Variable stiffness catheter for surgical applications, system for remote magnetic navigation surgical approach and method for manufacturing said catheter

Abstract

The present invention concerns a variable stiffness catheter (1) for surgical applications, a system (2) and a method for manufacturing said catheter, wherein said catheter (1) comprises at least one soft biocompatible hollow sleeve (S) and further including: - a tip sealing cap (10) at a distal end, - a working channel (15) enclosed within said sleeve (S) and extending from a proximal end to said distal end, for applying a treatment outside the catheter (1), through said tip sealing cap (10), - a plurality of fibers (F) enclosed within said sleeve (S), - an inlet attachable to a source (SV) of vacuum or pressure for applying vacuum or pressure inside said sleeve (S), said fibers (F) being assembled in at least one bundle such that applying vacuum inside said sleeve (S) induces fiber jamming resulting in a stiffening from a soft state to a stiff state.

Description

Variable stiffness catheter for surgical applications, system for remote magnetic navigation surgical approach and method for manufacturing said catheterField of the invention

[0001] The present invention relates to the field of surgery and in particular to catheters used for minimally-invasive approaches. The invention concerns various surgical applications, such as the cardiac and / or vascular or neurovascular or endoscopic applications, for example.Background of the invention

[0002] Minimally invasive surgery (MIS), such as cardiac ablation for treating arrhythmia, aims to deliver safer procedures with minimized lesions, reduced infection risks, improved surgical outcomes and shorter recovery times. Miniature surgical instruments with dexterous motion capabilities, called catheters, are used in MISs. Such a surgery can be performed either manually or remotely using a novel remote magnetic navigation (RMN) system. For example, documents EP3053625, US 6524303 and W00207794 disclose catheters for RMN approach by using at least one magnetic field, for example generated by electromagnetic generators disposed around at least one part of a patient’s body, to induce a displacement of at least one magnetically responsive element mounted on the catheter which is flexible enough to be actuatable by the magnetic field when introduced in the patient’s body for observation and / or applying a treatment. Such systems equipped with a magnetic catheter generates a controllable magnetic field using multiple permanent magnets or electro-magnets surrounding the patient body to steer the magnetic catheter inside the patient during surgical intervention. This allows the motion mechanism to be separated from the catheter, miniaturizing the catheters with simpler structures, enabling remote surgery execution by the doctors without exposure to X-rays during fluoroscopy, and reducing the training burdens on doctors. However, existing magnetic catheters can achieve only uni-curvature bending, limiting their workspace and dexterity. Therefore, many surgical applications are limited by these solutions, for example in regions involved in the cardiac ablation which are challenging to reach by the existing catheters due to the complex anatomy of the human heart.

[0003] A problem for such approaches concerns the control of the flexibility or stiffness of the tool during the surgery for navigating in the patient’s body. To improve the dexterity, researchers developed multi-segment catheters with variable stiffness (VS) capability. Research on VS has revolutionized miniature surgical instruments, including catheters for MISs, enabling advanced capabilities in stiffness modulation, multi -curvaturebending, and force control. For example, the documents US2023071158, US10967154, US9295511 or KR102221309B teach the use of catheters comprising with a filler material thermally deformable. However, such existing VS catheters made of phasechanging materials generally have the drawback of a slow softening and stiffening rates (up to 90 seconds) that lead to significant increase in the surgery duration. Also known in the field are systems, for example as disclosed in documents WO 2023 / 183952, US 2012 / 277729, US20230210351, EP3955982, or CN113924133, using layer or tubular jamming of concentric tubes separated by a gap to which vacuum can be applied so that friction is increased between adjacent tubes and induce stiffening to the device. These tubes (external, internal, and a middle tube in between an external and internal) are fabricated using braided or woven fibers but at least one of the tubes can be smooth or slick, for example at least on the inside walls of the inner tube. These solutions present the drawbacks of being expensive and complex to assemble, by requiring several tubes, and of limiting the possibility of reducing the size of the device, as well as having stiffness in the soft state which is increased by the fact that several tubes are used, with a global stiffness proportional to the number of tubes.

[0004] These catheters generally comprise one or two segments made using phase-changing materials whose stiffness can be reversibly changed from rigid to soft state by engaging and disengaging a thermal stimulus. Therefore, their segments can be selectively manipulated with sequential stiffening and softening of the corresponding segments to form complex multi -curvature shapes, thereby increasing the reachable and dexterous workspace of the catheters. Several phase-changing materials with low-melting-points have been used in the VS catheters such as the low-melting-point alloy and shape memory polymers, and they have achieved stiffness change factors (SCFs) (the stiffness ratio of the stiff state to the soft state) of at least 20.

[0005] However, despite the high SCFs of these devices, their complete stiffness change cycle from rigid to soft state and vice versa takes a time in the order of the minute (up to 5 minutes for the slowest) due to the slow heating and cooling rates of the materials. As a result, the doctor must wait a few minutes for the next manipulation of the catheter, which substantially prolongs the surgical procedure. In the case of cardiac ablation surgery, which usually involves multiple ablation sites and dozens of ablation points per site, the catheter must be re-positioned many times. With repeated slow heating and cooling processes, the accumulative waiting time can extend to hours when such VS catheters with phase-changing materials are used, compromising the surgical efficiency, increasing the costs and limiting patient access to treatments. In addition, the use of electric power for heating inside the human body imposes a heavy concern for patient safety.

[0006] On the other hand, there are other variable stiffness technologies that do not rely on phase-changing materials and thermal stimuli to trigger their stiffness change such asjamming technologies. They have drawbacks of having sizes and / or absolute stiffnesses ranges too large for being used in surgery, which is a challenging field because of the small dimensions but large deflections required and with a high precision. Moreover, robotic solutions with these VS mechanisms generally have a SCF below three while catheter for surgical applications require an SCF of at least four, for the safety of the patient.

[0007] In this context, there is still a need for efficient variable stiffness catheters of small size, having a fast change of state and a suitable SCF, while limiting the risk for the patient by its high precision and by avoiding the application of heat or power to the patient’s body.Summary of the invention

[0008] One purpose of the present invention is to overcome at least some drawbacks of the prior art by proposing a variable stiffness with fast change of state and with dimensions and SCF compatible with surgical applications, in particular for RMN approach.

[0009] This purpose is reached by a variable stiffness catheter for surgical applications comprising at least one soft biocompatible hollow sleeve and comprising a proximal end for holding the catheter and a distal end for surgical insertion in a patient’s body, said catheter further including: a tip sealing cap at the distal end for closing the catheter, a working channel enclosed within said sleeve and extending through said proximal and distal ends, up to a working end for applying a treatment outside the catheter, through said tip sealing cap, a plurality of fibers enclosed within said sleeve and having a length defining a distal segment of the catheter, an inlet attachable to a source of vacuum or pressure for applying vacuum or pressure inside said distal segment, wherein said fibers are held at only one of their ends and assembled in at least one bundle such that applying vacuum inside said distal segment induces a fiber jamming resulting in a stiffening of this segment, said distal segment thereby having variable stiffness defined by a soft state and a stiff state.

[0010] According to another feature, the catheter further comprises at least one distal magnetically responsive element, called magnet, disposed at said distal segment which is configured for a remote magnetic navigation surgical approach using a standard hospital-compatible remote magnetic navigation System for applying a magnetic field within the recommended magnitude range, by having a stiffness in the soft state allowing it to bend smoothly upon the application of said magnetic field and a stiffnessin the rigid state allowing it to maintain minimal deflection despite the presence or absence of said magnetic field, such that said catheter can be dynamically controlled by varying its shape during remote magnetic navigation in the patient’s body.

[0011] According to another feature, the variable stiffness catheter, further comprising at least one pair of tendons running through at least part of the length, preferably the whole length, of the catheter and connected to a handle comprising buttons for actuating the tendons which are free to translate along the length of the catheter and actuate it by this translation transmitted to the locations where they are fixed to the catheter, such that said catheter can be dynamically controlled by varying its shape during remote magnetic navigation in the patient’s body.

[0012] According to another feature, the catheter further comprises at least one first intermediate sealing cap spaced from the tip sealing cap by a distance equal or larger than the length of the fibers to delimit said distal segment, said inlet comprising a distal pressure channel inside said sleeve and extending from the source of vacuum or pressure to said distal segment, through said first intermediate sealing cap.

[0013] According to another feature, said fibers of the distal segment are held at only one of their ends by said distal and / or first intermediate sealing cap.

[0014] According to another feature, said proximal end is pluggable, in a fluid-tight manner, on a distal end of a standard catheter used for surgery applications, or of a rear tube, which further encloses at least the working channel, such that said standard catheter or rear tube is extended by said variable stiffness catheter and cooperates with said proximal end to form said inlet when connected to said source of vacuum or pressure.

[0015] According to another feature, for supporting the actuation of the catheter by the magnetic field, said inlet comprises at least one supporting rod and / or co-operates with said distal end of said standard catheter or rear tube which has a stiffness higher than the stiffness of said variable stiffness catheter at least in its soft state.

[0016] According to another feature, the catheter further comprises: a plurality of fibers enclosed within said sleeve and extending between said first intermediate sealing cap and said proximal end and having a length defining a first intermediate segment of the catheter, an intermediate inlet attachable to a source of vacuum or pressure for applying vacuum or pressure inside said first intermediate segment, wherein

[0017] said fibers are assembled in at least one bundle such that applying vacuum inside said first intermediate segment induces a fiber jamming resulting in a stiffening of this segment, said first intermediate segment thereby having variable stiffness defined by a soft state and a stiff state.

[0018] According to another feature, said first intermediate sealing cap comprises at least one intermediate magnetically responsive element, called magnet, said first intermediate segment being configured for a remote magnetic navigation surgical approach using a standard hospital-compatible remote magnetic navigation System for applying a magnetic field within the recommended magnitude range, by having a stiffness in the soft state allowing it to bend smoothly upon the application of said magnetic field and a stiffness in the rigid state allowing it to limit its deflection despite the presence or absence of said magnetic field, such that said catheter can be dynamically controlled by varying its shape during remote magnetic navigation in the patient’s body.

[0019] According to another feature, the catheter further comprises at least one additional intermediate sealing cap having an intermediate magnet and spaced from said first intermediate sealing cap by a distance equal or larger than the length of fibers enclosed therein and delimiting an additional intermediate segment also enclosing fibers, said inlet comprising a distal pressure channel and an intermediate pressure channel, inside said sleeve, and ex-tending from the source of vacuum or pressure to said distal segment and said first inter-mediate segment, respectively, through the respective intermediate sealing caps.

[0020] According to another feature, said first intermediate sealing cap and / or said additional intermediate sealing cap comprises an intermediate magnet for actuation by said magnetic field or a fixation for a tendon connected to a handle at the proximal end of the catheter and comprising buttons for impeding a translation movement to the tendon, such that said intermediate segments of the catheter can be dynamically controlled by varying its shape during remote magnetic navigation in the patient’s body.

