A variable stiffness mechanism for steerable percutaneous instruments: integration in a needle.

Needles are advanced tools commonly used in minimally invasive medical procedures. The accurate manoeuvrability of flexible needles through soft tissues is strongly determined by variations in tissue stiffness, which affects the needle-tissue interaction and thus causes needle deflection. This work presents a variable stiffness mechanism for percutaneous needles capable of compensating for variations in tissue stiffness and undesirable trajectory changes. It is composed of compliant segments and rigid plates alternately connected in series and longitudinally crossed by four cables. The tensioning of the cables allows the omnidirectional steering of the tip and the stiffness tuning of the needle. The mechanism was tested separately under different working conditions, demonstrating a capability to exert up to 3.6 N. Afterwards, the mechanism was integrated into a needle, and the overall device was tested in gelatine phantoms simulating the stiffness of biological tissues. The needle demonstrated the capability to vary deflection (from 11.6 to 4.4 mm) and adapt to the inhomogeneity of the phantoms (from 21 to 80 kPa) depending on the activation of the variable stiffness mechanism. Graphical abstract ᅟ.

A soft multi-module manipulator with variable stiffness for minimally invasive surgery.

This work presents a soft manipulator for minimally invasive surgery inspired by the biological capabilities of the octopus arm. The multi-module arm is composed of three identical units, which are able to move thanks to embedded fluidic actuators that allow omnidirectional bending and elongation, typical movements of the octopus. The use of soft materials makes the arm safe, adaptable and compliant with tissues. In addition, a granular jamming-based stiffening mechanism is integrated in each module with the aim of tuning the stiffness of the manipulator and controlling the interactions with biological structures. A miniaturized camera and a pneumatic gripper have been purposely designed and integrated on the tip of the manipulator making it usable in real working conditions. This work reports the design and the fabrication process of the manipulator, the theoretical and experimental evaluation of the stiffness and the analysis of the motion workspace. Finally, pick and place tests with the fully integrated system are shown.

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%.

An integrated system for wireless capsule endoscopy in a liquid-distended stomach.

The design and development of a functional integrated system for gastroscopy is reported in this paper. The device takes advantage of four propellers enabling locomotion in a liquid environment and generating a maximum propulsive force of 25.5 mN. The capsule has been equipped with a miniaturized wireless vision system that acquires images with a frame rate of 30 fps (frames per second). The overall size of the capsule is 32 mm in length and 22 mm in diameter, with the possibility of decreasing the diameter to swallowable dimensions. The capsule is remotely controlled by the user who can intuitively drive the device by looking at the video streaming on the graphical interface. The average speed of the device is 1.5 cm/s that allows for a fine control of the capsule motion as demonstrated in experimental tasks consisting of passing through circular targets. The video system performances have been characterized by evaluating the contrast, the focus, and the capability of acquiring and perceiving different colors. The usability of the device has been tested on bench and on explanted tissues by three users in real time target-identification tasks, in order to assess the success of the integration process. The lifetime of the capsule with active motors and vision system is 13 min, that is, a timeframe consistent with traditional gastroscopic examinations.