Patent Publication Number: US-2017368681-A1

Title: Highly articulated probes with anti-twist link arrangement, methods of formation thereof, and methods of performing medical procedures

Description:
RELATED APPLICATIONS 
     This application is a continuation application of U.S. application Ser. No. 14/343,915, filed Mar. 10, 2014, which is a 371 application of PCT/US2012/054802, filed on Sep. 12, 2012, which claims the benefit of U.S. Provisional Application No. 61/534,032, filed Sep. 13, 2011, the content of which is incorporated herein by reference in its entirety. 
     This application claims the benefit of U.S. Provisional Application No. 61/578,582, filed Dec. 21, 2011, the content of which is incorporated herein by reference in its entirety. 
     This application claims the benefit of U.S. Provisional Application No. 61/656,600, filed Jun. 7, 2012, the content of which is incorporated herein by reference in its entirety. 
     This application claims the benefit of U.S. Provisional Application No. 61/681,340, filed Aug. 9, 2012, the content of which is incorporated herein by reference in its entirety. 
     This application is related to U.S. Pat. No. 9,572,628, issued on Feb. 21, 2017, the content of which is incorporated herein by reference in its entirety. 
     This application is related to PCT Application No. PCT/US2012/040414, filed Jun. 1, 2012, the content of which is incorporated herein by reference in its entirety. 
     This application is related to U.S. Provisional Application No. 61/492,578, filed Jun. 2, 2011, the content of which is incorporated herein by reference in its entirety. 
     This application is related to PCT Application No PCT/US2012/032279, filed Apr. 5, 2012, the content of which is incorporated herein by reference in its entirety. 
     This application is related to U.S. Provisional Application No. 61/472,344, filed Apr. 6, 2011, the content of which is incorporated herein by reference in its entirety. 
     This application is related to PCT Application No PCT/US2011/060214, filed Nov. 10, 2011, the content of which is incorporated herein by reference in its entirety. 
     This application is related to U.S. Provisional Application No. 61/412,733, filed Nov. 11, 2010, the content of which is incorporated herein by reference in its entirety. 
     This application is related to PCT Application No PCT/US2011/057282, filed Oct. 21, 2011, the content of which is incorporated herein by reference in its entirety. 
     This application is related to U.S. Provisional Application No. 61/406,032, filed Oct. 22, 2010, the content of which is incorporated herein by reference in its entirety. 
     This application is related to PCT Application No PCT/US2011/044811, filed Jul. 21, 2011, the content of which is incorporated herein by reference in its entirety. 
     This application is related to U.S. Provisional Application No. 61/368,257, filed Jul. 28, 2010, the content of which is incorporated herein by reference in its entirety. 
     This application is related to U.S. patent application Ser. No. 11/630,279, filed Dec. 20, 2006, published as U.S. Patent Application Publication No. 2009/0171151, the content of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     Embodiments of the present inventive concepts relate generally to the field of robotics and, more particularly, to three-dimensional, flexible, steerable robotic devices, and methods of forming and controlling the same. 
     BACKGROUND 
     As less invasive medical techniques and procedures become more widespread, medical professionals, such as surgeons, may employ snake-like robotic systems having highly articulated multi-link probes to access parts of the human anatomy that were otherwise difficult to reach. With the use of such robotic systems, medical professionals may be able to replace open-cavity surgical procedures with less invasive procedures. 
     Robotic systems of the type described above may have multiple device channels, referred to as working channels, for guiding a variety of surgical and/or interventional tools during surgical procedures. Conventional articulating probes, which generally comprise a series of steerable links, are subject to twisting, from link to link, which can adversely affect the performance of the articulating probe. 
     SUMMARY 
     Embodiments of the present inventive concepts may be directed to articulating robotic systems, robotic system user interfaces, human interface devices for controlling robotic systems and methods of controlling robotic systems. 
     In an aspect, an articulating probe, comprises: a first mechanism comprising: a first link comprising a first longitudinal axis, a first articulation surface and a first motion-limiting element; a second link comprising a second longitudinal axis, a second articulation surface and a second motion-limiting element; an articulation joint comprising the first articulation surface and the second articulation surface and constructed and arranged to allow two degree-of-freedom articulation of the second link relative to the first link; and a motion resisting assembly comprising the first motion limiting element and the second motion limiting element, wherein the motion resisting assembly is constructed and arranged to resist rotation of the second link about the second longitudinal axis relative to the first longitudinal axis of the first link. 
     In some embodiments, the first articulation surface comprises a convex surface and wherein the second articulation surface comprises a concave surface. 
     In some embodiments, the convex, first articulation surface comprises a semi-spherical surface. 
     In some embodiments, the concave, second articulation surface comprises a semi-spherical surface. 
     In some embodiments, the first motion-limiting element comprises a pin and wherein the second motion-limiting element comprises a slot and wherein the pin of the first link engages the slot of the second link. 
     In some embodiments, the convex, first articulation surface comprises a semi-spherical surface and wherein the pin is positioned to extend from an equatorial plane of the semi-spherical surface. 
     In some embodiments, the first motion-limiting element comprises first and second pins and wherein the second motion-limiting element comprises first and second corresponding slots and wherein over a range of articulation motion of the second link relative to the first link, at least one of the first and second pins is at least partially engaged with the corresponding at least one of the first and second slots. 
     In some embodiments, at an articulation angle of zero of the second link relative to the first link, both of the first and second pins are partially engaged with the first and second corresponding slots. 
     In some embodiments, the first and second pins are angularly spaced apart 180 degrees about the first longitudinal axis relative to the first articulation surface. 
     In some embodiments, the first and second slots are angularly spaced apart 180 degrees about the second longitudinal axis relative to the second articulation surface. 
     In some embodiments, the first motion-limiting element comprises a single pin and wherein the second motion-limiting element comprises a single slot and wherein over a range of articulation motion of the second link relative to the first link, the pin is at least partially engaged with the slot. 
     In some embodiments, the pin is positioned on the first articulation surface and wherein the slot is positioned on the second articulation surface. 
     In some embodiments, the slot is positioned on the first articulation surface and wherein the pin is positioned on the second articulation surface. 
     In some embodiments, the convex, first articulation surface comprises a semi-spherical surface and wherein the pin is positioned on the first articulation surface between an equator and a pole of the first articulation surface and wherein the slot is positioned on the second articulation surface. 
     In some embodiments, the convex, first articulation surface comprises a semi-spherical surface and wherein the slot is positioned on the semi-spherical first articulation surface between an equator and a pole of the first articulation surface and wherein the pin is positioned on the second articulation surface. 
     In some embodiments, the first motion-limiting element comprises a single slot and wherein the second motion-limiting element comprises a single pin and wherein over a range of articulation motion of the second link relative to the first link, the pin is at least partially engaged with the slot. 
     In some embodiments, the convex, first articulation surface comprises a semi-spherical surface and wherein the slot is positioned on the semi-spherical first articulation surface and extends from an equator of the first articulation surface in a direction toward a pole of the first articulation surface of the first link and wherein the pin is positioned below the second articulation surface of the second link. 
     In some embodiments, the pin is positioned on the second link at a position that aligns with an equator of the semi-spherical first articulation surface of the first link, when the second link is at an articulation angle of zero relative to the first link. 
     In some embodiments, the second link further comprises a third motion-limiting element comprising a single slot that is spaced apart 120 degrees in position relative to the pin, the third motion limiting element comprising a second motion limiting assembly that is constructed and arranged to resist rotation of a third link having a mating pin about a third longitudinal axis relative to the second link about the second longitudinal axis. 
     In some embodiments, the first motion-limiting element comprises at least one rib and wherein the second motion-limiting element comprises at least one recess and wherein over a range of articulation motion of the second link relative to the first link, the at least one rib is at least partially engaged with the at least one recess. 
     In some embodiments, the first motion-limiting element comprises a plurality of ribs and wherein the second motion-limiting element comprises a plurality of corresponding recesses and wherein over a range of articulation motion of the second link relative to the first link, at least one of the plurality of ribs is at least partially engaged with the corresponding at least one of the plurality of recesses. 
     In some embodiments, the convex, first articulation surface comprises a semi-spherical surface and wherein the plurality of ribs are spaced about an equator region of the semi-spherical first articulation surface at regular angular intervals about the first longitudinal axis. 
     In some embodiments, the plurality of ribs comprises two ribs that are spaced at 180 degrees about the first longitudinal axis of the first link. 
     In some embodiments, the plurality of recesses comprises two recesses that are spaced at 180 degrees about the second longitudinal axis. 
     In some embodiments, the plurality of ribs comprises three ribs that are spaced at 120 degrees about the first longitudinal axis of the first link. 
     In some embodiments, the plurality of recesses comprises three recesses that are spaced at 120 degrees about the second longitudinal axis. 
     In some embodiments, the plurality of ribs comprises four ribs that are spaced at 90 degrees about the first longitudinal axis of the first link. 
     In some embodiments, the plurality of recesses comprises four recesses that are spaced at 90 degrees about the second longitudinal axis. 
