Abstract— For the actuation of a swimming microrobot, various types of electromagnetic actuation (EMA) systems were proposed. Compared with a conventional actuation system using an electric motor or shape memory alloy (SMA), EMA system has many advantages for a wireless actuation of a microrobot. This paper introduces a biomimetic swimming tadpole microrobot. The developed microrobot could be driven by an external uniform magnet field using 3-pairs of Helmholtz coils. The swimming microrobot consists of a buoyant body, NdFeB magnets, and silicone fin. Especially, the tadpole swimming microrobot has a single silicone fin which is directly linked to the NdFeB magnet. The external alternating magnetic field from 3- pairs of Helmholtz coils could generate the propulsion and steering force of the tadpole microrobot in 3-dimensional (D) space. The proposed swimming tadpole microrobot can be used in medical areas such as a capsule endoscope and drug delivery system. I. INTRODUCTION ECENTLY, interest in biomedical microrobots has increased worldwide. Because a microrobot can be very small, it can be used as a biomedical robot for minimally invasive surgery (MIS), diagnosis and drug delivery [1-4]. Since only a small incision needs to be made in MIS using a microrobot, the risk of infection is minimized and recovery time reduced. However, the size limitation of a microrobot makes it difficult to include certain components, such as a power source, actuator, and control board. To overcome this limitation, the actuation of microrobot using external magnetic fields has been investigated [2]. B. J. Nelson group proposed an artificial bacterial flagella (ABF) locomotive microrobot that mimics bacterial flagella * This research was supported by the Industrial Strategic Technology Development Program (10030037, CTO Therapeutic System) funded by the Ministry of Trade. Industry and Energy (MOTIE, Korea), and by Basic Science Research Program (2013025579) through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (MEST)". Hyunchul Choi, Cheong Lee, Gwangjun Go, and Seong Young Ko are with the School of Mechanical Engineering, Chonnam National University, Gwangju, 500-757, Korea (e-mail: anubis_jjang@hanmail.net, vdkqydh@naver.com, gwangjun124@gmail.com and sko@jnu.ac.kr) Semi Jeong and Kiduk Kwon are with Robot Research Initiative, Chonnam National University, Gwangju, 500-757, Korea (e-mail: semi@jnu.ac.kr and kdkwon@jnu.ac.kr). Jong-Oh Park and Sukho Park are with School of Mechanical Engineering, Chonnam National University, Gwangju 500-757, Korea (corresponding author phone: 82-62-530-1687; fax: 82-62-530-0267; e-mail: jop@jnu.ac.kr and spark@jnu.ac.kr). motion and is propelled by the rotational motion of the flagella in fluid [3]. The microrobot consists of a soft magnetic head and a spiral tail. The soft magnetic head rotates via an external rotational magnetic field control, and the spiral tail changes the rotational force into the propulsion force. In addition, for efficient locomotion in a fluid environment, biomimetic swimming robots, such as the fish robot, the jellyfish robot, and the tadpole robot, have been proposed [5-13]. Swimming microrobots using smart actuators, such as ionic polymer metal composites (IPMC), shape memory alloys (SMA), and piezoelectric (PZT) actuators, have also been developed. However, a smart actuator requires the integration of a battery into the wireless robot body. Therefore, it is very difficult to miniaturize the swimming microrobot. Swimming microrobots using electromagnetic fields have also been proposed [14-16]. The magnetic fields can be changed by the coil currents, and the swimming microrobot can be controlled by variations in the magnetic fields. However, almost previously proposed swimming microrobot can only move in solenoid coil or the 2D plane. This paper proposes a 3D swimming tadpole microrobot using 3-pairs of orthogonally Helmholtz coils. The 3D swimming tadpole microrobot has buoyant body, NdFeB magnets, and silicone fin. We demonstrate the 3D swimming locomotion of the tadpole microrobot with the designed actuation mechanism in a 3D water environment. First, we explain the electromagnetic actuation system. Second, we explain the actuation mechanism and design of 3D swimming tadpole microrobot. Finally, the locomotive performance of the 3D swimming tadpole microrobot is evaluated and demonstrated. II. ELECTRO MAGNETIC ACTUATION SYSTEM A. Theory of Helmholtz Coil Magnetic torque applied to a microrobot composed of a magnetic material in a magnetic field can be expressed by the following equations [14]: H M V T      0  (1) Biomimetic Swimming Tadpole Microrobot using 3-pairs Helmholtz Coils Hyunchul Choi, Semi Jeong, Cheong Lee, Gwangjun Go, Kiduk Kwon, Seong Young Ko, Jong-Oh Park* and Sukho Park*, Member, IEEE R 2014 5th IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob) August 12-15, 2014. São Paulo, Brazil 978-1-4799-3127-9/6/14/$31.00 ©2014 IEEE 841