Abstract
Analytical and finite element methods are employed to determine the contact pressure on the surface of a tissue being grasped by an endoscopic grasper, in Minimally Invasive Surgery (MIS). Normally, an endoscopic grasper is corrugated (teeth-like) in order to grasp slippery tissues. It is highly important to avoid damage to the tissues while grasping and manipulation during endoscopic surgery. Therefore, it is essential to determine the exact contact pressure on the surface of the tissue. To this end, initially a comprehensive closed form, finite element and experimental analysis of grasping contact pressure on viscoelastic materials which have similar properties as that of biological tissues is studied. The behavior of a grasper with wedge-like teeth, when pressed into a linear viscoelastic material is examined. Initially, a single wedge penetrating into a solid is studied and then is extended to the grasper. The elastic wedge indentation is the basis of the closed form analysis and the effects of time are included in the equations by considering the corresponding integral operator from viscoelastic stress-stain relations. In addition, a finite element analysis is carried out in Ansys-10 software. Finally, the experimental results are presented to validate both analytical and FEM results. The results of this study provide a closed form expression for grasping contact pressure force and contact area along with the variations of stress in tissue obtained through FEM analysis. The variation of contact pressure and the rate of growth of the contact area with time are presented.
Highlights
Invasive surgery (MIS), called endoscopic surgery, is regarded as a powerful technique that facilitates a faster patient recovery [1]
The endoscopic tools have a teeth-like grasper for easy grasping of various slippery tissues
Gray [7] and Fearing [8] employed an array of micro tactile capacitive sensors for use in an endoscopic surgery telemanipulator to test the sensing of organic tissues on a small scale
Summary
Invasive surgery (MIS), called endoscopic surgery, is regarded as a powerful technique that facilitates a faster patient recovery [1]. This surgical device is of great use during manipulation tasks such as grasping the internal organs, gentle load transfer during lifting, suturing and removing tissues [2]. Gray [7] and Fearing [8] employed an array of micro tactile capacitive sensors for use in an endoscopic surgery telemanipulator to test the sensing of organic tissues on a small scale. Bonakdar et al [27,28] recently studied the grasping contact pressure for both elastic and viscoelastic materials with different shapes of graspers analytically. The experimental tests will be carried out to validate our analysis
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