Action-reaction tube steering mechanism having meandering members

Abstract

The surgical system includes a steering mechanism. The steering mechanism comprises a first tube including a first meandering beam formed on the side wall of the tube and a second tube including a second meandering beam formed on the side wall of the tube. The first and second tubes are coaxially superimposed, and the first and second meandering beams are positioned so as to be at least partially aligned with each other and oriented toward different radial directions at an angle. The first and second tubes are connected to each other at the distal end of the first and second meandering beams. The first and second meandering beams define a bending segment that can be actuated to form a bend in the superimposed tube structure in response to a differential axial force applied to the first and second tubes.

Description

Technology Field

[0001] Related applications

[0002] The present application claims priority to U.S. Provisional Patent Application No. 63 / 273,679 filed on October 29, 2021, the subject matter of which is incorporated into this specification in its entirety by this reference.

[0003] Government funding

[0004] This invention was made with government support under grant numbers R44DK126606, R44DC019894, and R44EB031741 granted by the National Institutes of Health. The U.S. government holds certain rights to this invention.

[0005] Technology field

[0006] The present invention relates to a steering medical device configured to perform surgical operations. More specifically, the present invention relates to a steering medical device comprising an action-reaction tube steering mechanism that implements a meandering beam element. Background Technology

[0007] There is an urgent need in flexible endoscopy to create steerable surgical tools capable of providing dexterity to the tip of a flexible endoscope. When steered to the surgical site via the endoscope, these tools are particularly important for dexterity-driven tasks, such as tissue retraction and resection in colorectal endoscopy, or access-driven tasks, such as reaching corners to retrieve hard-to-reach kidney stones in flexible ureteroscopy. Controlled manually or robotically, these endoscopic trans-tools enable the surgeon to perform tasks that are difficult or impossible to accomplish with the basic functions of the endoscope alone. Prior art literature

[65535] U.S. Patent Application Publication US2019 / 0133705 (May 9, 2019) means of solving the problem

[0008] The surgical system includes a steering instrument. According to one aspect, the steering instrument includes a first tube having a first serpentine beam formed in its tubular sidewall and a second tube having a second serpentine beam formed in its tubular sidewall. The first and second tubes are nested concentrically, and the first and second serpentine beams are positioned to be at least partially axially aligned with each other and to face radially different directions at an angle. The first and second tubes are connected to each other distally from the first and second serpentine beams. The first and second serpentine beams define a bending segment that can be actuated to form a bend in the nested tube structure in response to different axial forces applied to the first and second tubes.

[0009] According to another aspect, the first tube may include a plurality of parallel first slots extending through the side walls of the first tube perpendicular to the central axis of the first tube. The first slots are angularly eccentric in a fore-and-aft manner. The first slots define a first meandering beam. The second tube may include a plurality of parallel second slots extending through the side walls of the second tube perpendicular to the central axis of the second tube. The second slots are angularly eccentric in a fore-and-aft manner. The second slots define a second meandering beam.

[0010] According to another aspect, the first meandering beam may include lateral beam portions extending parallel to each other on opposite sides of the first slots and longitudinal beam portions that alternately interconnect adjacent ends of the lateral beam portions. The second meandering beam may include lateral beam portions extending parallel to each other on opposite sides of the second slots and longitudinal beam portions that alternately interconnect adjacent ends of the lateral beam portions.

[0011] According to another aspect, the first and second meandering beams can be configured so that the adjacent transverse sections of the first and second meandering beams engage with each other at touch points located on opposite sides of the longitudinal beams connecting the transverse sections, where the touch points limit the deflection of the bending segments.

[0012] According to another aspect, the first and second meandering beams may be configured so that adjacent transverse portions of the first and second meandering beams contact at a contact point that limits the bending of the bending segment.

[0013] According to another aspect, the contact points can be configured to define the state in which the bend segment is fully bent.

[0014] According to another aspect, the bend segment can be configured such that differential axial forces applied to the first and second tubes push the contact points against each other to increase the stiffness of the bend segment in a fully bent state.

[0015] According to another aspect, the first tube may include a plurality of first meandering beams extending parallel to each other along the length of the bend segment, and the second tube may include a plurality of second meandering beams extending parallel to each other along the length of the bend segment.

[0016] According to another aspect, the first tube may include a plurality of parallel first slots extending through the side walls of the first tube perpendicular to the central axis of the first tube. The first slots may be arranged in rows of slots radially spaced apart from each other. Each row of the first slots may be eccentric in angle with respect to adjacent rows, wherein the first slots define a plurality of first meandering beams. The second tube may include a plurality of parallel second slots extending through the side walls of the second tube perpendicular to the central axis of the second tube. The second slots may be arranged in rows of slots radially spaced apart from each other. Each row of the second slots may be eccentric in angle with respect to adjacent rows, wherein the second slots define a plurality of second meandering beams.

[0017] According to another aspect, the first slots of each row may have the same length, and the second slots of each row may have the same length.

[0018] According to another aspect, the first slots of each row may be two different lengths arranged in an alternating pattern, where the second slots of each row may be two different lengths arranged in an alternating pattern.

[0019] According to another aspect, the steering mechanism may include a plurality of bend segments spaced apart axially along the length of the steering mechanism. The plurality of bend segments may include a first bend segment and a second bend segment. The first and second bend segments may each be formed by individual first meandering beams formed on a first pipe sidewall and second meandering beams formed on a second pipe sidewall that are axially aligned with each other.

[0020] According to another aspect, the first and second bending segments can be configured to bend in different directions when operated.

[0021] According to another aspect, the first and second bend segments can be separated into transition regions of the first and second tubes that do not have slots in the tube sidewalls.

[0022] According to another aspect, the first and second bending segments can be configured to be bent in opposite directions so as to take an S shape when the steering mechanism is operated.

[0023] According to another aspect, the respective positions of the first and second slots can be gradually adjusted with respect to the central axis so that they are bent out of plane in a spiral manner when the bending segment is actuated.

[0024] According to another aspect, the first and second slots may include contact aids that limit the bending movement of the bending segment in opposite bending directions.

[0025] According to another aspect, each contact aid may include a convex member protruding from the transverse member, located within a corresponding concave recess on an adjacent transverse member.

[0026] According to another aspect, each contact aid may have a dovetail structure, wherein a convex member is equipped with a dovetail pin and a concave housing is equipped with a dovetail tail.

[0027] According to another aspect, at least some of the first and second slots may include a stress relieving cutout at their ends.

[0028] According to another aspect, the steering mechanism may include a first insertion axis extending proximally from a first meandering beam and a second insertion axis extending proximally from a second meandering beam. The first and second insertion axes may be configured to be flexurally compliant to adopt a tortuous path with axial stiffness and torsional stiffness that sufficiently transmit force and torque to a bending segment of the steering mechanism located distally from the proximal end of the insertion axes, and to be flexurally compliant to exhibit the same flexural stiffness regardless of the direction of the load.

[0029] According to another aspect, the first insertion axis may include a polymer flexible tube located adjacent to and connected to the first tube, a braided wire reinforcing layer covered or embedded in the flexible tube, and a polymer jacket that covers the braided wire to help secure the braided wire on the flexible tube. The second insertion axis may include a polymer flexible tube located adjacent to and connected to the second tube, a braided wire reinforcing layer covered or embedded in the flexible tube, and a polymer jacket that covers the braided wire to help secure the braided wire on the flexible tube.

[0030] According to another aspect, the braiding density of the braided wire varies along at least one length of the first and second insertion axes, thereby allowing adjustment of flexibility, axial stiffness, and torsional stiffness along the length of the insertion axis.

[0031] According to another aspect, the flexible tubes can be fixed to each second tube by one of the following methods: embedding the tube in a flexible tube material, connecting the flexible tube to an outer tube with adhesive, or forming the flexible tube into a thin jacket attached to the outer tube.

[0032] According to another aspect, the first and second insertion axes may include respective portions of the first and second tubes extending proximally from their respective meandering beams and each tube sidewall may have a plurality of slots. The slots may extend orthogonally to the central axis of the first and second tubes and may be arranged in rows extending radially around the central axis. The slots may be configured to have bending ductility so that the first and second insertion axes can adopt a meandering path, exhibiting the same bending stiffness regardless of the direction of the load, and to have axial stiffness and torsional stiffness so as to transfer force and torque to a bending segment of a steering mechanism located distally from the proximal end of the insertion axes.

[0033] According to another aspect, the pitch of the slots arranged along the first and second insertion axes varies along the length of the first and second insertion axes, so that the flexibility, axial stiffness, and torsional stiffness of the first and second insertion axes are adjusted along the length.

[0034] According to another aspect, the steering mechanism may include a polymer jacket that covers the fold segment to prevent tissue from entering the slots.

[0035] According to another aspect, the slots defining the death penalty slots can be configured so narrowly that the organization cannot enter them.

[0036] According to another aspect, the steering mechanism may be a composite steering mechanism comprising a first and a second steering mechanism. The second steering mechanism may be configured to extend through the inner lumen of the first steering mechanism.

[0037] According to another aspect, the surgical system may include a transfer device configured to be inserted and manipulated to be positioned at the surgical site. The steering mechanism may be configured to have a bending segment located outside the transfer device, together with the rest of the steering mechanism that advances through the transfer device and is positioned within the transfer device and supported by it.

[0038] According to another aspect, the transfer device may include an endoscope, a flexible endoscope, or other steering mechanism.

[0039] According to another aspect, the transfer device may be configured such that a steering mechanism supported by the transfer device, together with a bending segment located outside the transfer device, can support a surgical instrument extending through the lumen of an overlapping tubular structure for tissue manipulation at the surgical site. Brief explanation of the drawing