     In some embodiments, the plurality of ribs comprises five ribs that are spaced at 72 degrees about the first longitudinal axis of the first link. 
     In some embodiments, the plurality of recesses comprises five recesses that are spaced at 72 degrees about the second longitudinal axis. 
     In some embodiments, the plurality of ribs comprises six ribs that are spaced at 60 degrees about the first longitudinal axis of the first link. 
     In some embodiments, the plurality of recesses comprises six recesses that are spaced at 60 degrees about the second longitudinal axis. 
     In some embodiments, the plurality of ribs comprises seven ribs that are spaced at 360/7 degrees about the first longitudinal axis. 
     In some embodiments, the plurality of recesses comprises seven recesses that are spaced at 360/7 degrees about the second longitudinal axis. 
     In some embodiments, the plurality of ribs comprises eight ribs that are spaced at 45 degrees about the first longitudinal axis of the first link. 
     In some embodiments, the plurality of recesses comprises eight recesses that are spaced at 45 degrees about the second longitudinal axis. 
     In some embodiments, an outer surface of the first link at a portion between neighboring ones of the ribs is planar. 
     In some embodiments, an inner surface of the second link at a portion between neighboring ones of the recesses is planar. 
     In some embodiments, an inner surface of the second link at a portion between neighboring ones of the recesses is curved. 
     In some embodiments, the first articulation surface comprises a convex surface and wherein the second articulation surface comprises a concave surface. 
     In some embodiments, the convex, first articulation surface comprises a semi-ellipsoidal surface. 
     In some embodiments, the concave, second articulation surface comprises a semi-ellipsoidal surface. 
     In some embodiments: the semi-ellipsoidal, convex, first articulation surface of the first link comprises the first motion limiting element; and the semi-ellipsoidal, concave, second articulation surface of the second link comprises the second motion limiting element. 
     In some embodiments, an outermost surface of the first and second links is circular in cross section about the respective first and second longitudinal axes. 
     In some embodiments, the semi-ellipsoidal surface of the first articulation surface has a major axis and a minor axis and wherein the major axis is greater in length than the minor axis. 
     In some embodiments, the semi-ellipsoidal surface of the second articulation surface has a major axis and a minor axis and wherein the major axis is greater in length than the minor axis. 
     In some embodiments, the first articulation surface comprises convex and concave regions and wherein the second articulation surface comprises concave and convex regions that correspond to the convex and concave regions of the first articulation surface. 
     In some embodiments: the first articulation surface of the first link comprises the first motion limiting element; and the second articulation surface of the second link comprises the second motion limiting element. 
     In some embodiments, an outermost surface of the first and second links is circular in cross section about the respective first and second longitudinal axes. 
     In some embodiments, the first and second links comprise outer links of the articulating probe. 
     In some embodiments, the first and second links comprise inner links of the articulating probe. 
     In some embodiments, the first motion-limiting element comprises a first magnet and wherein the second motion-limiting element comprises a second magnet, and wherein the first and second magnets are positioned on the first and second links respectively so as to magnetically engage each other. 
     In some embodiments, the first and second links each comprises a base having a lower surface and an upper shoulder, wherein: the first magnet is positioned on the upper shoulder of the base; and the second magnet is positioned on the lower surface of the base, and wherein the first and second magnets are aligned relative to each other so as to magnetically engage each other. 
     In some embodiments, the first and second magnets have opposed polarity. 
     In some embodiments, the first magnet comprises multiple first magnets and wherein the second magnet comprises multiple second magnets and wherein the multiple first and second magnets are positioned about the longitudinal axes of the respective first and second links at regular angular intervals. 
     In some embodiments, the first articulation surface comprises a convex surface and wherein the second articulation surface comprises a concave surface. 
     In some embodiments, the convex, first articulation surface comprises a semi-spherical surface. 
     In some embodiments, the concave, second articulation surface comprises a semi-spherical surface. 
     In some embodiments: the first magnet is positioned on the first articulation surface; and the second magnet is positioned on the second articulation surface, wherein the first and second magnets are aligned relative to each other so as to magnetically engage each other. 
     In some embodiments, the first and second magnets have opposed polarity. 
     In some embodiments, a subset of the first magnets has a first polarity and a remaining subset of the first magnets has a second polarity opposite the first polarity. 
     In some embodiments, the first magnets all have a same, first polarity and the second magnets all have a same, second polarity. 
     In some embodiments, the first magnet comprises multiple first magnets and wherein the second magnet comprises multiple second magnets and wherein the multiple first and second magnets are positioned about the longitudinal axes of the respective first and second links at regular angular intervals. 
     In some embodiments, the multiple first and second magnets comprise discrete magnetic elements embedded in the respective first and second articulating surfaces. 
     In some embodiments, the multiple first and second magnets comprise magnetic strips embedded in the respective first and second articulating surfaces. 
     In some embodiments, the first articulation surface comprises a convex surface and wherein the second articulation surface comprises a concave surface. 
     In some embodiments, the first motion-limiting element comprises a pin and wherein the second motion-limiting element comprises a slot and wherein the pin of the first link engages the slot of the second link, and wherein the pin of the first link interfaces with sidewalls of the slot of the second link to resist the rotation of the first link relative to the second link. 
     In some embodiments, the first mechanism comprises an outer link mechanism of the articulating probe. 
     In some embodiments, the first mechanism comprises an inner link mechanism of the articulating probe. 
     In some embodiments, the motion limiting assembly limits rotation of the second link to about 1 degree of rotation about its longitudinal axis. 
     In some embodiments, the articulating probe further comprises at least one steering cable opening through the first link and the second link extending in a direction that is parallel to the respective first and second longitudinal axes. 
     In some embodiments, the articulating probe further comprises at least one steering cable corresponding to links in the first mechanism that is selectively tensioned to retain the first and second articulation surfaces of the first and second links in physical contact and selectively released to allow for selective motion of the second link relative to the first link. 
     In some embodiments, the at least one steering cable opening comprises multiple steering cable openings and wherein the at least one steering cable comprises multiple steering cables. 
     In some embodiments, the articulating probe comprises two steering cable openings and two steering cables. 
     In some embodiments, the articulating probe comprises three steering cable openings and three steering cables. 
     In some embodiments, the articulating probe comprises four steering cable openings and four steering cables. 
     In some embodiments, the first link further comprises a first articulation axis and a second articulation axis, the first and second articulation axes normal to each other and normal to the first longitudinal axis of the first link; the second link further comprises a first articulation axis and a second articulation axis, the first and second articulation axes normal to each other and normal to the second longitudinal axis of the second link; and two-degree-of-freedom articulation of the second link relative to the first link comprises angular movement of the second link about the first and second articulation axes of the first link. 
     In another aspect, an articulating probe, comprises: a plurality of outer links, each outer link comprising a first longitudinal axis and an inner surface, the inner surface of each outer link having at least one first concave region that extends in a direction along the first longitudinal axis; a plurality of inner links, each inner link comprising a second longitudinal axis and an outer surface, the outer surface of each inner link having at least one second concave region that extends in a direction along the second longitudinal axis; an anti-twist member positioned between the first concave regions and the second concave regions of the plurality of inner links and the plurality of outer links to allow two degree-of-freedom articulation of the inner links with respect to each other and to allow two degree-of-freedom articulation of the outer links with respect to each other and to limit rotation of an inner link relative to a neighboring inner link and limit rotation of an outer link relative to a neighboring outer link. 
     In some embodiments, the first concave regions of the outer links and the second concave regions of the inner links comprise working channels of the probe. 
     In some embodiments, the anti-twist member comprises a tube-shaped member. 
     In some embodiments, the anti-twist member is continuous from a proximal link to a distal link of the plurality of inner and outer links. 
     In some embodiments, the anti-twist member is segmented from a proximal link to a distal link of the plurality of inner and outer links. 
     In another aspect, a method of performing a surgical procedure comprises: selecting the articulating probe as described herein; and manipulating the articulating probe to position at least one tool using the probe. 
     In another aspect, a system for performing a surgical procedure includes an articulating probe as described herein. 
     In another aspect, a method of forming an articulating probe comprises: providing a first mechanism comprising: forming a first link comprising a first longitudinal axis, a first articulation surface and a first motion-limiting element; forming a second link comprising a second longitudinal axis, a second articulation surface and a second motion-limiting element; forming an articulation joint comprising the first articulation surface and the second articulation surface and constructed and arranged to allow two degree-of-freedom articulation of the second link relative to the first link; and forming a motion resisting assembly comprising the first motion limiting element and the second motion limiting element, wherein the motion resisting assembly is constructed and arranged to resist rotation of the second link about the second longitudinal axis relative to the first longitudinal axis of the first link. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, features and advantages of embodiments of the present inventive concepts will be apparent from the more particular description of embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same elements throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the embodiments. 
         FIG. 1A  is a side view of first and second outer links of an articulating probe of a system for performing a medical procedure according to embodiments of the present inventive concepts.  FIG. 1B  is a lower perspective view of the first and second outer links of  FIG. 1A .  FIG. 1C  is a cutaway side view of the first and second outer links of  FIG. 1A .  FIG. 1D  is a cutaway side view of the first and second outer links of  FIG. 1A  illustrated with the second link articulated relative to the first link.  FIG. 1E  is a side perspective view of one of the first and second outer links of  FIG. 1A . 
