils, a pair of stationary Maxwell coils, and a new locomotive mechanism for the same 3-D locomotion and drilling of the microrobot as achieved by the previously proposed EMA system. For the performance evaluation of the proposed EMA system, we perform a 3-D locomotion and drilling test in a blood vessel phantom. In addition, the two EMA systems are compared to show that the newly proposed EMA system has 440% wider working space and 49% less power consumption than the previous EMA system.

Two-dimensional locomotive permanent magnet using electromagnetic actuation system with two pairs stationary coils

Two-dimensional electromagnetic actuation system (EMA) was developed to manipulate microrobot for the intravascular therapy. This system consists of two pairs of Helmholtz coils and Maxwell coils and a cylindrical type permanent magnet is used as a microrobot. It is verified that the microrobot can move without power line using electromagnetic field. We analyzed this locomotive mechanism of the microrobot using two-dimensional EMA system theoretically and validated the performance of the mechanism by various experiments. The position of the microrobot which is inside of region of interest (ROI) could be recognized by CCD camera. This position information is used for feedback signal, a simple proportional (P) controller is used for this EMA system. The final goal of this paper is to control the micro robot position precisely. Firstly, we demonstrate the autonomous locomotion of the microrobot along a predefined desired path. Secondly, we adopt an applicable joystick system as a master which the operators can use in a real operation and realize the path control of the microrobot.

Positioning of microrobot in a pulsating flow using EMA system

The purpose of this paper is the positioning control of the microrobot in a pulsating flow using electromagnetic actuation (EMA) System. Several types of EMA systems which are 2-dimensional and 3-dimensional locomotion control of microrobot were proposed and studied. Generally, these conventional researches of EMA systems showed the results of locomotion of microrobot in a fluid without flow. However, in the case of test of microrobot in a blood vessel, it is required that the experiments of locomotion should be performed in a pulsating flow like bloodstream. For that reason, we carried out basic locomotion research of the microrobot in the pulsating flow. For this experiment, we used simple 1-dimensional EMA system which consists of a pair of Helmholtz and Maxwell coils, and we set up a vascular simulator which can generate pulsating flow in the vessel phantom. The magnetized microrobot was inserted in the vascular simulator. The electromagnetic force which affects the motion of the microrobot was controlled by regulating input current to EMA system. The input current regulation was performed by considering the magnitude of flow rate and drag force of fluid to the microrobot. To measure the pressure variance of a pulsating flow in the vascular phantom, the pressure transducer was placed in front of the region of interest (ROI) and the control input which compensates the drag force to microrobot was generated by using the transducer signal. In addition, the position of microrobot was acquired through the CMOS camera and the feedback control loop was also implemented for accurate positioning control. The performance of the positioning control was evaluated by in-vitro experiments using vascular simulator. In addition, the feasibility of the position control of the microrobot was also evaluated by in-vivo animal experiments.

Position stabilization of microrobot using pressure signal in pulsating flow of blood vessel

The target of this paper is the pressure sensor based positioning control of the microrobot in a pulsating flow of blood vessel using an electromagnetic actuation (EMA) system. For treatment of these coronary arterial diseases, various type microrobots with a wireless locomotive actuating power using EMA were proposed. However, because the intravascular blood flows have pulsate fluctuating and high pressurized waves, it is estimated that the stable positioning control of the microrobot in the blood vessel was very difficult. In detail, the pulsating blood flow generates the pulse type drag force on the microrobot and the drag force makes the microrobots oscillating motion in the blood vessel. For the accurate positioning control of the microrobot, the pulse type drag force on the microrobot should be compensated. Therefore, for the compensation of the drag force on the microrobot, the pressure transducer in the blood vessel was introduced and the pressure signal of the blood flow was used. Through the pressure sensor based compensation of the drag force, the stabilization of the position of the microrobot could be tested and evaluated.

Electromagnetic actuation methods for intravascular locomotive microrobot

Heart diseases such as angina pectoris and myocardial infarction have been becoming the leading causes of death all over the world in recent years. The pharmacotherapy and the surgical operations have been executed for treating heart problems. The percutaneous coronary intervention (PCI) with catheter is frequently used for the treatment of coronary artery diseases, but the treatment of chronic total occlusion (CTO) is very difficult and challenging operation, since there is no efficient alternative therapy until now. For this reason, the microrobot to improve the intravascular treatment is one of the growing research areas. In this paper, various electromagnetic actuation (EMA) systems to supply driving power for the microrobot were proposed. The performance of the locomotion of microrobot in the 2D and 3D space were validated with in-vitro experiments and also the in-vivo tests were performed for demonstrating the movement of microrobot in the living rabbit.

Three-dimensional Locomotion and Drilling Microrobot Using Electromagnetic Actuation System

In this study, a novel electromagnetic microrobot system with locomotion and drilling functions in threedimensional space was developed. Because of size limitations, the microrobot does not have actuator, battery, and controller. Therefore, an electromagnetic actuation (EMA) system was used to drive the robot. The proposed EMA system consists of three rectangular Helmholtz coil pairs in x-, y- and z-axes and a Maxwell coil pair in the z-axis. The magnetic field generated in the EMA coil system could be controlled by the input current of the EMA coil. Finally, through various experiments, the locomotion and drilling performances of the proposed EMA microrobot system were verified.