Improvement of a Tunable Stiffness Organ-Grasping Device by Design of a Wavy-Shaped Beam Structure

Toshihiro Kawase,Takaaki Sugino,Shinya Onogi,Kenji Kawashima,Yoshikazu Nakajima

doi:10.3390/app11104581

Abstract

Tunable stiffness mechanisms can increase the noninvasiveness and stability of organ manipulation in laparoscopic liver resection. We have developed an organ-grasping device using beam-shaped tunable stiffness mechanism. Increasing the change ratio of stiffness will improve the performance of the device by offering high flexibility when adhering to the liver surface and high rigidity during the manipulation of the liver; however, optimal design of the beam has not been investigated. In this study, we investigate the wavy structure shape of the device that enhances the change in the ratio of stiffness. To increase the stiffness in a high-stiffness state, we used principal stress lines in the device to design the edge curve of the wavy shape material in the beams. We also investigated the arrangement of the wavy shape to decrease the stiffness in a low-stiffness state. Simulation using finite element method showed that the change ratio of stiffness was improved up to 13.0 by the new wavy shape arranged with the uniformly thick bottom of the waves.

Highlights

Noninvasive and stable manipulation of organs is important in laparoscopic liver resection
We investigate the shape of the wavy structure in the tunable stiffness organ grasping device that enhance the stiffness gain
To the functionality functionalityofoftunable tunablestiffness stiffness organ-grasping device, develdesigns of the beams used in the device to improve the stiffness gain

Summary

Introduction

Noninvasive and stable manipulation of organs is important in laparoscopic liver resection. The devices make contact with the liver on a small area and may apply large stress on the liver. Some researchers have addressed this issue and have developed mechanical devices to assist the liver manipulation with large contact area. Some devices were developed with multiple suction pads on a rigid [1,2] or soft body [3,4]. Multiple pads should adhere to the liver surface to enlarge the contact area, and the soft body that could follow the shape of liver without a complicated mechanism was more effective. Wire-driven mechanisms have been developed [7,8,9]; these require small and complicated mechanisms, and increase the complexity of the grasping device. To increase the stiffness in a highstiffness state, we design the wavy shape based on principal stress lines in the beams

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Discussion

Conclusion