         FIG. 2  is a lower perspective view of an outer link of an articulating probe of a system for performing a medical procedure according to embodiments of the present inventive concepts. 
         FIGS. 3A and 3B  are perspective views of outer links of an articulating probe of a system for performing a medical procedure according to other embodiments of the present inventive concepts. 
         FIG. 4  is a perspective view of first and second outer links of an articulating probe of a system for performing a medical procedure according to other embodiments of the present inventive concepts. 
         FIG. 5A  is a side view of first and second outer links of an articulating probe of a system for performing a medical procedure according to other embodiments of the present inventive concepts.  FIG. 5B  is a close-up side view of one of the first and second outer links of  FIG. 5A .  FIG. 5C  is a lower perspective view of the link of  FIG. 5B . 
         FIG. 6A  is a lower perspective view of first and second outer links of an articulating probe of a system for performing a medical procedure according to other embodiments of the present inventive concepts.  FIG. 6B  is a top perspective view of one of the first and second outer links of  FIG. 6A .  FIG. 6C  is a lower perspective view of the link of  FIG. 6B . 
         FIG. 7A  is a lower perspective view of first and second inner links of an articulating probe of a system for performing a medical procedure according to other embodiments of the present inventive concepts.  FIG. 7B  is a top perspective view of one of the first and second inner links of  FIG. 7A . 
         FIGS. 8A ( 1 ),  8 A( 2 ),  8 B( 1 ),  8 B( 2 ),  8 C( 1 ), and  8 C( 2 ) are top views of first and second outer links of an articulating probe of a system for performing a medical procedure according to other embodiments of the present inventive concepts. 
         FIG. 9  is a cross-sectional view of an inner link and an outer link including an anti-twist member positioned therebetween, in accordance with embodiments of the present inventive concepts. 
         FIGS. 10A-10C  are graphic demonstrations of a highly articulated probe device, according to embodiments of the present inventive concepts. 
         FIGS. 11A-11B  illustrate various configurations assumed by a highly articulated probe, according to embodiments of the present inventive concepts. 
         FIGS. 12A-12D  illustrate various views of a link of an outer sleeve, according to embodiments of the present inventive concepts. 
         FIGS. 13A and 13B  illustrate end and cross-sectional views, respectively, of a link of an inner core, according to embodiments of the present inventive concepts. 
         FIGS. 14A and 14B  illustrates one example of a feeder mechanism, according to embodiments of the present inventive concepts. 
         FIG. 15  illustrates devices for controlling the tension on cables, according to embodiments of the present inventive concepts. 
         FIG. 16  illustrates devices for controlling the tension on the cables of the outer sleeve, according to embodiments of the present inventive concepts. 
         FIG. 17  illustrates a device for controlling the tension on the cable of the inner sleeve, according to embodiments of the present inventive concepts. 
         FIG. 18  is a block diagram illustrating the components of a control system and the flow of information between those components, according to embodiments of the present inventive concepts. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the inventive concepts. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     It will be understood that, although the terms first, second, third etc. may be used herein to describe various limitations, elements, components, regions, layers and/or sections, these limitations, elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one limitation, element, component, region, layer or section from another limitation, element, component, region, layer or section. Thus, a first limitation, element, component, region, layer or section discussed below could be termed a second limitation, element, component, region, layer or section without departing from the teachings of the present application. 
     It will be further understood that when an element is referred to as being “on” or “connected” or “coupled” to another element, it can be directly on or above, or connected or coupled to, the other element or intervening elements can be present. In contrast, when an element is referred to as being “directly on” or “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). When an element is referred to herein as being “over” another element, it can be over or under the other element, and either directly coupled to the other element, or intervening elements may be present, or the elements may be spaced apart by a void or gap. There are numerous types of steerable multi-linked, highly articulated probes. Robert Sturges&#39; U.S. Pat. No. 5,759,151, which is hereby incorporated by reference in its entirety, discloses a flexible, steerable device for conducting exploratory procedures. The device includes at least one spine, each having stiffening means for selectively rendering the spine rigid and flexible along its length. A flexible sheath surrounds the spine and is axially slidably moveable relative to the spine so that the sheath will follow and conform to the shape of a spine in the rigid state and resist further flexure when the spine is in a relaxed state. A steerable distal tip is provided on the distal end of the device. Controls for the distal tip are mounted on the proximal end of the device. Mechanisms are provided on the distal end of the device for selectively activating and deactivating the stiffening means of the spine. An instrument conduit may be mounted on the sheath. Howard Choset&#39;s U.S. patent application Ser. No. 11/630,279, which is hereby incorporated by reference in its entirety, discloses a feeder mechanism for advancing and retracting both an inner core and an outer sleeve, as well as selectively applying tension to control cables used for steering and causing either the inner core or outer sleeve to transition between a rigid state and a limp state. 
     U.S. Pat. No. 6,610,007 discloses a steerable endoscope having an elongated body with a selectively steerable distal portion and an automatically controlled proximal portion. The endoscope body is inserted into a patient and the selectively steerable distal portion is used to select a desired path within the patient&#39;s body. When the endoscope body is advanced, an electronic motion controller operates the automatically controlled proximal portion to assume the selected curve of the selectively steerable distal portion. Another desired path is selected with the selectively steerable distal portion and the endoscope body is advanced again. As the endoscope body is further advanced, the selected curves propagate proximally along the endoscope body, and when the endoscope body is withdrawn proximally, the selected curves propagate distally along the endoscope body. This creates a serpentine motion in the endoscope body allowing it to negotiate tortuous curves along a desired path through or around and between organs within the body. 
       FIGS. 10A-10C  are graphic demonstrations of a highly articulated probe device, according to embodiments of the present inventive concepts. A highly articulated robotic probe  10 , according to the embodiment shown in  FIGS. 10A-10C , comprises essentially two concentric mechanisms, an outer mechanism and an inner mechanism, each of which can be viewed as a steerable mechanism.  FIGS. 10A-10C  show the concept of how different embodiments of the probe  10  operate. Referring to  FIG. 10A , the inner mechanism can be referred to as a first mechanism, an inner core or inner core mechanism  12 . The outer mechanism can be referred to as a second mechanism, an outer sleeve or outer sleeve mechanism  14 . Each mechanism can alternate between being rigid and limp. In the rigid mode or state, the mechanism is relatively inflexible such that it cannot be readily re-shaped. In the limp mode or state, the mechanism is highly flexible and thus either assumes the shape of its surroundings or can be re-shaped. It should be noted that the term “limp” as used herein does not denote a structure that passively assumes a particular configuration dependent upon gravity and the shape of its environment; rather, the “limp” structures described in this application are capable of assuming positions and configurations that are desired by the operator of the device, and therefore are articulated and controlled rather than flaccid and passive. 
     In some embodiments, one mechanism starts limp and the other starts rigid. For the sake of explanation, assume the outer sleeve  14  is rigid and the inner core  12  is limp, as seen in step  1  in  FIG. 10A . Now, the inner core  12  is both pushed forward by a feeding mechanism  16 , described below, and its “head” or distal end is steered, as seen in step  2  in  FIG. 10A . Now, the inner core  12  is made rigid and the outer sleeve  14  is made limp. The outer sleeve  14  is then pushed forward until it catches up or is coextensive with the inner core  12 , as seen in step  3  in  FIG. 10A . Now, the outer sleeve  14  is made rigid, the inner core  12  limp, and the procedure then repeats. One variation of this approach is to have the outer sleeve  14  be steerable as well. The operation of such a device is illustrated in  FIG. 10B . In  FIG. 10B  it is seen that each mechanism is capable of catching up to the other and then advancing one link beyond. According to one embodiment, the outer sleeve  14  is steerable and the inner core  12  is not. The operation of such a device is shown in  FIG. 10C . 
     In medical applications, once the probe  10  arrives at a desired location, the operator, typically a surgeon, can slide one or more tools through one or more channels of outer sleeve  14 , inner core  12 , or a channel formed between outer sleeve  14  and inner core  12 , such as to perform various diagnostic and/or therapeutic procedures. In some embodiments, the channel is referred to as a working channel, that can, for example extend between first recesses formed in a system of outer links and second recesses formed in a system of inner links. In some embodiments, the inner and outer links are of a type depicted in  FIGS. 1-9  described in detail herein. 
     In addition to clinical procedures such as surgery, probe  10  can be used in numerous applications including but not limited to: engine inspection, repair or retrofitting; tank inspection and repair; spying and surveillance applications; bomb disarming; inspection or repair in tightly confined spaces such as submarine compartments or nuclear weapons; structural inspections such as building inspections; hazardous waste remediation; biological sample recovery such as anthrax recovery; and combination of these. Clearly, the device of the present disclosure has a wide variety of applications and should not be taken as being limited to any particular application. 
