Design Innovation Paper

DragonFlex Smart Steerable Laparoscopic Instrument

[+] Author and Article Information
Filip Jelínek

BioMechanical Engineering Department,
Faculty Mechanical, Maritime & Materials Engineering,
Delft University of Technology,
Mekelweg 2,
Delft 2628 CD, Netherlands
e-mail: f.jelinek@tudelft.nl

Rob Pessers

Research & Development Group,
Stork Food & Dairy Systems B.V.,
Deccaweg 32,
Amsterdam 1042 AD, Netherlands
e-mail: rob.pessers@sfds.eu

Paul Breedveld

BioMechanical Engineering Department,
Faculty Mechanical, Maritime & Materials Engineering,
Delft University of Technology,
Mekelweg 2,
Delft 2628 CD, Netherlands
e-mail: p.breedveld@tudelft.nl

Manuscript received January 21, 2013; final manuscript received November 27, 2013; published online January 7, 2014. Assoc. Editor: Carl A. Nelson.

J. Med. Devices 8(1), 015001 (Jan 07, 2014) (9 pages) Paper No: MED-13-1007; doi: 10.1115/1.4026153 History: Received January 21, 2013; Revised November 27, 2013

Despite its success, e.g., in prostatectomy, da Vinci's steerable grasper EndoWrist from Intuitive Surgical has a complex design prone to steel cable fatigue, potential sterilization issues and high associated costs, all of which insinuate a need for an alternative. The aim of this paper is to demonstrate a design of a structurally simple handheld steerable laparoscopic grasping forceps free from cable fatigue, while attaining sufficient bending stiffness for surgery and improving on EndoWrist's maneuverability and dimensions. Having equal joint functionality to EndoWrist, DragonFlex's instrument tip contains only four parts, driven and bound by two cables mechanically fixed in the handle. Two orthogonal planar joints feature an innovative rolling link mechanism allowing the cables to follow circular arc profiles of a diameter 1.5 times larger than the width of the instrument shaft. Besides maximizing the cable lifespan, the rolling link was designed to equalize the force requirements on both cables throughout joint rotation, making the handling fluid and effortless. The smart joint design and stacked instrument construction enable control of seven degrees of freedom by only two cables and seven instrument components in tip, shaft and handgrip altogether. Two DragonFlex prototypes were developed by means of additive manufacturing technology, allowing grasping and omnidirectional steering over ±90 deg, exhibiting promisingly high bending stiffness and featuring extreme simplicity at 5 mm dimensions. DragonFlex concept sheds new light on the possibilities of additive manufacturing of surgical instruments, allowing for a feature-packed design, simple assembly, suitability for disposable use and potential MRI compatibility.

Copyright © 2014 by ASME
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Fig. 1

(a) Rigid [6] and steerable [7] laparoscopic instruments; (b) rigid instrument DOF [8]; and (c) additional steerable tip DOF

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Fig. 2

(a) Close-up of one of the EndoWrist's tips, Pericardial Dissector [15]; (b) impression of the EndoWrist's exploded view showing pulleys and driving cables [5], based on the original patent by Madhani and Salisbury [10]

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Fig. 3

Cable-ring mechanism-based Multi-Flex prototype [7,23,25] featuring a fully actuated ten DOF tip (excluding tip function), developed within the BITE-group of BioMechanical Engineering Dept., TU Delft, Delft, Netherlands

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Fig. 4

(a) Two generic cable driven joint elements with no cable support; once axisymmetric arced guides (c) are implemented, the cable bending radius RA is far superior to the pulley's radius RP (b) at a given element width W

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Fig. 5

(a) Hinge concept showing cables supported by inner and outer guides at CW and CCW bends; (b) hinge element, of width W, featuring four guides, of equal radius RB, with inner guides running along arc angle α

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Fig. 6

Improved rolling joint concept, of radius RR and angle γ, with cable moment arms A mutually equal at 0 deg and ±90 deg

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Fig. 7

Unless the cable moments arms are equalized, they may differ considerably depending on the cable guide constraints; at the extremes defined by inner and outer guide tangency, the moment arms B and C can differ by factors 2.2 and 1.3, respectively

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Fig. 8

In the optimized 5 mm wide joint design, the inner and outer cable moment arms change slightly during rotation, by 0.35 mm; nevertheless their mutual length difference is negligibly small: on average 0.084 mm and 0.16 mm at its maximum

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Fig. 9

Gears were incorporated in the rolling joint design to resist tangent forces and prevent slippage. Their pitch diameter exactly follows the arced rolling surfaces to prevent tooth jamming once radial forces are applied.

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Fig. 10

(a) Apart from translation along x and y axes, the rolling joint needs to resist two additional rotational DOF (x-z and y-z planes) and one translational DOF (z axis); (b) a protrusion was added to help allow only one required rotational DOF (x-y plane)

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Fig. 11

Three DOF grasper design showing the jaw flaps and the looped driving cables

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Fig. 12

Cables are smoothly guided along the instrument and enable parallelogram motion

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Fig. 13

(a) Upscaled plastic DragonFlex prototype demonstrating tip opening and pivoting in two DOF; (b) close-up picture highlighting the striking size difference between the 5 mm and 15 mm thick prototype tips

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Fig. 14

(a) Real-scale DragonFlex prototype components 3D-printed from a ceramic-filled epoxy resin; (b) individual solidified components after the printing process (courtesy of TNO)

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Fig. 15

(a) Real-scale ceramic DragonFlex prototype allowing seven DOF control by only seven structural components; (b) close-up on the tip showing joint and jaw actuation by Dyneema cables




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