Name: design and fabrication of an elastomeric unit for soft modular robots in minimally invasive surgery
Uploaded: 2015-11-14T14:00:00
Description: Watch this Scientific Journal Video about Design and Fabrication of an Elastomeric Unit for Soft Modular Robots in Minimally Invasive Surgery at JoVE.com

This work was supported by the EC within the framework of the STIFF-FLOP FP7-ICT-2011.2.1 European Project (#287728).

Note: This protocol describes the fabrication phases of a single module, which includes the fluidic chambers, stiffening channel, actuation pipelines and external sheath. The following procedure has to be executed under a fume hood and wearing lab coat and gloves for safety reasons. As previously mentioned, the fabrication process of the elastomeric unit is based on the sequential use of molds designed with CAD software. They are composed of the 13 pieces shown in Figure 2 and listed in Table 1</...

<ol>
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The technique described in this protocol enables the fabrication of a pneumatically actuated soft unit usable for modular compliant structures. Thanks to the design of the molds and their simple assembly, it is possible to fabricate one complete module in about 4 hours with 7 main steps. The process of fabrication involves specific materials, which are easily available, and work should be carried out under a fume hood. An external set up including air valves, air compressor and vacuum pump is necessary to activate the mo...

Recent trends in the medical field are pushing for a reduction in the invasiveness of surgical operations. Minimally Invasive Surgery (MIS) has been successfully improved in the last few years for abdominal operations. MIS procedures are based on the use of tools introduced through four or five access points (trocars) placed on the abdominal wall. In order to reduce the number of trocars, the instruments can be inserted by Single Port Laparoscopy (SPL) or Natural Orifice Translumenal Endoscopic surgery (NOTES)1. These procedures prevent external visible scars, but increase the difficulty for the clinicians in executing the surgery. This limitation is mainly due to the reduced points of access and to the rigid and semi-rigid nature of the instruments, which are not able to avoid or pass around organs2, 3. Dexterity and motility can be improved using articulated and hyper-redundant robots which can cover a wider and more complex workspace, thus enabling a specific target in the body to be reached more easily4, 5, 6 and to work as retraction systems when necessary7. A flexible manipulator can improve tissue compliance, thus making contact safer than by traditional tools.
However, these manipulators often lack stability when the target is reached and generally they cannot control the contact with the surrounding tissues8, 9. Studies on biological structures, such as the octopus arm10 and the elephant trunk11, have recently inspired the design of flexible, deformable and compliant manipulators with a redundant number of Degrees of Freedom (DoFs) and controllable stiffness12. These kinds of devices utilize passive springs, smart materials, pneumatic elements, or tendons13, 14, 15. Generally, manipulators fabricated with soft and flexible materials do not guarantee the generation of high forces.
The STIFF-FLOP (STIFFness controllable Flexible and Learnable manipulator for surgical OPerations) manipulator has been recently presented as a novel surgical device for NOTES and SPL inspired by the octopus&#8217;s capabilities. In order to overcome the limitations of previous soft manipulators, it has a soft body as well as high dexterity, high force and controllable stiffness16.
The architecture of the manipulator is based on a modular approach: multiple units, with the same structure and functionalities, are integrated together. The single unit is shown in Figure 1. It is based on an elastomeric cylinder obtained by a multiphase fabrication. The assembly steps of the mold components and the casting processes enable three empty chambers (for fluidic actuation) and one hollow central channel17 (for housing a granular jamming-based mechanism18) to be embedded. The chambers are placed at 120&#176;, so that their combined inflation produces omnidirectional motion and elongation. In addition an external braided sheath is placed externally to limit the outward radial expansion of the fluidic chambers when pressurized, thus optimizing the effect of the chamber actuation in the module motion (bending and elongation).
The central channel houses a cylindrical device composed of an external membrane filled with granular material. When a vacuum pressure is applied, it changes its elastic properties causing a stiffening which affects the entire module&#8217;s properties.
Motion and stiffness performances are controlled by an external setup including an air compressor and three pressure valves for actuating the chambers and one vacuum pump for activating the vacuum in the stiffening channel. An intuitive user interface allows control of actuation and vacuum pressures inside the module.
This paper details the fabrication process of the single module of this manipulator and reports the most significant results on basic motion capabilities. Considering the modular nature of the device, the assessment of the fabrication and performance of just one single module also enables the results to be extended and to predict the basic behavior of a multi-module manipulator integrating two or more modules.