     Inner core  12  and/or outer sleeve  14  are steerable and inner core  12  and outer sleeve  14  can each be made both rigid and limp, allowing probe  10  to drive anywhere in three-dimensions. Probe  10  can “remember” its previous configurations and for this reason, probe  10  can go anywhere in a three dimensional volume such as the intracavity spaces in the body of a patient such as a human patient.  FIGS. 11A-11B  illustrate examples of various configurations assumable by probe  10 . 
     As can be seen in  FIGS. 12A-12D and 13A and 13B , according to one embodiment, the outer sleeve  14  and inner core  12 , respectively, can be made up of concentric cylinders, outer links  22  and inner links  24 , respectively, although links of other shapes may be used, e.g. a dog bone configuration (not shown) as well as links of a type that are not concentric, e.g. backbone configuration, among others. In some embodiments, the ends of the links  22 ,  24  are not flat but instead one end  26  is an “outer” or convex outer mating surface and the other end  28  is an “inner” or concave inner mating surface. In some embodiments, the inner and outer surfaces can comprise semi-spherical surfaces with similar radii of curvature; however, as described herein, embodiments of the present inventive concepts are not limited thereto. The links  22  are “chained”, or nested back-to-back such that the concave end  28  of one mates with the convex end  26  of an adjacent link. Similarly, the links  24  are chained, or nested back-to-back. The result is a spherical-like joint, from a kinematic point of view. In the current embodiment, each link is able to rotate, or articulate on the adjacent link&#39;s head, acting as a spherical joint with approximately 10 to 20 degrees range of motion in any direction, although other ranges of motion are possible and potentially advantageous. According to one embodiment, the links  22  have a plurality of channels  30 , or cable openings, extending therethrough to accommodate, in some embodiments, a plurality of control cables. Alternatively, in some embodiments, the cable openings  30  can be configured to accommodate elongate devices such as elongate tools. 
     In some embodiments, the heads (i.e. the distal links) of both the outer sleeve  14  and the inner core  12  are steerable using three cables which are positioned at, for example, 120° from each other. As can be seen in  FIGS. 12A-12D , there are three small cylindrical channels  30  respectively, for cables to pass through. In the embodiment depicted in  FIGS. 13A and 13B , the inner link  24  has only one cable, in which case there is only a single hole  34  through its center. 
     It will be appreciated that although the embodiment described above utilizes cables such as conductive or non-conductive wires or other flexible filamentous structure, alternative means of manipulating the limp elements, such as miniature pneumatic or hydraulic pistons or other mechanical linkages situated between individual links, can be employed without falling outside the scope of the present inventive concepts. 
     The links, and hence probe  10 , can comprise virtually any material, including plastic or other magnetic resonance imaging compatible material. The outer sleeve  14  may assume a broad range of diameters, typically greater than 5 mm. Similarly, inner core  12  may assume a broad range of diameters, less than the diameter of outer sleeve  14  and typically more than 3 mm. The total number of outer links in an outer link assembly, or inner links in an inner link assembly links can vary over a large range but is typically greater than 10 outer or inner links. 
     As noted, the inner core  12  and outer sleeve  14  can be made rigid or limp using cables or other flexible filament structures. In some embodiments, outer sleeve  14  comprises a set of links  22  strung on three cables. The three cables can be positioned 120 degrees apart, making it possible to steer the sleeve in any direction. Radius of curvature of probe  10  is dependent on a number of factors including length of links  22  as well as mating dimensions between the ends of mating links  22 . When the cables are pulled towards the back of the outer sleeve  14 , the links  22  are pulled towards each other. When the pulling force increases, the friction force between adjacent links  22  increases until the whole outer sleeve  14  stiffens (i.e. enters the rigid mode). When the pulling force is released, the outer sleeve  14  becomes limp. Thus, the cables together with their respective tensioning assemblies (e.g. motor driven pulleys) form a locking device. The tensioning assemblies, along with the electronics for controlling the tensioning assemblies, form a means for controlling the tension on the cable. When the outer sleeve  14  is positioned one link position in front of the inner core  12 , and the inner core  12  is rigid, the distal link of the outer sleeve  14  can be oriented by pulling one or more of the three cables. In addition to advancing or retracting cable, the magnitude of the pulling force which is exerted on each cable can be monitored or controlled. By pulling the three cables with the same magnitude, the outer sleeve  14  becomes rigid without changing its shape. 
     The inner core  12 , like the outer sleeve  14 , consists of a set of links. According to one embodiment, in contrast to the outer sleeve  14 , the inner core  12  does not require a steering ability. In some embodiments, a steering feature is optional, and can be employed, in connection with the inner core  12 . In some embodiments, the inner core  12  can change between a rigid mode and a limp mode. Therefore, in embodiments where the inner core  12  need not be steerable, the links of the inner core  12  may be strung on a single cable, which enables a reduced diameter for probe  10 . 
     As mentioned above, a feeding mechanism  16  can be used to control the probe  10 . One type of feeding mechanism  16 , shown in  FIGS. 14A and 14B , inserts and retracts the probe  10  into and out of, respectively, a region of interest such as the esophagus, the peritoneal space, the pericardial cavity, or another internal space of a patient. The feeder  16  has two movable carts. A first cart  42 , carried in a first fixed tray  43 , advances and retracts the outer sleeve  14  while a second cart  44  carried in a second fixed tray  45  advances and retracts the inner core  12 . Each cart  42 ,  44 , and hence, each of the inner core  12  and outer sleeve  14 , is driven independently by separate linear actuators  46 ,  48  respectively. The linear actuators  46 ,  48  may carry shaft encoders (not shown) used for position control as is known to those of skill in the art. Alternatively or additionally, motor current may be monitored to determine a value for tension in a cable used to control position. Cable tension may be monitored with one or more sensors such as a load cell. Numerous positioning and other sensors may be included to provide information relative to cable tension; cart position; probe orientation and configuration; and other system parameters. Typical sensors include but are not limited to: optical sensors; magnetic sensors such as Hall effect sensors; force and pressure sensors such as accelerometers, strain gauges and mechanical switches; and combinations of these. One or more sensors may be positioned in multiple locations including but not limited to: feeding mechanism  16 , inner core  12  and outer sleeve  14 . 
     Each of the carts  42 ,  44  carries one or more motors necessary for controlling the cables of the inner core  12  and outer sleeve  14 . For example, as seen in  FIG. 15  and  FIG. 16 , the cart  42  carries motors  50 ,  51 ,  52  which control the tension on cables  54 ,  55 ,  56  of outer sleeve  14 . As shown in  FIG. 17 , second cart  44  has a motor  58  for controlling the tension on cable  59  of the inner core  12 . Each of the motors  50 ,  51 ,  52  and  58  may be provided with shaft encoders (not shown) used for position control as is known. In an embodiment where the inner core  12  is steerable, the inner core  12  requires two or more motors (e.g. to tension two or more cables) or another cable tensioning mechanism. 
       FIG. 18  is a block diagram illustrating the components of one embodiment of a control system and the flow of information between those components. The feeding mechanism  16  interfaces with a control computer  62  through a bus conversion module  64 . Outgoing data from the feeding mechanism  16  is input to the module  64  for conversion to a communication protocol, such as USB protocol, and is then input to a USB port  66  on the computer  62 . Incoming data to control software  68  may include motor current data, motor encoder data and/or cable tension data associated with each of the cables in the feeding mechanism  16 . Alternatively or additionally, incoming data to control software  68  may include data from one or more sensors located in feeding mechanism  16 , an inner core or an outer sleeve such as inner core  12  or outer sleeve  14  described herein. Joystick data (position data) may also be received from a joystick  70 . A monitor  72  may be responsive to video data from a camera mounted on the distal end of the outer sleeve  14  and/or inner core  12  to provide visual feedback to a user regarding the position of the distal end of the probe  10 . The control software  68  may output motor current limit commands and motor position commands which are input to the feeding mechanism  16 . 
     During operation of articulating probes, the outer sleeve link systems and inner core link systems are subject to twisting, from link to link. For example, during operation of the probe, an inherent amount of twisting can occur between neighboring links. Twisting of links can be cumulative over the system of links. Accordingly, while the angle of misalignment can be minor from individual neighboring link to link, the total amount of twisting of the distal link of the system relative to the proximal link can be large. As the number of links in a system increases, so too can the amount of cumulative twist. Such twisting can adversely affect the performance of the articulating probe. 
     Twisting can occur due to a number of factors, including a difference between the outer radii of the steering cables and the inner radii of the steering cable openings. Also, the neighboring links may become misaligned prior to, or during, a procedure. The twisting of links relative to each other can cause an inconsistent relation of steering input to steering output. Loss of alignment between user and robot coordinate systems can occur. As a result, for an operator to initiate a turn in a particular direction, the robot must be moved in a different direction to compensate for twist. In addition, links that are twisted relative to each other may be subject to a limited range of steering. Twisting can also cause neighboring links to become inadvertently locked together, and the steering cables can become pinched in the gaps between over-twisted links. This can, in turn, lead to binding of the cables, resulting in higher steering forces, or incomplete release of tension when in a limp mode of operation. Further problems due to twisting can include the binding of instruments inserted through internal channels of the link systems, possible occlusion of internal tool channels, as well as increased wear on electrical conduits present in the system. Twisting can also result in increased wear and friction between inner and outer links, causing neighboring links to bind, or preventing their ability to advance during a procedure. Also, twisting can result in the misalignment between the end of the probe and the target anatomy. 
