Abstract
Laparoscopic surgery is a representative operative method of minimally invasive surgery. However, most laparoscopic hand instruments consist of rigid and straight structures, which have serious limitations such as interference by the instruments and limited field of view of the endoscope. To improve the flexibility and dexterity of these instruments, we propose a new concept of a multijoint manipulator using a variable stiffness mechanism. The manipulator uses a magneto-rheological compound (MRC) whose rheological properties can be tuned by an external magnetic field. In this study, we changed the shape of the electromagnet and MRC to improve the performance of the variable stiffness joint we previously fabricated; further, we fabricated a prototype and performed basic evaluation of the joint using this prototype. The MRC was fabricated by mixing carbonyl iron particles and glycerol. The prototype single joint was assembled by combining MRC and electromagnets. The configuration of the joint indicates that it has a closed magnetic circuit. To examine the basic properties of the joint, we conducted preliminary experiments such as elastic modulus measurement and rigidity evaluation. We confirmed that the elastic modulus increased when a magnetic field was applied. The rigidity of the joint was also verified under bending conditions. Our results confirmed that the stiffness of the new joint changed significantly compared with the old joint depending on the presence or absence of a magnetic field, and the performance of the new joint also improved.
Highlights
Laparoscopic surgery is rapidly replacing traditional open surgery because it is less painful, has shorter recovery times, and has better cosmetic results (Li et al, 2014)
Multijoint manipulators can improve the degree of freedom (DOF) of movement in a constrained space and are widely used in the medical field and in search and rescue operations (Singh and Krishna, 2014)
The value of the elastic modulus includes the effect of the elasticity of the silicon casing used in enclosing the magneto-rheological gel (MRG)
Summary
Laparoscopic surgery is rapidly replacing traditional open surgery because it is less painful, has shorter recovery times, and has better cosmetic results (Li et al, 2014). Rigidity Tunable Flexible Joint mechanical restrictions cause internal interferences with other instruments and a limited view of the surgical area. To solve these structural problems, various types of surgical instruments and robots have been developed. Surgical manipulators comprising rigid links and tendon-driven mechanisms are typical structures of flexible surgical devices (Kim et al, 2014; Rosen et al, 2017; Julie et al, 2019) In such types of manipulators, it is difficult to stiffen the arbitrary part of the robot while keeping the distal and the proximal ends floppy (Cianchetti et al, 2014). The manipulator is very complex and expensive because it needs a considerably large automatic system and controller
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