Giada Gerboni

STIFF-FLOP surgical manipulator: Mechanical design and experimental characterization of the single module

This paper presents the concept design, the fabrication and the experimental characterization of a unit of a modular manipulator for minimal access surgery. Traditional surgical manipulators are usually based on metallic steerable needles, tendon driven mechanisms or articulated motorized links. In this work the main idea is to combine flexible fluidic actuators enabling omnidirectional bending and elongation capability and the granular jamming phenomenon to implement a selective stiffness changing. The proposed manipulator is based on a series of identical modules, each one consisting of a silicone tube with pneumatic chambers for allowing 3D motion and one central channel for the implementation of the granular jamming phenomenon for stiffening. The silicone is covered by a novel bellows-shaped braided structure maximizing the bending still limiting lateral expansion. In this paper one single module is tested in terms of bending range, elongation capability, generated forces and stiffness changing.

Magnetic Torsion Spring Mechanism for a Wireless Biopsy Capsule

The authors present a novel magnetomechanical elastic element that can be loaded remotely by varying the magnetic field surrounding it and that is able to store and release mechanical energy upon external triggering. The magnetic torsion spring (MTS) is used as the core component of a self-contained miniature biopsy capsule (9 mm in diameter and 24 mm long) for random tissue sampling in the small bowel. Thanks to the MTS concept, the biopsy mechanism can be loaded wirelessly by a magnetic field applied from outside the body of the patient. At the same time, magnetic coupling guarantees stabilization against the small bowel tissue during sampling. Extreme miniaturization is possible with the proposed approach since no electronics and no power supply are required onboard. [DOI: 10.1115/1.4025185]

A Soft Modular Manipulator for Minimally Invasive Surgery: Design and Characterization of a Single Module

This paper presents the concept design of a modular soft manipulator for minimally invasive surgery. Unlike traditional surgical manipulators based on metallic steerable needles, tendon-driven mechanisms, or articulated motorized links, we combine flexible fluidic actuators to obtain multidirectional bending and elongation with a variable stiffness mechanism based on granular jamming. The idea is to develop a manipulator based on a series of modules, each consisting of a silicone matrix with pneumatic chambers for 3-D motion, and one central channel for the integration of granular-jamming-based stiffening mechanism. A bellows-shaped braided structure is used to contain the lateral expansion of the flexible fluidic actuator and to increase its motion range. In this paper, the design and experimental characterization of a single module composed of such a manipulator is presented. Possible applications of the manipulator in the surgical field are discussed.

Tendon-Based Stiffening for a Pneumatically Actuated Soft Manipulator

There is an emerging trend toward soft robotics due to its extended manipulation capabilities compared to traditionally rigid robot links, showing promise for an extended applicability to new areas. However, as a result of the inherent property of soft robotics being less rigid, the ability to control/obtain higher overall stiffness when required is yet to be further explored. In this letter, an innovative design is introduced which allows varying the stiffness of a continuum silicon-based manipulator and proves to have potential for applications in Minimally Invasive Surgery. Inspired by muscular structures occurring in animals such as the octopus, we propose a hybrid and inherently antagonistic actuation scheme. In particular, the octopus makes use of this principle activating two sets of muscles-longitudinal and transverse muscles-thus, being capable of controlling the stiffness of parts of its arm in an antagonistic fashion. Our designed manipulator is pneumatically actuated employing chambers embedded within the robots silicone structure. Tendons incorporated in the structure complement the pneumatic actuation placed inside the manipulators wall to allow variation of overall stiffness. Experiments are carried out by applying an external force in different configurations while changing the stiffness by means of the two actuation mechanisms. Our test results show that dual, antagonistic actuation increases the load bearing capabilities for soft continuum manipulators and thus their range of applications.

Magnetic Mechanism for Wireless Capsule Biopsy

One of the main diagnostic limitations of current gastrointestinal (GI) capsule endoscopes is that they cannot get biopsies, thus requiring follow-up with flexible endoscopy whenever a suspicious lesion is identified. The ability of getting biopsies from a wireless capsule would save time and costs associated with the procedure, reducing at the same time invasiveness and discomfort for the patient. The Crosby capsule, designed in 1957, exploits a small tether to suck tissue, to activate spring-loaded knife and to manage device retrieval. However, invasiveness of the procedure is still relevant and requires sedation [1]. Two compact mechanisms have been recently proposed for wireless biopsy. The first takes advantage of a spring actuated rotational razor [2], while the second exploits Shape Memory Alloy (SMA) to actuate a micro-biopsy spike [3]. Due to the harsh environment of the GI tract and the absence of stabilization during sampling, both these devices have a limited efficacy. In order to improve efficacy while reducing capsule size, we propose a completely magneto-mechanical mechanism which does not require onboard batteries and actuators.