     Twisting between neighboring links can be as severe as 5 degrees of offset. Cumulative twisting of a distal link relative to a proximal link in a link system can be as large as 45 degrees. Embodiments described herein are directed to systems and methods for resisting or preventing the amount of twist of a second neighboring link relative to a first link, while still allowing for articulation of the links for steering purposes. 
       FIG. 1A  is a side view of first and second outer links of an articulating probe of a system for performing a medical procedure according to embodiments of the present inventive concepts.  FIG. 1B  is a lower perspective view of the first and second outer links of  FIG. 1A .  FIG. 1C  is a cutaway side view of the first and second outer links of  FIG. 1A .  FIG. 1D  is a cutaway side view of the first and second outer links of  FIG. 1A  illustrated with the second link articulated relative to the first link.  FIG. 1E  is a side perspective view of one of the first and second outer links of  FIG. 1A . 
     Referring to  FIG. 1A , first and second outer links  100   a ,  100   b  (generally  100 ) of the articulating probe are each constructed and arranged to have a longitudinal axis  102 Za,  102 Zb, an articulation joint (joint formed from articulating surfaces  104  and  110  shown specifically in  FIG. 1C ) and motion-limiting element  106 . Multiple outer links  100  are stacked and nested relative to each other. The links are configured to articulate relative to each other and are prevented from separating relative to each other by steering cables  109  (see  FIG. 1B ) that pass through one or more steering cable openings  108  of the multiple links  100 . In the present example, three steering cable openings  108  and three cables  109  are shown (see  FIG. 1B ); however fewer or more steering cable openings and steering cables can be employed, depending on the application of the articulating probe. 
     Illustrated in  FIG. 1C , the articulation joint comprises a convex articulation surface  104   a  of the first outer link  100   a  and a concave articulation surface  110   b  of the second outer link  100   b . The convex and concave surfaces engage each other throughout a range of articulation of the second outer link  100   b  relative to the first outer link  100   a , under control of the steering cables  109 . Tension that is present in at least one of the steering cables  109 , at any given time, between the proximal and distal ends of the articulating probe retain the articulating joints of the various links of the assembly in place. 
     Referring to the illustrations of  FIGS. 1A-1C , the respective longitudinal axes  102 Za,  102 Zb of the first and second outer links  100   a ,  100   b  are substantially in alignment with each other, or at an angle of zero degrees with respect to each other. In this position, the second outer links  100   b  can be considered to be in a non-articulated position relative to the first outer link  100   a . However, in the illustration of  FIG. 1D , the second longitudinal axis  102 Zb of the second link  100   b  is at a non-zero angle relative to the first longitudinal axis  102 Za of the first link  100   a . In this position, the second outer link  100   b  can be considered to be in an articulated position relative to the first outer link  100   a.    
       FIG. 2  is a lower perspective view of an outer link of an articulating probe of a system for performing a medical procedure according to embodiments of the present inventive concepts. In this view, first and second articulation axes  102 X,  102 Y of the outer link are illustrated. The first and second articulation axes  102 X,  102 Y are normal to each other and normal to the longitudinal axis  102 Z of the outer link. Over a permitted range of articulation, a second outer link  100   b  neighboring a first outer link  100   a  will be permitted to articulate over a range of angles about the first articulation axis  102 X as illustrated by arrow  103 X and will be permitted to articulate over a range of angles about the second articulation axis  102 Y as illustrated by arrow  103 Y, relative to the first and second articulation axes of the first outer link  100   a . In this manner, articulation is permitted or allowed in two degrees of freedom. Twisting or rotation of the second outer link  100   b  relative to a neighboring first outer link  100   a  in the direction illustrated by arrow  103 Z is undesirable, for various reasons described herein. Embodiments of the present inventive concepts described herein include a motion-resisting assembly of any of a number of various types for limiting, mitigating or otherwise resisting rotation or twisting of a second outer link relative to a neighboring first outer link of the articulating probe assembly, or of a second inner link relative to a neighboring first inner link of the articulating probe assembly. 
     Returning to  FIG. 1A , the first and second outer links  100   a ,  100   b  each include a motion limiting element, pin  106  (also visible in the perspective view of  FIG. 1E ), that operates in conjunction with a corresponding slot  112  of a neighboring link to provide a motion resisting assembly  106 ,  112  suitable for limiting rotation of the second link  100   b  relative to the first link  100   a . In particular, motion resisting assembly  106 ,  112  is suitable for limiting rotation of the second link  100   b  about its longitudinal axis  102 Zb relative to the longitudinal axis  102 Za of the first link  100   a.    
     At the same time, the motion resisting assembly  106 ,  112  operates to limit rotation of the first link  100   a  relative to the second link  100   b . In this manner, the motion resisting assembly  106 ,  112  can be said to limit rotation of the first link  100   a  and the second link  100   b  relative to each other. 
     In some embodiments, the pin  106  extends in an outward direction from a lower portion of the convex articulation surface  104  of the outer link  100 . In an embodiment where the convex articulation surface  104  is semi-spherical, the pin  106  can be positioned at, or along, an equator of the semi-spherical surface. In some embodiments, the pin  106  may be circular in cross-section to allow for pivoting of a slot  112  of a neighboring link during articulation. In other embodiments, the pin  106  can have a cross-sectional shape that is other than circular. 
     In some embodiments, the slot  112  can be formed in a pin extension or tab  114  that extends from a lower portion of the link  100 . The slot  112  can have a width W (see  FIG. 1B ) that is sized to accommodate the pin  106  width. In some embodiments, the pin  106  can be permitted to slide freely along the slot  112  in a direction of extension of the slot, while limiting gaps or play of the pin  106  between the sidewalls of the slot  112 . The slot  112  can have a length L that is sufficient to allow the pin  106  to slide between a range of desired articulation of neighboring links  100   a ,  100   b . A top portion of the slot  112  can be rounded to interface with the rounded, corresponding pin  106 . 
     In some embodiments, as illustrated in  FIG. 1C , each link  100  includes two pins  106  and two pin slots  112  for mating with pins of neighboring links. Each link, however, can include a single pin  106 , or more than two pins, or a single slot  112 , or more than one slot  112 , depending on the application. In the embodiment illustrated in  FIG. 1C , the first link  100   a  is in alignment with the second link  100   b  so that their respective longitudinal axes  102 Za,  102 Zb are in alignment. In this non-articulated state, the first and second pins  106  are at least partially engaged with the respective first and second slots  112  of the neighboring second link  100   b . In this position, the second link  100   b  is prevented, or otherwise limited, from rotating or twisting, about its longitudinal axis  102 Zb, relative to the longitudinal axis  102 Za of the first link  100   a , as the first and second pins  106  are engaged with their respective mating slots  112 . In particular, with any such twisting moment imparted on the second link  100   b , the sidewalls of the slots  112  of the second link abut the pins  106  of the first link  100   a  and thus prevent the first link  100   b  from rotating about its longitudinal axis  102 Zb. At the same time, the interaction of the pins  106  and slots  112  do not obstruct or limit articulation of the second link  100   b  relative to the first link  100   a , for example articulation of the second link  100   b  about the first and second articulation axes  102   x ,  102   y  of the first link  100   a  (see  FIG. 2 ). Free articulation of the second link  100   b  relative to the first link  100   a  is maintained, while mitigating or preventing undesired twisting of the second link relative to the first link. 
     Referring to  FIG. 1D , upon further articulation of the second link  100   b  relative to the first link  100   a , in the present embodiment, one of the pins  106 - 1  becomes disengaged from its corresponding slot  112 - 1 , while the other of the pins  106 - 2  becomes engaged more deeply into its corresponding slot  112 - 2 . Similarly, in this articulated position, the sidewalls of the slot  112 - 2  of the second link  100   b  interacting with the corresponding pin  106 - 2  of the first link  100   a  prevents twisting of the second link  100   b  about its longitudinal axis  102 Zb relative to the first link  100   a . At the same time, free articulation of the second link  100   b  relative to the first link  100   a  is maintained. 
     Referring to  FIGS. 1A-1E , the links  100   a ,  100   b  each include a lower portion  126  and an upper portion  128 . In some embodiments, the lower portion  126  includes the concave articulation surface  110  and the upper portion  128  includes the convex articulation surface  104  which combine to form the articulation joint. At an interface of the outer surfaces of the lower portion  126  and the upper portion  128 , a shoulder  120  can be provided. The shoulder  120  of a first link  100   a  and a lower surface  121  of the second link  100   b  operate to limit the amount of articulation of the second link  100   b  relative to the first link  100   a . For example, articulation can be limited to an angle that corresponds to the position at which the lower surface  121  of the second link  100   b  physically abuts the shoulder  120  of the first link  100   a.    
