Steerable extendable devices

Abstract

The present invention is a Distally Assembled Steerable Cannula (DASC), a robotically-manipulated device that can be deployed and extended within a patient's body by growing from its distal end, or can be used in non-medical applications. In some embodiments, growth occurs by sequentially assembling segments that interlock to form a rigid tube with a complex 3-D shape. The segments are individually transported through the growing cannula, and then assembled at the distal end. A segment can be wedge-shaped in profile, allowing adjustment of the local radius and plane of curvature of the cannula to be controlled by relative segment orientation.

What is claimed is: 
     
         1 . An elongatable, steerable apparatus capable of growing from a proximal end to a distal end through a process of assembly wherein one or more segments are added to the distal end of the apparatus, the apparatus comprising:
 a first segment having a lumen therethrough, the first segment having a proximal end and a distal end; and   a second segment having a lumen, a proximal end, and a distal end, wherein the second segment is deliverable via a segment transporter to the distal end of the first segment, wherein the segment transporter attaches the second segment to the first segment, wherein the second segment is capable of changing the growth direction of the distal end of the apparatus and of one or more subsequent segments.   
     
     
         2 . The apparatus of  claim 1 , apparatus capable of lengthening from a proximal end to a distal end through a process of assembly wherein one or more segments are added to the distal end of the apparatus, and wherein the apparatus grows along a desired curved path in space based on a tapered shape of each additional segment; or wherein the lengthening of the apparatus along the desired curved path in space is a result of stacking the one or more segments and the one or more segments comprise one or more straight, tapered, or offset segments. 
     
     
         3 . The apparatus of  claim 1 , wherein the at least first, second, or subsequent segments, may attach or interlock to each other by friction, abrasive contact surfaces, self-adhesive strips, hook and loop fasteners, hooks and eyes, ties, tabs, holes, buckles, belts, pins, elastic bands, rubber bands, snaps, clasps, magnets, zippers, DUAL LOCK™, or VELCRO™ tape fasteners. 
     
     
         4 . The apparatus of  claim 1 , wherein the lengthening of the apparatus along the desired curved path in space is a result of transporting the segments through a lumen in the apparatus. 
     
     
         5 . The apparatus of  claim 1 , wherein the apparatus is a cannula capable of growing from a proximal end to a distal end and capable of a non-linear configuration comprising:
 one or more segments having a lumen and substantially cylindrical in their uncompressed state and having a distal face and a proximal face that are non-parallel, wherein the one or more segments can be transformed into a non-cylindrical, substantially elliptical shape;   a segment transporter that transports one or more additional segments in their non-cylindrical, substantially elliptical shape through the substantially cylindrical segments; and   a coupling mechanism that engages the one or more segments to an adjacent segment, whereby at least one of the segments is transported through the lumen of the one or more substantially cylindrical segments to reach a distal location, and transformed to couple to the most distal of the segments, thereby growing the cannula.   
     
     
         6 . The apparatus of  claim 5 , wherein the segment transporter is capable of at least one of swiveling, rotating, coupling or transporting a segment. 
     
     
         7 . The apparatus of  claim 5 , wherein a swiveling axis of the segment is substantially parallel to a minor axis of the non-cylindrical, substantially elliptical shape of the segment. 
     
     
         8 . The apparatus of  claim 5 , wherein a distal face of a first segment is substantially perpendicular to a substantially cylindrical axis of the first segment, and a proximal face of a first segment is substantially non-perpendicular to the substantially cylindrical axis of the first segment;
 a distal face of a second segment is substantially non-perpendicular to a substantially cylindrical axis of the second segment, and a proximal face of a second segment is substantially perpendicular to the substantially cylindrical axis of the second segment; and   wherein the swiveling axis is substantially perpendicular to a plane formed by the substantially cylindrical axis and a normal to the substantially non-perpendicular face of the segment.   
     
     
         9 . The apparatus of  claim 5 , wherein the segments comprise one or more holes along a distal edge of the segment and one or more tabs that extend from a proximal edge of the segments, wherein the one or more tabs fit within the one or more holes to couple two adjacent segments; each segment comprises two or more tabs that are equally spaced around the circumference of the segment; or each segment comprises two holes that are substantially parallel to the swiveling axis. 
     
     
         10 . The apparatus of  claim 9 , wherein the tabs are substantially aligned with the major and minor axes of the substantially elliptical shape assumed by the rings when transformed; or
 wherein at least one first tab in the distal segment of a pair of adjacent segments enters a hole in the proximal segment of a pair of adjacent segments from the inside of the proximal segment, and at least one second tab on the non-opposite side of the distal segment enters a hole from the outside of the proximal segment to couple the segments.   
     