[0021] According to another feature, said fibers of said first intermediate segment are held at only one of their ends by said first intermediate and / or additional intermediate sealing cap.

[0022] According to another feature, the various segments include fibers of different materials having different bending moments and stiffnesses when submitted to vacuum.

[0023] According to another feature, said at least one bundle comprises fibers of only one material or comprises a mix of fibers of different materials.

[0024] According to another feature, the ratio of the stiffness in the rigid state by the stiffness in the soft state defines a factor, called stiffness change factor, the segment or segments of the catheter having a factor of at least three, preferably four or more, to be suitable for a safe navigation upon application of a magnetic field within the recommended magnitude range by a deflection of less than fourth in the rigid state compared to the soft state.

[0025] According to another feature, the stiffness in the rigid state limits the deflection of a segment such that the magnitude of the magnetic field required for a small deflection is higher than the magnitude inducing a large deflection in the soft state.

[0026] According to another feature, the material and / or diameter of the fibers and / or the number of fibers in a segment are adjusted for said remote magnetic navigation surgical approach, generally according to the size of the magnet and the material and diameters of the sleeve.

[0027] According to another feature, the stiffness in the soft state is comprised between 15 and 175 mN / mm, preferably between 50 and 100 mN / mm or preferably at least lower than 100 mN / mm.

[0028] According to another feature, the stiffness in the rigid state is comprised between 50 and 750 mN / mm, preferably between 250 and 500 mN / mm or preferably at least higher than 250 mN / mm.

[0029] According to another feature, the material and / or diameter of the fibers (F) and / or the number of fibers (F) in a segment (SI, S2, S3 and the material and diameters of the sleeve (S) are configured to be adjusted for a magnetic or mechanical navigation surgical approach by having a stiffness in the rigid state limiting the deflection of a segment (SI, S2, S3) such that the magnitude of the magnetic field or of the applied mechanical force to the tendons via a handle, required for a small deflection is higher than the magnitude of the magnetic field or applied mechanical force to the tendons via handle inducing a large deflection in the soft state.

[0030] According to another feature, the fibers have a diameter comprised between 5 and 160 pm, preferably between 50 to 150 pm or at least smaller than 145pm.

[0031] According to another feature, the segments have a length comprised between 30 and 100 mm, preferably 50 to 60 mm.

[0032] According to another feature, the outer diameter of the sleeve is comprised between 0,3 and 3 mm, preferably 0,5 to 2 mm, with an inner diameter preferably larger than 75% of the outer diameter.

[0033] According to another feature, the number of fibers in a segment is comprised between 50 to 10000, preferably more than 100.

[0034] According to another feature, said working end comprising a working tip, such as an ablation tip for example.

[0035] According to another feature, at least one of said distal magnet and / or intermediate magnet is / are tubular and included within the material of the sleeve or on the inner or outer surface of the sleeve.

[0036] According to another feature, at least one of said intermediate sealing caps includes a rigid supporting rod, preferably in carbon fiber, for limiting the risks of buckling at the junction between the segments during actuation of the catheter.

[0037] According to another feature, said catheter comprises a single soft biocompatible sleeve along its whole length or several individual sleeves, one for each segment.

[0038] Another purpose of the present invention is also to overcome at least some drawbacks of the prior art by proposing a system for surgical applications using an RMN approach.

[0039] This purpose is reached by a system for surgical applications through a remote magnetic navigation surgical approach, said system comprising at least one variable stiffness catheter according to the invention, at least one source of pressure or vacuum and a control unit for controlling the pressure or vacuum applied to at least one segment of said catheter by said source.

[0040] According to another feature, said variable stiffness catheter is a catheter with multiple segments and the control unit dynamically and synergically controls the pressure or vacuum applied to several segments.

[0041] According to another feature, said control unit controls the pressure or vacuum applied in synchronization with a standard hospital-compatible remote magnetic navigation system, for applying a magnetic field, within the recommended magnitude range, to the catheter during different periods of time determined as a function of the periods of time for the application of pressure or vacuum, or vice versa.

[0042] According to another feature, said control unit controls the periods and the values of pressure or vacuum applied to said catheter.

[0043] According to another feature, the system further comprises said remote magnetic navigation system controlling the tridimensional orientation in space and / or the magnitude amplitude of the magnetic field according to the periods and the values of pressure or vacuum applied to said catheter.

[0044] According to another feature, an injection of chemical compounds through the working channel is further controlled by the control unit or by a dedicated device synchronized with the control unit.

[0045] According to another feature, the system further comprises an electromagnetic source con-trolled by the control unit or a dedicated device synchronized with the control unit, for visualizing tissues of the patient and / or applying an electromagnetic treatment at the distal end through the working channel enclosing an electromagnetic conducting medium.

[0046] Another purpose of the present invention is also to overcome at least some drawbacks of the prior art which fails to manufacture VS catheters suitable for precise surgical applications using an RMN approach.

[0047] This purpose is reached by a method for fabricating a variable stiffness catheter according to the present invention, the method comprising:• manufacturing of at least one sleeve with a consistent sleeve wall thickness,• manufacturing of at least one bundle of fibers,• production of the distal segment involving :Insertion of at least one bundle of fibers inside said sleeve using an assistive tube,Insertion of a working channel through the distal segment,- Removal of the assistive tube, creation of the tip sealing cap, preferably by application of glue at the distal end of the distal segment for holding the fibers bundle, and insertion of a magnet at the tip sealing cap.

[0048] According to another feature, the method further comprises :• manufacturing of at least one second sleeve with a consistent sleeve wall thickness,• manufacturing of at least one second bundle of fibers, production of at least one intermediate segment involving : Insertion of a first fiber bundle inside said sleeve using an assistive tube, Insertion of the working channel and a distal pressure channel through the second sleeve,- Removal of the assistive tube,Creation of an intermediate sealing cap, preferably by application of glue at the distal end of the intermediate segment for holding the fibers bundle, preferably internally reinforced by a supporting rod,Insertion of a magnet at the intermediate sealing cap, Assembly, preferably with glue, of the segments co-aligned.

[0049] According to another feature, the fabrication of bundle of fibers comprises a prior fabrication of ultra-thin fibers having a diameter preferably less than 160pm or even between 30 to 100pm.

[0050] According to another feature, the fabrication of a bundle of fibers is performed via a first winding machine which pulls a melted polymer or composite filament through its spinning spool, and by mounting the filament onto a second winding machine which reformats the fibers into a fiber bundle with the desired number of fibers.

[0051] According to another feature, said melted polymer or composite filament is obtained via a 3D printing machine arranged close to said first winding machine directly pulling on the filament during its extrusion.Brief description of the drawings

[0052] Various technical features and advantages of the present invention will appear more clearly by reading the description of various examples of embodiments below, made in reference to the illustrative and non-limiting drawings, among which:

[0053] Figure 1 shows a schematic view of a system (2) for surgical applications through a remote magnetic navigation surgical approach, according to some embodiments;

[0054] Figure 2 shows a partially cut view of a distal end of a VS catheter (1) according to some embodiments;

[0055] Figure 3 shows a partially cut view of a proximal end of a VS catheter (1) according to some embodiments;

[0056] Figure 4 shows a partially cut view of a junction between two segments of a VS catheter (1) according to some embodiments;

[0057] Figure 5 shows a partially transparent view of two segments of a VS catheter (1) according to some embodiments;

[0058] Figure 6 shows a side view of a VS catheter (1) in a straight shape and connected to a vacuum source according to some embodiments;

[0059] Figure 7 shows a side view of the VS catheter (1) of figure 6 but with its distal segment bent upon application of a magnetic field according to some embodiments;

[0060] Figure 8 shows a side view of the VS catheter (1) of figure 6 but with its intermediate segment bent upon application of a magnetic field according to some embodiments;

[0061] Figure 9 shows a side view of the VS catheter (1) of figure 6 but with booth its intermediate and distal segments bent upon application of a magnetic field according to some embodiments;

[0062] Figure 10 shows a schematic view of dipping curing process for producing sleeves of a VS catheter (1) according to some embodiments;

[0063] Figure 11 shows a schematic view of a part of the steps used for manufacturing the intermediate segment of a VS catheter (1) according to some embodiments;

[0064] Figure 12 shows a schematic view of another part of the steps used for manufacturing the intermediate segment of a VS catheter (1) according to some embodiments;

[0065] Figure 13 shows a schematic view of a part of the steps used for manufacturing the distal segment and its assembly to an intermediate segment of a VS catheter (1) according to some embodiments;

[0066] Figure 14 shows a schematic view of another part of the steps used for manufacturing the distal segment to obtain a VS catheter (1) according to some embodiments;

[0067] Figure 15 shows a schematic view of the manufacturing of ultra-thin fibers to be used in a VS catheter (1) according to some embodiments;

[0068] Figure 16 shows a schematic view of the manufacturing of bundles of ultra-thin fibers to be used in a VS catheter (1) according to some embodiments;

[0069] Figure 17A shows a schematic view of a VS catheter (1) comprising three actuatable segments according to some embodiments, and Figures 17B, 17C and 17D show three various embodiments of the bundle of fibers held at only one end of each segment of the catheter;

[0070] Figure 18 illustrates the manufacturing (fabrication) of a single-segment catheter according to some embodiments;

[0071] Figure 19 illustrates the full manufacturing method (fabrication process) of a two- segment catheter according to some embodiments;

[0072] Fig. 20 illustrates examples of characterization of the stiffness and reaction time of the Fiber Jamming in the catheter scale, by varying the material, the diameter and the filling rate of the fibers according to some embodiments and, at the bottom, three different loading scenarios of the catheters;

[0073] Figure 21 illustrates additional Fiber Jamming characterization results by varying the diameter of the fibers and the filing rate of the catheter by the fibers according to some embodiments;Detailed description of embodiments

[0074] The present invention concerns various embodiments of variable stiffness (VS) catheters (1), as well as various embodiments of methods for manufacturing such VS catheter (1) and various embodiments of a system for surgical applications. Preferably, said catheter (1) comprises at least one soft biocompatible hollow sleeve (S) and further including:- a tip sealing cap (10) at a distal end,- a working channel (15) enclosed within said sleeve (S) and extending from a proximal end to said distal end, for applying a treatment outside the catheter (1), through said tip sealing cap (10),- a plurality of fibers (F) enclosed within said sleeve (S),- an inlet attachable to a source (SV) of vacuum or pressure for applying vacuum or pressure inside said sleeve (S), said fibers (F) being assembled in at least one bundle such that applying vacuum inside said sleeve (S) induces fiber jamming resulting in a stiffening from a soft state to a stiff state.