[0040] The above and other features and advantages of the present invention will be obvious to those skilled in the art by considering the description of the present invention with reference to the accompanying drawings, and similar reference numerals in the drawings refer to similar parts throughout the drawings unless otherwise stated, in the drawings: FIG. 1 is a perspective view illustrating a planar meandering beam member used as a standard for explaining the performance of a steering mechanism. FIG. 2a is a perspective view illustrating a pair of tubes having oblique beam members configured to overlap together to form a steering mechanism that can be implemented as a surgical system. FIGS. 2B and 2C are perspective views showing the tubes of FIG. 2A that are coaxially superimposed to form a steering mechanism, and manipulators of different bending states. Figures 3a and 3b illustrate the parameters of a meandering beam pattern implemented as a steering mechanism. FIGS. 4a and 4b are side and front / plan views of a bend segment of a steering mechanism formed by overlapping tubes and meandering members, showing a bend segment in a non-operational state. FIGS. 4c and 4d are side and front / plan views of the bend segment of FIGS. 4a and 4b illustrating the bend segment in an operating state. FIG. 5a is a plan view illustrating a cut pattern used to form a single meandering beam member pattern of a tube used to form a steering mechanism. FIGS. 5b, c, and d are plan, side, and bottom views of a tube having a single meandering beam member pattern formed through the cut pattern of FIG. 5a, respectively. FIG. 6a is a plan view illustrating the cut pattern used to form the double meandering beam member pattern of the tube used to form the steering mechanism. FIGS. 6b, c, and d are plan, side, and bottom views of a tube having a double meandering beam member pattern resulting from the cut pattern of FIG. 6a, respectively. FIG. 7a is a plan view illustrating the cut pattern used to form the triple meandering beam member pattern of the tube used to form the steering mechanism. FIGS. 7b, c, and d are plan, side, and bottom views of a tube having a triple meandering beam member pattern resulting from the cut pattern of FIG. 7a, respectively. FIG. 8a is a plan view illustrating a cut pattern used to form a quadruple meandering beam member pattern of a tube used to form a steering mechanism. FIGS. 8b, c, and d are plan, side, and bottom views of a tube having a quadruple meandering beam member pattern resulting from the cut pattern of FIG. 8a, respectively. FIG. 9a is a plan view illustrating a cut pattern used to form an n-fold meandering beam member pattern of a tube used to form a steering mechanism. FIGS. 9b, c, and d are plan, side, and bottom views of a tube having an n-fold meandering beam member pattern resulting from the cut pattern of FIG. 9a, respectively. FIG. 10a is a plan view illustrating a cut pattern used to form an n-fold meandering beam member pattern with angular spacing in a tube used to form a steering mechanism. FIGS. 10b, c, and d are plan, side, and bottom views of a tube having an n-fold meandering beam member pattern with an angular spacing resulting from the cut pattern of FIG. 10a, respectively. FIG. 11a is a plan view illustrating a cut pattern used to form a meandering beam member pattern in which the linear spacing gradually decreases in a tube used to form a steering mechanism. FIGS. 11b, c, and d are plan, side, and bottom views of a tube having a meandering beam member pattern with gradually decreasing linear spacing resulting from the cut pattern of FIG. 11a, respectively. FIG. 12a is a plan view illustrating a cut pattern used to form a meandering beam member pattern in which the cut portion and slot overlap angle gradually increase in a pipe used to form a steering mechanism. FIGS. 12b, c, and d are plan, side, and bottom views of a tube having a serpentine beam member pattern with a gradually increasing slot overlap angle and a cut portion resulting from the cut pattern of FIG. 12a, respectively. FIG. 13a is a perspective view illustrating a pair of tubes configured to overlap coaxially to form a steering mechanism, wherein the tubes are configured to have a single meandering beam member pattern having a progressive angular eccentricity. FIGS. 13b and 13c illustrate the tubes of FIG. 13a that overlap coaxially to form a steering mechanism, and show actuators of different bending states representing a meandering beam member pattern resulting from an out-of-plane bending profile. FIG. 14a is a perspective view illustrating a pair of tubes configured to overlap coaxially to form a steering mechanism, wherein the tubes are configured to have two discrete meandering beam member patterns at spaced positions along their lengths. FIGS. 14b and 14c are perspective views of the tubes of FIG. 14a that overlap coaxially to form a steering mechanism and show actuators of different bending states representing a linearly spaced discrete meandering beam member pattern resulting in an S-shaped bend when sagged. FIG. 15 illustrates the progression steps of the operation of the steering mechanism of FIG. 14a and 14b, showing how the S bend portion unfolds. FIGS. 16a-16d are the resulting top, side, and bottom views, along with a plan view illustrating a cut pattern used to form a meandering beam member pattern configured to include a contact aid that increases torsional stiffness and prevents overextension of the tube used to form a steering mechanism. FIG. 16a is a plan view illustrating a cut pattern used to form a meandering beam member pattern configured to include a contact aid that increases torsional stiffness and prevents overextension of the tube used to form a steering mechanism. FIGS. 16b, c, and d are top, side, and bottom views of a tube containing a single meandering beam member pattern formed through the cut pattern of FIG. 16a, respectively. FIG. 17 illustrates the configuration of other sections of a steering mechanism including an insertion shaft according to one exemplary configuration. FIG. 18 illustrates an exemplary tube configuration having a meandering beam member and a laser-patterned insertion axis. FIG. 19 illustrates an exemplary configuration of an insert shaft having variable stiffness generated through slot pitch variation. FIGS. 20a and 20b illustrate an exemplary configuration of two steering mechanisms superimposed coaxially to form a multi-degree-of-freedom steering mechanism system. FIG. 21a illustrates an exemplary configuration of a multi-degree-of-freedom steering mechanism system formed of two coaxially superimposed steering mechanisms, in which one of the superimposed steering mechanisms conveys a surgical tool to its distal end. FIG. 21b illustrates an exemplary configuration of a multi-degree-of-freedom steering mechanism system formed by two steering mechanisms that are conveyed side by side in the inner cavity of a third steering mechanism. FIG. 21c illustrates an exemplary configuration of a multi-degree-of-freedom steering mechanism system formed by two steering mechanisms that are conveyed side-by-side in the lumen of a flexible operable endoscope, which has an internal steering mechanism that conveys a surgical instrument at its distal end and acts as an external steering structure. FIG. 22 is a plan view illustrating exemplary configurations of a meandering beam member having stress-reducing cuts at their ends, with slots defining the meandering beam member. FIG. 23 illustrates an exemplary two-handed endoscope system comprising two multi-degree-of-freedom steering mechanisms that are conveyed to a flexible endoscope. Specific details for implementing the invention

[0041] Steerable instrument with serpentine beam elements

[0042] The present invention relates to a surgical system using steering instruments used in endoscopic surgical procedures. The surgical system may be operated manually, wherein the operation of the steering instrument is performed through manual control. The surgical system may be operated robotically, wherein the operation of the steering instrument is controlled by the surgeon or is performed via a robot pre-programmed to execute specific routines. The surgical system may also be operated in combination with manual and robotic operation.

[0043] In the present invention, the steering mechanism is an agonist-antagonist steering mechanism composed of a pair of tubes that overlap coaxially within one another. The tubes are cut through their individual sidewalls and include slots that define one or more longitudinally extending serpentine beam elements that deviate the neutral axis of each tube from the geometric axis. When the steering mechanism is assembled, the beam elements are axially aligned and positioned to face radially opposite each other, such as radially opposite each other at 180 degrees, to define a bending segment. The tubes are interconnected at the distal end of the bending segment, and the bending segment is actuated in an agonist-antagonist manner by applying an axial differential push / pull force to the tubes. The actuation causes the bending segment to bend in opposite directions based on the direction of application of the axial push / pull force. This configuration utilizes the bending characteristics of cylindrical form factor meandering beam members to generate bent segments.

[0044] In use, the bend segment may be used to steer the tubes and / or to manipulate tissue through the use of a surgical instrument carried by the tubes. In this specification, an assembled coaxial tube structure is illustrated and described as a steerable instrument, wherein the bend segment is used to control or "steer" the instrument. The bend segment is typically, but not always, located at the distal tip of the instrument.

[0045] The "steering" function of the bend segments can serve various purposes: delivering and using surgical instruments, approaching hard-to-reach locations on the patient's body, and guiding or directing other instruments to perform surgical procedures. In embodiments where the device is used to deliver and use surgical instruments, the bend segments may be used to manipulate tissue through the instruments. In other embodiments, hollow tubes may be used for fluid / drug delivery and / or aspiration. In embodiments where the device is used to provide access to a surgical site, the hollow configuration of the tubes enables the introduction of wires (e.g., ablation lasers), control cables (e.g., for operating mechanical instruments), or the instruments themselves (e.g., surgical probes, baskets). Actuable steering mechanisms may also be used to transport and guide other steering mechanisms. The term “steerable instrument” as used in this specification is intended to encompass a steerable coaxial tube having a bent segment composed of serpentine members configured to implement all these functions in any combination.

[0046] Serpentine beams are generally used in microelectromechanical systems (MEMS) to create flexural elements capable of undergoing precise zero-backlash deformation along multiple predefined axes. As shown in FIG. 1, the serpentine beam element (10) comprises a single beam of material that meanders forward and backward to a guide or working end (14) and is grounded at a fixed end (12). The forward and backward configuration of the beam element (10) increases the effective length for bending, thereby providing flexibility in in-plane and out-of-plane directions.

[0047] The serpentine beam member (10) has cross-sectional dimensions, i.e., width ( w ). thickness( t ), and effective length( l It can be configured to exhibit much higher axial and bending compliance than a single (straight) beam having the same cross-sectional area defined by ). This ductility is achieved through the careful design of the meandering beam, namely the width of the beam in Fig. 1 ( L a ), pitch of the beam ( L b ), and base dimensions ( L c It can be further 'tuned' by modifying parameters such as ). In the MEMS space, meandering beams are typically used as bearings in applications where traditional bearings such as ball bearings, bushings, and gears cannot be used on a small scale, along with inertial measurement units and nano positioners.

[0048] As described in this specification, a steerable medical device enhances the preferential bending of a millimeter-scale tube by utilizing the bending characteristics of a monolithic meandering beam member, wherein two or more tubes having this characteristic are combined to create preferential bending in multiple directions. Surgical systems implement steering mechanisms through manual control, robotic control, or a combination of manual and robotic control. Several exemplary configurations of this steering mechanism that can be implemented in a surgical system are disclosed below, the first of which is illustrated in FIGS. 2a-2c.

[0049] In FIG. 2a, the steering mechanism (20) comprises an inner tube (22) and an outer tube (24) configured such that the inner tube is inserted into the outer tube and overlaps, as roughly indicated by the dotted line in FIG. 2a. Each tube (22, 24) comprises one or more slots (26, 28) that form a meandering beam member (30, 32). Unlike traditional planar meandering beam members commonly used in MEMS, the meandering beam members (30, 32) formed in the tubes (22, 24) are bent because they are wound around the circumference of a cylinder. The beam members (30, 32) are formed through micro-machined slots (26, 28) in the side walls of the tubes (22, 24). In FIGS. 2a-2c, each tube (22, 24) comprises a single meandering beam member (30, 32) formed by a series of slots (26, 28) extending through radial portions of the tube sidewalls in a direction orthogonal to the central axis of the tube. The meandering beam members (30, 32) accordingly comprise lateral beam portions extending radially along the tube sidewalls between adjacent parallel slots (26, 28) and longitudinal beam portions extending axially along the tube sidewalls to alternately interconnect the ends of adjacent lateral beam portions (see FIG. 3a).

[0050] The slots (26, 28) are spaced apart from each other along the longitudinal direction of the tube and are angularly eccentric, that is, rotated relative to each other in the front and back directions, to form a serpentine pattern of each beam (30, 32). The slots (26, 28) and the corresponding beam members (30, 32) may be configured, that is, in size, spacing, number, dimensions, etc. Formed on the side walls of the tubes (22, 24), the cylindrical serpentine beam members (30, 32) locally reduce the bending stiffness along the side of the tube where they are formed. Consequently, this eccentrically deviates the neutral bending axis of the tube from its geometry, which promotes preferential bending of the tubes (22, 24) in the region of the beams (30, 32).

[0051] In the assembled state of the steering mechanism (20), the inner tube (22) is inserted into the outer tube (24) and advanced so that the beam members (30, 32) are aligned axially with each other, and the serpentine beam members (30, 32) are rotated so that they face opposite directions in the radial direction shown in FIGS. 2a-2c. Once the inner tube (22) is installed inside the outer tube (24) so ​​that the beam members (30, 32) are aligned axially and face opposite directions, the tubes are interconnected or fastened to each other at the distal end of the beam members. This connection or fastening is performed, for example, at the distal end (34) of the mechanism (20).

