Abstract² In endoscopic surgery, smaller incisions produce good clinical results for patients. Therefore, there is increasing demand for thinner instruments for endoscopic surgery. However, the small size of the end-effectors limits the functionality of the instruments. To solve this problem, we developed a least-incision transformable end-effector (LITE) with a mechanism to transform from a linear shape into a large end-effector after being inserted into the body. However, the linear shape and thus fewer degrees of freedom sometimes makes surgeons use these forceps in an undesirable manner, which can cause complications during surgery. Therefore, this paper proposes a bending mechanism that can be mounted onto forceps that use the LITE mechanism. We conducted in vivo experiments to evaluate the usefulness of this forceps. The developed bending forceps had a diameter of 8 mm with a 1-DOF bending mechanism. This link mechanism is comprised of one joint and two frames and enables the LITE forceps to be bent to one side by 45° upon pulling of a wire. We confirmed that our developed prototype can smoothly perform bending and grasping motions. The grasping force under bending conditions of 0° – 45° was at least 3.8 N. The extent of change in the 45° bending angle was 2.8° ± 0.2° or 19.4° ± 1.2° for loads of 1.96 and 3.92 N, respectively, applied to the tip of the forceps. An in vivo experiment was performed on a pig was under simulated surgery conditions to evaluate the usefulness of the developed prototype. We confirmed that transformation, removal, grasping and bending motions could be performed in vivo. I. INTRODUCTION In endoscopic surgery, smaller incisions bring good clinical results to patients, such as reducing the length of hospital stay and convalescence, reducing postoperative pain, and cosmetic improvements. Therefore, demand for thinner instruments for endoscopic surgery, including single-port surgery (SPS) [1] and needlescopic surgery (NS), has been increasing. However, thinner instruments have smaller end-effectors, which severely limit their functionality. Difficulty with grasping organs and the risk of damage to organs because of sharp tips require surgeons with special skills, patience, and the ability to work under stress. Oshima et al. developed a three-fingered nine-degrees-of-freedom hand whose parts can be inserted through trocars and assembled inside the abdominal cavity [2]-[4]. Thus, the use of larger and more functional devices is possible inside the T. Abe, H. Nakaji and R. Nakamura are with Chiba University, 1-33, Yayoi-cho, Inage-ku, 263-8522 Japan (corresponding author to provide phone: 043-290-3270; fax: 043-290-3934; e-mail: ryoichin@faculty.chiba-u.jp) abdominal cavity. However, the assembly method has drawbacks such as lacking or losing parts. We developed a least-incision transformable end-effector (LITE) mechanism, which transforms form a linear shape into a larger end-effector after being inserted in the body [5][6]. This transformation method not only has no risk of lacking or losing parts but also requires a single hole for trocar, and thus, it is less invasive. We applied this mechanism to grasping forceps. LITE forceps can decrease pressure on the organs because the tip parts are approximately twice as large as conventional forceps with the same diameter. Therefore, the LITE forceps can decrease the difficulty of grasping organs and reduce the risk of damage to organs. However, because of the linear shape and fewer degrees of freedom (DOF), surgeons must sometimes use this forceps in an undesirable manner, which can cause complications during surgery. Another salient problem is that the visibility of the operative field is decreased by the increased size of the tip. To solve these problems, a better bending mechanism was developed in this study to be mounted onto forceps using the LITE mechanism. II. LITE FORCEPS WITH BENDING MECHANISM We designed 1-DOF bending forceps with an 8 mm diameter as the prototype for LITE forceps with a bending mechanism. Fig. 1 shows the proposed transformation procedure. The transformation of the LITE mechanism occurs in a two-step process enabled by pulling two wires mounted on the tip parts of the forceps from outside the abdominal cavity. After the transformation, the width of the tip is 14 mm. A semicircular pipe (10 mm diameter) is used to prevent unintended transformation during insertion or transforming because of the multiple joints in this mechanism and to support the removal action. After the first transformation, the fixing rod is used to prevent breakdown. Fixing after the second transformation is performed by placing the support pipe around the bending joint, as shown in step 5 in Fig. 1. The opening/closing motion of the tip parts is driven by pushing/pulling the grasping rod. A. Bending Mechanism Fig. 2 shows the structure of the developed bending mechanism. A link mechanism exists for one joint and two frames; this enables the forceps to be bent to one side by 45° upon pulling of the wire. In the LITE mechanism, because the fixing rod and grasping rod run through inner frames (Fig. Development of the Bending Mechanism for Forceps with Least-Incision Transformable End-Effector Mechanism for Endoscopic Surgery: Development of the Operating Interface and In Vivo Experiment T. Abe, H. Nakaji, and R. Nakamura The Fourth IEEE RAS/EMBS International Conference on Biomedical Robotics and Biomechatronics Roma, Italy. June 24-27, 2012 978-1-4577-1198-5/12/$26.00 ©2012 IEEE 919