[0075] In some embodiments, the catheter (1) is actuated (bent) using a Remote Magnetic Navigation (RMN) approach while some embodiments use a common technique of tendons actuated by a handle, and a combination of both kinds of actuation is also possible, for example at various portions of the catheter along it entire length. The catheter is generally configured to be steered (e.g., controllably bent or curved), particularly at its distal end regions. Any of these apparatuses may include one or more actuating steering members that are configured to be actually, e.g., from a proximal end of the device, to steer the device. The actuating steering members may be any appropriate steering member, including mechanical steering (e.g., one or more tendons, cables, wires, etc., actuators, etc.), pneumatic steering, magnetic steering, thermal steering (e.g., using a shape memory alloy or shape memory polymers, etc.). The surgical applications are preferably cardiac and / or vascular, but can be of other types, such as endoscopy, otolaryngology, urology, pulmonology or neuro-surgery for example, such that the present invention is not limited to these examples of applications.However, the present invention is particularly advantageous for such applications because of its unrivaled ability to be actuatable in small structures with complex shapes, while limiting the risk of undesired movements in such structures (organs or tissues) of the patient’s body and allowing a minimally-invasive surgical (MIS) approach. In the embodiments comprising tendons, the latter are preferably integrated at the tip (or at any one of the caps or anywhere along the length of the catheter) run through the entire device down to the proximal end, where they are connected to a handle, enabling the user to bend the device, for example via control buttons. This kind of actuation is a common working principle for different devices and the present application thus doesn’t provide further explanation about it, not illustrations in the figures because those of skills in the art will understand that the tendons can run through the device inside any portion as long as they can be actuated for a free translation through the caps up to the distal tip or the furthest cap (or location) to which they are connected. In addition, in some embodiments, the catheter is configured for image capture, for example with an optic fiber system transmitting light from a source to the tip or with a light source at the tip. A camera associated with the catheter and connected to the optic fiber or placed at the tip itself (called a camera-on-a-chip) can thus be used for capturing images. Such cameras connected to a display allow the user to obtain images of the explored structures in real time, as they are captured at the tip of the device.

[0076] In a general manner, the VS catheter (1) is based on fiber jamming (FJ) of individual (distinct) fibers held at only one of their ends or of the ends of the segment, and arranged in a bundle or bundles, wherein the fibers are mainly parallel to each other and run close to each other along a longitudinal axis of the catheter. The term parallel used here should not be interpreted as limiting because the fiber being free and held only at one of their ends, they may have random path diverging from each other. This arrangement of fibers in bundles is advantageous in that it is simple and cheap to manufacture, but also that it allows a great reduction of size of the device, while achieving large changes in stiffness enabling the device to have a high efficiency for the procedures which it is used for, but also that it can undergo rapid stiffness changes (within tens or hundreds of microseconds). By holding the fiber at only one end (of the fibers or of the segment) and preferably arranging the fibers primarily (or mainly or substantially) parallel to each other, the friction between them under vacuum induces a significant stiffness change in devices with diameters of only a few millimeters. The term “fibers held at only one of their ends” used herein should be interpreted in reference to a given segment (and meaning that one segment holds fibers at only of its ends) and not to the fibers themselves, because a bundle of fibers can in fact cross the border between two segments (e.g., cross a sealing cap) and thus in fact form two bundles with one on each side of this border, such that, in each of these sides, the fibers are held at one end of the segment, as shown for example in figure 17C, while figures 17A and 17B show examples of fibers held at only one of their own ends. This level ofstiffness modulation is challenging to achieve using conventional tubular jamming approaches, where tubes are fabricated from a fiber braid or woven fiber structure. Consequently, the fiber jamming approach described herein enables the development of miniaturized devices (with an external diameter of a few millimeters) that exhibit substantial variable stiffness functionality while also being less expensive and less complex to manufacture. Contrarily to the prior art, all fibers are not connected with each other throughout their length and are only connected in a one single area at the top or the bottom of a bundle via glue, but inside the bundle they are not braided, woven or knitted to form a sort of tissue or a tube like in some documents of the prior art. In addition, the present invention doesn’t require any heat or electricity going through fibers or external or internal tubes or sleeves, and the change of stiffness can be obtained by the jamming of the fibers by only applying vacuum, which is cheaper and / or more reliable in time (life time of the device) and / or safer for the patients.

[0077] In some embodiments, the variable stiffness catheter (1) further comprises at least one distal magnetically responsive element, called magnet (Ml), disposed at said distal segment (SI) which is configured for a remote magnetic navigation surgical approach using a standard hospital-compatible remote magnetic navigation System (3) for applying a magnetic field within the recommended magnitude range, by having a stiffness in the soft state allowing it to bend smoothly upon the application of said magnetic field and a stiffness in the rigid state allowing it to maintain minimal deflection despite the presence or absence of said magnetic field, such that said catheter (1) can be dynamically controlled by varying its shape during remote magnetic navigation in the patient’s body.

[0078] In some embodiments, not exclusive from the previous ones, the variable stiffness catheter (1) further comprises at least one pair of tendons running through at least part of the length, preferably the whole length, of the catheter and connected to a handle comprising buttons for actuating the tendons which are free to translate along the length of the catheter and bend it by this translation transmitted to the locations where they are fixed to the catheter, such that said catheter can be dynamically controlled by varying its shape during remote mechanical navigation in the patient’s body. Accordingly, the following description may refer to the presence of magnets in the various segments of the catheter because it mainly refer to magnetic remote navigation, but those of skills in the art will appreciate from the present disclosure that the magnets at each level (cap or tip or any point along the length of the catheter) can be replaced (or complemented) by latches or any types of fixations for the tendons allowing mechanical remote navigation.

[0079] In some embodiments, the catheter comprises at least two VS segments (SI, S2) filled with fibers of different materials (for example PLA (polylactide acid) and copper fibers) and two magnets to manipulate the two segments via a controllable magnetic field from a hospital-compatible RMN system (3). Upon selective vacuum application, one segment can be stiffened while the other segment remains soft for manipulation. In thisexample of configuration, the copper segment (S2) has a higher stiffness range, whose stiff state provides strong anchoring for the manipulation of the distal PLA segment (SI) which has a lower stiffness range. When the catheter forms the desired curve, the two segments can be locked in shape upon vacuum application by a vacuum source (SV), for example for an ablation procedure to proceed. Figures 6, 7, 8 and 9 shows an example of this capability of the VS catheter (1) with 2 segments. It can be seen, in particular in figure 9, that it is able to achieve a double curvature, for example by bending the proximal segment (S2) as in figure 8 and then applying vacuum to this segment (S2) so that it remains stiff, and then apply a magnetic field in another direction to bend the distal segment as in figure 9. The differential and synergic control of the two segments is particularly advantageous, especially because of its unique speed stability. The stiffness change processes require only the on-off switches of the vacuum application with instant stiffness change in the catheter, making this process significantly faster than that of the existing VS catheters that rely on phase-changing mechanisms. The examples of materials of the fibers, such as PLA and copper are of course not limiting the scope at all because many other material can be used and they may be chosen for the bending moment and stiffness. The bundle of fibers made from rougher material generally being stiffer when submitted to vacuum. Any metallic, polymer, plastic or composite-based fibers can also be used. For obtaining ultrathin fibers however, polymer materials are interesting for many reasons including the cost and eventually their ecologic advantages (for PLA in particular). Thanks to the fiber jamming technique the change of stiffness occurs very quickly, almost instantaneously, generally below 500ms or 300ms and even below 100ms, which is at least two orders of magnitude faster than the reaction times of the existing variable stiffness catheter. For example, the stiffening occurs in about 100ms for a sleeve having an inner diameter of 2 mm or 0,5mm and the change back to the soft state lasts the same time except for a sleeve with a diameter of 0.5mm which takes about 250ms.

[0080] The present invention also concerns (for example as illustrated in Fig. 1) a system (2) for surgical applications using a RMN approach, by comprising at least one VS catheter (1) according to some embodiments of the present invention, connected to at least one vacuum source (SV) and at least one RMN system (3) for applying magnetic fields in synchronization with the application of vacuum.

[0081] Existing devices using jamming of layers or braid or large and / or square fibers are filled with a few tens of fibers with diameters of at least 500pm in thick sleeves and 10 times larger than the size of the cardiovascular catheters which typically have diameters of 2.33mm (generally 0,3 to 3mm). This dimension requirement imposes formidable challenges in catheter fabrication with FJ integration to achieve desirable performance. Moreover, the stiffness change factor (SCF : ratio of the stiffness in rigid state by the stiffness in soft state) of such devices is below 3, which is not sufficient for the cardiovascular catheter applications as they require an SCF of at least 4 Therefore, the existingfabrication approaches do not enable manufacturing a large number of ultra-thin fibers and packaging them in the scale of diameters of 2.33mm suitable for example for cardiac catheters. To overcome this challenge, the strategy of the present application to achieve a high SCF is to incorporate as many thin fibers as possible by an innovative fabrication procedure (manufacturing method) preferably including a precise method to produce fibers as thin as 50pm (but possibly from 5 to 200pm, with preferred diameters below 140pm), and a process to pack up to 1000 fibers (or more, depending on their diameters and with a minimum of 100), within a 2mm diameter space (inner diameter of the sleeve / catheter). This fabrication procedure enabled the inventors of the present application to reach the purposes of the present invention by identifying most relevant parameters such as the materials and / or numbers and / or diameters of the fibers, within ranges of values which have never explored and were even unconsidered or unenvisioned yet. By parametric optimization experiments, an optimal SCF up to 6.5 was obtained, but higher SCF can be obtained by further tuning the parameters identified herein. To tune the catheter stiffness range for the magnetic field magnitude, which differs for various surgery applications, the present application also proposes the use of hybrid fiber bundles composition, for example with PLA and copper fibers with different material composition ratios. Furthermore, by using a method to measure the stiffness change time of FJ, which has not yet been achieved in the prior arts, the measurements show the FJ stiffness enabled to show that changes occur within 300ms (or even 100ms), which is two orders of magnitude faster than the change rate of the existing VS catheters. Compared to the existing VS catheters, the proposed FJ catheter achieves adequate and ultra-fast stiffness changes with safe materials and simple control. In addition, it eliminates the need for heating or electric power working inside the human body. Furthermore, our novel fabrication can be adopted to produce other FJ catheters for different specific MIS procedures. Therefore, our proposed FJ-based VS catheter has strong potential to refine MIS by reducing procedure time and costs, and enhancing safety for both patients and surgeons. The values given above are not limiting and the detailed description below further explain the relevant parameters.

[0082] In a general manner, the present invention proposes a fast-changing variable stiffness catheter (1) using fiber jamming, for surgical applications and in particular finely tuned for RMN approach. This catheter comprises at least one soft biocompatible hollow sleeve (S) which has a wall with a thick-ness delimiting an inner diameter and an outer diameter of the sleeve. Generally, the outer diameter is 2,3mm and the thickness is 150pm, so that the inner diameter is 2mm, but sleeve of outer di -meters ranging from 0,3mm to 3mm (or even 5) are within the sizes suitable for the applications envisaged. In preferred embodiments, the inner diameter will be between 0,5 and 2 mm, and preferably larger than 75% of the outer diameter (e.g., for a thin wall of the sleeve). The material is generally silicone but other flexible and biocompatible are possible. The sleeve (S) comprises a proximal end for holding the VS catheter (1) and a distal end forsurgical insertion in a patient’s body. The term “patient” is not limiting and can in fact concern an animal and should even be interpretated as also covering any organ or tissue or structure. Said catheter (1) may comprise several segments (SI, S2, S3) each having an individual sleeve, but a single soft biocompatible sleeve (S) along the whole length of the catheter (all the segments) is also possible, such that the present description refers in a non-limiting manner to “the sleeve” whatever the number of segments.