Feedback Control of Soft Robot Actuators via Commercial Flex Bend Sensors

Soft robotics is an emerging field that takes advantage of compliant materials and makes use of nonstandard actuators. Flexible fluid actuators (FFAs) use fluid pressure to produce high deformation of elastomeric-based structures. However, closed-loop control of such actuators is still very challenging due to the lack of robust, reliable, and inexpensive sensors that can be integrated onto highly deformable actuator structures, involving very low cost materials and manufacturing. This paper presents a systematic approach to implement the feedback control of FFA-based soft robotic bending modules by using commercial flex bend sensors. A flex bend sensor detects the module curvature in one direction, and its response is processed by an on board microcontroller and sent to the central control system. Such sensor integration enables the closed-loop control of modular robotic architectures, often used in soft robotics. Once integrated with the soft module, the sensor response was calibrated by the use of a ground truth electro-magnetic tracking system in order to characterize its behavior when combined with the relative FFA. A feedback control using a low-pass filter and a proportional-integral controller was designed and used to evaluate the dynamic response and the position accuracy of the integrated module. With such closed-loop control, the module tip is positioned with less than 1 mm accuracy, which can be considered a relevant result in the soft robotics field.

Attaining high bending stiffness by full actuation in steerable minimally invasive surgical instruments

Abstract Introduction: Steerable instruments are a promising trend in minimally invasive surgery (MIS), due to their manoeuvring capabilities enabling reaching over obstacles. Despite the great number of steerable joint designs, currently available steerable tips tend to be vulnerable to external loading, thus featuring low bending stiffness. This work aims to provide empirical evidence that the bending stiffness can be considerably increased by using fully actuated joint constructions, enabling left/right and up/down tip rotations with the minimum of two degrees of freedom (DOF), rather than conventional underactuated constructions enabling these rotations with more than two DOF. Material and methods: A steerable MIS instrument prototype with a fully actuated joint construction was compared to state-of-the-art underactuated steerable instruments in a number of tip deflection experiments. The tip deflections due to loading were measured by means of a universal testing machine in four bending scenarios: straight and bent over 20°, 40° and 60°. Results and conclusions: The experimental results support the claim that a fully actuated joint construction exhibits a significantly larger bending stiffness than an underactuated joint construction. Furthermore, it was shown that the underactuated instrument tips show a considerable difference between their neutral positions before and after loading, which could also be greatly minimised by full actuation.

A novel linear elastic actuator for minimally invasive surgery: development of a surgical gripper

Minimally invasive surgery (MIS) applications require lightweight actuators that can generate a high force in a limited volume. Among pressure driven actuators, fluid elastic actuators demonstrate high potential for use in the medical field. They are characterized by nearly no friction and wear and they can be made of low-cost biocompatible elastomers. However, when compared to traditional piston-cylinder fluid actuators, fluid elastic actuators often result in smaller output forces as well as weaker return forces. This work is about the design of a linear elastic actuator (LEA) which is able to develop relevant pulling-pushing force in one direction. The LEA is composed of entirely disposable materials and it requires a simple manufacturing process. Thanks to its design, the LEA can be compared to traditional piston-cylinders actuators in terms of output forces (up to 7 N) with the advantage of using relative low working pressures (0, 2 MPa). The actuator has been used for the actuation of a gripper for MIS, as a case study. The whole range of gripping forces developed by the tool actated by the LEA has been evaluated, thus verifying that the gripping device, is able to meet the force requirements for accomplishing typical surgical tasks.

Highly dexterous 2-module soft robot for intra-organ navigation in minimally invasive surgery

For some surgical interventions, like the Total Mesorectal Excision (TME), traditional laparoscopes lack the flexibility to safely maneuver and reach difficult surgical targets. This paper answers this need through designing, fabricating and modelling a highly dexterous 2‐module soft robot for minimally invasive surgery (MIS).

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° 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%.