Abstract:
A flexible device insertion tool including an elongated stiffener with one or more suction ports, and a vacuum connector for interfacing the stiffener to a vacuum source, for attaching the flexible device such as a flexible neural probe to the stiffener during insertion by a suction force exerted through the suction ports to, and to release the flexible device by removing the suction force.

Description:
CLAIM OF PRIORITY IN PROVISIONAL APPLICATION 
       [0001]    This patent document claims the benefit and priority of U.S. Provisional Application No. 61/649,175, filed on May 18, 2012, hereby incorporated by reference. 
     
    
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the United States Department of Energy and Lawrence Livermore National Security, LLC for the operation of Lawrence Livermore National Laboratory. 
     
    
     FIELD OF THE INVENTION 
       [0003]    The present invention relates to flexible neural probes and interfaces, and more particularly to a vacuum-actuated insertion tool for percutaneous insertion or implantation of flexible neural probes and other flexible devices which are not sufficiently rigid to penetrate a percutaneous region unassisted. 
       BACKGROUND OF THE INVENTION 
       [0004]    Microelectrode neural probes and interfaces are an essential tool in neuroscience. They typically comprise a multi-electrode array (MBA) configuration with exposed metal pads or electrodes located on rigid silicon shanks and connected, via interconnection traces, to output leads or to signal processing circuitry on a monolithic substrate. The exposed metal pads/electrodes provide a direct electrical interface with the neurons of a biological entity&#39;s nervous system to stimulate and/or record neural activity. Such neural probes can. target the neuronal activity of neurons, enabling researchers and clinicians to better explore and understand neurological diseases, neural coding, neural modulations, and neural topologies, as well as treat debilitating conditions of the nervous system. Moreover, the ability to analyze neuronal activity using neural probes has led to the development of new neuro-therapeutic devices implemented through brain-machine interfaces. These interfaces use neural probes implanted to bypass damaged tissue and stimulate neural activity, so that a patient can regain lost communication and/or control with respect to some aspect of the patient&#39;s nervous system. Implantable neural probes and interfaces in particular enable extended interaction with neural tissue. 
         [0005]    The flexibility of polymer-based intracortical neural implants provide an attractive alternative over conventional silicon-based neural probes and interfaces for reliable and stable long-term recording, stimulation, and/or monitoring of neuronal activities in the brain. Such flexible MEA probes are typically fabricated using multiple layers of polymers (e.g. biocompatible polymers such as polyimide, Parylene-C, and polyurethanes) coated layer by layer after each metal film deposition and patterning, to insulate the patterned conductive wiring and lines. The resulting electrode array is completely flexible and may enable extended interaction with neural tissue by mitigating the risk of silicon breakage and minimizing potential tissue damage caused by micromotion between the brain and the implant, for long-term safety and functional stability. 
         [0006]    However, the low mechanical stiffness of flexible polymer-based MEAs can cause bending or buckling when percutaneously penetrated/inserted into tissue, e.g. the pial membrane of the brain. In particular, the viscoelastic and inhomogeneous properties of the brain make the mechanics of probe insertion a complex problem with direct insertion difficult. 
         [0007]    What is needed therefor is an insertion tool and method for percutaneously inserting/implanting flexible devices by providing adequate stiffness to the flexible device to enable tissue penetration and insertion, 
       SUMMARY OF THE INVENTION 
       [0008]    One aspect of the present invention includes a flexible device insertion tool, comprising: a rigid-body shank having a handle end and an opposite insertion end, a suction channel extending between the handle and insertion ends, at least one suction port(s) in fluidic communication with the suction channel, and a connector port at the handle end in fluidic communication with the at least one suction port(s) via the suction channel; and a vacuum connector having a first port adapted to connect to a vacuum source, a second port in fluidic communication with the first port, and means for mounting the rigid-body shank on the vacuum connector so that the connector port. of the rigid-body shank is aligned with the second port, and the first port is in fluidic communication with the at least one suction port(s), whereby, upon connecting a vacuum source to the first port, mounting the rigid-body shank on the vacuum connector, and activating the vacuum source, a flexible device positioned adjacent the at least one suction port(s) is releasably attached to the rigid-body shank by a suction force exerted by the at least one suction port(s) during insertion. 