[0083] According to preferred embodiments, said VS catheter (1) includes a tip sealing cap (10) at the distal end for closing the catheter (1), in a fluid-tight manner (Air-tight and liquid-tight). Preferably, a working channel (15) is enclosed within said sleeve (S) and extending through said proximal and distal ends, up to a working end for applying a treatment outside the catheter (1), through said tip sealing cap (10), once inserted in the patient’s body. In some embodiments, said working end comprises a working tip, such as an ablation tip for example.

[0084] Furthermore, the catheter (1) comprises a plurality of fibers (F) enclosed within said sleeve (S) and having a length defining a distal segment (SI) of the catheter (1). The segment (SI) in fact has a length equal or larger than the length of the fibers, to enclose them but preferably not much long-er for a better control of the whole length of the segment. In some embodiments, the catheter further comprises an inlet attachable to a source (SV) of vacuum or pressure for applying vacuum or pressure inside said distal segment (SI) and at least one distal magnetically responsive element, called magnet (Ml), dis-posed at the distal end. This magnetically responsive element (Ml) can be a real magnet, but the magnets used in surgery are generally rather external for applying a magnetic field onto a magnetically responsive element (comprising iron, cobalt or nickel). The term “magnet (Ml, M2)” is thus not limiting. The term “at the distal end” is not limiting either because it’s preferrable that the magnet is mostly in distal portion of a given segment, but it can be exactly at the tip or in the vicinity of the distal end or even more proximal as long as it allows to impart movements to the VS catheter (1) as explained below. In some embodiments, said proximal end is pluggable, in a fluid-tight manner, on a distal end of a standard catheter (SC) used for surgery applications, or of a rear tube (RT), which preferably further encloses at least the working channel (15) and has a stiffness higher than the stiffness of said variable stiffness catheter (1) in its soft state, such that said standard catheter (SC) or rear tube (RT) is extended by said variable stiffness catheter (1) and cooperates with said proximal end to form said inlet when connected to said source (SV) of vacuum or pressure. The length of said variable stiffness catheter (1) is around generally about 50 cm for example, while the standard catheter (SC) generally has a length of 135 cm. However, the VS segments (SI, S2, S3), generally have a length comprised between 10 and 100mm, preferably 40 to 60mm while the fibers are generally a bit shorter, except for a single segment or for the most proximal segment in multiple segments. Indeed, when the proximal end doesn’t comprise an intermediate sealing cap, these segments can have fibers longer than thesegment and thus protruding in the rear tube (RT) or standard catheter (SC). Preferably, for supporting the actuation of the VS catheter (1) by a magnetic field as explained below, said inlet comprises at least one supporting rod (16) and / or co-operates with said distal end of said standard catheter (SC) or rear tube (RT) which has a stiffness higher than the stiffness of said variable stiffness catheter (1), at least in its soft state.

[0085] Advantageously, said fibers (F) are assembled in at least one bundle such that applying vacuum in-side said distal segment (SI) induces a fiber jamming resulting in a stiffening of this segment, said distal segment (SI) thereby having variable stiffness defined by a soft state and a stiff state. Furthermore, said distal segment (SI) is configured for a remote magnetic navigation surgical approach using a standard hospital-compatible remote magnetic navigation system (3) for applying a magnetic field within the recommended magnitude range. Such remote magnetic navigation (RMN) systems (3) are well known in the field of surgery and designed to be hospitalcompatible by using recommended magnitudes of magnetic fields (or magnetic field densities: MFDs). These recommended MFDs are comprised between 10 and 120 milliTesla (mT). Preferred values for the surgical applications aimed are between 20 and 80 mT or even 30 to 50 mT, but the VS catheter (1) of the present invention are suitable for a large range as, for example, in commercially available systems, in which some goes up to 120 mT and some have a range between 80 and 120 mT while some others use around 20 mT for neurovascular application. The present invention is adapted to these magnitudes, thanks to the arrangements and properties of the magnets and the fibers bundles having a stiffness in the soft state allowing it to bend smoothly upon the application of said magnetic field and a stiffness in the rigid state allowing it to maintain minimal deflection despite the presence or absence of said magnetic field. Thereby, this small catheter (1) using fiber jamming (FJ) for obtaining variable stiffness can be dynamically controlled by varying its shape during remote magnetic navigation in the patient’s body.

[0086] In some embodiments, the VS catheter (1) further comprises at least one first intermediate sealing cap (11) spaced from the tip sealing cap (10) by a distance equal or larger than the length of the fibers (F) to delimit said distal segment (SI). In such embodiments, said inlet comprises a distal pressure channel (Cl) inside said sleeve (S) and extending from the source (SV) of vacuum or pressure to said distal segment (SI), through said first intermediate sealing cap (11). The proximal end may still be pluggable onto a rear tube but the inlet for applying pressure or vacuum in the distal segment requires a channel (Cl) through the intermediate cap (11). In various embodiments, said fibers (F) of the distal segment (SI) are held at only one of their ends by said distal (10) and / or first intermediate (11) sealing cap. In some of these embodiments with an intermediate cap (11), the VS catheter (1) comprises a plurality of fibers (F) enclosed within said sleeve (S) and extending between said first intermediate sealing cap (11) and said proximal end and having a length defining a first intermediatesegment (S2) of the catheter (1), similarly to the distal segment (SI). In addition, at least one intermediate magnetically responsive element, called magnet (M2), disposed at said first intermediate sealing cap (11) (the same definition and interpretation as for the first magnet (Ml) applying also here). In these embodiments, an intermediate inlet is attachable to a source (SV) of vacuum or pressure for applying vacuum or pressure inside said first intermediate segment (S2). Furthermore, as for the distal segment (SI), said fibers (F) are assembled in at least one bundle such that applying vacuum inside said first intermediate segment (S2) induces a fiber jamming resulting in a stiffening of this segment, said first intermediate segment (S2) thereby having variable stiffness defined by a soft state and a stiff state. Accordingly, said first intermediate segment (S2) is also configured for a re-mote magnetic navigation surgical approach using a standard hospital-compatible remote magnetic navigation System (3) for applying a magnetic field within the recommended magnitude range, by having a stiffness in the soft state allowing it to bend smoothly upon the application of said magnetic field and a stiffness in the rigid state allowing it to limit its deflection despite the presence or absence of said magnetic field, such that said catheter (1) can be dynamically controlled by varying its shape during remote magnetic navigation in the patient’s body. Such embodiments having two segments or more (see below) have the advantages of enabling complex movements with more than one curvature and of allowing complex movement when the catheter is advanced with-in the patient’s body, in particular by adjusting (precisely tuning) both MFD of the vacuum or pressure applied to the segments, in a dynamical and differential and synergic manner. The pressure or vacuum to be applied is generally between -95kPa and 300kPa (in the case where a positive pressure is preferred to inflate a bit the segment), but generally used between 0 and -90 kPa.

[0087] In some of the “multiple-segments” embodiments, the VS catheter (1) further comprises at least one additional intermediate sealing cap (12) having an intermediate magnet (M2) and spaced from said first intermediate sealing cap (11) by a distance equal or larger than the length of fibers enclosed therein and delimiting an additional intermediate segment (S3) also enclosing fibers (F), said inlet comprising a distal pressure channel (Cl) and an intermediate pressure channel (C2), inside said sleeve, and extending from the source (SV) of vacuum or pressure to said distal segment (SI) and said first intermediate segment (S2), respectively, through the respective intermediate sealing caps (11, 12). The number of segments is not really limited except maybe by the procedure for controlling them. In some of these embodiments, said fibers (F) of said first intermediate segment (S2) are held at only one of their ends by said first intermediate (11) and / or additional intermediate (12) sealing cap. In some embodiments, at least one of said distal magnet (Ml) and / or intermediate magnet (M2) is / are tubular and included within the material of the sleeve (S) or on the inner or outer surface of the sleeve (S). In some embodiments, at least one of said intermediate sealing caps (11, 12) includes a rigid supporting rod, preferably in carbon fiber, for limiting therisks of buckling at the junction between the segments (SI, S2, S3) during actuation of the catheter (1). In this way, the buckling of the catheter is prevented, in particular for the pressure channels which have to remain open for restoring pressure or vacuum when necessary.

[0088] The stiffnesses of the various segments, both in the soft and rigid state, preferably increase from the distal end toward the proximal end, such that the more proximal segments provide a rigid support for the actuation of the more distal segments. Therefore, the various segments (SI, S2, S3) of some embodiments include fibers (F) of different materials having different bending moments and stiffnesses when submitted to vacuum. In some embodiments, said at least one bundle comprises fibers (F) of only one material or comprises a mix of fibers (F) of different materials. In some of the illustrated examples, the fibers of one of the segments are made from a polylactide acid (PLA) or from Copper fibers or by a mix of both materials, preferably with more copper than PLA at least for the more proximal segments. Generally, the fiber-filling rate of the segments is between 20 and 70%, preferably 45%. Advantageously, the stiffness change occurs in less than a second, particularly within 300ms or 100ms or even less.

[0089] In some of the preferred embodiments, the ratio of the stiffness in the rigid state by the stiffness in the soft state defines a factor, called stiffness change factor (SCF), the segment (SI) or segments (SI, S2, S3) of the catheter (1) having a SCF factor of at least three, preferably four or more, to be suitable for a safe navigation upon application of a magnetic field within the recommended magnitude range by a deflection of less than fourth in the rigid state compared to the soft state. Prefer-ably, the stiffness in the rigid state limits the deflection of a segment (SI, S2, S3) such that the magnitude of the magnetic field required for a small deflection is higher than the magnitude inducing a large deflection in the soft state. It has been discovered by the inventors of the present invention that obtaining a VS catheter (1) suitable for RMN approach was feasible by using a large number of small diameter and correctly arranging them into a soft sleeve. Thereby, in preferred embodiments, the material and / or diameter of the fibers (F) and / or the number of fibers (F) in a segment (SI, S2, S3) are adjusted for said remote magnetic navigation surgical approach, generally according to the size of the magnet (Ml, M2) and the material (silicone or others) and diameters (outer diameter of 0,3 to 5mm) of the sleeve (S). For a correct bending without requiring a large MDF, the stiffness in the soft state is generally comprised between 15 and 175 milli-Newtons per millimeter (mN / mm), preferably between 50 and 100 mN / mm or preferably at least lower than 100 mN / mm. Also, for a negligible (or tolerable) deflection in the stiff state, the stiffness in the rigid state is generally comprised be-tween 50 and 750 mN / mm, preferably between 250 and 500 mN / mm or preferably at least higher than 250 mN / mm. Furthermore, in some of the preferred embodiments, the fibers (F) have a diameter comprised between 5 and 160 pm, preferably between 50 to 150 pm or at least smaller than 145pm. Such small size is difficult to obtain but proves very good results since themaximum number of fibers can be increased to improve the jamming phenomenon. In addition, in some of the preferred embodiments, the number of fibers (F) in a segment (SI, S2, S3) is comprised between 50 to 10000, preferably more than 100. By having more than 100 fibers and preferably much more, for example above 200 or 300, but without filling the sleeve more than 80% or even 50% (the preferred value being 45%), a strong fiber jamming enables a suitable SCF while preserving a low stiffness in the soft state.