[0052] In the assembled state of the steering mechanism (20), the beam members (30, 32) define a bendable portion or bend segment (40) that can be actuated to cause the formation of a bend along its length. The actuation of the bend segment (40) is achieved by a relative axial movement of the overlapping tubes (22, 24) in a push / pull manner. When a pushing force is applied to the tubes, the inner tube (22) is pushed into the outer tube (24) toward the connection with the outer tube. In the exemplary configuration of FIGS. 2a-2c, the pushing force on the inner tube (22) forces it toward the distal end (23) of the steering mechanism (20). When a pulling force is applied to the tubes, the inner tube (22) is pulled out of the outer tube (24) away from the connection with the outer tube. In the exemplary configuration of FIGS. 2a-2c, the pulling force on the inner tube (22) forces it away from the distal end (23).

[0053] Of course, the axial pushing and pulling force is not limited to being applied only to the inner tube (22). The pushing and pulling force may be applied to the inner tube (22), the outer tube (24), or both the inner tube and the outer tube. For example, the pushing force is a differential axial force (f) on the tubes (22, 24) in net opposite directions relative to each other, as shown in FIG. 2b. inner , f outer ) can be established by applying. As another example, the pulling force is a differential axial force (f) on the tubes (22, 24) in net opposite directions relative to each other, as shown in FIG. 2c. inner , f outer It can be set by authorizing ).

[0054] As shown in FIGS. 2b and 2c, the bending segment (40) is configured to be operable in both directions, that is, a pushing operation causes bending and flexion in the first direction of the bending segment, and a pulling operation causes deflection and bending in the opposite direction. This is because the tubes (22, 24) overlap together so that the serpentine members (30, 32) are axially aligned and the neutral axes of each tube are diagonally opposite and radially reversed (radially opposite). When the tubes (22, 24) are fastened at the distal end (34) of the steering mechanism (20), a differential axial force (f) applied to the proximal end of the bending segment inner , f outer In response to ), the bending segment (40) is bent. The bending occurs around the compound neutral axis of the tubes (22, 24). As shown in FIGS. 2b and 2c, the bending can be reversed simply by reversing the direction of the differential axial force applied to the proximal end.

[0055] In the exemplary configurations of FIGS. 2a-2c and other exemplary configurations described herein, the serpentine beam members of the inner and outer tubes are axially aligned so as to completely overlap each other and rotated to face each other radially. The axial alignment of the bend segment formed by the serpentine beam members may deviate from this configuration. For example, the axial alignment of the serpentine beam members may partially overlap and / or the beam members may be configured to face each other in a radial direction that is not necessarily 180 degrees apart. This may be useful in embodiments where it is desirable for the bend section to be bent in a non-planar direction. In these non-180-degree embodiments, the bend section may generate a combination of bending and twisting that creates an out-of-plane helical bend when actuated.

[0056] Nitinol as a Tube Material

[0057] The tubes used to construct the steering mechanisms described in this specification may be made of Nitinol, a superelastic alloy of nickel and titanium. While the serpentine beam profile may be utilized in tubes made of any common engineering material, the steering mechanisms disclosed in this specification, configured to manipulate tissues and operate surgical instruments, require a combination of properties in which many common materials are less desirable than in Nitinol. Although materials other than Nitinol, such as stainless steel, have been proven suitable for the construction of steering mechanisms, Nitinol has been proven to be the best. This does not mean that other materials, such as stainless steel or even some plastics, are unsuitable, but simply that Nitinol is ideal in terms of performance.

[0058] Conventional materials such as steel, titanium, or aluminum, which exhibit high Young's modulus (200 GPa, 100 GPa, and 70 GPa, respectively) but have very low yield strain (0.1-0.2%), limit the amount of bending that can be achieved before permanent plastic deformation and fracture in tubes produced from these materials. Accordingly, these metals are ideal for embodiments of surgical instruments / tools requiring strength, (torsional) rigidity, and (bending) stiffness, such as cutters, grippers, and probes, but are less suitable for embodiments requiring flexibility and elasticity.

[0059] Conversely, many medical-grade plastics commonly used in the construction of flexible medical tubules and other instruments (such as polyether block amide (PEBA), nylon, or polyimide, which have much higher yield strain (10-100%) but low Young's modulus (0.1-2.0 GPa)) severely limit the achievable stiffness of tubules produced from these materials. Accordingly, these plastics are ideal for embodiments requiring strength, flexibility, and elasticity, but are less suitable for embodiments requiring (torsional) rigidity and (bending) stiffness.

[0060] Nitinol combines the most desirable properties of these conventional metal and plastic materials. Nitinol provides high bending stiffness (Young's modulus 40–80 GPa) and the ability to undergo large deformation before plastic deformation (yield deformation >8%). These properties are essential for creating steering mechanisms capable of generating large distal forces to bend auxiliary medical tools and manipulate patient tissues, while generating large displacements for high dexterity and a large reachable workspace. This combination of physical properties makes Nitinol ideal for constructing the steering mechanisms described in this specification.

[0061] In applications where a steering mechanism is configured to deliver medical tools, fluid flow, or suction / irrigation while being delivered via a flexible delivery platform (such as a flexible endoscope or other steering device), maintaining very thin walls is of paramount importance to maximize the internal space of the steering mechanism through which the tool, fluid, or suction is delivered. Maintaining thin walls introduces issues related to kink resistance, along with torsional and axial stiffness. Ideal materials possess high Young's modulus, high shear modulus, and high yield strain. Nitinol possesses all of these characteristics.

[0062] The superelastic properties of Nitinol (exhibiting a low stiffness behavior range of 1% to 8%) reduce the operating force required for a given distal bend compared to similar metals, which greatly promotes the use of the material for manual actuation devices that require mechanical input from a human to generate the proximal force required to bend the tip of the device.

[0063] Beam Profile Generalizability

[0064] The configuration of the serpentine cut pattern creates a 'spine' on one side of the tube and a serpentine pattern on the opposite side. Various parameters of the serpentine cut pattern can be modified to alter the bending characteristics of the tube. These parameters shown in Figures 3a and 3b include the following:

[0065] - Pitch - The longitudinal spacing (h) between continuous meandering members. When all other parameters are constant, a larger pitch (smaller spacing) increases bending ductility and decreases torsional stiffness.

[0066] - Slot Overlap Angle - The 'width' of the serpentine meander, standardized to the pipe circumference and expressed as an angle (). The overlap angle between adjacent slots. All other parameters being constant, bending ductility increases as the overlap angle increases.

[0067] - Cut Fraction - Total angle occupied by the slot (r o α). When all other parameters are constant, bending ductility increases as the incision area increases.

[0068] - Number of Parallel Serpentines - The number of serpentine members. As the number of parallel serpentines increases, bending ductility decreases and torsional stiffness increases.

[0069] - Slot Width - The width (λ) of individual slots. When all other parameters are constant, increasing the slot width creates a larger bending angle for the steering mechanism.

[0070] From a purely kinematic perspective, the maximum bending angle of a single meandering beam member can be calculated given the design variables listed above. The pipe circumference φ In the region of = 2π - α, it is not incised, leaving a slotless spine (solid backbone), while the total width of the pattern is specified by the angle parameter α. Since the size of the spine relative to the size of the tube affects its stiffness, it must be selected so that the tube is not too stiff for operation but remains robust. The spine dimensions also determine the position of the neutral axis relative to the centerline: this distance ( γ ) can be obtained by the following relationship and:

[0071] (1)

[0072] Here, γ o , γ i , A o , and A i They are the neutral axis positions and areas of circular sectors formed by the outer and inner radii of the non-incision area, respectively:

[0073]

[0074]

[0075]

[0076] (2)

[0077] Here r o and r i These are the outer and inner radii of the tube, respectively.

[0078] The slot overlap angle (β) determines how far the slots are from the centerline of the tube where they self-contact, which is the physical limit of the tube bend. This distance from the centerline is given as follows, as shown in Fig. 3b:

[0079] (3)

[0080] Next, we need to determine the relationship between the slot closure and the change in the length of the device. Here, it is assumed that the change in the total length of the sheath is proportional to the change in the length of a set of slots; in other words, for each slot spacing (h), the maximum change in the length of that segment of the tube is the slot height (λ). Accordingly, the following can be obtained:

[0081] (4)

[0082] Here is the length of the external neutral axis (this length does not change and is a design input). As can be seen in the right half of Fig. 3b, there are three lengths all associated with the same bending angle (θ). is the centerline length of the device and is the length of the device at the meandering pattern end points. Then

[0083] (5)

[0084] By using a common bending angle, these lengths can be related.

[0085] (6)

[0086] Here, κ n , κc, and κ s ε₀, ε₀, and ε₀ are the curvatures of the neutral axis, centerline, and the oblique beam end point, respectively. If we define the relationship between the curvatures using the geometric structure of the tube:

[0087] (7)

[0088] Here and γ are the distances from the centerline to the neutral axis as solved using equations (1) and (2). Using this curvature relationship and equation (5), the maximum bending angle of the tube due to the closing of the meandering slots and self-contact can be solved:

[0089] (8)

[0090] Using the derived relationship, the maximum bending angle of the patterned tube can be calculated. Alternatively, given a desired bending angle or curvature, the problem can be solved for other desired parameters. Accordingly, the bending segments of the steering mechanism can be adjusted to the specific procedure for which it was designed.

[0091] FIGS. 4a-4d illustrate how the aforementioned meandering beam parameters define the bending profile of the steering mechanism (50) having a bending segment (50) formed by a meandering beam member (54) defined by a series of slots (56) cut through the sidewall of the tube. FIGS. 4a and 4b show the front and side views of the steering mechanism (50) in a non-operational state, in which the bending segment (52) is not bent and has a straight configuration coaxial with adjacent parts of the tube. In this state, the meandering beam member (54) is not bent, and the configuration / spacing of the slots (56) is uniform throughout the bending segment (52).

[0092] As best illustrated in FIG. 3b, the meandering beam members (54) include transverse beam sections (54a) that extend along the pipe sidewall between adjacent slots (56) and longitudinal beam sections (54b) that extend axially along the pipe sidewall and alternately interconnect the ends of the adjacent transverse beam sections.

[0093] FIGS. 4c and 4d show front and side views of a steering mechanism (50) in an operating state in which a bending segment (52) is bent to form a bending configuration. In the operating state of the bending segment (52), the meandering beam members (54) are bent at the longitudinal beam portions (64b), and the adjacent transverse beam portions (54a) come into contact with each other at the contact point (58) at the end opposite the bending point. From this, it can be seen how the parameters of the tube, such as pitch (λ) and slot width (h), determine the maximum curvature of the bending segment (52).

[0094] Contact at the contact point (58) defines the fully bent state of the bend segment (52). When the bend segment (52) is in the fully bent state, the differential axial force applied to the tubes maintains the bend segment in the fully bent state. The increase in the differential axial force applied to the aforementioned tubes required to reach the fully bent does not cause additional bending because the contact at the contact point (58) prevents its occurrence. However, preferably, the increase in the differential axial force will increase the (torsional) stiffness and (bending) stiffness of the bend segment (52). This may be particularly useful when the steering mechanism (50) is used for tissue manipulation. In this case, the rigid / stiff bend segment (52), supported by the conveying device, can manipulate the tissue without itself being bent as a result of the force acting with the tissue.