     Continuing to refer to  FIGS. 1A-1E , in some embodiments, a recess  122  can be formed in the shoulder  120  of the lower portion. The recess  122  can be formed to have a shape that accommodates the pin extension or tab  114 . In this manner, the slot  112  of the tab  114  can engage its corresponding pin  106 , while maintaining the outer profile of the links  100   a ,  100   b  so that their outer perimeters are not increased. In some embodiments, the tab  114  and corresponding recess  122  can be constructed and arranged so that they do not limit articulation of the second link  100   b  relative to the first link  100   a . In other words, at the greatest degree of articulation, the shoulder  120  of the first link  100   a  makes contact with the lower surface  121  of the neighboring link  100   b  while a clearance is maintained between the tab  114  and the surface of the corresponding recess  122 . In other embodiments, the tab  114  and corresponding recess  122  can be configured so that the interface of the tab  114  and recess  122  provides an articulation-limiting function, while a clearance is maintained between the shoulder  120  and corresponding lower surface  121  of the neighboring links  100   a ,  100   b.    
     Continuing to refer to  FIGS. 1A-1E , in some embodiments, the links  100   a ,  100   b  comprise outer links of an articulating probe having a plurality of articulating inner links and a plurality of articulating outer links. In some embodiments, recesses  124  are provided at an interface between inner regions of the outer links and corresponding outer regions of the inner links. The recesses  124  correspond to working channels of the articulating probe to allow for delivery of functional elements from the proximal end to the distal end of the articulating probe, as described herein. 
     In some embodiments, for example in the embodiment depicted in  FIGS. 1A-1E , the convex articulation surface  104   a  of the first outer link  100   a  comprises a semi-spherical convex surface and the concave articulation surface  110  of the second outer link  100   b  comprises a semi-spherical concave surface. In some embodiments, the radius of the convex articulation surface  104   a  of the first outer link  100   a  can be the same as the radius of the concave articulation surface  110   b  of the second outer link  100   b . In some embodiments, the radius of the convex articulation surface  104   a  of the first outer link  100   a  can be greater than the radius of the concave articulation surface  110   b  of the second outer link  100   b . In some embodiments, the radius of the convex articulation surface  104   a  of the first outer link  100   a  can be less than the radius of the concave articulation surface  110   b  of the second outer link  100   b.    
     In some embodiments, for example in the embodiment depicted in  FIGS. 1A-1E , the convex articulation surface  104   a  of the first outer link  100   a  comprises a semi-spherical convex surface and the concave articulation surface  110   b  of the second outer link  100   b  comprises a semi-conical concave surface. An advantage of this configuration is that the contact region of the resulting articulation joint corresponds to a circular region. As a result, the resulting interface is less likely to bind, since the region of contact is reduced. Also, the mating properties of the convex and concave articulation surfaces can be more readily controlled, since the interface is less susceptible to variation in manufacturing process parameters such as variation in texture, material, friction, and the like. The resulting interface also allows for greater tolerance variation in the links, reducing manufacturing costs. 
     In one example, assuming a semi-spherical convex articulation surface, variation in the spherical diameter can affect the amount of surface contact between the convex and concave surfaces. This can result in variation of the steering forces, variation in the amount of compression between neighboring links and binding of the articulation surfaces. Assuming a semi-conical concave articulation surface, any variation in the convex surface as a result of manufacturing or use have little effect on the contact angle and location of contact between the convex and concave articulation surfaces. Variations in the size of the convex surface may have an effect on how far into the semi-conical surface the convex surface engages, but, owing to the geometry, the contact angle will be the same, despite the variations. 
     The angle of the semi-conical surface can be varied to accommodate tradeoffs between steerability and payload of the resulting articulating probe. The angle of the semi-conical surface controls the contact point between the convex, semi-spherical and the concave, semi-conical articulation surfaces. In general, as the contact point is lowered to a wider region of the cone, the strength of the interface, and therefore the strength of the articulating probe, is improved. As the contact point is raised to a narrower region of the cone, steerability of the articulating probe is improved. 
     In some embodiments, the angle of the semi-conical surface can be approximately 23°, or 46° included. This angle can be suitable when considering the combined factors of outer link geometry, material strength, and material friction properties. A range of angles were subject to testing, and compression testing indicated that the 23 degree conical provided optimal compression, in other words, the least amount of compression, as a result of where the concave conical surface comes in contact with the convex spherical mating surface, while still providing optimal friction for locking ability in a rigid state, as recorded in friction/steering test results. Steeper angles, for example a 14 degree angle, resulted in the outer links sticking or binding to each other under compression, while more gradual angles, for example, angles greater than about 23 degrees resulted in reduced locking while in a rigid state. However, with a different combination of geometry, friction and material strength, conical angles less than 23 degrees or greater than 23 degrees may be desirable. 
     In the embodiments depicted herein, the system of outer links  100  employ three steering cables spaced apart from each other at 120 degree intervals. The steering cables are selectively tensioned to retain the articulation surfaces of the links in a rigid position and are selectively released to allow for selective motion of the links in a limp position. Other numbers of steering cables can be employed, for example two, four, or more, and they can be spaced apart at regular angular intervals or at different angles. 
       FIG. 3A  is a perspective view of first and second outer links of an articulating probe of a system for performing a medical procedure according to other embodiments of the present inventive concepts. 
     Referring to  FIG. 3A , in this embodiment, the motion resisting assembly comprises one or more slots  312  positioned on an external portion of the convex articulation surface  304  of the link  100   c ,  100   d . The motion resisting assembly further comprises one or more corresponding pins  306 , in this example two opposed pins, that are positioned on tabs  314  configured to engage the corresponding slots  312  of a neighboring link  100   c ,  100   d.    
     In some embodiments, the convex articulation surface  304  of the links  100   c ,  100   d  is semi-spherical. In such an arrangement, the pins  306  of a neighboring second link  100   d  can be positioned such that when the neighboring links are at an articulation angle of zero, and therefore, their respective longitudinal axes are aligned, the pins  306  of the neighboring second link  100   d  are aligned with the equator of the semi-spherical convex articulation surface  304  of the first link  100   c . The slots  312  can be oriented to extend along the outer surface of the semi-spherical convex articulation surface  304  in a direction that is along a meridian curve, or longitude curve, from the equator of the surface  304  to a pole of the surface  304 . In some embodiments, the length L of the slots  312  can be extended beyond the equator of the surface  304 , to accommodate articulation of the neighboring second link  100   d  relative to the first link  100   c . In some embodiments, at a maximum articulation angle, the lower surface  321  of the second link  100   d  abuts a shoulder  320  of the first link  100   c  to limit articulation. A recess  322  formed in the shoulder  320  accommodates the tab  314  in this position, without interfering with free articulation of the second link  100   d  relative to the first link  100   c . Alternatively, the tab  314  and corresponding recess  322  can be configured to provide an articulation-limiting function. 
     In the present embodiment, with any such twisting moment imparted on the second link  100   d , the sidewalls of the slots  312  of the first link  100   c  abut the pins  306  of the second link  100   d  and thus prevent the second link  100   d  from rotating about its longitudinal axis relative to the first link  100   c . At the same time, the interaction of the pins  306  and slots  312  do not obstruct or limit articulation of the second link  100   d  relative to the first link  100   c , for example articulation of the second link  100   d  about the first and second articulation axes  102   x ,  102   y  of the first link  100   c  (see  FIG. 2 ). Free articulation of the second link  100   d  relative to the first link  100   c  is maintained, while mitigating or preventing undesired twisting of the second link  100   d  relative to the first link  100   c    
     In some embodiments, two pins  306  and slots  312  can be positioned on each link  100   c ,  100   d  at opposed 180 degree positions, as shown in  FIG. 3A . 
     Referring to  FIG. 3B , in other embodiments, a single pin  306  and a single slot  312  can be positioned on each link  100   d ′,  100   d ″,  100   d ′″. In an example embodiment, the pin  306  and slot  312  of each link  100   d ′,  100   d ″,  100   d ′″ can be positioned at an angular distance of 120 degrees apart from each other about the perimeter of the link  100   d ′,  100   d ″,  100   d ′″. During assembly, each respective link  100   d ′,  100   d ″,  100   d ′″, can be seated into its respective position by rotating each link by 120 degrees relative to the neighboring link as the links progress from the proximal end to the distal end of the articulating probe. Engagement of the single pin  306  and slot  312  is sufficient for mitigating or preventing undesired twisting of the link  100   d ″ relative to an adjacent link, e.g.  100 ′ and  100 ′″, since the pin  306  and corresponding slot  112  remain engaged throughout the range of articulation. 
       FIG. 4  is a perspective view of first and second outer links of an articulating probe of a system for performing a medical procedure according to other embodiments of the present inventive concepts. 
     Referring to  FIG. 4 , in this embodiment, the motion resisting assembly comprises one or more pins  406  positioned on an external portion of the convex articulation surface  404  of the link  400   a ,  400   b . The motion resisting assembly further comprises one or more corresponding slots  406  that are positioned within the concave articulation surface  410   a  and configured to engage the corresponding pins  406  of a neighboring link  400   a ,  400   b . In the embodiment illustrated in  FIG. 4 , a single pin  406  and a single corresponding slot  412  are used. 