[0090] Various embodiments of the present application also concern a system (2) for surgical applications through a remote magnetic navigation surgical approach. Such system (2) includes at least one variable stiffness catheter (1) according to any one of the embodiments disclosed herein, at least one source (SV) of pressure or vacuum and at least one a control unit (CU) for controlling the pressure or vacuum applied to at least one segment (SI, S2, S3) of said catheter (1) by said source (SV). Such source can be a vacuum pump (to evacuate air out of segments) and the use of pressure regulators (for a precise control the pressure) is preferred, as well as pressure sensors for measuring the ap-plied pressure and providing feedback to the control unit (for example able to display it to the surgeon). In some embodiments, the VS catheter (1) of this system (2) is a multiple segment catheter (as in Fig. 1 or Fig. 17 for example) and the control unit (CU) is therefore operatively configured for dynamically and synergically controlling the pressure or vacuum applied to several segments (SI, S2, S3). Preferably, said control unit (CU) controls the periods and the values of pressure or vacuum applied to said catheter (1). In addition, in preferred embodiments, said control unit (CU) controls the pressure or vacuum applied in synchronization with a standard hospital-compatible remote magnetic navigation system (3), for applying a magnetic field, within the recommended magnitude range, to the catheter (1) during different periods of time determined as a function of the periods of time for the application of pressure or vacuum, or vice versa. In some embodiments, the system (2) further comprises said remote magnetic navigation system (3) controlling the tridimensional orientation in space and / or the magnitude amplitude of the magnetic field according to the periods and the values of pressure or vacuum applied to said catheter (1). An example of such embodiment is illustrated in a non-limiting manner with the RMN system (3) being able to apply magnetics fields of various magnitude and direction thanks to 4 magnets. However, other configurations are possible and known, such that no further detail is needed in the present application. Also, all the functions performed by the control unit, for the control of vacuum could be implemented in a RMN system, such that the example of figure 1 is also obtained by other alternatives.

[0091] In some embodiments of the system (2), an injection of chemical compounds through the working channel (15) is further controlled by the control unit (CU) or by a dedicated device synchronized with the control unit (CU). Thereby, the catheter can be navigated inside the patient’s body and apply a treatment at its distal tip. In the same way, someembodiments of the system (2) further comprise an electromagnetic source controlled by the control unit (CU) or a dedicated device synchronized with the control unit (CU), for visualizing tissues of the patient and / or applying an electromagnetic treatment at the distal end through the working channel (15) enclosing an electro-magnetic conducting medium. Such medium can be an optic fiber conducting a laser for example, as known in endovascular surgery.

[0092] Various embodiments of the present application also concern a method for fabricating a variable stiffness catheter (1) according to any of the embodiments disclosed herein.The method preferably comprises a prior manufacturing of ultra-thin fibers, for example as detailed below in reference to figure 15. In general, the method comprises the manufacturing of at least one sleeve (S) preferably with a consistent sleeve wall thickness (preferably 150pm or less and with a diameter comprised between 0,3 to 3 mm as already mentioned). Such consistent wall thickness can be obtained for example by the known dipping-curing process as illustrated in figure 10. The, the method comprises the production of at least one bundle of fibers (F) by packing the thin fibers held parallel to each other so that they can enter the sleeve (for example as illustrated in figure 16). Accordingly, the method comprises the production of the distal segment (SI), for example as illustrated in figures 13 and 14 for a catheter comprising at least one segment, or in figure 18 for a single segment catheter. This production includes (in reference to figures 13 and 14):Insertion (e.i) of at least one bundle of fibers (F) inside said sleeve (S) using an assistive tube (AT),Insertion (e.ii) of a working channel (15) through the distal segment (SI),- Removal of the assistive tube (AT), creation (e.iv) of the tip sealing cap (10), preferably by application of glue at the distal end of the distal segment (SI) for holding the fibers (F) bundle, and insertion (e.v) of a magnet (Ml) at the tip sealing cap (10).

[0093] In the embodiments with a multiple segment catheter, the method also comprises the manufacturing of at least one second sleeve (S) with a consistent sleeve wall thickness and of at least one second bundle of fibers (F). More specifically, this method further comprises the production of at least one intermediate segment (S2, S3), for example as illustrated in figures 11 and 12 for a catheter comprising at least one segment, or in figure 19 for a catheter comprising two segments. This production includes (in reference to figures 13 and 14):Insertion (d.iii) of a first fiber (F) bundle inside said sleeve (S) using an assistive tube (AT),Insertion (d.ii) of the working channel (15) and a distal pressure channel (Cl) through the second sleeve (S),- Removal of the assistive tube (AT),Creation (d.iv) of an intermediate sealing cap (11, 12), preferably by application of glue at the distal end of the intermediate segment (S2, S3) for holding the fibers (F) bundle, preferably internally reinforced by a supporting rod (16), Insertion (d.v) of a magnet (M2) at the intermediate sealing cap (11, 12), Assembly (e.iii), preferably with glue, of the segments (SI, S2, S3) co-aligned.

[0094] The term «application of glue» is herein used in a generic sense and the material used as a glue may be varied but preferably being biocompatible (like the preferred silicone example), at least for the glue parts which can be in contact with the exterior of the catheter. However, other kind of sealing caps could be employed as alternatives, for example with a tight insertion and / or com-pressing means for resisting to the range of pressure and vacuum described herein.

[0095] In preferred embodiments, the fabrication of bundle of fibers (F) comprises a prior fabrication of ultra-thin fibers having a diameter preferably less than 160pm or even between 30 to 100pm. In some embodiments, the fabrication of a bundle of fibers (F) is performed via a first winding machine (WM1) which pulls a melted polymer or composite filament (FI) through its spinning spool, and by mounting the filament (FI) onto a second winding machine (WM2) which reformats the fibers into a fiber bundle with the desired number of fibers. In some of these embodiments, said melted polymer or composite filament (FI) is obtained via a 3D printing machine (PH) arranged close to said first winding machine (WM1) directly pulling on the filament (FI) during its extrusion, for example as illustrated in figure 15.

[0096] According to the above general description of possible combinations of features in various embodiments, it will be understood that the invention may be implemented in various ways. However, to better explain the issues and the challenges faced, as well as the identification of relevant parameters for reaching the goals described herein, further details of preferred embodiments will now be described in reference to the illustrative and non-limiting figures. It should be noted that the following description is for a complete information of preferred examples but limiting the scope in any way.

[0097] Figure 1 shows a schematic view of a system (2) for surgical applications through a remote magnetic navigation surgical approach, according to in some embodiments. In this example, the system (2) comprises the VS catheter and its control unit for controlling the vacuum, applied by a distinct source (SV) which could be integrated in the control unit (CU). This example of system (2) further includes an example of magnetic navigation system (3) which could of course be distinct or rather integrate the control unit (CU), but the only necessary feature is the synchronization in time. A further feature not necessary but particularly advantageous is the synchronization also in terms of magnitude or density of the magnetic field (MFD) and of magnitude of the pressure or vacuum applied. Indeed, by a fine dynamic and synergic tuning of both magnitudes, a precise control can be obtained, especially with more than one segments having different stiffnesses.

[0098] Figure 2 shows a partially cut view of a distal end of a VS catheter (1) according to some embodiments, while Figure 3 shows a partially cut view of a proximal end of a VS catheter (1) according to some embodiments. The sleeve is preferably in silicone (and the glue used for the assembly is thereby also preferably in silicone) but other biocompatible materials could be used, as long as they allow a flexible soft state. Figure 4 shows a partially cut view of a junction between two segments of a VS catheter (1) according to some embodiments and Figure 5 shows a partially transparent view of two segments of a VS catheter (1) according to some embodiments. These figures illustrate Examples of design and fabrication of the VS-FJ catheter (1), as described below.

[0099] The FJ VS catheter has two segments, connected by a long rear tube (which can be a rear PTFE tube or a standard catheter) to a source of vacuum or pressure (SV), possibly through a rear tubing assembly (not shown) for example for connecting various tubes and rapid switch between various pressures or for providing entries to the various channels (15, Cl, C2) in the catheter. In this last case, at the rear tubing assembly, the rear tube (RT), the working (15) and vacuum channel (Cl) can be decoupled into three independent outlets. The two segments have similar structures with a magnet at the tip of each segment followed by the fibers (Fig. 1). They are encapsulated inside the silicone sleeve with silicone glue at the distal end (or tip) to fix the fibers and seal the segments (Fig. 5), but they can be held by a glue at the proximal end (such as the more proximal sealing cap and it’s also possible to fix some fibers at one end and other at the other end. In addition, one tube serving as the working channel (15) is placed through the two segments for future installation of a treatment device, such as an ablation tip for example, and another tube, called vacuum channel (Cl) is positioned up to the distal (or “first”, for example PLA) segment (SI) for vacuum application (Fig. 2, 3 and 4 for example). In some embodiments, the vacuum application for the intermediate (or “second”, for example copper) segment (S2) is served through the long PTFE tube or standard catheter (SC). Between the two segments, there is a supporting carbon fiber (CF) rod (16) extending from the tip of the second segment into the PLA fibers of the first segment to serve as a stiff support.

[0100] During open-volume surgeries, such as those involving the heart or stomach, the precise positioning of surgical tools requires two degrees of freedom. Thus, we develop a two- segment FJ catheter to address this need effectively. The first segment uses the 100% PLA fiber bundle with a low stiffness range to allow a wide bending range, while the second segment is filled with the 100% copper fiber bundles with a high stiffness range not only to allow adequate motion range but also to provide rigid anchoring for the first segment manipulation. Both segments use 45% filling rate and 050pm fibers. This two- segment catheter is then tested in the RMN system with the goals of demonstrating the selective manipulation of the two segments to achieve multi -curvature bending and examining if the stiffened segment can stay unaffected when the other segment is beingmanipulated. Then, to simulate a real surgical scenario, the two-segment catheter is also tested in a 3D phantom of a human heart for manipulation by the RMN system.