[0095] The steering mechanism (50), or any of the various steering mechanisms disclosed herein, and the transfer device that transports it through its interior may be varied. For example, the steering mechanism (50) may be transported through a rigid endoscope or a flexible endoscope. Alternatively, the steering mechanism (50) may be transported through another steering mechanism configured according to one or more exemplary configurations disclosed herein. As yet another alternative, the serpentine bending segment (52) may be implemented as a built-in component of the flexible endoscope transfer device. In this case, the bending segment may be configured larger to facilitate the transport of surgical tools and other components through the inner lumen of the bending segment. This will enable the transport of, for example, a camera or other device.

[0096] Different Serpentine Configurations

[0097] FIGS. 5a–12d illustrate various exemplary serpentine beam member configurations that are implemented in the tubes of a steering mechanism to form bend segments. FIGS. 5a–12d illustrate these various serpentine beam patterns within a single tube, with the understanding that this pattern will be implemented in two tubes, which are assembled as previously described to form the steering mechanism and its bend segments. The variety of configurations of the serpentine beam member(s) determines the bending characteristics of the bend segments they form. In each of these exemplary configurations, the bend segment is depicted as being located at the distal end of the tube. However, the location of this bend segment is limited. All bend segment configurations disclosed in FIGS. 5a–12d can be applied at any location along the length of the steering mechanism.

[0098] Single-Serpentine

[0099] A tube (60) having a bend segment (62) formed in a single meandering beam pattern is shown in FIGS. 5a-5d. FIG. 5a is a plan view showing the distal end of the tube (60), where the tip (70) configured to connect the tube to another overlapping tube (not shown) is indicated by a circle. However, the bend segment (62) can be located at any position along the tube (60).

[0100] In FIG. 5a, the tube (60) appears to be cut and spread along the spine (68) (see FIG. 5d) to aid in the visualization of the meandering beams (64) and slots (66) defining the beam. Top, side, and bottom views of the tube (60) are shown in FIG. 5b–5d, respectively. This single meandering beam member (64) extends longitudinally on the low-rigidity side of the tube (60) opposite the spine (68). The single meandering beam pattern of FIG. 5a–5d provides the highest bending ductility (single meandering beam with the longest meander) and the lowest torsional rigidity. This pattern is best suited for small (<1.5 mm tube diameter) medical devices with low torsional load requirements, such as applications requiring steering of energy tools (laser fibers) or tools requiring only axial force (nitinol baskets).

[0101] The common design rules to be followed when designing a single meandering pipe (60) are as follows:

[0102] - Slot overlap angle (r o β): The overlap angle for a single meander must be between 10 and 180 degrees.

[0103] - Incision area (σα): The incision area must be between 190 and 320 degrees. If it is smaller, the tube becomes too stiff (limiting overall curvature), and if it is larger, the non-incisional 'spine' will become too vulnerable.

[0104] - Slot width (λ): 25 µm–200 µm. The lower limit is limited by the kerf (i.e., spot size) of the laser used to manufacture the serpentine beam members, which is typically 25 µm. The lower limit value may vary depending on improvements in the manufacturing method. The upper limit value is also increased in other situations where a larger tube than the one described above is used or where the application requires a larger cap / increased bend per gap.

[0105] Double-Serpentine

[0106] A tube (80) having a bent segment (82) formed in a double meandering beam pattern is shown in FIGS. 6a-6d. FIG. 6a is a plan view showing the distal end of the tube (80), where the tip (90), configured to connect the tube to another overlapping tube (not shown), is indicated by a circle. However, the bent segment (82) can be located at any position along the tube (80).

[0107] In FIG. 6a, the tube (80) appears to be cut and unfolded along the spine (92) (see FIG. 6d) to aid in the visualization of the meandering beams (84) and slots (86) defining the beam. Top, side, and bottom views of the tube (80) are shown in FIG. 6b–6d, respectively. The double meandering pattern shown in FIG. 6a–6d is created by effectively forming two meandering beam members (84) (reflectively symmetric with respect to the tube centerline) that extend parallel from the preceding two slots into a single slot (68) that is rotationally eccentric and connected to two slots (86) of equal length. The individual meandering beams of the double meandering beam pattern are identified as 84a and 84b in FIG. 6a. The double meandering beam configuration offers good bending ductility and appropriate torsional stiffness, making it most suitable for applications of appropriate inner diameter (1.5-3 mm tube diameter) that require higher torsional stiffness due to interaction forces with the tissue.

[0108] Triple-Serpentine

[0109] A tube (100) having a bent segment (102) formed in a triple meandering beam pattern is shown in FIGS. 7a-7d. FIGS. 7a is a plan view showing the distal end of the tube (100), where a leading end (112) configured to connect the tube to another overlapping tube (not shown) is indicated by a circle. However, the bent segment (102) can be located at any position along the tube (100).

[0110] FIG. 7a shows a plan view that helps visualize the serpentine beams (104) and slots (106) defining the beam, as if the tube (100) is cut longitudinally along the spine (110) (see FIG. 7d). Top, side, and bottom views of the tube (100) are shown in FIG. 7b–7d, respectively. The secure triple serpentine pattern in FIG. 7a–7d includes three serpentine beams (104) extending parallel to each other on the low-rigidity side of the tube. This effectively forms three serpentine beams (104) extending parallel to each other by forming two incisions (106, 108) of different lengths that are staggered longitudinally. The individual serpentine beams (104) of the triple serpentine beam pattern are identified as 104A, 104B, and 104C in FIG. 7a.

[0111] The triple meandering beam profile of the tube (100) provides adequate bending ductility and high torsional rigidity, making it best suited for larger inner diameter applications (2-3 mm tube diameter) where tissue manipulation is likely to generate high torsional forces by creating large off-axis loads. The triple meandering beams (104) are arranged around the circumference of the tube at 100-degree increments. The beam (104B) on the opposite side of the slotless vertebra (110) typically has a larger overlap angle than the two "side" beams (104A, 104C).

[0112] Quadruple-Serpentine

[0113] A tube (120) having a bend segment (122) formed in a quadruple meandering beam pattern is shown in FIGS. 8a-8d. FIG. 8a is a plan view showing the distal end of the tube (120), where a leading end (134) configured to connect the tube to another overlapping tube (not shown) is indicated by a circle. However, the bend segment (122) can be located at any position along the tube (120).

[0114] FIG. 8a shows a plan view that helps visualize the oblique beams (124) and slots (126) defining the beam, as if the tube (120) is cut longitudinally along the spine (130) (see FIG. 8d). Top, side, and bottom views of the tube (120) are shown in FIG. 8b–8d, respectively. The secure quadruple oblique pattern in FIG. 8a–8d includes three oblique beams (124) extending parallel to each other on the low-rigidity side of the tube. This effectively forms three oblique beams (104) extending parallel to each other by forming two cuts (126) of equal length that are staggered longitudinally. The three oblique beams (124) of the quadruple oblique beam pattern are identified as 124A, 124B, and 124C in FIG. 8a. The fourth meandering step pattern (124D) extends along the spine (130) as shown in FIG. 8d.

[0115] The quadruple meandering beam pattern shown in FIGS. 8a-8d differs from the previous patterns of FIGS. 5-7 in that the slotless vertebra is replaced by another meandering beam (132) having much higher bending stiffness than the other three meandering beams (123A, 124B, 123C). The higher bending stiffness along the vertebra (130) is due to the smaller overlap angle of the slots (126) along the vertebra.

[0116] The quadruple meandering configuration of the tube (120) provides appropriate bending ductility and high torsional rigidity, making it most suitable for steering mechanisms of larger inner diameters (2-3.5 mm tube diameter) where the transport and tissue manipulation of more robust tools are required to yield high torsional loads. As with the triple meandering pattern, beams are arranged around the circumference of the tube in 90-degree increments, with one meandering beam on each of the four "sides" of the tube. Two beams having the highest bending rigidity (beam 132) and the lowest bending rigidity (beam 114B), which are generated by the lowest and highest overlap angles, are positioned on opposite sides above the spine and on the upper part of the tube (120), while two side beams (beams 114A and 114C) have the same overlap angle and have uniform bending rigidity in that direction.

[0117] An additional advantage of the quadruple meandering configuration is that, while still shifting the neutral axis to one side of the cross section, the bending stiffness of the tube (120) can be controlled independently in two orthogonal planes—the operating plane and the plane orthogonal to the operating plane / tube cross section plane. For example, these bidirectional bending stiffnesses can be the same for a single tube. This is useful for reducing parasitic torsional deformation, which can result from unequal stiffnesses and misalignment of tubes. This can also simplify the modeling and control of the multi-tube steering mechanism described in this specification.

[0118] n-Serpentine

[0119] The number of parallel meandering members can theoretically be increased indefinitely. Likewise, meandering beam patterns can be located at positions at any angle around the circumference of the tube. The number of parallel meandering members is ultimately limited by the circumference of the tube and manufacturing limits. Examples of tubes (140, 160) having n-fold meandering beam member bend segments (142, 162) are shown in FIGS. 9a-9d and 10a-10d, respectively.

[0120] FIGS. 9a-10d shows a plan view that helps visualize the slots defining the serpentine beams, as the tube (140, 160) is depicted as being cut longitudinally along the spine (150, 170) (see FIG. 9d). A tube (120) having a bend segment (122) formed in an n-fold serpentine beam pattern is shown in FIGS. 9a-9d. FIGS. 9 and 10 are plan views showing the distal ends of the tubes, where the tip (148, 168), configured to connect the tube to another overlapping tube (not shown), is indicated by a circle. However, the bend segments (142, 162) may be located at any position along the tube (140, 160).

[0121] In FIGS. 9a-9d, the slots (146) are arranged in groups of three cuts that are linearly aligned around the circumference of the tube (140) and have the same length and spacing with respect to the circumference of the tube. These groups are staggered, that is, rotated relative to each other around the tube axis so that adjacent groups are eccentric in the rotational direction relative to each other. This can be referred to as the angular spacing of the slots (146) or groups of slots. The arrangement of the slots (146) that are angularly spaced into groups creates meandering beams (144) that extend parallel to each other along the length of the tube (140).

[0122] Likewise, in FIGS. 10a-10d, the slots (166) are arranged in groups of three cuts that are linearly aligned around the circumference of the tube (160) and have the same length and spacing with respect to the circumference of the tube. These groups are staggered, that is, rotated relative to each other around the tube axis so that adjacent groups are eccentric in the rotational direction relative to each other. This can be referred to as the spacing of the slots (166) or the groups of slots. The arrangement of the slots (166) that are angularly spaced into groups creates meandering beams (164) that extend parallel to each other along the length of the tube (160).

[0123] The configuration of the serpentine beams (144, 164) in FIGS. 9a-10d is due to the difference in the spacing of each slot (142, 162). The pitch or spacing between the slots (142, 162) is the same. What causes the difference between the tubes (140, 160) in FIGS. 9a-9d and 10a-10d is the spacing between the groups of slots (142, 162). In FIGS. 9a-9d, the spacing between each pair of slots (142) within a group is centered on adjacent slots. In FIGS. 10a-10d, the spacing between each pair of slots (162) within a group is located near the ends of adjacent slots. Consequently, the beam (144) in FIGS. 9a-9d differs in configuration from the beam (164) in FIGS. 10a-10d.