         [0009]    Another aspect of the present invention includes a flexible device insertion tool, comprising: a vacuum connector section having a connector port adapted to fluidically connect to a vacuum source; and an elongated rigid-body shank section connected to and extending from the vacuum connector section to an insertion end, said elongated rigid-body shank section having a suction channel in fluidic communication with the connector port and extending to the insertion end, and at least one suction port(s) in fluidic communication with the connector port via the suction channel, whereby, upon connecting a vacuum source to the connector port of the vacuum connector section and activating the vacuum source, a flexible device positioned adjacent the at least one suction port(s) is releasably attached to the rigid-body shank section by a suction force exerted by the at least one suction port(s) during insertion. 
         [0010]    Another aspect of the present invention includes a rigid-body shank for inserting a flexible device, comprising: an elongated shank body having a handle end and an opposite insertion end, a suction channel extending between the handle and insertion ends, at least one suction port(s) in fluidic communication with the suction channel, and a connector port at the handle end in fluidic communication with the at least one suction port(s) via the suction channel and adapted to fluidically connect to a vacuum source, whereby, upon connecting a vacuum source to the connector port and activating the vacuum source, a flexible device positioned adjacent the at least one suction port(s) is releasably attached to the shank body by a suction force exerted by the at least one suction port(s) during insertion. 
         [0011]    Another aspect of the present invention includes a vacuum connector for flexible device insertion tools, comprising: a connector body having a first port adapted to connect to a vacuum source, a second port in fluidic communication with the first port, and means for mounting a rigid-body shank on the connector body so that a connector port of a suctioning system of the rigid-body shank is aligned with the second port, whereby upon connecting a vacuum source to the first port and activating the vacuum source, a suction force generated by the vacuum source may be transferred to a flexible device via the suctioning system of the rigid-body shank, to releasably attach the flexible device to the rigid-body shank during insertion. 
         [0012]    Another aspect of the present invention includes a method of percutaneously inserting a flexible device, comprising: providing a rigid-body shank having a handle end and an opposite insertion end, a suction channel extending between the handle and insertion ends, at least one suction port(s) in fluidic communication with the suction channel, and a connector port at the handle end in fluidic communication with the at least one suction port(s) via the suction channel; providing a vacuum connector having a first port adapted to connect to a vacuum source, a second port in fluidic communication with the first port, and means for mounting the rigid-body shank on the vacuum connector so that the connector port of the rigid-body shank is aligned with the second port and the first port is in fluidic communication with the at least one suction port(s); mounting the rigid-body shank on the vacuum connector; positioning a flexible device adjacent the at least one suction port(s); connecting a vacuum source to the first port of the vacuum interface connector and activating the vacuum source to releasably attach the flexible device to the rigid-body shank by a suction force exerted by the at least one suction port(s); percutaneously inserting the rigid-body shank with the suction-attached flexible device; deactivating the vacuum source to release the flexible device from the rigid-body shank; and removing the rigid-body shank, leaving the flexible device remaining inserted. 
         [0013]    And another aspect of the present invention includes a method of inserting a flexible device, comprising: providing a flexible device insertion tool having a vacuum interface connector section having a connector port adapted to fluidically connect to a vacuum source, and an elongated rigid-body shank section connected to and extending from the vacuum interface connector section to an insertion end, said elongated rigid-body shank section having a suction channel in fluidic communication with the connector port and extending to the insertion end, and at least one suction port(s) in fluidic communication with the connector port via the suction channel; positioning a flexible device adjacent the at least one suction port(s); connecting a vacuum source to the connector port of the vacuum interface connector section and activating the vacuum source to releasably attach the flexible device to the rigid-body shank section by a suction force exerted by the at least one suction port(s); percutaneoulsy inserting the rigid-body shank section with the suction-attached flexible device; deactivating the vacuum source to release the flexible device from the rigid-body shank section; and removing the rigid-body shank section, leaving the flexible device remaining inserted. 
         [0014]    Generally, the present invention is directed to a vacuum-actuated, flexible device insertion tool and method which uses a vacuum source to temporarily attach a flexible device to a rigid shank of the insertion tool to provide the necessary stiffness to penetrate into neural tissue and insert or implant the flexible device therein, and which can be subsequently removed after insertion, leaving the flexible probe in place. In this manner, the present invention provides a mechanism of stiffening flexible polymer probes to assist with penetration in neural tissue, while also providing the ability to immediately remove the stiffener after the probe is positioned in place. Immediate removal of the stiffening shank helps to reduce surgery time as well as tissue inflammatory response. It is appreciated that the flexible device may be a MEA device having a generally flexible construction which makes percutaneous insertion difficult without assistance, and which may have various device shapes, number of metal layers, number of electrodes, etc. For example, the encapsulated MEA device may be a MEA neural probe or interface useful for a variety of applications in peripheral and cortical nerve stimulation and recording, including as a chronic, fully-implanted neural interface capable of extended operational lifetime due to reduced modes of failure through interface delamination. 