     
         11 . The apparatus of  claim 1 , wherein the apparatus is an elongatable, steerable cannula capable of growing from a proximal end to a distal end through a process of assembly wherein one or more segments are added to the distal end of the cannula;
 wherein the first segment is a first flexible segment substantially cylindrical in axial cross section when uncompressed and substantially elliptical when compressed, having a first lumen therethrough, the first segment having a first proximal face substantially perpendicular to a first substantially cylindrical axis and provided with one or more first male coupling elements, and a first distal face substantially non-perpendicular to the substantially cylindrical axis and provided with a first plurality of female coupling elements;   wherein the second segment is a second flexible segment substantially cylindrical in axial cross section when uncompressed and substantially elliptical when compressed, having a second lumen therethrough, the second segment having a second proximal face substantially non-perpendicular to a second substantially cylindrical axis and provided with one or more second male coupling elements, and a second distal face substantially perpendicular to the second substantially cylindrical axis and provided with a second plurality of female coupling elements;   a flexible shaft provided with grippers able to grip said first and said second segment to compress and allow to decompress said segments, swivel or allow to swivel said segments about axes substantially parallel to the minor axes of said first and second segments when compressed and substantially elliptical, and transport said segments through said lumen;   wherein said flexible shaft transports said second segment through said lumen of said first segment, then rotates said second segment as required around an axis substantially coincident with the longitudinal axis of the flexible shaft, brings the proximal face of said second segment in contact with the distal face of said first segment, allows said second segment to decompress while allowing two of said second male coupling elements to enter two of said first plurality of female coupling elements from the inside and two of said second male coupling elements to enter two of said first plurality of female coupling elements from the outside; and   wherein said flexible shaft transports said first segment through said lumen of said second segment, rotates said first segment as required around an axis substantially coincident with the longitudinal axis of the flexible shaft, brings the proximal face of said first segment in contact with the distal face of said second segment, then allows said first segment to decompress while allowing two of said first male coupling elements to enter two of said second plurality of female coupling elements from the inside and two of said first male coupling elements to enter two of said second plurality of female coupling elements from the outside.   
     
     
         12 . The apparatus of  claim 11 , wherein the segments comprise a superelastic nickel-titanium material. 
     
     
         13 . The apparatus of  claim 11 , wherein the first and second male coupling elements comprise interlocking male and female elements such that the adjacent segments are mechanically interlocked when the segments are decompressed;
 wherein a plurality of first and second segments are arranged in an alternating pattern within the cannula;   wherein the angle between the first proximal face and second distal face is varied by varying the relative orientation of the first and second segments when coupled together;   wherein the relative orientation is varied as required by rotating the second segment substantially about an axis substantially coincident with the longitudinal axis of the flexible shaft prior to coupling the second segment to the first segment;   wherein the minor axis of the compressed, substantially elliptical second segment is substantially perpendicular to the plane defined by the substantially non-perpendicular second proximal face and the second substantially cylindrical axis, and wherein the minor axis of the compressed, substantially elliptical first segment is substantially perpendicular to the plane defined by the substantially non-perpendicular first distal face and the first substantially cylindrical axis, and wherein the second segment is swiveled about its minor axis and its major axis is substantially parallel to the first cylinder axis during transport by the flexible shaft, and wherein the first segment is swiveled about its minor axis and its major axis is substantially parallel to the second cylinder axis during transport by the flexible shaft;   wherein the second segment is rotated as required relative to the first segment prior to allowing the second segment to decompress, and wherein the first segment is rotated relative to the second segment prior to allowing the first segment to decompress; or   wherein the grippers are supported by a fork that is compressed by a sliding tube, or the grippers are supported by a flexible ring that is expanded by applying tension to a wire attached to its distal end.   
     