[0124] Methods for Variable Curvature

[0125] In the tubes of FIGS. 5a-19d, the configuration of the serpentine beam members is defined by slot cutting patterns. The length and spacing of the slot(s) at each axial position along the length of each group, i.e., the bend segment / tube, as well as variations in the relative positions of the slots / spaces at each axial position, contribute to the resulting serpentine beam(s), which are bent uniformly along the length of the bend segment. All cutting patterns disclosed in FIGS. 5-10 can be modified, for example, to increase or decrease the number of bends in the serpentine beam patterns, to increase or decrease the pitch of the serpentine beam patterns, or to increase or decrease the curvature of the bend segment by a combination of these modifications.

[0126] An exemplary configuration of a bend segment generating variable bend segment curvature is illustrated in FIGS. 11a-12d. Variable bend segment curvature can be implemented, for example, by producing a tip-first bend or by correction through the accumulation of friction between two overlapping tubes. Variable curvature can be induced through variations in pitch, cut portion, slot overlap angle, or a combination of these parameters.

[0127] For example, in FIG. 11, the variable curvature of a tube (180) having a single meandering beam member bend segment (182) is realized through a linear reduction in pitch. In this example, all slots (186) have the same length, width, and rotational spacing, and the pitch between slots gradually decreases from proximal to distal. Consequently, the width of the meandering beam member (184) gradually decreases from proximal to distal. When the distal end of the bend segment (182) is configured to coincide with the distal end of the tube (180), a 'tip-first' bend is created because the bending stiffness of the meandering beam member (186) is lowest at the distal end of the bend segment (182) and increases in the proximal direction.

[0128] In another example, in FIG. 12, a variable curvature bend segment (202) of a single meandering beam member (200) is implemented with a uniform pitch in which the lengths of the slots (206) and the overlap of adjacent slots increase from proximal to distal along the bend segment. Consequently, the pitch spacing of the meandering beam member (204) decreases linearly from proximal to distal. Then, a 'tip first' bend is created because the bending stiffness of the meandering beam member is lowest at the distal end of the bend segment and increases in the proximal direction.

[0129] Method for Inducing Out-Of-Plane Bending

[0130] In some applications, it may be desirable for the steering mechanism to have an out-of-plane 'twist' to prevent collision with itself at large bending angles. This is illustrated in the exemplary steering mechanism configurations of FIGS. 13a-13c. In FIGS. 13a-13c, the steering mechanism (220) includes a bend segment (222). In FIGS. 13a-13c, the bend segment (222) is located at the distal end (224) of the steering mechanism (220). However, the bend segment (222) may be located at any desired position along the length of the tube (200).

[0131] The steering mechanism (220) includes an inner tube (230) and an outer tube (140). The inner tube (230) has a bend segment (232) comprising a serpentine beam member (234) defined by a series of slots (236) cut through the sidewalls of the tube. The outer tube (240) has a bend segment (242) comprising a serpentine beam member (244) defined by a series of slots (246) cut through the sidewalls of the tube. In each tube (230, 240), the slots (236, 246) are gradually angularly eccentric along the length of each bend segment (232, 243). In the assembled state of the steering mechanism (220) shown in FIGS. 13b and 13c, the inner tube (230) is positioned inside the outer tube (2400) such that each bend segment (232, 242) is axially aligned and rotated 180 degrees to face in the opposite direction.

[0132] The steering mechanism (220) is configured to bend the bend segment (222) in opposite directions as shown in FIGS. 13b and 13c by operation through axial pushing and pulling forces through the tubes (230, 240). In FIG. 13b, the bend segment (222) is actuated by a pushing force in which the inner tube (230) is pushed toward the outer tube (240), as indicated by the arrow labeled PUSH in FIG. 13c, the bend segment (222) is actuated by a pulling force in which the inner tube (230) is pulled toward the outer tube (240), as indicated by the arrow labeled PULL in FIG. 13c.

[0133] Through a pushing and pulling operation, the steering mechanism (220) can be operated in opposite directions while controlling the pushing and pulling force applied to the tubes. As shown in FIGS. 13b and 13c, the angular eccentricity between the slots (236, 246) and the beams (234, 244) causes the neutral axis of each tube (230, 240) to twist in a spiral shape around the geometric axis of the tube. Consequently, when the bending segment (222) is actuated, it is bent in an out-of-plane spiral shape as shown in the drawings. If the tubes (230, 240) are configured to include a bend segment (232, 242) having slots (236, 246) and beams (234, 244) configured in the same way, the bend segment (222) will operate in the same out-of-plane spiral shape, but will operate in the opposite direction depending on the pushing and pulling force applied to the steering mechanism (220) as shown in FIG. 13b and 13c.

[0134] The size of the out-of-plane bend is determined by the amount of angular eccentricity between consecutive slots (236, 246). This capability may be useful for preventing self-collision between the proximal end of the distal end of the steering mechanism (220) at large bends (>180 degrees), or for preventing the proximal section of the bend segment (222) itself from obstructing the camera's field of view in applications where the mechanism is configured to transport an endoscope camera.

[0135] Methods for Locally Modifying the Bend Direction

[0136] In some applications, it may be useful for the steering section of the steering mechanism to include a reversal of the bending direction. This may be particularly important in applications where two steering mechanisms are transported through a flexible endoscope in a two-hand configuration. In this configuration, the steering mechanism can be configured to achieve triangulation, for example, by bending slightly out of the camera's field of view and then returning to the field of view.

[0137] A steering mechanism (240) having a plurality of bend segments (242, 244) is illustrated in FIGS. 14a-14c. One bend segment (242) is located distally on the steering mechanism (240), and another bend segment (244) is located proximally. The steering mechanism (240) includes an inner tube (250) installed within an outer tube (260) so that the tubes are interconnected at the distal end or the leading end (246) of the steering mechanism. The inner tube (250) includes two meandering members (252, 254) defined by two discrete sections of slots (256, 258) that are cut through the side wall of the tube and arranged to conform to any method disclosed in this specification, such as the method disclosed in FIGS. 2a-2c. The inner tube (260) is cut through the side wall of the tube and includes two oblique beam members (262, 264) defined by two discrete sections of slots (266, 268) arranged to conform to any method disclosed in this specification, such as the method disclosed in FIG. 2a-2c. When the steering mechanism (240) is assembled, the beam members (252, 262) are aligned with each other to form a bent segment (242), and the beam members (254, 264) are aligned with each other to form a bent segment (244).

[0138] The bend segments (242, 244) may be rotated angularly relative to each other and separated by a solid section of the tube defining a transition area (248) as shown in FIGS. 14a-14c. Alternatively, the bend segments may meet in a transition area where a series of slots (254, 264) define a bend segment (242) that gradually decreases from the proximal direction toward the end point (e.g., as disclosed in FIGS. 11a-11d), or conversely, a series of slots (254, 264) define a bend segment (242) that gradually increases from the proximal direction toward the end point. In the exemplary configuration of FIGS. 14a-14c, the bend segments (242, 244) are rotated 180 degrees relative to each other so that the steering mechanism (240) takes on an S-shaped configuration when the bend segments are actuated.

[0139] FIG. 15 illustrates the incremental actuation of the bend segments (242, 244) of the steering mechanism (240). As shown in FIG. 15, the bend segments (242, 244) are configured to produce bends in opposite directions separated by a slotless transition region. As the bend segments (242, 244) are actuated, their curvature increases until they are fully bent at the final frame. From this, it can be seen that the reach of the steering mechanism (240) can be configured for the intended application.

[0140] Increasing Stiffness through Contact Aids

[0141] The steering mechanism can be configured to exhibit a dramatic change in bending or torsional stiffness beyond the desired bending or torsional angle through contact aids and self-impact. This may be desirable to prevent over-extension of the steering mechanism or to create a stable, high-rigidity platform for other tools or devices passing through the steering mechanism. This can be useful, for example, when the tip of the steering mechanism is guided to the surgical site while a tool passing through the lumen of the steering mechanism is used to perform a surgical procedure requiring as rigid support as possible, such as tissue resection. In these scenarios, a transport device, such as an endoscope (rigid or flexible), can transport the steering mechanism to the approximate area of ​​the surgical site, allowing the steering mechanism to navigate to the precise location of the surgical site. While the endoscope certainly provides the required degree of rigid support, it is of no use if the steering mechanism fails to do so. Accordingly, the steering mechanism may include a feature in the form of a contact aid that enhances stiffness so that the curvature of the steering mechanism is held in place during operation.

[0142] This example is illustrated in FIGS. 16a-16d. FIG. 16a shows a plan view of the distal end of a tube (280) including a bend segment (282) located at the distal end of the tube, indicated by circles configured to connect the tube to another overlapping tube (not shown). However, the bend segment (282) may be located at any position along the tube (280). The plan view shows the tube (280) cut longitudinally along the spine (292) (see FIG. 16d) to aid in visualizing the oblique beam (284) and the slots (286) defining the beam. Top, side, and bottom views of the tube (280) are illustrated in FIGS. 16b-16d, respectively.

[0143] The slots (286) define a serpentine beam (284) comprising a plurality of beam members (294) extending forward and backward as described in this specification. As best illustrated in FIG. 16a, the slots (286) are configured to have contact aids in the form of dovetail components that prevent the slots from opening infinitely, thereby increasing the rigidity of the steering mechanism at a defined bending angle. In the configurations of FIG. 16a-16d, the slots (286) define a pin (296) on one side of each beam member (294) and a tail (298) located opposite the pin. Consequently, the pin (296) of each beam member (294) is located at the tail (298) of the immediately adjacent beam member (294).

[0144] The pins (296) and tails (298) have a roughly trapezoidal configuration, with the pins separated from the tails that are accommodated within the width of the slots (286) forming them. The trapezoidal configuration of the pins (296) and tails (298) creates interference with both bending directions, providing a hard stop for both closing and opening of the bending segment (282). Accordingly, if a surgical tool transported to a surgical site, for example, via a steering mechanism within coaxial tubes, includes the aforementioned dovetail configuration, the operation of the tool resulting in a force opening the curvature of the bending segment (282) will be blocked by the interaction of the pins (296) and tails (298).

[0145] As an additional component, the pins (296) and tails (298) also serve to increase torsional rigidity by limiting relative twisting between the serpentine members (294). Accordingly, when a twisting force is applied to the bending segment (282), such as due to the use of a surgical tool being transported to the surgical site via a steering mechanism, the rotation of the serpentine members (294) relative to each other will be blocked by the interaction of the pins (296) and tails (298).

[0146] It should be understood that the contact aids are not limited to the dovetail components shown in FIGS. 16a-16d. For example, similar or identical results may be achieved through slots configured to define a keyhole-shaped component protruding from a beam member and located in a corresponding keyhole-shaped recess of an adjacent beam member. In fact, similar or identical results may be achieved through a convex component protruding from a beam member and located in a corresponding concave recess on an adjacent beam member. Furthermore, the slots may be configured to produce one or more contact aids, such as two or more dovetail components, on each beam member, which can further improve the (torsional) stiffness of the bend segment and resistance to rotation in response to operating forces encountered during use.