<table border="0">
	<tbody>
		<tr>
			<td>Ecoflex 00-50 Trial Kit</td>
			<td>SmoothOn</td>
			<td></td>
			<td>Used for the fabrication of the soft unit, combining equal amounts of liquid parts A (the base) and B (the catalyst)</td>
		</tr>
		<tr>
			<td>Latex</td>
			<td>Antichit&#224; Belsito</td>
			<td></td>
			<td>Used for the fabrication of the granular jamming membrane</td>
		</tr>
		<tr>
			<td>Peroxide-Cured Silicone Tubing</td>
			<td>Cole Parmer</td>
			<td>T-06411-59</td>
			<td>Used for actuating the chambers and applying vacuum</td>
		</tr>
		<tr>
			<td>PET expandable braided sleeving</td>
			<td>RS</td>
			<td>408-249</td>
			<td>Used for the fabrication of the external braided sheath</td>
		</tr>
		<tr>
			<td>Silicone Rubber</td>
			<td>Momentive</td>
			<td>127374</td>
			<td>Used to fix the actuation tubes to the module</td>
		</tr>
		<tr>
			<td>Parafilm</td>
			<td>Cole Parmer</td>
			<td>EW-06720-40</td>
			<td>Used to fix the latex membrane to the vacuum tube</td>
		</tr>
		<tr>
			<td>Fume hood Secuflow</td>
			<td>Groupe Waldner</td>
			<td></td>
			<td>Working space</td>
		</tr>
		<tr>
			<td>Precision scale</td>
			<td>KERN EW</td>
			<td></td>
			<td>Used to weight silicone, latex and coffee powder</td>
		</tr>
		<tr>
			<td>Oven/degasser</td>
			<td>Heraeus</td>
			<td></td>
			<td>Used to degass the silicone and reduce its cure time</td>
		</tr>
		<tr>
			<td>Vacuum pump</td>
			<td>DVP Vacuum Technology</td>
			<td></td>
			<td>Used to apply vacuum to the latex membrane</td>
		</tr>
	</tbody>
</table>

design and fabrication of an elastomeric unit for soft modular robots in minimally invasive surgery

In recent years, soft robotics technologies have aroused increasing interest in the medical field due to their intrinsically safe interaction in unstructured environments. At the same time, new procedures and techniques have been developed to reduce the invasiveness of surgical operations. Minimally Invasive Surgery (MIS) has been successfully employed for abdominal interventions, however standard MIS procedures are mainly based on rigid or semi-rigid tools that limit the dexterity of the clinician. This paper presents a soft and high dexterous manipulator for MIS. The manipulator was inspired by the biological capabilities of the octopus arm, and is designed with a modular approach. Each module presents the same functional characteristics, thus achieving high dexterity and versatility when more modules are integrated. The paper details the design, fabrication process and the materials necessary for the development of a single unit, which is fabricated by casting silicone inside specific molds. The result consists in an elastomeric cylinder including three flexible pneumatic actuators that enable elongation and omni-directional bending of the unit. An external braided sheath improves the motion of the module. In the center of each module a granular jamming-based mechanism varies the stiffness of the structure during the tasks. Tests demonstrate that the module is able to bend up to 120&#176; and to elongate up to 66% of the initial length. The module generates a maximum force of 47 N, and its stiffness can increase up to 36%.

The various phases of the fabrication, described in the Protocol, are illustrated in Figure 3.
In order to evaluate the effectiveness of the technique and the outcomes of the final prototype, the module was tested in different working conditions. An external setup allows control of both the actuation and stiffness of the module. It includes an air compressor that activates three valves. They are connected to the siliconic tubes integrated in the chambers and allow their pressu...

Watch this Scientific Journal Video about Design and Fabrication of an Elastomeric Unit for Soft Modular Robots in Minimally Invasive Surgery at JoVE.com

Design and Fabrication of an Elastomeric Unit for Soft Modular Robots in Minimally Invasive Surgery

This paper describes the design and fabrication of a soft unit for surgical manipulators. The base module includes three flexible fluidic actuators to achieve omnidirectional bending and elongation, and a granular jamming-based mechanism to enable stiffness control. A complete mechanical characterization is also reported.

In recent years, soft robotics technologies have aroused increasing interest in the medical field due to their intrinsically safe interaction in ...

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