[0101] Figures 6, 7, 8 and 9 illustrate an example of demonstration of the capacities of the VS catheter in some embodiments, with examples of MFD. The values below for these examples of curvatures and MFD are not limiting at all but rather only provided as the real values used in some experiments. Initially, the catheter is positioned vertically with the two segments stiffened (Fig. 6). Then the first segment is softened for manipulation by changing the direction of a 40 mT magnetic field. While the first segment is moved leftwards, the second segment remains still, which validates the sufficient rigidity of the 100% copper fiber bundle in the vacuumed state (Fig. 7). In the second test, the second segment is manipulated to the right in an 80 mT magnetic field and the stiffened first segment stays straight during the procedure (Fig. 8). Although the rigid first segment cannot withstand the 80 mT MFD, the movement of the softened second segment occurs quickly before any deformation of the first segment occurs. The second segment is then stiffened, followed by the softening of the first segment for upward manipulation with a 40 mT MFD, resulting in a multi-bending curve (Fig. 9). In addition to the multisegment curving capability, the overall actions of the catheter are performed fluently with a whole set of curve forming, including three rounds of stiffness switching and individual bending of the two segments, taking less than 10s.

[0102] To fabricate the catheter, a large quantity of ultra-thin fibers of two material types is first obtained. In the illustrated examples, the materials selected were enameled copper wires (050, 75, 100pm), and PLA fibers (050 pm) extracted from a 3D printer (Ultimaker S5, Ultimaker B. V.) using a first winding machine (WDM1) to pull the heated PLA filament. Once the fibers are prepared, the winding spool will be mounted onto a second winding machine (WDM2) which reformats the fibers into a fiber bundle (Fig. 16). By applying specific numbers of rotations of the winding frame, a bundle with the desired number of fibers is obtained. The second step involves preparing the external sleeve for packing the fiber bundle. A good example of sleeve to choose is silicone rubber (DragonSkin 0020, Smooth-On, Inc. with Elastic modulus at 100% strain: 0.34MPa) which, in the form of thin skin, is neither too brittle to break during manipulation, nor too stiff to affect the jamming effect. Preferably, a dipping-curing process is employed to form silicone sleeves with a consistent wall thickness (~150pm) as briefly illustrated in Fig. 10 as a standard technique.

[0103] With all the components ready, the catheter fabrication proceeds with copper fiber segment construction first (Fig. 11 and 12) and then the PLA fiber segment (Fig. 13 and 14). Both of the segments are fabricated similarly, involving the insertion of the fibers via an assistive tube, the insertion of the working and vacuum channels, the glue application and the magnet insertion. The main difference of the two segment fabrication lies with the supporting CF rod at the tip of the second segment and the location of the vacuum channel tip which stays in the first segment. Some key relativepositions for the catheter fabrication process are provided in Fig. 19 which illustrates the components with their true proportions.

[0104] Figure 11 and 12 show schematic views of various parts of some steps used for manufacturing the intermediate segment of a VS catheter (1) according to some embodiments;

[0105] Figures 13 and 14 show schematic views of various parts of some steps used for manufacturing a distal segment (SI) and its assembly to an intermediate segment (S2) to obtain a VS catheter (1) according to some embodiments, but most of these steps could be applied for an assembly on a rear tube (RT) or a standard catheter (SC) instead of the intermediate segment (S2). In addition, an example of manufacture of a catheter with a single distal segment (SI) is also illustrated on figure 18 with more details. Also, figure 19 illustrates in more details an example of manufacture of a two-segment catheter. The manufacture of a catheter with three segments is not shown but will easily be understood by these figures and their explanations. Furthermore, below is a more detailed explanation of preferred embodiments of the manufacturing method of catheters with 2 segments in reference to Figures 11, 12, 13 and 14:

[0106] Steps d show the fabrication of the proximal segment (S2):

[0107] Step d.i: The silicone sleeve is first inserted into the right side of the PTFE tube, followed by the insertion of the assistive tube on the right side into to PTFE tube. Step d.ii: Then the copper fiber bundle is inserted from the right, followed by the insertion of the working and vacuum channels reinforced with 00.3mm assistive CF rods inside. Step d.iii: By further pushing the two reinforced channels, the copper fibers are fully placed inside the silicone sleeve. Step d.iv: With the removal of the assistive tube, silicone glue is then applied at the right tip. Step d.v:, immediate insertion of the magnet and then the supporting CF rod. Step d.vi: Extra silicone glue is then applied to seal the first intermediate segment (S2).

[0108] Steps e show the fabrication of the distal segment (SI):

[0109] Step e.i: The assistive tube is first inserted into the silicone sleeve, followed by the insertion of the PLA fiber bundle. Step e.ii: The halfway first segment is inserted onto the tip of the second segment along the working channel. Step e.iii: The silicone sleeve is then rubbed leftwards and fixed at the tip of the second segment with silicone glue. Step e.iv: With the removal of the assistive tube, the right end of the PLA fibers is fixed with silicone glue. Step e.v: immediate insertion of the magnet. Step e.vi: The tip of the first segment is then sealed with extra silicone glue, followed by the removal of the two assistive CF rods from the working and vacuum channels.

[0110] Figure 18 illustrates the manufacturing (fabrication) of a single-segment catheter according to some embodiments. The Steps “c” shows an example of such fabrication processes with copper fibers:Step c.i: A first assistive tube (AT) with a wedged tip is inserted into the silicone sleeve. Step c.ii: insertion of the copper fibers. Step e.iii: Insertion of the working channel. Stepc.iv: The fibers and the working channel are repositioned to leave 6mm empty space at the tip of the silicone sleeve and 5mm of the working channel sticking out of the silicone sleeve. Step c.v: Silicone glue is then applied to the tip of the silicone sleeve. Step c.vi: immediate insertion of the magnet. Step c.vii: Extra glue is then applied to seal the tip. Step c.viii: The excessive copper fibers on the other end are inserted into a second assistive tube (AT) with a wedged tip. Step c.ix: insertion of the second assistive tube (AT) into a silicone tube with 4mm of the silicone sleeve inside the silicone tube. Step c.x: removal of the second assistive tube and application of silicone glue to fix the silicone sleeve with the silicone tube, to complete the fabrication.

[0111] Figure 19 illustrates the full manufacturing method (fabrication process) of a two- segment catheter according to some embodiments.

[0112] Steps a of Fig. 19 show an example of a proximal segment (S2) fabrication with an example of true proportions and key dimensions:Step a.i: The rear tube (RT), generally in PTFE, is inserted into the 60mm long silicone sleeve by 14mm, leaving 46mm of the silicone sleeve for the second segment. The assistive tube (AT) with a wedged tip is then inserted. Step a.ii: Copper fibers are inserted from the right, followed by the insertion of the working and vacuum channels with 100mm of the working channel and 20mm of the vacuum channel sticking out of the copper fibers, preferably with an assistive rod (AR). Step a.iii: Copper fibers are further pushed in with a 40mm length staying out of the PTFE tube and 6mm empty space at the tip of the silicone sleeve. Step a.iv: The assistive tube is then removed, followed by the silicone glue application at the tip of the silicone sleeve. Step a.v: The magnet and the supporting CF rod (15mm long) are immediately inserted after glue application. Step a.vi: Extra silicone glue is applied to seal the second segment.

[0113] Steps b of Fig. 19 show an example of Distal segment (SI) fabrication:Step b.i: The assistive tube with a wedged tip is inserted into the 50mm long silicone sleeve, followed by the insertion of the PL A fibers. Step b.ii: The halfway first segment is inserted onto the tip of the second segment with a gap of around 1mm. Step b.iii: The silicone sleeve of the first segment is rubbed onto the tip of the second segment, followed by the removal of the assistive tube and trimming of the PLA fibers down to 40mm. The silicone sleeve is then fixed using a small amount of silicone glue to the tip of the second segment. Step b.iv: The tip of the first segment is filled with silicone glue to fix the PLA fibers. Step b.v: The magnet is inserted immediately after the silicone glue application. Step b.vi: Extra silicone glue is applied at the tip to seal the first segment, followed by the removal of the assistive CF rods in the working and vacuum channels.

[0114] Fig. 20 illustrates example of characterization of the stiffness and reaction time of the Fiber Jamming in the catheter scale, as follows: a, The force-deflection curves of the FJ segments with 45% filling rate and 050pm PLA fibers at different vacuum levels. The slopes of the individual linear fitting lines,representing the stiffness, are annotated with matching gray values. The SCF values are in parentheses. b, The SCFs of FJ with 050pm PLA fibers at different filling rates, c, The SCFs of FJ with PLA fibers of different diameters at 45% filling rate. To reach 45% filling rate, the numbers of fibers with 50, 75 and 100pm diameters are 720, 320 and 180, respectively. d, The SCFs of FJ with 050pm Copper and PLA fibers at the optimal filling rates. e, The stiffness and SCFs (white numbers) of FJ at 45% filling rate using the hybrid 050pm fiber bundles with different PLA-copper compositions. f, One typical force profile of the FJ transition from soft to stiff and from stiff to soft states (FJ sample: 45% filling rate with 050pm PLA fibers). High and low force levels represent the soft and stiff states of the FJ, respectively. The transition times in between the two force levels indicate the FJ reaction times.

[0115] Figure 21 illustrates additional FJ characterization results as follows: a, The stiffness ranges of FJ with 050pm PLA fibers at different filling rates. b, The stiffness ranges of FJ with PLA fibers of different diameters at 45% filling rate. c, The stiffness ranges of FJ with 050pm PLA and copper fibers at the optimal filling rates. d, FJ reaction times with 050pm PLA fibers at different filling rates. e, FJ reaction times with PLA fibers of different diameters at 45% filling rate.

[0116] It will be thus understood from figures 20 and 21 that various parameters enable the VS catheter (1) to reach the purposes of the present invention. Fiber jamming characterization and optimization. To investigate FJ performance in terms of stiffness variation in the catheter scale and determine the optimal FJ configuration, we conducted detailed characterization using the 3 -point bending tests by varying different parameters: filling rate, fiber diameter and fiber material. Moreover, the FJ reaction times are also measured via our novel method. With the focus on the FJ performance, all characterizations are implemented using the single-segment catheters with 40mm- long FJ segments.

[0117] Prior to the investigation, the force profiles are firstly obtained to understand the FJ behavior (Fig. 20a) via the 3-point bending tests. The initial steeper slope of the curve (0 to 0.2mm deflection) represents the high stiffness of the fiber bundle with the static friction preventing the relative sliding of the fibers. The lower stiffness observed from 0.4 to 1mm deflection is attributed to the lower kinetic friction of the fiber sliding after overcoming the static friction. The overall stiffness of FJ in the stiff state is calculated using linear fitting of the force curves within 1mm deflection. By increasing the vacuum level, the FJ stiffness and the SCF both increase (Fig. 20a), demonstrating that the stiffness of the catheter could be continuously modulated.