[0147] Methods for Delivery through Flexible Endoscopes

[0148] If the steering mechanism disclosed in this specification is configured to be conveyed via other flexible conveying devices, such as other steering sheaths, flexible endoscopes, or endoscopes having internal serpentine beam bend segments, the distal working end of the steering mechanism containing the bend segment(s) and the serpentine beam member(s) will be separated from the proximal actuation end by a considerably long distance, such as 70 cm to 2000 cm. Additionally, the portion between the proximal actuation end and the distal working end of the steering mechanism will generally follow a curved path. To enable the transmission of differential force and common mode torque from the proximal actuation end to the steerable distal working end through a curved profile, the steering mechanism may be conveyed via an insertion shaft that provides preferential bending, axial, and torsional characteristics. The insertion shaft may replace the proximal portion of the steering mechanism's sheath, and the distal end of the sheath containing the bend segment is maintained by a nitinol tube connected to the insertion shaft.

[0149] When transported via flexible endoscopes or other flexible transport systems, it is important that the insertion shaft exhibits an appropriate degree of bending ductility so that it can assume a twisted shape forced by the curved profile of the transport system. Furthermore, the bending stiffness of the insertion shaft must be ductile in all directions to prevent the steering mechanism from settling into a preferred (lowest stiffness) configuration that generates a torsional deadband (described later) and produces a 'snapping' effect (i.e., it must exhibit the same bending stiffness regardless of the direction of the load). Finally, the insertion shaft must exhibit appropriate axial and torsional stiffness to sufficiently transmit force and torque from the proximal actuation system of the steering mechanism to the distal working end.

[0150] Torsional 'snapping' occurs due to the rapid release of energy resulting from a sudden transition from one low-energy (low-stiffness) state to another as the tube rotates while constrained within a curved path. When this occurs, the tube snaps from one low-energy state to another, and the steering tip is observed to rotate rapidly and uncontrollably between two angles. Snapping can be prevented if the insertion shaft has ductility in all directions (i.e., the bending stiffness is the same regardless of the direction of the load).

[0151] Snapping can occur even in tubes with high torsional ductility due to curved path constraints and friction at the contact surface between the tubes. As the tube rotates at the proximal end, friction is generated at the contact surface between the tube and the path, which is a function of the tube's bending stiffness (the greater the stiffness, the greater the friction). If the tube also has low torsional stiffness, torsional energy accumulates within the tube up to a certain critical angle of rotation (torsional windup), and at that point, the stored torsional energy is rapidly released by overcoming the interface friction, causing sudden and uncontrollable unwinding at the distal end. This can be prevented by creating a tube with low bending stiffness and high torsional stiffness.

[0152] Fixation to flexible polymer tube insertion shafts

[0153] In FIG. 17, the steering mechanism (300) comprises a bending segment (302) formed by coaxial inner and outer tubes (304, 306) in which serpentine beam members (308) are formed. The bending segment (302) and the beam members (308) that aid in defining the bending segment may have any configuration described herein. The difference between this steering mechanism (300) and other configurations described herein is that each of the inner tube and outer tube (304, 306) occupies only the distal section (330) of the mechanism instead of extending along the length of the steering mechanism (300) from the proximal end (310) to the distal end (312). Instead, each of the inner tube and outer tube (304, 306) of the bending segment (302) is connected to an insertion shaft (320) that extends from the tubes / distal section (330) to the proximal end (310).

[0154] The insertion shafts (320) are themselves tubular in their configuration and are configured so that one overlaps the other, providing the same function as described in this specification for other steering mechanism configurations in terms of controlling the transport and operation of the bending segment (302). The difference, of course, lies in their configuration and material composition. Although the insertion shaft (320) shown in FIG. 17 is connected to the outer tube (306) of the bending segment (302), it should be understood that the identification of the tube—outer or inner tube—is not important because the configuration of the insertion shaft is the same in either case. Accordingly, the description of the insertion shaft (320) describes the insertion shaft of the outer tube (306) and the insertion shaft of the inner tube (304).

[0155] The insert shaft (320) may have various configurations using different materials and / or components selected to provide desired performance characteristics such as axial-to-axial friction, tube stiffness (axial and torsional), and flexibility. In the exemplary configuration of FIG. 17, the insert shaft (320) comprises a flexible polymer tube (332) connected to the tube (306), a braided wire (352) wrapped around the outside of the flexible tube for reinforcement, and a polymer jacket (354) covering the braided wire. The construction of the insert shaft (320) may be configured such that the configuration changes along its length to exhibit variable stiffness characteristics. This may be achieved continuously through a gradual increase or decrease in braided wire density and / or the inclusion of longitudinal braided members. This may also be achieved discretely through the use of different jacket materials with varying stiffness at different locations along the tube. Generally, assuming all other characteristics remain constant, a higher braid density will exhibit higher bending ductility, torsional stiffness, and torsional resistance, while an insert axis with a lower braid density will exhibit higher axial stiffness.

[0156] As shown in FIG. 17, the steering mechanism (300) comprises three sections, each configured to provide structural and functional characteristics set forth in the prior description so that the steering mechanism (300) functions as described in this specification. In particular, the mechanism (300) comprises a distal section (330), a transition section (340), and a proximal section (360) having a bending segment (302). Components of the insertion shaft (320) (i.e., a flexible tube (332), a braided wire (352), and a jacket (354)) may have portions that occupy all three sections (330, 340, 350) of the steering mechanism (300).

[0157] As described above, the bend segment (302) is formed from one or more meandering members of tubes (304, 306) according to any of the exemplary configurations described in this specification. The coaxial tubes (304, 306) forming the bend segment (302) are interconnected at the distal end (312) of the mechanism. The distal end (306) may also include a radio-opaque marker (314) for visualization during image processing.

[0158] At the distal end (330), the steering mechanism (300) is secured to a flexible polymer tube (332) by passing through an adhesive bend segment or by being embedded in a polymer forming a tube. The flexible tube (332) may be a single medical-grade polymer material with or without a braided wire (352) reinforcement layer (e.g., nylon 12, PEBA, or polyimide) or a composite material composed of multiple other materials. The flexible tube (332) may be configured to exhibit required material properties—high omnidirectional bending ductility, high axial stiffness, and high torsional stiffness—through the selection and inclusion of the material and the configuration of the braided reinforcement layer. As shown in the detail of the distal section (330), the bend segment (302) of the steering mechanism (300) may be embedded in the tube (332) itself or in any of the other polymer materials. In any case, the material into which the bend segment (302) is embedded may be formed into a thin jacket (334) so ​​as not to affect the dexterity or operation of the bend segment. Accordingly, the insertion shaft (320) at the distal end (330) of the steering mechanism (300) may include only this thin jacket (334) covering the bend segment (302).

[0159] In the proximal section (350) of the steering mechanism (300), the insertion shaft (320) comprises a flexible tube (332) and a braided wire (352) reinforcing the tube (332). In the proximal section (350), the braided wire (352) may be coarsely woven (i.e., low braid density), which produces high axial stiffness to facilitate the transmission of force for the pushing and pulling operation of the bending segment (302). A polymer jacket (354) covers the braided wire (352) and the flexible tube (332). The jacket (354) may be composed of a material configured to cooperate with the material of an adjacent structure to which the insertion shaft contacts. For the insertion shaft (320) fixed to the exterior (306), the jacket (354) may contact a conveying mechanism, such as a flexible endoscope, to facilitate low friction so that the steering mechanism (300) can move freely within it. With respect to the insertion shaft fixed to the inner tube (304), the jacket (354) can contact the flexible tube (332) of the insertion shaft fixed to the outer tube (306) to promote low friction so that the inner insertion shaft can move freely within the outer insertion shaft, which helps prevent twisting and snapping.

[0160] In the transition section (340), the insertion shaft (320) has the same basic configuration as the proximal section (350), namely, a flexible tube (332), a braided wire (352), and a polymer jacket (354). One difference between the proximal section (350) and the transition section (340) is that the braided wire in the transition section (340) is woven more densely (i.e., higher braiding density) compared to the proximal section, which yields higher bending ductility, torsional stiffness, and torsional resistance.

[0161] In the transition section (340), since this section of the tube is expected to be located within the active bending section of a conveying device, such as a steerable endoscope, the insertion shaft (320) may have lower bending stiffness and thus undergo a smaller radius of curvature than the rest of the insertion shaft. This can be achieved through either the use of a higher density or low-durometer jacket layer (354) material of the braided reinforcement (352) (as illustrated).

[0162] Since there is an inverse relationship between flexibility and axial / torsional stiffness, it is desirable for the proximal section (350) to have axial and torsional stiffness so that it can transmit axial and torsional forces from the proximal end to the distal end. To achieve this characteristic, the proximal section (350) may be configured to have higher axial and torsional stiffness and lower bending ductility over a much longer length of the tube configured to be located within the passive section of the endoscope. This can be achieved through either a lower density of the braided reinforcement (352) and / or the use of a jacket layer (354) material with higher stiffness (higher hardness).

[0163] The materials used to construct the components of the insertion shaft (320) of the steering mechanism (300) may vary. In one specific configuration of the insertion shaft (320), the flexible tube (332) may be made of PTFE material, the braided wire (352) may be stainless steel, the polymer jacket (354) may be made of polyamide material, and the jacket (334) may be a thin layer of PTFE tube material or PEBA material connected to the PTFE tube, for example, through an adhesive.

[0164] Methods of Fixation

[0165] In one exemplary configuration of the steering mechanism (300), the inner and outer tubes (304, 306) of the bend segments (302) may be attached to the individual insertion shafts (302), that is, the flexible tubes may be attached to the individual flexible tubes (332) through overlapping adhesive bend segments that are fitted over the end portions of the inner / outer tubes and secured with a biocompatible adhesive. For excellent adhesion, the polymer surface to be bonded may be treated at a microstructural level (e.g., through plasma etching) to increase surface activity (especially in the case of materials composed of fluorinated polymers such as PTFE), and the metal surface may be cleaned of surface contamination and roughened.

[0166] Since this overlapping fold segment inherently adds wall thickness to the entire tube assembly, the total thickness of the overlapping fold segment can be reduced by selectively laser cutting the polymer jacket layer (354) before bonding to reduce the outer diameter of the insertion axis (332) at the overlapping position. For the insertion axis (332) having the braided wire (352), the jacket layer (354) can be extended distally past the braid / liner end (a secondary manufacturing process referred to as 'catheter tipping') to seal the fold segment (302) partially or entirely. This is further described below under the heading "Encapsulation" in this specification.

[0167] Laser-patterned Nitinol insertion shafts

[0168] Instead of configuring the insertion shaft with separate components (flexible polymer tube, braided wire, and jacket), the tube forming the bend segment extends along the entire length of the steering mechanism, and the insertion shaft can be formed through laser-cut slot patterns formed on its sidewall. Unlike the slots forming the meandering members of the bend segment(s), the slots forming the insertion shaft section are configured to exhibit omnidirectional bending ductility necessary to facilitate transport through a flexible transport device, such as a flexible endoscope.