     
         14 . The apparatus of  claim 1 , wherein the apparatus is an elongatable, steerable cannula capable of growing from a proximal end to a distal end through a process of assembly wherein one or more segments are added to the distal end of the cannula, wherein:
 the first segment is a first expandable segment substantially cylindrical in axial cross section having a first lumen therethrough, the first segment having a first proximal face substantially perpendicular to a first substantially cylindrical axis and provided with a first plurality of male coupling elements, and a first distal face substantially non-perpendicular to the substantially cylindrical axis and provided with a first plurality of female coupling elements;   the second segment is a second expandable segment substantially cylindrical in axial cross section having a second lumen therethrough, the second segment having a second proximal face substantially non-perpendicular to a second substantially cylindrical axis and provided with a second plurality of male coupling elements, and a second distal face substantially perpendicular to the second substantially cylindrical axis and provided with a second plurality of female coupling elements;   a flexible shaft provided with an expanding member to expand and orient said first and said second segments, and transport said segments through said lumens;   wherein said flexible shaft transports said second segment through said lumen of said first segment, rotates said second segment as required around an axis substantially coincident with the longitudinal axis of the flexible shaft, brings the proximal face of said second segment in contact with the distal face of said first segment, then expands said second segment and allows second plurality of male coupling elements to enter said first plurality of female coupling elements from the inside; and   wherein said flexible shaft transports said first segment through said lumen of said second segment, rotates said first segment as required around an axis substantially coincident with the longitudinal axis of the flexible shaft, brings the proximal face of said first segment in contact with the distal face of said second segment, then expands said first segment and allows first plurality of male coupling elements to enter said second plurality of female coupling elements from the inside.   
     
     
         15 . The apparatus of  claim 1 , wherein the apparatus is an elongatable, steerable cannula capable of growing from a proximal end to a distal end through a process of everting, the cannula further comprising:
 an expandable tube having a relatively flexible inner wall of relatively small diameter and an relatively inflexible outer wall of relatively large diameter;   a device for everting the tube to grow the cannula from its distal end by progressively transforming the inner wall into an outer wall;   a steering mechanism for controlling the direction in which the cannula grows by varying the rate at which the inner wall is transformed into outer wall according to location around the circumference of the inner wall, wherein the expandable tube is optionally a braided superelastic nickel-titanium wire or an elastomer.   
     
     
         16 . A method of making an elongatable, steerable cannula capable of growing from a proximal end to a distal end through a process of assembly wherein one or more segments are added to the distal end of the cannula, the method comprising:
 obtaining a first flexible segment substantially cylindrical in axial cross section when uncompressed and substantially elliptical when compressed, having a first lumen therethrough, the first segment having a first proximal face substantially perpendicular to a first substantially cylindrical axis and provided with one or more first male coupling elements, and a first distal face substantially non-perpendicular to the substantially cylindrical axis and provided with a first plurality of female coupling elements;   positioning a second flexible segment substantially cylindrical in axial cross section when uncompressed and substantially elliptical when compressed, having a second lumen therethrough, the second segment having a second proximal face substantially non-perpendicular to a second substantially cylindrical axis and provided with one or more second male coupling elements, and a second distal face substantially perpendicular to the second substantially cylindrical axis and provided with a second plurality of female coupling elements;   inserting a flexible shaft provided with grippers able to grip said first and said second segment to compress and allow to decompress said segments, swivel or allow to swivel said segments about axes substantially parallel to the minor axes of said first and second segments, and transport said segments through said lumen;   wherein said flexible shaft transports said second segment through said lumen of said first segment, then allows said second segment to decompress while allowing two of said second male coupling elements to enter two of said first plurality of female coupling elements from the inside and two of said second male coupling elements to enter two of said first plurality of female coupling elements from the outside; and   wherein said flexible shaft transports said first segment through said lumen of said second segment, then allows said first segment to decompress while allowing two of said first male coupling elements to enter two of said second plurality of female coupling elements from the inside and two of said first male coupling elements to enter two of said second plurality of female coupling elements from the outside.   
     
     
         17 . The method of  claim 16 , wherein the steps are further defined as:
 obtaining a first expandable segment substantially cylindrical in axial cross section having a first lumen therethrough, the first segment having a first proximal face substantially perpendicular to a first substantially cylindrical axis and provided with a first plurality of male coupling elements, and a first distal face substantially non-perpendicular to the substantially cylindrical axis and provided with a first plurality of female coupling elements;   positioning a second expandable segment substantially cylindrical in axial cross section having a second lumen therethrough, the second segment having a second proximal face substantially non-perpendicular to a second substantially cylindrical axis and provided with a second plurality of male coupling elements, and a second distal face substantially perpendicular to the second substantially cylindrical axis and provided with a second plurality of female coupling elements; and   inserting a flexible shaft provided with an expanding member to expand and orient said first and said second segments, and transport said segments through said lumens;   wherein said flexible shaft transports said second segment through said lumen of said first segment, rotates said second segment as required around an axis substantially coincident with the longitudinal axis of the flexible shaft, brings the proximal face of said second segment in contact with the distal face of said first segment, then expands said second segment and allows said second plurality of male coupling elements to enter said first plurality of female coupling elements from the inside; and   wherein said flexible shaft transports said first segment through said lumen of said second segment, rotates said first segment as required around an axis substantially coincident with the longitudinal axis of the flexible shaft, brings the proximal face of said first segment in contact with the distal face of said second segment, then expands said first segment and allows said first plurality of male coupling elements to enter said second plurality of female coupling elements from the inside.   
     