[0118] The first parameter investigated is the filling rate with 050pm PLA fibers at maximum vacuum (-95kPa). As the filling rate is increased from 20%, the average SCF initially increases, peaks at a filling rate of approximately 40% and then drops (Fig. 20b). Thestandard deviations (SDs) of the SCFs are greater than 1 at low filling rates, representing a poor repeatability of VS performance of the catheter (Fig. 20b). At the low filling rates, the FJ segment is somewhat hollow and, upon vacuum application, the cylindrical FJ segment is squeezed into a flattened body. Consequently, testing the FJ segments at different orientations results in SCFs that can range from 3.6 to 8.2 in these examples (Fig. 20b). As the filling rate is increased to more than 45%, the SD drops below 0.75, representing consistent FJ performance (Fig. 20b). At high filling rates, the FJ segment becomes more densely packed with the fibers, and, therefore, its crosssection remains circular after vacuum application, which yields similar SCFs at different orientations (Fig. 20b). However, the higher filling rates come with higher stiffness in the soft state due to the increased initial friction caused by fiber congestion (Fig. 21a), resulting in lower SCFs (Fig. 20b). By comparison, the most optimal filling rate for the catheter is determined to be 45% as this value leads to a relatively high SCF (6.54) and low SD (0.5).

[0119] With the optimal filling rate at 45%, the fiber diameter is then investigated with PLA fibers at -95kPa vacuum. The results show that increasing fiber diameters from 50 to 100pm reduces the SCF from 6.5 to 4 (Fig. 20c). The decrease in the SCFs is primarily due to the reduced stiffness in the stiff state as the fiber diameter increases (Fig. 21b). At the same filling rate, fewer fibers can be included in the sleeve when using thicker fibers. The reduced number of fibers leads to fewer contact points between the fibers, resulting in reduced friction and thus lower bending stiffness in the stiff state. Therefore, 050pm is chosen as the optimal fiber diameter for the catheter.

[0120] Copper fibers are also tested at the best three filling rates using -95kPa vacuum. The SCF and SD of the catheters with copper fibers also decrease with increasing filling rate (Fig. 20d). Due to the smoother surface, the copper fibers exhibit SCFs 0.2, 0.66 and 1.32 lower than the PLA fibers at 40, 45 and 50% filling rates, respectively. However, the absolute stiffness of the copper fiber catheter in the stiff state is approximately double that of the PLA fiber catheter (Fig. 21c). Thus, the copper fiber is a potential option for making high-stiffness catheters. Based on these experiments optimizing the three variables, the best FJ configuration is determined to be a filling rate of 45% with 50pm fiber diameter, applicable to both PLA and copper fibers.

[0121] The utilization of the two materials (PLA and copper) with different stiffness provides the possibility to customize catheter stiffness by mixing them with different ratios into hybrid fiber bundles. Therefore, hybrid fiber bundles with 75%-25%, 50%-50% and 25%-75% PLA-copper ratios are prepared and tested. It can be seen that the stiffness ranges of the hybrid fiber bundles gradually shifted from that of a 100% PLA bundle to that of a 100% copper bundle as the percentage of copper fibers increases and the percentage of PLA fibers decreases (Fig. 20e). However, the SCFs of the hybrid bundles remain stable, averaged at 5.1, as the fiber ratio changes. Importantly, thisstiffness customization allows us to configure the stiffness of the multi-segment catheters.

[0122] FJ technology is known for its fast reaction upon vacuum application. However, the actual reaction time (time required for a complete stiffness change from the soft to the stiff state or vice versa) has not been previously reported due to the lack of a precise measurement method. Here, we devised a method to measure the FJ reaction time (see Method section). We first obtain the force profile during vacuum switching which yields different force levels in the vacuumed / rigid and non-vacuumed / soft states (Fig. 20f). By measuring the transition times between the two force levels, the reaction (stiffening and softening) times of FJ are obtained (Fig. 20f). Vacuum tubes of different diameters (2 and 0.5mm for the PTFE tube and the vacuum channel, respectively) with 2m length are attached to the catheters for testing. The results show that the reaction times are mostly below 100ms, except the softening times with 00.5mm tube, which reach approximately 250ms. Despite the variation, the FJ reaction is very fast with most stiffness transitions occurring within 300ms, which is at least two orders of magnitude faster than the reaction times of the existing VS catheters.

[0123] Figures 20h, 20i and 20j illustrate different loading scenarios of the catheters: h: The single-segment catheter in the 3-point bending test, i: The single-segment catheter in a magnetic field, j : The two-segment catheter in a magnetic field.

[0124] After determining the optimal configuration for the FJ segment (45% filling rate, 050pm) and the FJ reaction times, the catheters can be placed under an external magnetic field caused either by a regular permanent magnet or an array of electrical magnets. Commercially available hospital-compatible RMN system can be used to demonstrate how catheters respond to the magnetic field in terms of bending angles in their soft and stiff states (Fig.20i). In the stiff state, the single-segment catheters are tested under an increasing magnetic field magnitude or density (MFD) with a fixed direction perpendicular to the catheter to assess their rigidity (Fig. 6-9). By softening the distal segment (SI) and stiffening the intermediate segment (S2) the catheter can be bent to a configuration presented in Fig. 7.

[0125] In the stiff state, the catheters remain rigid at their recommended MFDs, with minimal deflections. In preferred embodiments, the FJ VS catheter is equipped with two segments to achieve multi -curvature bending to reach more challenging surgical sites. When the stiffened catheter with two segments made of the same fiber configuration is placed in the magnetic field, the distal segment (SI) is subject to one bending moment M, while the intermediate segment (S2) is subject to a tripled moment 3M (Fig. 20j). Due to the relatively low stiffness of FJ segment, when the distal segment is just stiff enough to withstand the bending moment, the intermediate segment will not be able to withstand the tripled moment. Therefore, the two segments cannot have the same stiffness range and it is necessary to customize the stiffness ranges of FJ segments. Aviable choice is to assign a low stiffness range to the first segment and endow the second segment with a high stiffness range.

[0126] Hybrid fiber bundles by mixing fibers of two different materials and stiffness with different ratios provide a solution for stiffness customization, and the experimental results show that the stiffness ranges of the fiber bundles change with different PLA and copper fiber percentages. The characterization results from the pure PLA and copper bundle along with the three hybrid fiber bundles will be used to evaluate their potential performance in the RMN system and then to design the two FJ segments in the two- segment catheter.

[0127] For the soft and stiff states of the different types of fiber bundles, it is possible to calculate the MFDs needed to achieve small deflection (2 to 10mm, preferably 5mm or less) and big deflection (12 to 30mm, generally between 15 and 20mm). To analyze the results, the 100% PLA fiber bundle is taken as an example. Ideally, the FJ catheter needs to be bent with large deflections in the soft state under the magnetic field and stay within small deflections in the stiff state. The soft 100% PLA bundle needs an MFD of around 26 to 35 mT to achieve large deflections, while its stiff state requires 58 mT to reach 5mm deflection, which is larger than 35 mT. Therefore, the 100% PLA fiber bundle is eligible for the catheter application, and so are the other four types of fiber bundles as their MFDs needed for small deflection in their stiff states are higher than the MFDs for big deflections in their soft states. With the calculation, the recommended MFDs for each fiber bundle type in the soft state are given as 30, 50, 60, 70 and 80 mT for 100% PLA, 75% PLA - 25% copper, 50% PLA - 50% copper, 25% PLA - 75% copper and 100% copper, respectively.

[0128] The next is to consider the material configuration for the two-segment catheter. As already mentioned, the distal segment should have a low stiffness range, therefore, the 100% PLA fiber bundle can be assigned to this segment. The intermediate segment, when stiffened, needs to be rigid enough to support the manipulation of the distal segment with minimal deflection. In this scenario, the intermediate segment is subject to a tripled moment which is equal to the condition when placed in the magnetic field with a tripled MFD (Fig. 20j). Therefore, the stiff intermediate segment needs to withstand an MFD three times stronger than the one needed for the soft 100% PLA bundle to achieve large deflection, which is around 90 mT. Therefore, in the non-limiting example of mix of fibers, 25% PLA - 75% copper and 100% copper fiber bundles are qualified for the intermediate segment. For guaranteed performance, the 100% copper fiber bundle is used in the second segment of our two-segment catheter.

[0129] As mentioned above, the 100% PLA fiber bundle can be chosen for the distal segment of the two-segment catheter. In the surgical scenario, the distal segment will be in direct contact with the surgical points and thus prioritize larger bending angles for more working space and higher dexterity.

[0130] Figure 15 shows a schematic view of the manufacturing of ultra-thin fibers to be used in a VS catheter (1) according to some embodiments and Figure 16 shows a schematic view of the manufacturing of bundles of ultra-thin fibers to be used in a VS catheter (1) according to some embodiments. Such examples are not limiting but the method illustrated in figure 15 is particularly advantageous for the production of ultra-thin polymer fibers, for example as PLA (polylactic acid). An example of such production is detailed hereafter without implying any limitation: The PLA fibers are produced by winding machine I (WDM) pulling melted PLA filament from the nozzle of an Ultimaker 3D printer. The printer does not have the function to extrude PLA, however, during the material loading process, the printer will extrude melted filament at a fixed speed for up to 3 minutes, which allows us to obtain enough amount of fibers. When the printer head starts to extrude PLA filaments, the initially extruded filament will be quickly attached to the spool of winding machine I. Then winding machine I (WDM1) is started and the spool starts spinning from Orad / s to the set velocity with a 5s linear acceleration. Without this gentle acceleration, the high speed of the spinner will immediately break the soft filament.

[0131] Due to the high speed of the spool and the slow extrusion of the melted PLA filament, the spool will pull the initially thick strand into very thin fibers. Increasing the spinning speed of the spinning spool (0100mm) enables to obtain PLA fibers of smaller diameters. Through testing different spool spinning speeds and measuring the resultant fiber diameters, fibers with 50pm, 75pm and 50pm in diameters were obtained for making the catheters that are used in the characterization detailed in the present description as non-limiting examples.

[0132] The present application describes various technical features and advantages with reference to the figures and / or to various embodiments. Those skilled in the art will understand that the technical features of a given embodiment can indeed be combined with features of one or more other embodiment s) unless the reverse is explicitly mentioned or these characteristics are incompatible or the combination does not work. In addition, the technical features described in a given embodiment can be isolated from the other features of this mode unless the reverse is explicitly mentioned, in particular because the functional considerations provided in the present application will provide a sufficient explanation so that the structural adaptations possibly necessary are within the reach of those skilled in the art. Therefore, the embodiments described in the present application should be considered by way of illustration and the invention should not be limited to the details given above.