         [0015]    In one example embodiment, the vacuum-actuated removable insertion tool comprises two main components: (1) a metal, silicon or polymer based stiffener with a suction channel in a rigid-body insertion shank of the stiffener that provides suctioning capability to a flexible probe; and (2) a vacuum connector that provides an interface between the stiffener and the vacuum source and provides a mounting structure for the stiffener if the stiffener is provided as an independent component. Generally, the stiffener is constructed of a sufficiently rigid material capable of withstanding multiple insertions and removals without buckling and breakage, i.e. having a buckling strength that is significantly greater than the force needed to penetrate that specific tissue and overcome the friction applied to the moving probe shank during insertion and removal. In another example embodiment, the flexible device insertion tool may be provided with the stiffener and vacuum connector connected as an integrated unit. In this case the tool includes a vacuum connector section having a connector port adapted to fluidically connect to a vacuum source, and an elongated rigid-body shank section connected to and extending from the vacuum connector section to an insertion end. The elongated rigid-body shank section has a suction channel in fluidic communication with the connector port and extends to the insertion end 
         [0016]    In operation, a flexible device may be positioned and aligned along the one or more suction ports of the stiffener, e.g. under a microscope. While the shank remains aligned, the vacuum source (which is connected to the vacuum connector) may be activated to produce in the channel a suction force against the flexible device, to pull and keep the device in place and in close contact with the stiffening shank during implantation. The vacuum connector and the stiffener together operate to apply a suction force to the flexible device to hold it in place during insertion. Upon percutaneously inserting the probe and placing it precisely within tissue, the vacuum pressure is disabled or deactivated, to remove the suction force and release the device from the stiffener. After detaching the flexible device, the stiffener may be removed from the tissue, leaving the flexible device remaining inserted or implanted. In this manner, the invention provides a simple and effective method of attaching an insertion scaffold to a flexible polymer probe using a vacuum source. The insertion scaffold can be immediately removed by releasing the vacuum once the probe is positioned in the tissue. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The accompanying drawings, which are incorporated into and form a part of the disclosure, are as follows: 
           [0018]      FIG. 1  is an exploded cross-sectional view of an example schematic embodiment of the flexible device insertion tool of the present invention having an open suction channel which may be used, for example, for percutaneous applications. 
           [0019]      FIG. 2  is an assembled cross-sectional view of the example schematic embodiment of the flexible device insertion tool of  FIG. 1 . 
           [0020]      FIG. 3  is an exploded perspective view of a flexible device and an example embodiment of the stiffener of the present invention having an open suction channel. 
           [0021]      FIG. 4  is a top view of another example embodiment of the insertion shank of the present invention having support beams/ribs bridging the open suction channel. 
           [0022]      FIG. 5  is a cross-sectional view taken from  FIG. 4  illustrating a section of the insertion shank without a support rib. 
           [0023]      FIG. 6  is a cross-sectional view taken from  FIG. 4  illustrating a section of the insertion shank with a support rib. 
           [0024]      FIG. 7  is an assembled cross-sectional view of another example schematic embodiment of the flexible device insertion tool of the present invention having a partially-enclosed suction channel which may be used, for example, for full implant applications. 
           [0025]      FIG. 8  shows plan views of the top and bottom portions of an example insertion shank having a partially-enclosed suction channel. 
           [0026]      FIG. 9  shows an assembled cross-sectional view of another example schematic embodiment of the flexible device insertion tool of the present invention where the insertion shank and the support structure are connectable in an in-line arrangement. 
           [0027]      FIGS. 10A-D  shows an alternative method of fabricating an insertion shank of the present invention with support ribs forming multiple suction ports. 
           [0028]      FIGS. 11A-D  shows an alternative method of fabricating an insertion shank of the present invention similar to  FIG. 10  without support ribs to form an open channel section with a single vacuum port. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Turning now to the drawings,  FIGS. 1 and 2  show an example schematic embodiment of the flexible device insertion tool of the present invention, generally indicated at reference character  10 , and comprising a rigid-body stiffener  25 , and a vacuum connector  11  upon which the stiffener  25  may be mounted and secured to provide connection to a vacuum source (not shown), The insertion tool  10  is also shown with a flexible device  21  positioned against and temporarily connected to the stiffener  25  so as to be percutaneously insertable together with the stiffener. 