     
         18 . The method of  claim 16 , wherein making an elongatable, steerable cannula capable of growing from a proximal end to a distal end through a process of everting, the cannula comprises:
 obtaining a flexible, expandable tube capable of being everted,   positioning a device for everting the tube to grow the cannula from its distal end by progressively transforming the inner wall into an outer wall, rigidifying the outer wall as it is formed; and   inserting a steering mechanism for controlling the direction in which the rigid outer wall grows by varying the rate, according to location around the circumference of the inner wall, at which the inner wall is transformed into the outer wall.   
     
     
         19 . An adjustable structure comprising one or more flexible strips, the one or more flexible strips having a length and a width, comprising:
 one or more fastening elements that join a first edge of the flexible strip in a first region to a second edge of the flexible strip in a second region; and   one or more elements positioned between the first and second edge that vary the width of the flexible strip along its length, wherein the strip can be formed into a tube with a curved 3-D shape.   
     
     
         20 . The adjustable structure of  claim 19 , further comprising at least two flexible bands separated by a gap, wherein a gap between the flexible strips can be adjusted to vary the width of the adjustable structure. 
     
     
         21 . The adjustable structure of  claim 20 , wherein the gap can be adjusted by a screw, or the gap can be adjusted by at least one of: interleaved fingers, a cam, a screw and a nut plate, or wedges; or
 wherein the width of the strip can be varied using a expandable region, or the width of the strip can be varied using a corrugated region.   
     
     
         22 . A stylet for assembling and disassembling a continuously assembled distally curved cannula comprising:
 a stylet having a head and a guide having a proximal and a distal end, wherein a strip of flexible material enters the proximal end of the guide and exits at the distal end, wherein the strip that exits in the distal region of guide forms the cannula; and   a joiner that joins a first region of the strip to a second region of the strip to form the cannula, wherein a width of the strip can vary along its length, wherein the joiner transforms the strip into the cannula, and optionally, wherein the stylet comprises a guide through or along which the strip traverses from the proximal to the distal end during assembly of the cannula, or traverses from the distal to the proximal end during disassembly.   
     
     
         23 . A method of forming an elongatable tube having a lumen, a proximal portion, and an elongating distal portion comprising:
 obtaining a flexible strip having at least a first and a second edge of material having a length and a width;   winding the flexible strip into a tubular shape;   joining the at least first edge to the second edge of the flexible strip;   transporting an unwound section of the strip through the lumen from the proximal portion to the elongating distal portion;   wherein a distal section of the strip forms the proximal portion of the tube and wherein a proximal section of the strip forms a distal portion of the tube.   
     
     
         24 . The method of  claim 23 , wherein a stylet within the lumen of the elongatable tube is actuated to perform at least one of winding, joining, or transporting the strip;
 wherein the width of the flexible strip has a third edge and wherein the joining comprises joining the first edge of a first section of the flexible strip to at least one of the second or third edge of a second section of the flexible strip; or the width of the flexible strip is locally varied along the length of the flexible strip to determine the local tube radius and plane of curvature;   wherein the step of joining is further defined as comprising the step of overlapping the first edge of a first section of the flexible strip with the second edge of a second section of the flexible strip by a distance controlled by the stylet; or   wherein the distance is locally varied along the length of the flexible strip to determine the local tube radius and plane of curvature of the elongatable tube.   
     
     
         25 . A mechanical system comprising:
 a flexible strip of material capable of being wound and joined to itself to form a flexible elongatable tube having a lumen;   an stylet able to move along the along a longitudinal axis of the flexible elongatable tube;   wherein the stylet is actuatable to perform at least one of winding or joining the flexible strip, wherein the stylet adjusts the width or overlap of the flexible strip to produce a change in the elongation direction of the flexible elongatable tube;   wherein the flexible elongatable tube further comprises:   two or more adjacent bands each having a length, wherein each of the bands are approximately parallel to the length of the strip, each band and having an interior and an exterior edge, wherein each of the bands is separated by a spacer;   a stylet that adjusts the position, shape, or size of the spacer to locally vary a gap separating the bands;   wherein the bands can be formed into a curved tube by changing the size of the gap between the bands such that a local radius and plane of curvature of the flexible elongatable tube is determined by the gap.