[0169] FIG. 18 illustrates an insertion shaft portion (360) formed in a tube (362), which constitutes part of a steering mechanism. The tube (362) may be an outer or inner tube of a steering mechanism having any of the bend segment configurations disclosed herein. Only the insertion shaft portion (360) is shown in FIG. 18. It should be understood that the insertion shaft portion (360) is merely one section of the tube, and the bend segment implemented in the steering mechanism is located at the circumference of the insertion shaft portion, that is, to the left of the insertion shaft portion as seen in FIG. 18.

[0170] The insertion axis portion (360) is formed through a repeating pattern of slots (268) that alternate in a rotational direction along the length of the insertion axis. The distal section (364) of the insertion axis portion (360) has slots (368) arranged at a small pitch, which yields flexibility in that portion. The slot pitch increases toward the proximal section (366), which reduces the degree of flexibility. The laser-cut slot pattern of the insertion axis portion (360) is a circumferential brick pattern that serves to reduce the rigidity of the tube while maintaining the neutral axis at the geometric center of the tube, so that the tube is bent in all directions without a single preferential direction. Alternative patterns such as intermittent spirals, cell patterns, or interlocking patterns, puzzle piece patterns, etc., may also be implemented.

[0171] Eliminating Axial-Torsional Coupling

[0172] Axial-torsional coupling occurs when a pure tensile or compressive load is applied to a laser-patterned nitinol axis, inducing torsion in the axis. This commonly occurs when the tube is cut in a helical manner with a handedness that wraps around the circumference, or, conversely, when patterned in an 'interrupted spiral' pattern where a repeating slot pattern 'twists' around the circumference. High axial-torsional coupling of the insertion axis is detrimental to the overall function of the overlapping meandering beam tubes forming the bend segments. To function properly, the high-rigidity vertebrae of the meandering beam pattern tubes must be maintained diagonally opposite, and any relative torsion induced by the insertion axis when differential forces are applied can cause the vertebrae to become misaligned.

[0173] To prevent this, the incision patterns used in the design of the insertion axes must eliminate any axial / torsional coupling. This can be achieved by selecting only patterns with orthogonal incisions, which then eliminates the orientation. This can also be achieved by carefully designing patterns that are handed to offset the relative torsion between the two tubes with an axial / torsional coupling of the same and opposite direction by very carefully matching the chiral characteristics of the internal tubes and the insertion axes constituting them. In other words, if the two tubes containing the insertion axes are configured to twist by exactly the same amount under the same and opposite tensile forces, the torsional coupling effect is nullified, and the vertebra of the meandering section will maintain alignment and allow bending.

[0174] Variable Insertion Shaft Stiffness:

[0175] The laser cutting pattern forming the insertion axis portion so that the tube exhibits variable stiffness characteristics can also be configured to vary along the length of the tube. This is illustrated in FIG. 19, which shows a plan view of a tube (370) having a slot pattern defining three sections of the insertion axis. The tube (370) may be the outer or inner tube of a steering mechanism having any of the bend segment configurations disclosed herein. FIG. 19 is illustrated as if it has been cut longitudinally and unfolded to clarify the slot pattern of the tube. As shown in FIG. 19, the tube (370) includes a flexible section (372), a transition section (374), and a stiffness section (376) of the insertion axis, all defined by laser-cut slots (378) through the sidewalls of the tube.

[0176] The flexible section (372) is configured to exhibit axial and torsional stiffness to transmit axial under-torsional forces to the bending segment (not shown). The flexible section (372) is also configured to exhibit bending ductility to easily adapt to the active bending section of a transfer device such as a flexible endoscope.

[0177] The rigid section (376) of the tube (370) is configured to extend through the passive part of the transfer device, so it is significantly longer than the flexible section (372) and the transition section (374) and forms most of the insertion axis. Since there is an inverse relationship between flexibility and axial / torsional rigidity, it is desirable that most of the insertion axis, i.e., the rigid section (376), have as much axial and torsional rigidity as possible to transmit axial force and torque from the proximal end to the distal end, thereby limiting the amount of tube stretch resulting from the application of differential operating forces.

[0178] The transition section (374) is configured to produce a gradual transition from the flexible section (372) to the rigid section (345) and vice versa. Since parts of the transition section (374) may also be located within the active bending section of the transfer device, a certain degree of bending ductility may prove desirable.

[0179] The characteristics of the sections (372, 374, 476) can be configured through the pattern of the slots (378) of the tube (370). In the configuration shown in FIG. 19, the slots (378) are configured in an orthogonal cell pattern, which is uniform throughout the entire length of the insertion axis. The rigidity of the tube is determined by the pitch distance between the slots. In the flexible section (372), the pitch of the slots (378) is small and the slots are spaced apart so that they are uniformly close. In the rigid section (376), the pitch of the slots (378) is large and the slots are spaced further apart uniformly. In the transition section (378), the pitch varies so that it gradually increases from the flexible section (372) to the rigid section (376). However, the same effect will be achieved by the cut piece, slot width, total number of slots, or a combination of these parameters.

[0180] Methods for Achieving Multi-Degree-of-Freedom Bending

[0181] having a serpentine beam bend segment n In a certain steering mechanism comprising a set of pairs of coaxial tubes, since each steering mechanism can be inserted / retracted, rotated, and bent in both directions separately and individually, the total number of operable degrees of freedom is 3 n is. By superimposing one steering mechanism inside another, the degrees of freedom are doubled, that is n=2 If it is 3 n =6 degrees of freedom. These degrees of freedom (DoF) can be further increased by superimposing additional steering mechanisms.

[0182] For example, a 6-DoF mechanism (400) is illustrated in FIG. 20a-b. In FIG. 20a-b, a first steering mechanism (410) is installed within a second steering mechanism (420). The first steering mechanism (410) includes an overlapping inner tube and outer tube (412, 414), which are fixed to the distal end of the first steering mechanism. A bend segment (416) of the first steering mechanism is configured to include serpentine beam members according to the exemplary configuration shown and described in this specification. The bend segment (416) can be actuated by a pushing and pulling force applied to the inner tube and outer tube (412, 414). The second steering mechanism (420) includes an overlapping inner tube and outer tube (422, 424), which are fixed to the distal end of the second steering mechanism. The bending segment (426) of the second steering mechanism (420) is configured to have serpentine beam members according to the exemplary configuration shown and described in this specification. The bending segment (426) can be actuated by a pushing and pulling force applied to the inner tube and outer tube (422, 424). It should also be noted that the first steering mechanism (410) and / or the second steering mechanism (420) may have each insertion shaft portion (418, 428) including the slot configurations described above with reference to FIGS. 18 and 19.

[0183] Each of the first and second steering mechanisms (410, 420) can be operated in its individual 3-DoF manner, namely insertion / retraction, rotation, and bending / folding. As shown in FIG. 20b, the outer second steering mechanism (420) is considered the 'parent' actuator and the inner first steering mechanism (410) is considered the 'child'. This is because the operation of the child steering mechanism (410) is implicitly coupled to the operation of the parent steering mechanism (420), but the child can move independently relative to an inertia frame determined in the parent direction. As shown in FIG. 20b, the bending segment (426) of the parent steering mechanism (420) is actuated to create a bend that the child steering mechanism (410) follows, which controls the direction of the child steering mechanism when it departs from the parent. The departure direction of the child steering mechanism (410) is also controlled by the other three degrees of freedom of the parent steering mechanism (420), namely insertion / retraction and rotation. This allows the child steering mechanism (410) to be controlled by its own three degrees of freedom from the departure direction. Accordingly, the mechanism (400) can utilize the 6-DoF function.

[0184] In the design of the child steering mechanism (410), it is important that the insertion shaft (418) be flexible enough to enable the full expected range of bending of the bending segment (426) of the parent steering mechanism (420), while having sufficient rigidity for both axial and torsional directions to transmit rotation and force to the distal end of the child steering mechanism (410). The child insertion shaft (418) must also have omnidirectional ductility to prevent mechanical bias or preferential bending axes that could also limit the bending range of the parent steering mechanism (420). This can be achieved, for example, by configuring the child insertion shaft (418) according to the configuration described in this specification with reference to FIGS. 18 and 10. In the exemplary configuration of FIGS. 20a-b, the steering mechanisms (410, 420) are equipped with laser-cut nitinol insertion shafts (318, 428) having brick-shaped members that generate omnidirectional ductility. This same logic can be extended to mechanisms in which an arbitrary number of steering mechanisms overlap to form a multi-degree-of-freedom system.

[0185] The parent / child mechanism (400) of FIG. 20a-b can be implemented in various ways. For example, referring to FIG. 21a, the 6-DoF mechanism (400) can be configured such that the child sheath, i.e., the outer shell (414), itself is configured to transport a surgical tool such as a laser fiber (430).

[0186] Likewise, a multi-armed system can be created by overlapping multiple child steering mechanisms (410) within a single parent steering mechanism (420), so that the children can utilize 6 degrees of freedom since they are housed within the same parent. In this case, the parent steering mechanism (420) can be a different steering mechanism (see FIG. 21b) or a flexible endoscope (see FIG. 21b). In this exemplary configuration, each child steering mechanism (410) can be configured to transport a surgical tool as illustrated.

[0187] Methods for Stress Concentration Reduction

[0188] It is known that material stress increases and concentrates around sharp or abrupt discontinuities in the material, and if this stress is not properly relieved, it can cause material failure. FIG. 22 illustrates a portion of a tube (450) configured to form a portion of a bent segment (452) having a serpentine beam member (454) defined by a plurality of slots (456) cut through the sidewalls. To reduce stress concentration that may form at the end or root of each slot (456), the base of each slot may include a stress relief cut (458) that extends axially from the root in the direction of the central axis of the tube (450). In the exemplary configuration of FIG. 22, the cut (458) is similar to a T-shape. Other shapes, such as circular or elliptical cuts, may also be used. When the roots of the slots (456) are extended axially, the surface area where bending stress can be relieved increases, thereby reducing stress concentration in the slot roots, which otherwise would cause stress concentration as described above.

[0189] Suture (Encapsulation)

[0190] The sealing of the nitinol tubing used to construct the steering mechanisms described herein may be implemented in various ways, such as when the mechanism forms a part of the mechanism including an insertion shaft (see FIG. 17). For example, the nitinol tubing constituting the steering mechanisms described herein may be used to seal the slots, ensure watertightness, and prevent tissue from being 'pinched' within the slots during normal operation (e.g., low-hardness PEBA material sold by Arkema, Inc., PEBAX 35D® 　It may be located within other low-hardness biocompatible materials. This suture layer may also serve the purpose of electrically insulating the nitinol tip, which may be important for clinical applications requiring the use of electrosurgery. This suture layer may have a radiopaque component to improve the visibility of the steering tip for medical imaging. The suture material must be carefully selected so that its bending stiffness does not significantly reduce the bending capability of the steering mechanism.

[0191] As another alternative, "pinching" can be prevented by configuring the slot width to be small / narrow so that tissue cannot enter the space. In fact, the slot width can be configured to be so small / narrow that even liquid cannot pass through. Accordingly, the configuration of a fold segment with a narrow slot width can be used to prevent tissue pinching and also to form the fold segment watertight.