[0133] List of acronyms and / or non-limiting examples of materials used : Variable Stiffness (VS) Fiber Jamming (FJ)- Minimally-invasive surgery (MIS)- Remote Magnetic Navigation (RMN)Sleeves (S): Silicone (DragonSkin0020)Sealing caps (10, 11, 12) : Glue, preferably Silicone glue (Sil-poxy) Working channel (15): Polytetrafluoroethylene (PTFE)- Rear tube (RT): PTFE- PLA fibers (F): Polylactide Acid (PLA) Supporting rod (16): Carbon fiber (CF) Copper fibers (F): CopperSilicone tube : silicone- PU tube: Polyurethane (PU)Magnet (Ml, M2, M3): Neodymium+Iron+Boron (NdFeB) Assistive tube (AT): PTFEAssistive rod (AR): Carbon fiber

[0134] List of references used in the figures:1 variable stiffness catheter10 tip sealing cap11 first intermediate sealing cap12 additional intermediate sealing cap15 working channel16 supporting rodS sleeve- F fibers51 distal segment52 first intermediate segmentSV source of pressure or vacuumSC standard catheter- Ml distal magnet- M2 intermediate magnetCl distal pressure channelC2 intermediate pressure channelCU control unit2 system for surgical applications3 remote magnetic navigation systemAT assistive tube- RT rear tubePH 3D printerWM1 first winding machine- WM2 second winding machineFI filament

Claims

Claims1. A variable stiffness catheter (1) for surgical applications comprising at least one soft biocompatible hollow sleeve (S) and comprising a proximal end for holding the catheter (1) and a distal end for surgical insertion in a patient’s body, said catheter (1) further including:- a tip sealing cap (10) at the distal end for closing the catheter (1),- a working channel (15) enclosed within said sleeve (S) and extending through said proximal and distal ends, up to a working end for applying a treatment outside the catheter (1), through said tip sealing cap (10),- a plurality of fibers (F) enclosed within said sleeve (S) and having a length defining a distal segment (SI) of the catheter (1),- an inlet attachable to a source (SV) of vacuum or pressure for applying vacuum or pressure inside said distal segment (SI),- at least one distal magnetically responsive element, called magnet (Ml), disposed at the distal end, wherein said fibers (F) are held at only one of their ends and assembled in at least one bundle such that applying vacuum inside said distal segment (SI) induces a fiber jamming resulting in a stiffening of this segment, said distal segment (SI) thereby having variable stiffness defined by a soft state and a stiff state.

2. The variable stiffness catheter (1) according to claim 1, further comprising at least one distal magnetically responsive element, called magnet (Ml), disposed at said distal segment (SI) which is configured for a remote magnetic navigation surgical approach using a standard hospital-compatible remote magnetic navigation System (3) for applying a magnetic field within the recommended magnitude range, by having a stiffness in the soft state allowing it to bend smoothly upon the application of said magnetic field and a stiffness in the rigid state allowing it to maintain minimal deflection despite the presence or absence of said magnetic field, such that said catheter (1) can be dynamically controlled by varying its shape during remote magnetic navigation in the patient’s body.

3. The variable stiffness catheter (1) according to claim 1 or 2, further comprising at least one pair of tendons running through at least part of the length, preferably the whole length, of the catheter and connected to a handle comprising buttons for actuating the tendons which are free to translate along the length of the catheter and bend it by this translation transmitted to the locations where they are fixed to the catheter, such that said catheter can be dynamically controlled by varying its shape during remote magnetic navigation in the patient’s body.

4. The variable stiffness catheter (1) according to any one of the preceding claims, further comprising at least one first intermediate sealing cap (11) spaced from the tip sealing cap (10) by a distance equal or larger than the length of the fibers (F) to delimit said distal segment (SI), said inlet comprising a distal pressure channel (Cl) inside said sleeve (S) and extending from thesource (SV) of vacuum or pressure to said distal segment (SI), through said first intermediate sealing cap (11).

5. The variable stiffness catheter (1) according to any one of the preceding claims, wherein said fibers (F) of the distal segment (SI) are held at only one of their ends by said distal (10) and / or first intermediate (11) sealing cap.

6. The variable stiffness catheter (1) according to any one of the preceding claims, wherein said proximal end is pluggable, in a fluid-tight manner, on a distal end of a standard catheter (SC) used for surgery applications, or of a rear tube (RT), which further encloses at least the working channel (15), such that said standard catheter (SC) or rear tube (RT) is extended by said variable stiffness catheter (1) and cooperates with said proximal end to form said inlet when connected to said source (SV) of vacuum or pressure.

7. The variable stiffness catheter (1) according to claim 4, wherein, for supporting the actuation of the catheter (1), said inlet comprises at least one supporting rod (16) and / or cooperates with said distal end of said standard catheter (SC) or rear tube (RT) which has a stiffness higher than the stiffness of said variable stiffness catheter (1) at least in its soft state.

8. The variable stiffness catheter (1) according to any one of the claims 2 to 4, further comprising:- a plurality of fibers (F) enclosed within said sleeve (S) and extending between said first intermediate sealing cap (11) and said proximal end and having a length defining a first intermediate segment (S2) of the catheter (1),- an intermediate inlet attachable to a source (SV) of vacuum or pressure for applying vacuum or pressure inside said first intermediate segment (S2), wherein said fibers (F) are assembled in at least one bundle such that applying vacuum inside said first intermediate segment (S2) induces a fiber jamming resulting in a stiffening of this segment, said first intermediate segment (S2) thereby having variable stiffness defined by a soft state and a stiff state.

9. The variable stiffness catheter (1) according to claim 8, further comprising at least one intermediate magnetically responsive element, called magnet (M2), disposed at said first intermediate segment (S2) which is configured for a remote magnetic navigation surgical approach using a standard hospital-compatible remote magnetic navigation System (3) for applying a magnetic field within the recommended magnitude range, by having a stiffness in the soft state allowing it to bend smoothly upon the application of said magnetic field and a stiffness in the rigid state allowing it to limit its deflection despite the presence or absence of said magnetic field, such that said catheter (1) can be dynamically controlled by varying its shape during remote magnetic navigation in the patient’s body.

10. The variable stiffness catheter (1) according to claim 9, further comprising at least one additional intermediate sealing cap (12) spaced from said first intermediate sealing cap (11) by a distance equal or larger than the length of fibers enclosed therein and delimiting an additionalintermediate segment (S3) also enclosing fibers (F), said inlet comprising a distal pressure channel (Cl) and an intermediate pressure channel (C2), inside said sleeve, and extending from the source (SV) of vacuum or pressure to said distal segment (SI) and said first inter-mediate segment (S2), respectively, through the respective intermediate sealing caps (11, 12).

11. The variable stiffness catheter (1) according to any one of claims 8 to 10, wherein said first intermediate sealing cap (11) and / or said additional intermediate sealing cap (12) comprises an intermediate magnet (M2) for actuation by said magnetic field or a fixation for a tendon connected to a handle at the proximal end of the catheter and comprising buttons for impeding a translation movement to the tendon, such that said intermediate segments (S2, S3) of the catheter can be dynamically controlled by varying its shape during remote magnetic navigation in the patient’s body.

12. The variable stiffness catheter (1) according to claim 10 or 11, wherein said fibers (F) of said first intermediate segment (S2) are held at only one of their ends by said first intermediate (11) and / or additional intermediate (12) sealing cap.

13. The variable stiffness catheter (1) according to claims 8 to 12, wherein the various segments (SI, S2, S3) include fibers (F) of different materials having different bending moments and stiffnesses when submitted to vacuum and / or said at least one bundle comprises fibers (F) of only one material or comprises a mix of fibers (F) of different materials.

14. The variable stiffness catheter (1) according to any one of the preceding claims, wherein:- the ratio of the stiffness in the rigid state by the stiffness in the soft state defines a factor, called stiffness change factor (SCF), the segment (SI) or segments (SI, S2, S3) of the catheter (1) having a factor of at least three, preferably four or more, to be suitable for a safe navigation upon application of a magnetic field within the recommended magnitude range by a deflection of less than fourth in the rigid state compared to the soft state;- the stiffness in the soft state is comprised between 15 and 175 mN / mm, preferably between 50 and 100 mN / mm or preferably at least lower than 100 mN / mm;- the stiffness in the rigid state is comprised between 50 and 750 mN / mm, preferably between 250 and 500 mN / mm or preferably at least higher than 250 mN / mm.

15. The variable stiffness catheter (1) according to any one of the preceding claims, wherein the material and / or diameter of the fibers (F) and / or the number of fibers (F) in a segment (SI, S2, S3) are adjusted for said remote magnetic navigation surgical approach, generally according to the size of the magnet (Ml, M2) and the material and diameters of the sleeve (S), by having a stiffness in the rigid state limiting the deflection of a segment (SI, S2, S3) such that the magnitude of the magnetic field required for a small deflection is higher than the magnitude inducing a large deflection in the soft state.

16. The variable stiffness catheter (1) according to any one of the preceding claims, wherein the material and / or diameter of the fibers (F) and / or the number of fibers (F) in a segment (SI, S2, S3 and the material and diameters of the sleeve (S) are configured to be adjusted for amagnetic or mechanical navigation surgical approach by having a stiffness in the rigid state limiting the deflection of a segment (SI, S2, S3) such that the magnitude of the magnetic field or of the applied mechanical force to the tendons via a handle required for a small deflection is higher than the magnitude of the magnetic field or applied mechanical force to the tendons via handle inducing a large deflection in the soft state.

17. The variable stiffness catheter (1) according to any one of the preceding claims, wherein the fibers (F) have a diameter comprised between 5 and 160 pm, preferably between 50 to 150 pm or at least smaller than 145pm, and the number of fibers (F) in a segment (SI, S2, S3) is comprised between 50 to 10000, preferably more than 100 and / or the outer diameter of the sleeve (S) is comprised between 0,3 and 3 mm, preferably 0,5 to 2 mm, with an inner diameter preferably larger than 75% of the outer diameter.

18. System (2) for surgical applications through a remote magnetic navigation surgical approach, said system (2) comprising at least one variable stiffness catheter (1) according to any one of claims 1 to 12, at least one source (SV) of pressure or vacuum and a control unit (CU) for controlling the pressure or vacuum applied to at least one segment (SI, S2, S3) of said catheter (1) by said source (SV).

19. System (2) according to claim 13, wherein said variable stiffness catheter (1) is a catheter (1) according to any one of claims 6 to 12 and wherein the control unit (CU) dynamically and synergically controls the pressure or vacuum applied to several segments (SI, S2, S3).

20. A method for fabricating a variable stiffness catheter (1) according to any of the claims 1 to 12, the method comprising:• fabrication of ultra-thin fibers having a diameter preferably less than 160pm or even between 30 to 100pm, via a first winding machine (WM1) which pulls a melted polymer or composite filament (FI) through its spinning spool, said melted polymer or composite filament (FI) being obtained via a 3D printing machine (PH) arranged close to said first winding machine (WM1) directly pulling on the filament (FI) during its extrusion,• manufacturing of at least one sleeve (S) with a consistent sleeve wall thickness,• manufacturing of at least one bundle of fibers (F), by mounting the filament (FI) onto a second winding machine (WM2) which reformats the fibers into a fiber bundle with the desired number of fibers,• production of the distal segment (SI) involving :Insertion (e.i) of at least one bundle of fibers (F) inside said sleeve (S) using an assistive tube (AT),Insertion (e.ii) of a working channel (15) through the distal segment (SI),- Removal of the assistive tube (AT), creation (e.iv) of the tip sealing cap (10), preferably by application of glue at the distal end of the distal segment (SI) for holding the fibers (F) bundle, and insertion (e.v) of a magnet (Ml) at the tip sealing cap (10).

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