         [0030]    As shown in  FIGS. 1 and 2 , the stiffener  25  has an elongated insertion shank  15 , with a handle end  16 , an opposite insertion end  17 , and a channel  18  extending between the handle and insertion ends. In particular, the channel  18  is open on one side, with the opening forming a single elongated port along the side of the insertion shank. The stiffener also includes a connector port  19  that is in fluidic communication with the channel  18  and the single elongated port.  FIG. 3  also shows a perspective view of the stiffener  25 , illustrating the open channel  18  forming the single elongated suction port along the insertion shank  15 . As can be seen in  FIG. 3 , the channel  18  is surrounded by a raised perimeter having a support surface  27  against which the device  21  contacts when positioned for insertion. The port  19  is also shown near the handle end  16  at the bottom of the channel  18 . Traditional semi-conductor fabrication processes (e.g. photolithography, wet/dry/etch, etc.) may be used to fabricate the stiffener, such as for example fabricating the stiffener from a silicon-on-insulator (SOI) wafer. 
         [0031]    Also in  FIGS. 1 and 2 , the vacuum connector  11  is shown having a fastener for mounting or otherwise connecting the stiffener  25  to the vacuum connector  11  so that the connector port  19  of the rigid-body shank  15  is aligned with one of the ports of the vacuum connector  12 . Various types of fasteners may be used, such as for example various types of clamps (e.g. screw-in clamp), clips, screws, bolts, ties, for securing the stiffener to the vacuum connector. It is appreciated that the fastener  20  in  FIGS. 1 and 2  may be removable from the body of the vacuum connector  11  to enable positioning of the stiffener  25  on the vacuum connector  11  first, followed by fastening (e.g. clamping) of the fastener  20  on the stiffener. In the alternative, the fastener may be adapted to securably receive the stiffener in a single motion, such as by a latching mechanism, or using a resiliently biasing arm and slidably securing the stiffener under said arm. It is also appreciated that the fastener may provide either a temporary connection, such that stiffeners may be removed and replaced, or a permanent connection, whereby the stiffener and vacuum source are considered an integrated unit. In this regard, adhesives may also be considered fasteners for connecting the stiffener to the vacuum connector. In the alternative the stiffening shank and vacuum support structure/connector may be otherwise integrated as a unitary structure (e.g. for single use). By separating the stiffener from vacuum connector, the stiffener may be discarded after use but the connector reused. 
         [0032]    The vacuum connector  11  is also shown having first and second vacuum ports  12  and  13  respectively in fluidic communication with each other. The second vacuum port  13  is adapted to connect to a vacuum source, and the first vacuum port  12  is positioned so that when the stiffener  25  is connected to the vacuum connector  11 , the first vacuum port  12  aligns with the port  19 , and the open channel and the suction port of the stiffener is in fluidic communication with the vacuum source. Furthermore, when a flexible device such as  21  is positioned against the shank  15 , a suction force is produced through the open port and against the device to attach the device to the stiffener. An O-ring  112  is also shown provided at the first port  12  to seal the interface between the port  19  and the first vacuum port  12  when the stiffener is secured to the vacuum connector. This particular design may be used, for example, for percutaneous applications where full implantation is not desired, since a portion of the inserted device will remain outside and exposed. 
         [0033]      FIGS. 4-6  show an example embodiment of the stiffener  26  of the insertion tool of the present invention, having a similar general shape as the stiffener  25  of  FIGS. 1-3  with an elongated insertion shank  22  along which a channel  18  is formed. In this embodiment, however, support ribs  23  are also provided and distributed along the channel  18  to provide additional support surfaces (similar to surfaces  27 ) against which the device  21  contacts when positioned for insertion. Moreover, the support ribs  23  form multiple suction ports  24 , each of which exerts a vacuum/suction force against a device positioned thereagainst, and the support ribs  23  help maintain a planar orientation of the device. It is appreciated that the support ribs  23  may be formed using traditional semi-conductor fabrication processes (e.g. photolithography, wet/dry/etch, etc.) as discussed for the stiffener of  FIGS. 1 and 2 . In the alternative it is appreciated that the ribs may be formed, for example, using two SOIs, as described for the embodiment of  FIGS. 7 and 8 . In the case of  FIG. 8 , support ribs may be formed on the top shank  50  prior to being bonded or otherwise attached to the bottom shank. 