     In some embodiments, the convex articulation surface  404  of the links  400   a ,  400   b  is semi-spherical. In such an arrangement, the pin  406  of each link can be positioned to lie on the convex articulation surface  404  at a position above the equator of the semi-spherical convex articulation surface  404 , and between the equator and the pole of the surface  404 . 
     The slots  412  can be oriented to extend along the inner surface of the semi-spherical concave articulation surface  410   a  in a direction that is oriented along a meridian curve, or longitudinal curve, from the equator of the surface  410   a  toward a pole of the surface  410   a . In some embodiments, the length L of the slots  412  can accommodate articulation of the neighboring second link  400   b  relative to the first link  400   a . In some embodiments, at a maximum articulation angle, the lower surface  421  of the second link  400   b  abuts a shoulder  420  of the first link  400   a  to limit articulation. 
     In the present embodiment, with any such twisting moment imparted on the second link  400   b , the sidewalls of the slot  412  of the second link  400   b  abut the pin  406  of the first link  400   a  and thus prevent the second link  400   b  from rotating about its longitudinal axis relative to the first link  400   a . At the same time, the interaction of the pin  406  and slot  412  do not obstruct or limit articulation of the second link  400   b  relative to the first link  400   a , for example articulation of the second link  400   b  about the first and second articulation axes  102   x ,  102   y  of the first link  400   a  (see  FIG. 2 ). Free articulation of the second link  400   b  relative to the first link  400   a  is maintained, while mitigating or preventing undesired twisting of the second link  400   b  relative to the first link  400   a.    
       FIG. 5A  is a side view of first and second outer links of an articulating probe of a system for performing a medical procedure according to other embodiments of the present inventive concepts.  FIG. 5B  is a close-up side view of one of the first and second outer links of  FIG. 5A .  FIG. 5C  is a lower perspective view of the link of  FIG. 5B . 
     Referring to  FIGS. 5A-5C , in some embodiments, the motion resisting assembly comprises a plurality of lobes, or ribs,  150 , spaced apart from each other about an outer perimeter of the convex articulation surface  104  of the link  100 ;  100   f . In some embodiments, the convex articulation surface  104  is semi-spherical and the plurality of lobes  150  are spaced apart about an equator region of the convex articulation surface  104 . In other embodiments, the lobes  150  can be placed between the equator region and the polar region of the convex articulation surface. The lobes  150  can be linked to each other by planar outer linking surfaces  152 ; however, the linking surfaces can alternatively be curved or angular, depending on the application. The motion resisting assembly further comprises a plurality of recesses  154  spaced apart from each other about an inner surface of the lower portion of the concave articulation surface  110 . The recesses  154  are similarly linked to each other by planar inner linking surfaces  156 , which otherwise can also be curved or angular, depending on the application. The lobes  150  and outer linking surfaces  152  of a first neighboring link  100   e  are positioned to correspond with the recesses  154  and inner linking surfaces  156  of a second neighboring link  100   f . In this manner, throughout the range of articulation of the second link  100   f  relative to the first link  100   e , at least one of the plurality of recesses  154  and/or planar inner linking surfaces  156  remains engaged with the corresponding lobes  150  and/or outer linking surfaces  152  of the neighboring link. In some embodiments, in a position where the second link  100   f  is in position at a zero-degree articulation angle relative to the first link  100   e , at least top portions of all lobes  150  and outer linking surfaces  152  can be in position to engage at least bottom portions of all recesses  154  and inner linking surfaces  156 . On the other hand, at a position of full articulation limited by contact of the lower surface  121  of the second link  100   f  and the shoulder  120  of the first link  100   e , such as in the example depicted in  FIG. 5A , the leftmost lobes  150  and corresponding recesses  154  are fully engaged, the central lobes  150  and recesses  154  are partially engaged and the rightmost lobes  150  and recesses  154  are not engaged. 
     In the present embodiment, with any such twisting moment imparted on the second link  100   f , the inner walls of the recesses  154  and inner linking surfaces  156  of the second link  100   f  abut the lobes  150  and outer linking surfaces  152  of first link  100   e  and thus prevent the second link  100   f  from rotating about its longitudinal axis. At the same time, the interaction of the recesses and lobes  154 ,  150  and inner and outer linking surfaces  156 ,  152  do not obstruct or limit articulation of the second link  100   f  relative to the first link  100   e , for example articulation of the second link  100   f  about the first and second articulation axes  102   x ,  102   y  of the first link  100   e  (see  FIG. 2 ). Free articulation of the second link  100   f  relative to the first link  100   e  is maintained, while mitigating or preventing undesired twisting. 
     In the embodiment of  FIGS. 5A-5C , six lobes  150  and corresponding recesses  154  are depicted so as to be evenly distributed about the links in mating hexagonal shapes. In various embodiments, any of a number of lobes  150  and recesses  154  can be employed. For example, any of two through eight, or more, lobes  150  can be employed and two through eight, or more, recesses  154  can be employed. The number of lobes  150  can be the same as, or different than the number of recesses  154 . The lobes and/or recesses can be evenly distributed at angular intervals about the links or can be unevenly distributed. The outer linking surfaces  152  can be planar, or otherwise curved or angular, depending on the application. Similarly, the inner linking surfaces  156  can be planar, or otherwise curved or angular, depending on the application 
       FIG. 6A  is a lower perspective view of first and second outer links of an articulating probe of a system for performing a medical procedure according to other embodiments of the present inventive concepts.  FIG. 6B  is a top perspective view of one of the first and second outer links of  FIG. 6A .  FIG. 6C  is a lower perspective view of the link of  FIG. 6B . 
     Referring to  FIGS. 6A-6C , in some embodiments, the motion resisting assembly comprises a convex first articulation surface  604  on an upper portion  128  of a first link  100   g  and a concave second articulation surface  610  in a lower portion of a second link  100   h  neighboring the first link  100   g.    
     In some embodiments, the convex first articulation surface  604  is semi-ellipsoidal. In some embodiments, the concave second articulation surface  610  is semi-ellipsoidal. In some embodiments, the semi-ellipsoidal surface has a major axis Amajor and a minor axis Aminor in the plane of the first and second articulation axes  102   x ,  102   y  (see  FIG. 2 ). Referring to  FIGS. 6B and 6C , the major axis Amajor can have a greater length than the minor axis Aminor for both the convex first articulation surface  604  and the concave second articulation surface  610 . 
     Interaction of the corresponding convex and concave semi-ellipsoidal articulation surfaces  604 ,  610  of the neighboring links permit free articulation of the second link  100   h  relative to the first link  100   g . The articulation can be limited for example, by positioning of the lower surface  121  of the second link  100   h  relative to the shoulder  120  of the first link  100   g , as described herein in connection with various other embodiments. 
     In the present embodiment, with any such twisting moment imparted on the second link  100   h , the elongated shapes of the mating semi-ellipsoidal surfaces  604 ,  610  of the neighboring links prevent the second link  100   h  from rotating about its longitudinal axis  602 Zh relative to the longitudinal axis  602 Zg of the first link  100   g . At the same time, the interaction of the semi-ellipsoidal surfaces  604 ,  610  does not obstruct or limit articulation of the second link  100   h  relative to the first link  100   g , for example articulation of the second link  100   h  about the first and second articulation axes  102   x ,  102   y  of the first link  100   g  (see  FIG. 2 ). Free articulation of the second link  100   h  relative to the first link  100   g  is maintained, while mitigating or preventing undesired twisting of the second link relative to the first link. 
       FIG. 7A  is a lower perspective view of first and second inner links of an articulating probe of a system for performing a medical procedure according to other embodiments of the present inventive concepts.  FIG. 7B  is a top perspective view of one of the first and second inner links of  FIG. 7A . 
     Referring to  FIGS. 7A-7B , in some embodiments, the motion resisting assembly comprises a first articulation surface  704  on an upper surface of a first link  700   i  and a second articulation surface  710  on a lower surface of a second link  700   j  neighboring the first link  700   i.    
     In the present example of  FIGS. 7A and 7B , the first and second links  700   i ,  700   j  comprise inner links of the articulating probe. The first and second inner links  700   i ,  700   j  are configured to be positioned within the longitudinal openings present in the arrangement of outer links. 
     In some embodiments, the first and second links  700   i ,  700   j  (generally  700 ) include a central cable opening  732  that passes through the links  700  in a longitudinal direction of the links  700  along their respective longitudinal axes  702 Zi,  702 Zj. The cable opening  732  is configured to receive an operating cable for the inner mechanism of the articulating probe. In some embodiments, the outermost surface portions  734  of the first and second links lie on a circle. In some embodiments recesses  724  can be provided to accommodate working channels of the articulating probe that are formed between the inner regions of the outer links and outer regions of the inner links, as described herein. In a case where three working channel recesses  724  are present, then the links are generally shaped to have three lobe regions  736   a - c  surrounding the cable opening  732 . 