[0192] Likewise, a liner material that improves lubrication and facilitates the passage of the tool may be positioned within the inner diameter of the steering tube. As previously mentioned, this liner material must be carefully selected so as not to interfere with the bending of the steering tip.

[0193] Application Example: A Bimanual Steerable instrument for Flexible Endoscopy

[0194] In an exemplary application combining multiple exemplary configurations described in this specification, a combination of various serpentine assist steering mechanisms may be a bimanually dexterous manipulation system (460) conveyed via a dual-channel flexible endoscope (462) having lighting LEDs (464) and a camera (466). This is illustrated in FIG. 23. As shown in FIG. 23, the flexible endoscope (462) is equipped with a pair of 6-DoF steering mechanisms (470, 480). The first steering mechanism (470) includes a child steering mechanism (472) that is superimposed within a parent steering mechanism (474) and conveys a surgical tool (476). The second steering mechanism (480) also includes a child steering mechanism (482) that is superimposed within a parent steering mechanism (484) and conveys a surgical tool (486). The flexible and operable endoscope (460) provides three additional degrees of freedom to the system (460), i.e., the steering mechanism (470 480).

[0195] As can be seen in FIG. 23, the parent steering mechanisms (474, 484) include double serpentine bend segments as described in this specification with reference to FIG. 14a-c. When actuated, the parent steering mechanisms (474, 484) take on an S-shape, providing a stable platform by increasing the rigidity of the self-collision of the slots (see FIG. 4). The child steering mechanisms (472, 482) are 3-DoF (roll, insert / retract, and bend / bend) steering mechanisms, each independently operable, that penetrate each parent steering mechanism (474, 484). The child steering mechanisms (472, 482) transport tools (476), such as forceps and electrosurgical probes, to interact with the tissue as illustrated. The system / platform (460) of FIG. 23 can be used in various surgeries, such as gastroscopic surgery requiring simultaneous retraction and cutting, such as endoscopic submucosal dissection (ESD).

[0196] The foregoing are exemplary configurations. While it is impossible to describe every conceivable combination of components and methods for the purpose of describing all possible configurations, those skilled in the art will recognize many additional combinations and substitutions. All such changes, modifications, and variations, as well as additional combinations and substitutions that may be derived from the exemplary configurations and descriptions disclosed herein, are encompassed within the scope and concept of the appended claims.

Claims

Claim 1 A surgical system comprising a steering mechanism including a first tube having a first meandering beam formed on the side wall of the tube; and a second tube having a second meandering beam formed on the side wall of the tube, wherein the first and second tubes are coaxially superimposed, and the first and second meandering beams are positioned to be at least partially axially aligned with each other and angularly different radial directions; wherein the first and second tubes are connected to each other at the distal end of the first and second meandering beams; wherein the first tube includes a non-incisional spine extending longitudinally along the first tube, and the first meandering beam extends longitudinally along the first tube on the opposite side of the non-incisional spine; and wherein the first and second meandering beams define a bending segment that can be actuated to form a bend in the superimposed tube structure in response to a differential axial force applied to the first and second tubes. Claim 2 A surgical system according to claim 1, wherein the first tube has a plurality of parallel first slots that are always extended through the side wall of the first tube perpendicular to the central axis of the first tube, and the first slots are angularly eccentric in a front-rear direction, wherein the first slots define the first meandering beam; and the second tube has a plurality of parallel second slots that are always extended through the side wall of the second tube perpendicular to the central axis of the second tube, and the second slots are angularly eccentric in a front-rear direction, wherein the second slots define the second meandering beam. Claim 3 A surgical system according to paragraph 2, wherein the first meandering beam comprises transverse sections extending parallel to each other on opposite sides of the first slots and longitudinal sections that alternately interconnect adjacent ends of the transverse sections; and the second meandering beam comprises transverse sections extending parallel to each other on opposite sides of the second slots and longitudinal sections that alternately interconnect adjacent ends of the transverse sections. Claim 4 A surgical system according to paragraph 3, wherein the first and second meandering beams are configured such that adjacent transverse beam portions of the first and second meandering beams contact each other at a contact point located on the opposite side of the longitudinal beam portion connecting the transverse beam portions, wherein the contact point limits the bending of the bending segment. Claim 5 A surgical system according to claim 1, wherein the first and second meandering beams are configured such that adjacent transverse portions of the first and second meandering beams contact each other at a contact point that limits the bending of the bending segment. Claim 6 A surgical system configured to define the complete bending state of the above-mentioned bending segment in paragraph 5. Claim 7 A surgical system according to claim 6, wherein the bending segment is configured such that the differential axial force applied to the first and second tubes pushes the contact points against each other to increase the stiffness of the bending segment in the fully bent state. Claim 8 A surgical system according to claim 1, wherein the first tube has a plurality of first meandering beams extending parallel to each other along the length of the bending segment, and the second tube has a plurality of second meandering beams extending parallel to each other along the length of the bending segment. Claim 9 A surgical system according to claim 8, wherein the first tube has a plurality of parallel first slots extending through the side wall of the first tube perpendicular to the central axis of the first tube, wherein the first slots are arranged in a row of slots spaced apart from each other in the radial direction, wherein each row of the first slots is eccentric in angle with respect to adjacent rows, and the first slots define the plurality of first meandering beams; and wherein the second tube has a plurality of parallel second slots extending through the side wall of the second tube perpendicular to the central axis of the second tube, wherein the second slots are arranged in a row of slots spaced apart from each other in the radial direction, wherein each row of the second slots is eccentric in angle with respect to adjacent rows, and the first slots define the plurality of second meandering beams. Claim 10 A surgical system according to claim 9, wherein the lengths of the first slots of each row are the same and the lengths of the second slots of each row are the same. Claim 11 A surgical system according to claim 9, wherein the first slots of each row are arranged alternately in two different lengths, and the second slots of each row are arranged alternately in two different lengths. Claim 12 A surgical system according to claim 1, wherein the steering mechanism comprises a plurality of bend segments spaced apart axially along the length of the steering mechanism, wherein the plurality of bend segments comprise a first bend segment and a second bend segment, and wherein the first and second bend segments are each formed by a first meandering beam formed on the side wall of the first tube and a second meandering beam formed on the side wall of the second tube, each of which is aligned axially with each other. Claim 13 A surgical system according to claim 12, wherein the first and second bending segments are configured to bend in different directions when operated. Claim 14 A surgical system according to claim 12, wherein the first and second bending segments are separated into transition regions of the first and second tubes in which there are no slots in the tube sidewalls. Claim 15 A surgical system according to claim 12, wherein the first and second bending segments are configured to be bent in opposite directions to take an S shape when the steering mechanism is operated. Claim 16 A surgical system according to paragraph 2, wherein the positions of the first and second slots are gradually adjusted with respect to a central axis so that the bending segment is bent in an out-of-plane spiral manner when operated. Claim 17 A surgical system according to paragraph 2, wherein the first and second slots have contact aids that restrict the bending motion of the bending segment in opposite bending directions. Claim 18 A surgical system according to claim 17, wherein each of the above contact aids has a convex member protruding from a transverse member and located within a corresponding storage portion of an adjacent transverse member. Claim 19 In claim 17, a surgical system having a dovetail configuration in which each contact aid has a convex member equipped with a dovetail pin and a concave receiving part equipped with a dovetail. Claim 20 A surgical system according to paragraph 2, wherein at least a portion of the first and second slots has stress-relieving incisions at their ends. Claim 21 A surgical system according to claim 1, wherein the steering mechanism comprises a first insertion shaft extending proximally from the first meandering beam and a second insertion shaft extending proximally from the second meandering beam, and the first and second insertion shafts have axial stiffness and torsional stiffness to sufficiently transmit force and torque to a steering mechanism located distally from the proximal end of the insertion shaft, and have bending ductility to take a meandering path and omnidirectional ductility to exhibit the same bending stiffness regardless of the direction of the load. Claim 22 A surgical system according to claim 21, comprising: a polymer flexible tube in which the first insertion axis is connected adjacently to the first tube; a braided wire reinforcing layer covering or embedded therein of the flexible tube; and a polymer jacket covering the braided wire to help fix the braided wire in the flexible tube; and a polymer flexible tube in which the second insertion axis is connected adjacently to the second tube; a braided wire reinforcing layer covering or embedded therein of the flexible tube; and a polymer jacket covering the braided wire to help fix the braided wire in the flexible tube. Claim 23 A surgical system according to claim 22, wherein the braiding density of the braided wire varies along the length of at least one of the first and second insertion axes to adjust the flexibility, axial stiffness, and torsional stiffness along the length of the insertion axis. Claim 24 A surgical system according to claim 22, wherein the flexible tube of the first insertion shaft is fixed to the first tube by one of the following: embedding the first tube into the material of the flexible tube of the first insertion shaft, connecting the flexible tube of the first insertion shaft to the first tube with an adhesive, and forming the flexible tube of the first insertion shaft into a thin jacket of the material attached to the first tube; and the flexible tube of the second insertion shaft is fixed to the second tube by one of the following: embedding the second tube into the material of the flexible tube of the second insertion shaft, connecting the flexible tube of the second insertion shaft to the second tube with an adhesive, and forming the flexible tube of the second insertion shaft into a thin jacket of the material attached to the second tube. Claim 25 A surgical system according to claim 21, wherein each portion of the first and second tubes is provided with the first and second insertion axes extending proximally to each of the meandering beams and having a plurality of slots in each of the tube sidewalls, wherein the slots are arranged in rows extending orthogonally to the central axis of the first and second tubes and extending radially around the central axis, and wherein the first and second insertion axes have bending ductility to allow them to take a meandering path and have omnidirectional stiffness to exhibit the same bending stiffness regardless of the direction of the load, and are configured to have axial stiffness and torsional stiffness to transmit force and torque to a bending segment of the steering mechanism located distally from the proximal end of the insertion axes. Claim 26 A surgical system according to claim 25, wherein the pitch of the slots arranged along the first and second insertion axes varies along the length of the first and second insertion axes to adjust the flexibility, axial stiffness, and torsional stiffness of the first and second insertion axes according to their length. Claim 27 A surgical system according to paragraph 2, further comprising a polymer jacket that covers the bending segment to prevent tissue from entering the first and second slots. Claim 28 A surgical system according to paragraph 2, wherein the slots are configured to be narrow enough so that tissue cannot enter the slots. Claim 29 A surgical system according to claim 1, wherein the steering mechanism comprises a composite steering mechanism including first and second steering mechanisms, wherein the second steering mechanism is configured to extend through the lumen of the first steering mechanism. Claim 30 A surgical system according to claim 1, further comprising a transfer device configured to be inserted and operated to be positioned at a surgical site, wherein the steering mechanism advances through the transfer device and has a bending segment located outside the transfer device, and the remainder of the steering mechanism is located within the transfer device and supported by it. Claim 31 In paragraph 30, the above-mentioned transfer device is a surgical system equipped with an endoscope, a flexible endoscope, and other steering mechanisms. Claim 32 A surgical system according to claim 30, wherein the transfer device is configured such that the steering mechanism supported by the transfer device, having a bending segment located outside the transfer device, can support a surgical tool extending through the lumen of an overlapping tubular structure for manipulating the surgical site.

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