         [0034]      FIG. 7  shows another example embodiment of the flexible device insertion tool of the present invention generally indicated at reference character  30 . Similar to  FIGS. 1-3 , the tool  30  includes a vacuum connector  31  having first and second vacuum ports  33 ,  34  in fluidic communication with each other, and a fastener  42  for temporarily or permanently securing a stiffener  43  to the vacuum connector. And an O-ring  34  is also shown for enhancing the connection with an attached stiffener. 
         [0035]    In particular, the stiffener  43  is shown having an insertion shank  35  with a handle end  36 , an insertion end  37  and a channel  38  extending between a port  39  and a suction port  41 , and providing fluidic communication therebetween. The channel  18  includes an enclosed section  40  near the handle end  36 , and an open section which form the open port  41 . As such, the channel  38  may be characterized as a partially-enclosed suction channel, which may be useful for inserting/implanting fully implanted devices because the enclosed section is necessary to deliver the vacuum force to the suction port  41  near the insertion end  37  to enable the depth of penetration and insertion necessary to fully implant the device in the tissue. Similar to the embodiment shown in  FIGS. 1-3 , traditional semi-conductor fabrication processes (e.g. photolithography, wet/dry/etch, etc.) may be used to fabricate the stiffener with partially-enclosed suction channel. For example, the stiffener with enclosed and open sections of the channel may be created using two SOI wafers to produce a top shank portion and a bottom shank portion separately, and subsequently joined (e.g. bonded) together.  FIG. 8  illustrates an example top shank  50  and bottom shank  54  of such a stiffener fabricated according to such process. The top shank  50  is shown having a top shank channel  52  extending between a port  51  (for communicating with the vacuum connector) and an end  53 . And the bottom shank  54  is shown having a bottom shank channel  56  extending between a first end  55  and a second end  57 . When combined, the first end  55  is positioned adjacent the port  51  to enclose the channel from  55  to  53 , which an open suction port is formed between  53  and the insertion end  57 . 
         [0036]      FIG. 9  shows another embodiment of the insertion tool of the present invention where the stiffener is adapted to connect in-line with the vacuum connector. In particular, the stiffener is shown having an elongated insertion shank  65  with a channel  68  extending between a handle end  66  and an insertion end  67 , and enabling fluidic communication between port  69  and the suction port  71  where a device  73  is shown attached by vacuum suction. And the vacuum connector  61  is shown having a first vacuum port  62 , and a second vacuum port  63  adapted to connect to a vacuum source (not shown). Moreover, the first and second ports  62 ,  63  and the port  69  of the stiffener are arranged in-line along a longitudinal axis of the stiffener. A fastener  72 , as previously described for other embodiments, is also shown for securing the stiffener to the vacuum connector in the inline arrangement. And an O-ring  64  is also shown providing a seal between the first port  62  and the port  69 . 
         [0037]    And  FIGS. 10A-D  and  11 A-D show alternate example embodiments of the insertion tool and fabrication methods thereof of the present invention. In particular,  FIGS. 10A-D  shows the progression of steps, and starting with a tubular structure  80  made of a material with a suitably high Young&#39;s Modulus, which may be, for example, hollow metal wire (e.g. tungsten, chromium, gold, iridium, titanium), micro-hypodermic needles, biocompatible polymers, ceramics (e.g. sapphire, alumina, silicon carbide, titanium-nitride, tungsten carbide, zirconium carbide, zirconium nitride) and sheet metal alloys. A linear array of slots or apertures  81  is shown formed (e.g. laser cut) on one side of the tubular structure  80  adjacent one end, with that end being subsequently capped at  82  (e.g. by heating the end about the material&#39;s melting temperature) to form a closed seal so that the suction force is only applied through the slots. The entire tubular structure  80  is then flattened so that the array of apertures is positioned on one side of the flattened structure. Similarly, in  FIGS. 11A-D , a tubular structure  90  is shown provided and formed with a single elongated aperture  91  on one side of the structure. An end cap  82  is also formed to close off the end near the aperture, followed by flattening of the structure  90  with the single aperture positioned on one side of the flattened structure. 
         [0038]    While particular operational sequences, materials, temperatures, parameters, and particular embodiments have been described and or illustrated, such are not intended to be limiting. Modifications and changes may become apparent to those skilled in the art, and it is intended that the invention be limited only by the scope of the appended claims.