     In some embodiments, the first articulation surface  704  comprises convex features and concave features. For example, referring to  FIG. 7B , the first articulation surface  704  is convex in profile between points G and H on the surface  704  between the first and second lobes  736   a ,  736   b . At the same time, the first articulation surface  704  is concave in profile between points E and F on the surface  704  between the third lobe  736   c  and the saddle region  738  between the first and second lobes  736   a ,  736   b.    
     Similarly, the second articulation surface  710 , as shown in  FIG. 7A  comprises concave features and convex features that correspond with those of the first articulation surface  704  of a neighboring link. In particular, the second articulation surface  710  is concave in profile between points C and D on the surface  710  between the first and second lobes  736   a ,  736   b . At the same time, the second articulation surface  710  is convex in profile between points A and B on the surface  710  between the third lobe  736   c  and the saddle region  738  between the first and second lobes  736   a ,  736   b.    
     Accordingly, the convex features of the first articulation surface  704  mate with, or otherwise interface with, the concave features of the second articulation surface  710  of a neighboring link. Similarly, the concave features of the first articulation surface  704  mate with, or otherwise interface with, the convex features of the second articulation surface  710  of a neighboring link. 
     Interaction of the corresponding convex and concave features of the first and second articulation surfaces  704 ,  710  of the neighboring links permit free articulation of the second link  700   j  relative to the first link  700   i . For example, the concave feature between points C and D of the second articulation surface interacting with the corresponding feature on the neighboring first articulation surface permits free articulation in a first plane; while the convex feature between points A and C of the second articulation surface interacting with the corresponding feature on the neighboring first articulation surface permits free articulation in a second plane. 
     In the present embodiment, with any twisting moment imparted on the second link  700   j , the opposed convex and concave features of the first and second articulation surfaces  704 ,  710  prevent the second link  700   j  from rotating about its longitudinal axis  702 Zj relative to the longitudinal axis  702 Zi of the first link  700   i , or otherwise limit or mitigate such rotation. At the same time, the interaction of the opposed convex and concave features does not obstruct or limit articulation of the second link  700   j  relative to the first link  700   i , for example articulation of the second link  700   j  about the first and second articulation axes  702   x ,  702   y  of the first link  700   i . Free articulation of the second link  700   j  relative to the first link  700   i  is maintained, while mitigating or preventing undesired twisting of the second link relative to the first. 
     The inventive concepts of the present embodiment including opposed and mating convex and concave features is not only applicable to inner links  700 , but also can be applied to the outer links  100  of the articulating probe. 
       FIG. 8A-8C  are top views of first and second outer links of an articulating probe of a system for performing a medical procedure according to other embodiments of the present inventive concepts. 
     Referring to the embodiment of  FIG. 8A , first magnets  802   k  are positioned about the shoulder  120  of a first link  800   k . The first magnets  802   k  can be positioned at regular angular intervals about the shoulder  120 . In the present example embodiment, a 90 degree interval is illustrated. Similarly, second magnets  802   l  are positioned about the lower surface  121  of a second link  800   l  to correspond with those of the first link. In some examples, the ends of the first magnets  802   k  positioned on the shoulder  120  of the first link  800   k  have a first polarity, for example South (S), and ends of the second magnets  802   l  positioned on the lower surface  121  of the second link  800   l  have a second polarity, for example, North (N). In other embodiments, mating pairs of the first and second magnets  802   k ,  8021  can be selected so as to have opposite polarities, and the polarities of all magnets of a given link do not need to have the same orientation. 
     Referring to the embodiment of  FIG. 8B , first magnets  802   m  are positioned about the convex first articulating surface  804  of a first link  800   m . The first magnets  802   m  can be positioned at regular angular intervals about first articulating surface  804 . In the present example embodiment, a 90 degree interval is illustrated. Similarly, second magnets  802   n  are positioned about the concave second articulating surface  810  of a second link  800   n  to correspond with those of the first link  800   m . In some examples, the first magnets  802   m  positioned on the first link  800   m  have a first polarity, for example South (S), and the second magnets  802   n  positioned on the second link  800   n  have a second polarity, for example, North (N). In other embodiments, mating pairs of the first and second magnets  802   m ,  802   n  can be selected so as to have opposite polarities, and the polarities of all magnets of a given link do not need to have the same orientation. 
     Referring to the embodiment of  FIG. 8C , first magnetic strips  802   p  are positioned circumferentially about the convex first articulating surface  804  of a first link  800   p . The first magnetic strips  802   p  can be positioned at regular angular intervals about first articulating surface  804 . In the present example embodiment, two strips at a 180 degree interval are illustrated. Similarly, second magnetic strips  802   q  are positioned about the concave second articulating surface  810  of a second link  800   q  and are oriented to correspond with those of the first link  800   p . In some examples, the first magnetic strips  802   p  positioned on the first link  800   p  have a first polarity, for example South (S), and the second magnetic strips  802   q  positioned on the second link  800   q  have a second polarity, for example, North (N). In other embodiments, mating pairs of the first and second magnets  802   p ,  802   q  can be selected so as to have opposite polarities, and the polarities of all magnets of a given link do not need to have the same orientation. 
     In some embodiments, the first and second magnets are positioned so as to magnetically engage each other over a range of articulation angles of the second link relative to the first link. The magnetic engagement between the magnets of the neighboring links permits articulation of the second link relative to the first link. The articulation can be limited for example, by positioning of the lower surface  121  of the first link relative to the shoulder  120  of the second link, as described herein in connection with various other embodiments. 
     In the present embodiments of  FIGS. 8A-8C , with any such twisting moment imparted on the second link, the magnetic interaction of the neighboring links prevent the second link from rotating about its longitudinal axis relative to the longitudinal axis of the first link, or otherwise limit or mitigate such rotation. At the same time, the magnetic interaction does not obstruct or limit articulation of the second link relative to the first link. Free articulation of the second link relative to the first link is maintained, while mitigating or preventing undesired twisting of the second link relative to the first. The embodiments illustrated in  FIGS. 8A-8C  can be employed in connection with any of the other embodiments described herein to further restrict or limit twisting of the links. 
     In the present example embodiment, the magnets are illustrated as being applied to outer links of the articulating probe, however, the principles of this concept of the invention are equally applicable to inner links, as well. 
       FIG. 9  is a cross-sectional view of an inner link and an outer link including an anti-twist member positioned therebetween, in accordance with embodiments of the present inventive concepts. 
     Referring to  FIG. 9 , an articulating probe includes an assembly of outer links  100   r  having a central opening. An assembly of inner links  700   s  is positioned through the central opening of the inner links. As described herein the plurality of outer links  100   r  have recesses  124  on their inner sidewalls and the plurality of inner links  700   s  have recesses  724  on their outer sidewalls. Together, the opposed recesses  124 ,  724  form working channels for the articulating probe for the purposes described herein, and for other purposes. 
     An anti-twist member  942  is positioned in at least one of the working channels  125 . In some embodiments, the anti-twist member comprises a tube-shaped member that is hollow or solid in cross-section. In other embodiments, the anti-twist member  942  comprises a flexible material that permits articulation of neighboring inner links and articulation of neighboring outer links. At the same time, the tube can exhibit strength or rigidity when subjected to a twisting motion between neighboring links. In some embodiments, the anti-twist member  942  can be configured to extend along an entire length, or nearly the entire length, of the working channel  125  of the articulating probe, from its proximal to distal end. In some embodiments, the anti-twist member  942  can be segmented so that it extends through portions of the working channel  125 . In some embodiments, the anti-twist member  942  can be affixed to a recess  724  of the inner link  700   s  or a recess  124  of the outer link  100   r . In some embodiments, the anti-twist member  942  can be affixed to both a recess  724  of the inner link  700   s  and a recess  124  of the outer link  100   r.    
     In some embodiments, the tube-shaped anti-twist member  942  can be fixed at its proximal and distal ends. The torsional rigidity of the anti-twist member  942  will determine the degree to which it prevents twisting. 
     In the present embodiments of  FIG. 9 , with any such twisting moment imparted on a second link neighboring a first link, the presence of the anti-twist member prevents the second link from rotating about its longitudinal axis relative to the longitudinal axis of the first link. At the same time, the anti-twist member does not obstruct or limit, or minimally obstructs or limits, articulation of the second link relative to the first link. Free articulation of the second link relative to the first link is maintained, while mitigating or preventing undesired twisting. The embodiments illustrated in  FIG. 9  can be employed in connection with any of the other embodiments described herein to further restrict or limit twisting of the links. 
     As described herein, the systems and methods of the present inventive concepts prevent, mitigate, or otherwise restrict, torsional rotation, or twisting, of links in a system of links in a highly articulated robotic system. The systems and methods can be applied to both an inner link mechanism and an outer link mechanism of the robotic system. In some embodiments, rotation of a second link relative to a first link can be limited to about 1 degree of rotation. Other rotational limit amounts are equally applicable, depending on the configuration, and the inventive concepts are not limited thereto. 
     While the present inventive concepts have been particularly shown and described above with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art, that various changes in form and detail can be made without departing from the spirit and scope of the present inventive concepts described and defined by the following claims.